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SAGE 189] CORNELL UNIVERSITY LIBRARY 8 ‘DEPARTMENT, OF SCIENTIFIC AND INDUSTRIAL RESEARCH. FUEL RESEARCH BOARD. SPECIAL REPORT No. 3. The Coal Fire “A RESEARCH BY MARGARET WHITE FISHENDEN, D. Se. “LATE BEYER FELLOW. OF THE “UNIVERSITY QF MANCHESTER FOR THE MANCHESTER CORPORATION AIR POLLUTION ADVISORY BOARD | LONDON: ‘ConiNTeD) BY HIS MAJESTY’S STATIONERY OFFICE. FOR THE DEPARTMENT OF SCIENTIFIC AND INDUSTRIAL RESEARCH. _'To be purchased through any Bookseller or directly from HLM. STATIONERY OFFICE at the addresses given overleaf,’ 1920 ’ Price 4S, net... DEPARTMENT OF SCIENTIFIC AND INDUSTRIAL | RESEARCH, 4 i “LST OF OFFICIAL PUBLICATIONS. “The publications named ‘sel can Be purchaskd through any Bookseller or directly from i. M. STATIONERY OFFICE at the following addresses : - IMprria Housz, Kincsway, Lonpon, W.C.2, and} ' 28 ABINGDON. Srrésr,’ Lonpon, S.W.1 ; 37 Perer STREET, MANCHESTER ; z St. ANDREW’s CRESCENT, CARDIFF ; -23° FortH Street, EDINBURGH ; _or from E. PONSONRY, Libis 116 Grartox semen Dupin. The offices of the Departmerit are unable te supply them directly. , . ‘N.B. —Applications by post: to the above addresses should quote the aescription i in full of , the pebliasone wanted, and should be accompanied by ae pte as. indicated i in this list, ' : ce oh be shes 7 ig . “ANNUAL REPORTS. OF THE. DEPARTMENT. Report of the Committee of the Privy Council for Scientific and _* © Industrial Research’ for the bed 191 5-16. oe 8336.) Price 3d. (by post, 4d.), Ditto ditto. EGTO—1 Je (Ca. 8718) Price 3d. . by post, 4d. coh Ditto’ | ditto: , ‘Ucn (Ca. si y dee a | ae "(by post, 6d.). Ditto ditto 1918-19. (Cmd, 320.) Price 6d. soaehee ; (by post, 8d.). Ditto. ditto — 1919-20 - are ress.) FUEL RESEARCH BOARD, Report of the Fuel Research . Board on their. Scheme of Research _.and on the Establishment of a Fuel Research Station. 1917. Price 2d. (by post, 23d.). Report of the Fuel, Research Board for the years, 1918 and tgiys Price 1s. 6d. (by post, 1s. 83d.). SPECIAL Ruvoxt SERIES : 8 No. 1. Report on. Pulvérised. Coal Systems in meses by | _Lednard C. Harvey (wth plates and warren) 1919. Price 2s. 6d. (by post, 2s. 834d.). No. 2. The Peat Resources. of Ireland. A lecturs given before cd the Royal Dublin Society, on the 5th March rgro, by Professor Pierce F. Purcell, , Assoc. M.Inst.C. EB. Price od. (by post, 11d.) ¥, (Continued on page 3 of cover) CONTENTS l- Fishenden. The coal fire. 1920. 2- Great Britain--Scientific and Industrial Research Department--Fuel Research Board. The winning, preparation and use of peat in Ireland. 1921. 3- <--- Physical and chemical survey of the national coal resources. 1922. DEPARTMENT OF SCIENTIFIC AND INDUSTRIAL RESEARCH. FUEL RESEARCH BOARD. SPECIAL REporT No. 3, ‘The Coal Fire A RESEARCH BY MARGARET WHITE FISHENDEN, D.Sc. LATE BEYER FELLOW OF THE UNIVERSITY OF MANCHESTER FOR THE MANCHESTER CORPORATION AIR POLLUTION ADVISORY BOARD LONDON: PUBLISHED BY HIS MAJESTY’S STATIONERY OFFICE FOR THE DEPARTMENT OF SCIENTIFIC AND INDUSTRIAL RESEARCH. To be purchased through any Bookseller or directly from H.M. STATIONERY OFFICE at the addresses given on cover. 1920 43 Price 4, net. 4 4-4— fr; Car ASV G6 AIR POLLUTION ADVISORY BOARD Chairman—Councillor E. D. SIMON. Councillor J. Bow1z, Mr. E. R. Braysuaw, Mr. W. Buckxiey, Mr. R. H. CLAYTON, Alderman S. Dixon, Professor H. B. Dixon, Dr. C. DREYFus, Alderman J. FILDES, Principal J. C. M. Garnett, Professor W. W. H. Grr, Councillor C. W. GopBERT, Mr. J. W. Grauam, Mr. H. P. Grec, Councillor R. S. Harper, Mr. E. G. Hitter, Mr. J. Hopcson, Alderman W. T. Jackson, Councillor A. James, Mr. W. C. JENKINS, Alderman W. Kay, Councillor J. J. Kenpatt, Professor E. Knecut, Councillor W. MELLAND, Councillor W. R. MELtor, Mr. P. OcpEn, Councillor M. J. O’LoucHin, Mr. A. J. PENNINGTON, Alderman F. S. Prius, Councillor E. Prerce, Major E. F. Prrxrncron, Mr. H. A. RaTCLiFFE, Dr. A. Reg, Captain F. S. Sivnatt, Mr. W. THomson, Mr. H. M. THORNTON, Alderman W. Wa ker, Professor F. E. Weiss, Mr. P. S. WORTHINGTON. EXECUTIVE COMMITTEE Chairman—Epwarp G. Hitter, B.Sc., M.Inst.C.E., M.I.Mech.E., Chief Engineer National Boiler Insurance Co., representing the Manchester Association of Engineers. R. H. Crayton, B.Sc., Chemical Manufacturer. H. B. Dixon, C.B.E., M.A., F.R.S., Professor of Chemistry, Manchester University. W. W. Hatpane Ges, B.Sc., M.Sc., Tech., Professor of Applied Physics, College of Tech- nology, Manchester. Councillor HoyvLe, Public Health Committee. E. Knecut, Ph.D., M.Sc., Tech., F.I.C., Associate Professor of Applied Chemistry, College of Technology, Manchester. Councillor W. MELLAND, J.P., Chairman of the Statistical Sub-Committee. Alderman F. S, Puitiips, Chairman of the Salford Gas Committee. Councillor E. D. Simon, B.A., M.I.Mech.E,, M.I.C.E., Chairman of the Air Pollution Advisory Board. F. 5. Sinnatt, M.B.E., M.Sc.Tech., F.1I.C., Lecturer in Fuels, Manchester University, Director of Research, Lancashire and Cheshire Coal Research Association. W. Tomson, F.R.S.E., Chairman of the Manchester and Salford Sanitary Association. Ae PREPATORY NOTE BY THe DIRECTOR OF PUBL RESEARCH In the years 1917-18 grants were made by the Department of Scientific and Industrial Research to the Manchester Air Pollution Board in connection with inquiries being conducted by Dr. Margaret Fishenden on some of the problems of domestic heating. Reports on the preliminary inquiries of Dr. Fishenden and on her experimental work during the past two years have been before the Fuél Research Board, and conferences with the Chairman of the Air Pollution Board, Mr. Simon, and with her, have been held from time to time. The investigation into the efficiency of open fires has yielded a collection of carefully ascertained data, from which it is believed that a new departure can be made in dealing with the whole question of the use of smokeless solid fuel in domestic fires. The work is of so important a character that, with the concurrence of the Manchester Air Pollution Board, it is now published in the form of a Special Report. It is hoped that in this way the work will receive the wide publicity which it deserves. ‘FUEL RESEARCH BoarD, DEPARTMENT OF SCIENTIFIC AND INDUSTRIAL RESEARCH, 16 AND 18 OLD QUEEN STREET, WESTMINSTER, LONDON, S.W.1. August, 1920. li INTRODUCTION THE tests made by Dr. Margaret Fishenden during the years 1916-19 on the coal fire, the results of which form the subject of the following report, have been carried out under the auspices of the Manchester Air Pollution Advisory Board, a sub- committee of the Manchester City Council. When the Board decided in 1915 to take up actual experimental work, special consideration was given to the direction in which the most useful results might be expected. It was felt that while any effective work on the consumption of coal and the production of smoke in industry must necessarily be undertaken on a large scale, and would be beyond the means of the Board, the open coal fire offered a unique opportunity for valuable work. The results of such work as had already been put forward suggested that the heating efficiency of the different types of coal grates varied over wide limits. The validity of the basis of comparison adopted in these early tests, however, was doubtful, the coal fire haying been considered as an apparatus which owed its effect to convection, and computations of radiant energy had rested only upon the roughest of comparative tests. It was hoped that a thorough investigation would prove which factors made for efficiency, and it was thought possible that specifications for grate construction could be drawn up, which might perhaps be embodied in local bye-laws after the manner of specifications for drainage, the general use of which would result in a great saving of coal and reduction in smoke. Dr. Fishenden’s researches have proved this hope to be illusory, for they have shown that the effects upon the actual heating efficiency of coal fires of such varia- tions in fire grate design as are exhibited in the grates of different makers, are relatively unimportant. They have, however, given other results of practical value, for which reason, although the book is primarily a technical one for the use of those engaged in research work or in the manufacture of grates, it may be desirable in this introduction to give a short, clear summary of the practical results obtained for the benefit of the general reader. Methods of Test.—The methods of measurement adopted for the determination of the radiant energy emitted were based upon the general plan of the “ Leeds” tests, but owing to the peculiarly variable conditions associated with coal fires, iv INTRODUCTION considerable modifications of working became necessary. Ultimately a method of measuring radiant energy given out by a coal fire, so as to arrive at its radiant efficiency, that is, the percentage of the total heat of the combustion of the coal which is radiated out into the room, was perfected. Details will be found on pages 2-4. A preliminary report was circulated over a year ago among all those who were known to be interested in this branch of the work, and the method has been subject to very little effective criticism. It may, in the opinion of the Board, be taken as sufficiently accurate for practical purposes. Each separate measurement of radiant efficiency still occupies about I0 hours, but owing to the varying rate of radiation, no shorter time has been found to give satisfactory results. Efficiency of the Coal Five —The first question to be considered was a definition of the efficiency of the coal fire. The heat generated from a coal fire goes in three directions : (x) Heat is radiated into the room. (2) Heat is carried up the flue by the warm air and gases, part of which escapes through the chimney, whilst part, heating the walls of the flue on its passage, is gradually conducted through the walls to the outside or to adjacent rooms. (3) Heat is given up to the walls and convected from them into the room, or conducted elsewhere. The heat completely wasted from a heating point of view is— (a) That which escapes from the top of the chimney, though even this is doing useful work in causing ventilation. (0) That which is conducted through the walls at the back of the fire to the outside. Where the chimney is an inside wall, a part of (0) is utilised in heating adjoining rooms. It is difficult to arrive at a satisfactory definition of the efficiency of a coal fire. At the same time it is clear that the efficiency is much greater than has been gener- ally assumed. In the case of an inside chimney, the only final loss is the heat in the gas escaping from the top of the chimney. -When the draught is only just what is necessary for hygienic purposes, this also is doing useful work, so that in that particular case there is no loss as regards the heat actually generated by the coal, and the efficiency might fairly be said to approach Ioo per cent. There is of course always a certain loss in unburnt products in the form of ash, soot, or gas. For practical purposes the most important point is undoubtedly the amount of heat radiated into the room, and our principal experimental work has been in, first of all, perfecting a system for measuring this heat, and subsequently testing it under various conditions. (x) Practical Results—A number of coal grates have been tested, including what are supposed to be the best and the worst types. Working with ordinary vi INTRODUCTION bituminous coal, the radiant efficiency lies in all cases between 20 pet cent and 24 per cent. It has been proved that the supposed great variation in radiant efficiency between different grates does not exist. (2) Coke.—Experiments show that there is a great difference in the radiant efficiency obtained from wet and dry coke respectively. This is a matter which requires a good deal of further investigation, and is a promising field of research and reform. (3) Low Temperature Carbonisation Coke.—The radiant efficiency of low tem- perature carbonisation cokes averaged 30 to 33 per cent in a grate which gives a radiant efficiency with coal of 25 per cent. We have not been able to explain this increased efficiency as yet. It does, however, confirm the fact, accepted by all smoke abatement reformers, that it is exceedingly desirable that a fuel of this nature should be put on the market at a reasonable price. (4) Salts——We have tested several of the preparations that are so widely advertised as doubling the value of a ton of coal. They consist generally of common salt, with a small percentage of other chemicals added. In every case we have found, as was to be expected, that they had no effect whatever on the quantity of heat given out to the room from a given weight of coal. (5) Draught.—The tables on pages 24 and 58 show : (a) That over the limits likely to be encountered in practice with domestic grates the radiant efficiency is independent of the draught. (b) That as the draught is reduced, a smaller proportion of the heat is wasted in gases leaving the chimney. The amount so saved is absorbed by the walls, and must be given out into the rooms adjacent to the flue, or partly to the outer wall, as the case may be. There are some practical deductions to be drawn from this fact. It is well known that one objection to the coal fire is that the usual excessive draught causes anybody sitting near the fire to be cold behind and hot in front. This excessive draught is wasteful for two reasons—because more actual heat is wasted up the chimney, and because more heat is required to keep anybody in the room sufficiently warm in face of the strong draught. A fair draught is required to start the fire, but as soon as it is burning satisfactorily, the draught should be cut down to a minimum. One practical deduction is, therefore, that every coal fire should be fitted with an easily adjustable register for regulating the draught. The room will in this way be kept comfortably warm with quite a small consumption of coal, and the coal fire, instead of being relatively inefficient, may become quite an efficient means of heating a room. It should be pointed out that the register must be placed about a foot above the opening of the chimney, as otherwise smoke and dust will be driven into the room when it is closed. Another very obvious deduction from these tests, and one very consistently INTRODUCTION vil ignored by architects, is that a fireplace should for efficiency never be placed on an outside wall. It is quite possible under certain conditions that 25 per cent of the heat given out by the coal may be wasted by conduction through to the open air, whereas, as has already been pointed out, if the coal fire were on an inside wall, and the draught were properly reduced, almost the whole of the heat of the coal might be useful for the actual heating of the house. In the modern barless hearth-grate the amount of air passing through the coal is reduced, as ingress to air beneath the grate is limited; there is, however, com- paratively little reduction in the total draught up the chimney, the greater part of which enters the chimney flue directly, and without coming into contact with the coal. The whole question of draught offers probably the most important field for the saving of coal in domestic grates. Future Work.—There is in this country a strong popular prejudice in favour of the coal fire, which is generally believed to be not only the pleasantest but also the healthiest way of heating a room. It certainly gives adequate ventilation, ample radiant heat, and pleasant variation of the conditions in a way that no other source of heat can do, but, as at present installed, its efficiency is comparatively low, and it causes much smoke and dirt. While it is desirable that the coal fire should be largely replaced by central heating, gas fires and electric heaters, yet it is certain that very large numbers of coal fires will continue to be used. It is accordingly of urgent importance that the conditions of efficiency for the coal fire should be further investigated. The work already done by Dr. Fishenden indicates that practical results are most likely to be found in two directions : (xr) By the development of a practical method of making some form of semi- coked coal at a reasonable price ; (2) By a further study of the whole question of draught in connection with coal fires ; and the work is being continued with special reference to these points. Conclusion.—The work of the Board has been carried on by means of grants of £150 for the first year, £256 for the second, and £232 for the third year from the Advisory Council of the Department of Scientific and Industrial Research. In addition to this, the City Council has given an annual grant of £250, and accom- modation and facilities for the tests have been afforded at the College of Technology through the courtesy of the Principal, J. C. Maxwell Garnett, Esq. Supplement- ary accommodation for the work was kindly placed at our disposal by the Director of Education, Spurley Hey, Esq. Thanks are due to Captain F. S. Sinnatt, M.B.E., Director of Research Lancashire and Cheshire Coal Association, and Mr. E. L. Rhead, M.Sc.Tech.F.I.C., M.Am.I.M.E., for dealing with measure- ments of calorific value. The Board is glad to take this opportunity of expressing Vill INTRODUCTION its appreciation of the wisdom and far-sightedness of the Manchester City Council in giving financial support to this research work. The Board feels that the Manchester City Council is setting an excellent example in this matter, and it is to be hoped that other cities may take up similar work. The Board is of opinion that this report is laying a foundation from which practical results of great value may be expected. It is estimated that about 36 million tons of fuel are burnt annually in domestic grates in the British Isles, and in view of the present scarcity and the high prices of coal, any research which will tend to substantial economy in its consumption is of urgent national importance. E. D. SIMON, Chairman of the Air Pollution Advisory Board. THE COAL FIRE BEING AN INVESTIGATION CARRIED OUT FOR THE AIR POLLWTION BOARD OF THE CORPORATION OF MANCHESTER By MarcGareT WHITE FISHENDEN, D.Sc. Late Beyer Fellow of the University of Manchester GENERAL CONSIDERATIONS: INTRODUCTORY THE energy of combustion liberated by fuel burning in open fire grates appears partly as radiation and partly as conducted and convected heat. Owing, however, to the continuous interchanges which take place from one form of energy to another, these cannot be considered as independent elements in the aggregate heating effect of the fire. : The radiant energy which is emitted in all directions by the burning fuel and its surroundings appears as heat only when it strikes some object by which it is partly absorbed ; it is therefore instrumental in directly warming the occupants of the room and the walls and furniture in its path. These latter now themselves become low temperature sources of heat, which in their turn emit radiation and warm the air of the room by convection. The air also absorbs heat from the hot surroundings of the fire which have been heated by radiation and conduction from the burning fuel in the grate. For these reasons the heat imparted to the air of the room cannot be regarded as a factor irrelative to the radiation or conduction from the fire. Imperfect combustion, denoted by the smoke and soot which rise from the fire, reduces the total heat available, and there is a further important loss in the hot air and gases which pass up the flue and escape through the chimney ; but it must be borne in mind that this heat is not wholly wasted, but serves to some extent (depend- ing upon the position and construction of the flue) to warm the upper rooms of the house—an important matter in cold winters. There may be with open fires (depending upon the design of the grate) a considerable loss of energy through direct radiation up the chimney flue, which, being absorbed by the walls of the chimney shaft, passes away gradually by con- duction, or is partly absorbed by the air which is drawn up the flue. The complicated nature of the alternations of energy which are thus associated with the heating of rooms by open fires, renders it impracticable to express the heating efficiencies in such a manner as to account completely for the total calorific t B 2 THE. COAL FIRE value of the fuel consumed. All forms of open fire, however, depend for their heating effect mainly upon radiation, the energy accounted for by the heating of the room air and walls being comparatively small. For this reason, in the experiments to be described, the comparisons of the heating efficiencies of various fuels burning in open fire grates have been based mainly upon determinations of the radiant energy thrown into the room. Direct measurements of the temperature and volume of the air entering and passing through the room, however, and of the temperature in the flue at the ceiling level, were also made where possible, and from them the waste in the hot flue gases calculated. The chief factors which govern the comfort of the occupants of the room may be specified roughly as follows: (x) the intensity and distribution of the radiation from (or to) the fire, walls and windows of the room, and (2) the temperature, volume, velocity and distribution of the air passing through the room. That is to say, an occupant of the room, himself a source of heat which must be kept uniform, is directly heated by radiation from the fire, but loses heat by radiation to the colder walls and windows of the room, and by convection to the air which comes into contact with his body. MEASUREMENTS OF RADIATION Methods of Measurement.—The methods adopted for the determination of the radiant energy emitted into the room from open fires followed the general plan of the “Leeds ” tests (p. 78) and consisted of two parts: (rt) By means of a radiometer the energy passing through a surface of 12” square opposite the centre front of the fire, and 34-4” away, was measured, and was expressed in B.Th.U. per square foot per hour. (2) By means of a thermopile attached to a direct reading indicator eighty-one observations were taken at intervals of 20° on the surface of an imaginary hemisphere with its centre at the centre of the fire. ‘ The semi-circumference of a circle of radius 34-4” is 108”; this can be divided into nine lengths of 12”, each of which subtends an angle of 20° at the centre. The surface of the hemisphere was therefore divided into 81 areas by lines of “ latitude ” and “ longitude”’ 20° apart, and thermopile readings were taken at the centre of each area (see Diagram 40). From these readings, after correction for variation of area with “ latitude,’ the ratio of the total radiation through the hemisphere to the central reading (the “ distribution factor” ) was obtained. The centre reading, as obtained in absolute value by the radiometer determination, was then multiplied by this factor to obtain the heat equivalent of the total radiant energy thtown into the room. This, expressed as a percentage of the total calorific value of the fuel consumed, is the “ radiant efficiency ” of the fire. Comparisons of Measuring [nstruments.—A brief examination of some different available types of measuring instruments was first made, including the Harcourt radio-thermometer (p. 99), the Richmond radiometer (p. 85), the Bone-Callendar- Yates bolometer (p.87), the Rubens and other thermopiles, and Mr. Bond’s segment radiometer (p. 87), which he kindly lent for the purpose. THE COAL FIRE 3 Comparisons between the readings of the Harcourt and Richmond instruments gave results which differed on the average by only about 1 per cent ; the Richmond radiometer, however, owing to the care expended upon the details of its design, was more reliable and accurate in individual readings, and was therefore adopted for determinations of the centre reading in the measurements of radiant efficiency. This radiometer was later compared with a Bone-Callendar-Yates bolometer with very satisfactory results, the values given by the two instruments differing by not more than 2 per cent, which was within the error of experiment. Centre readings of the radiation from a rapidly varying coal fire were taken over intervals of several hours, simultaneously with the Richmond radiometer and a Rubens thermopile, and showed approximately the same proportional variations. Similar results were obtained with a larger thermopile of different pattern ; this, being more sensitive, was chosen for final measurements (Diagram 1). re front of fire fram @ Th U pur sq fl por hour cont CURVE I Heat absorbed by Radiometer da 4 inches. fri Time in minutes since fire was lighted ¥ x ' CuRVE 2 OL 160. ‘imo in minutes since fire was hghtea DiacGRAM 1.—Simultaneous variation of the indications of radiometer and thermopile, both 34:4” from the centre front of rapidly varying coal fires. Direct approximate check measurements of the radiant efficiency of a coal fire made with the Bond segment radiométer gave rather low values, a result in agreement with the experience of other observers. The investigations were greatly complicated by the continuous variation of the source of radiation, and on this account certain modifications of method, which will -be described later, became necessary. Determinations of the Radiation falling on One Square Foot Area opposite the Centre Front of a Fire and 34:4" away.—All fires were lighted with known weights of fuel of predetermined calorific value, and were stoked at suitable intervals with weighed quantities of fuel. The residues of cinder and ash remaining in the grates at the end of an experiment were collected and their calorific value measured ; this, subtracted from the total calorific value of the fuel added, gave the calorific value of the fuel burned. THE COAL FIRE Readings of the Richmond radiometer placed 34-4” from the approximate centre front of the fire were taken at intervals of a few minutes over the entire period between the lighting and the dying out of the fire ; from these, the heat received, expressed in B.Th.U. per square foot per hour, was calculated, and plotted against the time since the fire was lighted. The summation of these curves gave the aggregate amount of heat received over the whole period of burning. This, multiplied by the distribution factor, and expressed as a percentage of the total calorific value of the fuel consumed, is the radiant efficiency of the fire. Fora given grate this efficiency is not a constant, but may vary considerably with the nature of the fuel used, and probably also to a slight extent with other factors. It will, for example, be higher when burning a dry fuel than when burning a damp fuel where part of the heat is wasted in vaporising the moisture present. : Determinations of the Distribution Factor.—The procedure at first adopted for the determination of the distribution factor was, by means of readings of the Richmond radiometer taken simultaneously in the centre position, to correct each of the 8x readings for variation with time. Later it was discovered that the varia- tions of the readings of thermopiles in different positions with time, were not pro- portional ; a modified method was therefore devised. It was found that there was little systematic variation of the distribution of radiation from “west” to “east” on any of the arcs 80° ‘‘north,”’ 60° “‘north,”’ 40° ‘‘north,”’ 20° “north,” 0°, 20° ‘“‘south,” 40° ‘‘ south,” 60° “ south,’’ 80° “‘ south,” with time; the mean distribution on each of these arcs was therefore determined from a number of readings taken at intervals over a day “ run,” the readings for each arc being corrected for the slight time varia- tion by the variations in the 0° reading of that arc. Next day the fire was again lighted and centre readings of the thermopile indicator for 80° ‘‘ north,’’ 60° “ north,” 40° “ north,” 20° “‘ north,”’ 0°, 20° “‘ south,” 40° “‘ south,” 60° “‘ south,”’ 80° “‘ south”’ were taken successively and repeatedly over the whole time of burning of the fire. The readings in each of these positions were then plotted against the time since the fire was lighted, and the averages over the entire period for each position calculated. Combining these with the previously found distributions around the horizontal arcs gave, by simple calculation, the average distribution factor. 4 RADIATION FROM COAL FIRES RADIANT EFFICIENCY OF CoAL FIRES IN GRATE “ A.”’—This was a small modern barless grate, 18” wide and 11” deep from back to front, built entirely of firebrick (packed behind with asbestos), and with sloping back and slightly lowered hearth. Two holes leading to apertures in the sides of the grate provided air inlets (Diagram 2). The experiments were carried out in a large rectangular room 60’ by 30’, kindly made available for the work by the Director of Education, Mr Spurley Hey (Diagram 3). The chimney flue was 45’ high. —_ Measurements of Radiation falling on One Square Foot Area 34-4" from Centre Front of Grate “ A.”—The fires were lighted with 7} Ibs. of coal (Arley washed cobbles of calorific value 14,500 B.Th.U. per lb.) and } 1b. wood and were fed at suit- able intervals (subject to the rate of burning of the fire) with 24 Ibs. of coal. THE COAL FIRE 5 Diagram 4, Curves 1, 2 and 3, shows the variation with time of the radiation falling on the Richmond radiometer 34-4” from the centre front of the fire. Curve x is for a fire fed with 2% lbs. coal 60, 120, 180, 240 and 300 minutes after lighting ; curve 2 for a fire fed with 24 lbs. of coal 60, 120, 180, 240, 300 and 360 minutes after lighting ; and curve 3 for a fire fed at 60, 150, 240, 330 minutes after lighting, with 24 lbs. coal ; in this case the draught was restricted somewhat by partly blocking the air inlets, and the rate of burning of the coal con- sequently reduced. It will be seen from the curves that the radiation emitted by the fire varied, as would be expected, in a more D1aGRAM 2.—Grate “A.” or less regular manner in the successive intervals between any two stokings, falling to a minimum when a fresh supply of coal was added, and rising thence, as the coal blazed and became incandescent, to a maximum which corresponded with the time at which the fire was blazing most fiercely, and which was found some 18 minutes after stoking. A diminution in the radiation followed, as the flame died FIREPLACE FIREPLACE Lr La ey | | i of | [ ig ete eee ee ee 3 q : | af [odie ee DiaGram 3.—Plan of large experimental room. away and the glowing fuel in the hot grate gradually burned and died down ; this was interrupted by the addition of a new supply of coal, when a similar cycle of changes was repeated. The shape of the curves between any two mendings of course varied consider- 6 THE COAL FIRE ably with the draught and consequent rate of burning, the maxima being more sharply marked for rapid rates of burning; and it was not found possible to reach a state in which the mean radiation emitted over the successive intervals was constant. For the first hour or two after lighting, the fuel burned slowly, and the radiation thrown out during the first intervals was low, but increased in the successive intervals until a stage was reached where the coal was being consumed more quickly than it was being supplied, and when the fire just before stoking therefore fell so low that in the following interval it burned up slowly and gave a lower radiation value (see Curve 1, Hour 5; Curve 2, Hour 4). In the next interval an increase was per haur CuRVE I mmches from centre front of fire Heal absorbad by Radiometer 34 4 B Th. U. por sq. 29 40 60 €0 100 120 140 160 180 200 220 240 260 260 900 320 Tumo in minutes since fire was lighted. CurRVE 2 inches from centre front of fire Heat absorbed by Radiometer 34 4 B Th U perrq Tl per hour 180 200 320 340 380 380 Time in minutes since fire was lighted CuRVE 3 inches from centre front of fio a g 2 Hoat absorbed by Radiometer 34 4 8. Th. U por on N. per hour, 120 140-160 200 220 : ke Time in minutes since fire was lighted DiaGRAM 4.—Variation with time of the heat absorbed by the radiometer 34-4” from the centre front of coal fires in grate “‘ A.” 420 440 480 . ee ani lighted with 73 lbs. coal and fed with 2} lbs. coal 60, 120, 180, 240, and 300 minutes after ghting. Curve 2.—Fire lighted with 7} Ibs. coal and fed with 2} Ibs. coal 60, 120, 180, 240, 300, and 360 minutes after lighting. teat : ; see aa. with 74 lbs. coal and fed with 2} lbs. coal 60, 150, 240, and 330 minutes after lighting. again shown. The residue of cinder and ash left in the grate amounted to from 2 to 3 lbs. ; Distribution of Radiation from Grate “ A.’’—In Table I. the average distribution of the radiation from the grate as given by the thermopile readings is shown; the readings have been reduced to an arbitrary centre value of 100. The distribution is expressed graphically in Diagram 5. It will be noticed that the fire threw its most intense radiation upwards at an angle of about 60° to the horizontal plane through the approximate centre of the fire; this result is in agreement with that anticipated as the surface of the fire sloped down from back to front at an angle THE COAL FIRE 7 varying with the amount of coal left unburned, but probably averaging less than 30°; the normal to the surface of the fire sloping upward at an angle of 60° or more. Passing downwards from the maximum the radiation decreased continuously, slowly near the central vertical plane, but more rapidly as the angle to “east” or “west” increased. The total amount of radiant energy passing through the upper half of the hemisphere was more than three times that passing through the lower half. oe “> ™ *g oF a °. °° wn DiaGram 5.—Distribution of radiation from coal fires in grate ‘A’ over an imaginary hemisphere of radius 34°4”, with its centre at the centre of the fire. Curve 1.—Vertical distribution. Curve 2.—Horizontal distribution. Passing ‘‘ east” or “‘ west’ from the vertical plane through the centre of the fire the intensity of radiation fell off continuously. The mean figure for the distribution factor worked out at 31, 32, 32, 31, 32, 35 for the first, second, third, fourth, fifth and sixth hours respectively ; no coal was added to the fire after the sixth hour, and the value of 35 corresponds to a dying-out fire. An average value of 32:5 was adopted. Radiant Efficiency of Grate ‘‘ A.’’—In Table II. the mean energy received over one square foot area 34:4” from the centre front of the fire over successive hours THE COAL FIRE TABLE I 2 é “ee ae DISTRIBUTION OF RADIATION FROM COAL FIRES IN GRATE A Thermopile Readings. Cosine | Correction Total To “West.” To “East.” Total. vanetion Corrected | a gee ee of Area. 80°. 60°. | 40°. 20°. | °°. 20°, | 40°. 60°. 80°. | 80° North 47 | 119 . 132 | 135 | 136 | 135 | 132 | 112} 50 998 O°174 ae 60° North . 56 | 126 | 143 | 150 | 152 | 150 | 141 | 123 | 51 | 1092 | naa aie 40° North . 24 | 110 147 149 148/136) 117 | 82) 23 936 | | Z 20° North . 19 | 61 | gr 112 130/128) 117) 69] 10 737 | 9°940 | = 0° a II 48 81. 97: 100} 89) 71 44 9 550° T0090 § 55° 20° South. - 8} 25) 46, 57; 65| 63) 55} 32 8 359 | vee oe . 40° South . 4| 13] 22, 29] 34] 32) 26] 15 4 179 | 0°76 4 60° South . oO 3 Qf Tae) G2.) wt 8 3 ° 57 | 0-500 2 ; 80° South . ° Bol a. | 4 4 3 I oO 20 | 0°174 7 i oe ee ey Totals 169 | 506 | 674 | 744 | 781 | 748 670 | 481 | 155 | 3183 tele ater 3183_ Distribution Factor= waa 8. TABLE II RADIANT EFFICIENCY OF COAL FIRES IN GRATE “A” Fires lighted with 74 lbs. of coal and 4 Ib. of wood. Heat absorbed by Radiometer 34°4 inches from centre front of fire. B.Th.U. per square foot per hour. Time. Experiment II. oes (iareh 25,199) een 2} Ibs. of coal added at 2} Ibs. of coal added at 2h Ibs. of coal added at | 60, 120, 180, 240, 300 mins. 60, 120, ee 300, 360 60, 150, 240, 330 mins. ist hour 67 IIo 74 2nd hour 172 214 145 3rd hour 229 227 155 4th hour 235 176 187 5th hour 198 258 218 6th hour 267 229 179 7th hour 195 217 I6I 8th hour 133 193 109 goth hour 68 I12 76 roth hour 34 50 45 tith hour 15 17 20 Total Heat absorbed by _ + Radiometer in B.Th.U. per square foot from lighting to dying out of os 2 1613 1803 1369 Total Calorific Value in / a B.Th.U. of Fuel burned. aS a 265,000 306,080 233,000 Radiant Efficiency | per ea ~ = Soe pe Rx cent —— Be 5 y Ioo . 19°8 per cent I9°5 per cent Ig'I per cent THE COAL FIRE 9 after lighting, as obtained from the radiometer time curves, is shown for the runs illustrated in Diagram 4. This, summed for the entire duration of the experi- ments and multiplied by the distribution factor (32:5) gives the total radiation thrown into the room, which expressed as a percentage of the total calorific value of the coal burned is the radiant efficiency of the fire. This, it will be seen, amounted to 19°5 per cent. RADIANT EFFICIENCY OF COAL FIRES IN GRATE “‘ B,”’—This was a small modern fire grate, open, barless and with a raised hearth consisting of a movable metal grid resting on legs, and a vertical firebrick back. A small fender, with adjustable doors for draught regulation, closed in the space beneath the hearth (Diagram 6). Fire | -6 iE ile 1 g— — —4+ | | —fLan— Dracram 6.—Grate ‘‘B.” DiaGRam 7.—Plan of small experimental room. The grate was built up about a yard above the floor of the small experimental room (Diagram 7). The chimney flue was go feet high. The fires were lighted with 5 lbs. of coal and 4 Ib. of wood, and were fed hourly with 24 lbs. of coal (selected tops from the Haighmore seam of the South Kirkby Colliery, Pontefract). No slack was used, but pieces of coal of roughly similar size—about six or eight to the pound—were chosen. The fire was not poked except immediately before stoking, when the ash was raked down, the remaining fire drawn to the front of the hearth, and fresh coal added evenly over the grate, piling up a little at the back. Measurements of Radiation falling on One Square Foot Area 34:4" from Centre Front of Fire “ B.”—Representative curves are included to illustrate the variation of the heat absorbed by the radiometer 34-4” from the approximate centre front 10 . THE COAL BIRE of the fire with time ; radiation is expressed in B.Th.U. per square foot per hour and time in minutes since the fire was lighted (Diagram 8). Curves I and 2 are for an aperture of 5” in the fender below the hearth, Curve 3 for an aperture of 2” and therefore a reduced draught. As before, the radiation emitted by the fire was found to pass through certain definite phases, falling to a minimum when fresh coal was added, and rising thence to a maximum concurrent with the time at which the fire was blazing most violently. CuRVE I Heat absorbed by Radiometer 34 4. inches from centre front of fire 8 Th U per sq. ft. per hour 120 146 160 390 320 340 360 Timo in minutes uince fire «es kghied. b 5 5 CurvE 2 8 3 6 Heat absorbed by Radiometer 34 4 inches from centre front of fire @ Th U per sq ft per hour Time in minutes since fire was lighted. o 3 3 CurvE 3 8 inches from centre front of fire Heal absorbed by Radiometer 34 4 8 Th. U. per sq. ft. per hour Time in minutes since fire was hehled Diacram 8.—Variation with time of the heat absorbed by the radiometer 34°4” from the centre front of coal fires in grate ‘‘ B.” Curve 1.—Fire lighted with 5 lbs. coal and fed with 2 lighting. 5” aperture in fender below hearth. Curve 2.—Fire lighted with 5 lbs. coal and fed with 2} lbs. coal 60, 120, 180, 240, 294 $ lbs. coal 60, 120, 180, 240, and 300 minutes after lighting. 5” aperture in fender below hearth. and 350 minutes after Curve 3.—Fire lighted with 5 lbs. coal and fed with 2} lbs. coal i ighti 2” aperture in fender below hearth. : oal 60, 120, 180, 240, and 300 minutes after lighting A diminution in the radiation followed, at first rapidly and afterw With the reduced draught (Curve 3) the maxima ae rather es oe marked, and the diminution which accompanied the gradual disappearance of a flame was followed by a period of nearly uniform, or even slightly increasing, radia- tion, which appeared to be attributable to the gradual creeping of orcn towards the front of the fire. When the draught aperture was large (Curves 1 ae the fire burned up very quickly, and the mean radiation over the successive intervals between stoking increased rapidly for an hour or two, after which there was ‘ diminution owing to the rate of burning of the coal having exceeded the ae of THE COAL FIRE II supply ; at the end of the experiment when no more coal was added the fire died out very quickly. On the other hand, with a smaller draught aperture, the coal at first burned less swiftly, but there was a steady increase over successive intervals. Moreover, at the end of the experiment the fire died out less quickly than before, the radiation emitted after the last stoking being considerably greater than with the wider draught inlet. The average radiation per pound of coal burned was almost exactly the same in the three cases. The residues of unburned cinder and ash averaged nearly 2 lbs. Distribution of Radiation from Grate ‘“‘ B.’”’—The distribution of the radiation from grate ““B” is shown in Table III. and Diagram 9g, and is very similar to TABLE III DISTRIBUTION OF RADIATION FROM COAL FIRES IN GRATE “B” Thermopile Readings. Cosine Correction Total To “ West.” To “East.” Total. Spat nies Corrected. of Area, 80°. | 60°. 40°. 20°, °°. r 20°. 40°. 60°. 80°. 80° North. . | 47 | 107 | 120 | 116 112-| 109 | 106) 92 41} 850 Orl74 148 60° North . IoO | 144 ; 155 154 | 152 | 143 | 138 | 126 gI 1203 0*500 605 40° North. . 66 | 127 | I53 | 16r | 156 | 148 | 129 | 100 50 I0go 0:766 835 20° North. . | 44; 94. 125 | 138 | 139 | 130 | 112| 77) 35 894 0940 837 0° as 26; 54| 79| 96} 100} 97 78} 55 | 22 607 1-000 607 20° South. . 16 35 50 63 66 63 52 36 I5 396 0-940 372 40° South. . I5 23 30 38 41 40 33 23 13 256 0+766 196 60° South. . 12 I7 21 24 25 25 24 19 13 180 0+500 go 80° South... TO | 14) 16) 17} 17] 17! 16] 14! Io 131 o-T74 23 Totals . . 336 | 615 | 749 | 807 | 808 772 | 688 | 542 | 290 3713 3713 100 Distribution Factor= =37°1. that for grate “ A,” the maximum readings again being shown at 60° north. The decrease to ‘‘-east ” or “‘ west,” however, is less abrupt and much smaller than would be indicated by a ‘‘ cosine ” law such as is followed by the radiation from a point source; and rather more radiation is thrown downwards into the room, owing to the fact that whilst with grate ‘“‘ A’”’ the wall was built up solidly to the hearth of the grate, grate ‘‘B ” had an aperture beneath the hearth through which radiation from underneath the fire was projected. Grate ‘‘ B”’ was not quite symmetrical, the readings to the “ east” being greater than readings to the “ west.” The distribution factor for six separate determinations worked out at 34, 37, 39, 36, 35, 42; a mean value of 37 was adopted. As a check on this figure an approximate value for the distribution was calculated from theoretical considerations by Dr. J. Prescott, Lecturer in Mathematics in the College of Technology, who obtained a value of 30. Radiant Efficiency of Grate “‘ B.””—In Table IV. calculations of the radiant efficiency of grate “‘B”’ are presented. This was equivalent to about 21 per cent of the total calorific value of the coal burned, and did not vary with the aperture in 12 THE COAL FIRE —Distribution of radiation from coal fires in grate ‘‘B”’ over an imaginary hemisphere of radius 34°4”, ’ with its centre at the centre front of the fire. DIAGRAM 9. Curve 2.—Horizontal distribution. Curve 1.—Vertical distribution. the fender. THE COAL FIRE 13 Preliminary experiments which had been made with this grate as originally installed with sloping firebrick back, indicated a radiant efficiency of about 26 per cent, but the methods of measurement not having yet been well established at this period, the figure must be taken as approximate only. TABLE IV RADIANT EFFICIENCY oF CoaL FIRES IN GRATE “B” Fires lighted with 5 lbs. of coal and 4 lb. of wood. Heat absorbed by Radiometer 34°4 inches from centre front of fire. B.Th.U. per square foot per hour. Time ExPERIMENT I. EXPERIMENT IT. EXPERIMENT III. p (November 8, 1916. (December 13, 1916.) (November 1, 1916.) 5-inch aperture in fender 5-inch aperture in fender 2-inch aperture in fender beneath grate. 2} Ibs. of | beneath grate. 2} lbs. of beneath grate. 2} lbs. of coal added at 60, 120, 180, | coal added at 60, 120, 180, | coal added at 60, 120, 180, 240, 300 mins. 240, 300, 360 mins. 240, 300 mins. * Ist hour 88 48 54 2nd hour 218 163 115 3rd hour 278 254 210 4th hour 270 282 270 5th hour 254 234 270 6th hour 218 206 266 7th hour zs : ‘ 40 274 147 8th hour . és 4 36 28 goth hour ‘ F ou 4 4 Total Heat absorbed by Radiometer in B.Th.U. per square foot from lighting to dying out © offire “R.’ . . . 1370 I501 1364 Total Calorific Value in B.Th.U. of Fuel burned. OGRE? he ae 240,000 275,000 240,000 Radiant Efficiency per Rx 37 cent Gre x 100. 21°I per cent 20-2 per cent 21-0 per cent RADIANT EFFICIENCY OF COAL FrirEs IN GRATE “ C.”—This was a very large grate of rather old-fashioned design, with vertical firebrick back and sides, and a base of metal grid 104” from back to front and 28” wide (Diagram ro). Five horizontal iron bars, each }” thick and 2}” apart, formed the front of this grate, which was built up about a yard above the floor in the large experimental room (Diagram 3). There was no fender beneath the grate, nor draught restriction of any kind. The fires were lighted with 15 Ibs. of coal and } lb. of wood, and were fed hourly with 74 Ibs. of coal (calorific value 14,600 B.Th.U. per Ib., from the S. Kirkby Colliery, Pontefract). The coal in this grate burned very fiercely, and except for the few minutes immediately succeeding stokings, the fires were almost white hot from side to side. From 4} to 5% lbs. of unburned cinder and ash were left in this grate at the end of the runs. Distribution of Radiation from Grate ‘‘ C.”—Five distinct measurements of the 14 THE COAL FIRE distribution factor for this grate resulted in values of 414, 41}, 40}, 40 respectively ; a single value of 454 was rejected as improbable, and a mean value of 41 employed. The possibility of any systematic alteration of this factor with time was investigated. values relative to the first, second and third hours after lighting the fire being obtained separately and yielding results of 404, 403, 40 respectively. Average values of the individual readings—reduced to an arbitrary centre reading of 10o— are given in Table V., while Diagram 11 shows the results graphically. TABLE V DISTRIBUTION OF RADIATION FROM COAL FIRES IN GRATE “C”’ | Thermopile Readings. Cosine Correction Total To “ West.” To “East.” Total. (ns Gorrested. of Area. 80°. 60°. 40°, 20°. °°. 20°. 40°. 60°. 80°. 80° North. . 38 86 | 119 | 128 | 131 | 121 | 109 83 39 85 . 4 O°174 148 ou North. . 79 | 124 | 133 | 135 | 129 | 126 | 114 | 105 71 IOI6 0°50 508 a Morth. 75 98 | 113 | 126 | 129 | 123 | 109 95 74 942 0-766 722 cnt North. . 50 73 QI | 107 | 117 | 110 95 79 55 777 0-94 730 e - + | 36|-60/ 77] 89| 100; 97) 86} 70} 43 658 I-00 658 20° South. . 43 | 62 76 | 83] 92] 88 76} 59} 41 620 0°94 582 4o° South . . | 41 | 50] 56] 65) 65} 61] 53] 45] 35 471 0-766 361 60° South . 49| 49) 55| 63 | 64) 59| 50} 45] 45 479 050 239 80° South... 68 | 68) 58) 61] 60} 62] 68] 75] 83 603 Or174 105 Totals . . | 479 | 670 | 778 | 857 | 887 | 847 760 | 656 | 486 4050 Distribution Factor —1°5° — 40°5. mere) The greatest concentration of radiation was met with at 60° north, the readings passing downwards, gradually lessening to 40° south or 60° south ; itt increase rat place at 80° south, probably attributable to radiation from underneath the fire which was visible from this position. ; Passing “ east” or “‘ west” from the vertical plane through the centre of th fire, the intensity of radiation fell off conti 5 haus oo iS tinuously, though more slowly than would Measurements of Radiation falling upon One Square Foot Area 34:4" from Front of Grate “ C.’’—The radiation falling upon one square foot aréa 34-4” fro he centre front of the fire as measured by the heat absorbed by the a a he position, is shown graphically in Diagram 12, Curves 1, 2 3, where it i 1 he against the time in minutes since the fire was lighted. The mean a — successive hours and the calculation of radiant efficiency are given in Tabl “VL This result is of some special interest as the temperatures cicnea b the he were unquestionably the highest met with: the intensity of the radlatio pene was much greater than in any of the fires previously tested, the rate i ae being also much more rapid. The average amount of heat per hour absorbed ioe radiometer was relatively low during the first hour after lighting the ire, byt bi THE COAL FIRE ts Hee D1aGRAM 10.—Grate “C.” DiacRAM 1y.—Distribution of radiation from coal fires in grate ‘‘C ”’ over an imaginary hemisphere of radius 34°4” with its centre at the centre of the fire. Curve 1.—Vertical distribution. Curve 2.—Horizontal distribution. 16 THE COAL FIRE CurvE 1 anches from centre front of fire Heat absorbed by Radiometer 34 4 B Th U per sq. ft per hour 120 140 160 300 320 340 Time in minutes since fire was lighted. CuRVE 2 Heat absorbed by Radiometer 34 4 Inches from centre front of fire B Th U. per sq ft per hour 320 340 360 380 400 420 440 460 480 Time in minutes since fire was lighted : 520 54C CuRVE 3 Heal absorbed by Radiometer 34 4 aichea from centre front of fire B Th U. per sq. ft. per hour. 120 140 160 220 320 360 4 Time in minutes since firo waa lighted S80 '800 8077380 Diacram 12.—Variation with time of the heat absorbed by the radiometer 34'4” from the centre front of coal fires in grate ‘‘ C.” Curve 1.—Fire lighted with 15 lbs. coal and fed with 74 lbs. coal 60, Curve 2.—Fire lighted with 15 lbs. coal and fed with 7% lbs. after lighting. Curve 3.—Fire lighted with 15 lbs. coal and fed with Ibs. coal at 6: 8 i after lighting. 73 0, 120, 180, 240, 300, and 360 minutes 120 minutes after lighting. coal at 60, 120, 180, 240, 300, and 360 minutes FHE COAL FIRE 17 accelerated over the second and third hours, after which it remained approximately uniform until the fire was allowed to die out, when, of course, the radiation was steadily reduced. As with other fires, the addition of coal was accompanied by a sudden drop in radiation, followed by a quick rise to a maximum which on the average happened 18 minutes after stoking; the radiation then decreased slowly for the remainder of the hour, again dropping suddenly when coal was supplied. Similar cycles were repeated. TABLE VI RADIANT EFFICIENCY OF COAL FIRES IN GRATE ‘*C”’ Fires lighted with 15 Ibs. coal and 4 Ib. wood. Heat absorbed by Radiometer 34°4 inches from centre front of fire B.Th.U. per square foot per hour. Time. EXPERIMENT I. Experiment II. EXPERIMENT III. (August 15, 1917). (August 28, 1917). (September 4, 1917). 7% lbs. coal added at 60, 7 lbs. coal added at 60, 7% Ibs. coal added at 60, 120 mins. 120, 180, 240, 300, 360 mins. |120, 180, 240, 300, 360 mins. Hour 1 74 147 95 Hour 2 343 372 448 Hour 3 642 682 822 Hour 4 598 746 837 Hour 5 251 734 785 Hour 6 91 -778 690 Hour 7 48 821 694 Hour 8 5 590 326 Hour 9 z ‘ A a I61 79 Hour 10 j 2 : is 60 44 Hour 11 : : “ ni 14 4 Hour 12 ‘ j : an 2 Total Heatin B.Th.U. per square foot absorbed by Radiometer from lighting to ae out of fire. “R.” 2052 5107 4824 Total Calorific Value in B.Th.U. of Fuel burned. “Ce 396,000 835,000 835,000 Radiant Efficiency Rx 41 , —— x 100 - 21°2 per cent 25°I per cent 23°7 per cent Radiant Efficiency of Grate ‘‘ C.”’—The radiant efficiency indicated for this grate in three experiments was 21-2, 25-I, 23-7 per cent ; the first figure is probably low, as the mortar used in building up the grate was not yet dry when the run was made ; the experiment was also a short one. The probable value of the radiant efficiency may thus be taken as about 24 per cent of the calorific value of the fuel burned (Table VI.). RADIANT EFFICIENCY OF COAL FIRES IN GRATE “‘ D.’’—This was a small, old- fashioned grate of register type, 7” only from back to front and 14” wide, with three 3” iron bars one and a half inches apart. The canopy and sides of the grate were of Cc ‘8 THE COAL FIRE iron and the vertical back of firebrick. The base consisted of a horizontal iron grating, the space beneath which was closed in front by a fender with sliding doors for adjustable air inlets (Diagram 13). A large plate damper in the flue provided further for draught control. This grate was installed in the experimental room at the College of Technology (Diagram 7). The fires were lighted with 5 lbs. of coal and $ lb. of wood, and were fed at suitable intervals with 24 lbs. of coal. Distribution of Radta- tion from Grate “ D.’’—The average distribution of the radiation from this grate as disclosed by the thermopile readings is shown in Table VII. and Diagram 14. It will be observed that the distribution is dissimilar to - that associated with the flatter fires of grates “A” and ‘‘B”; the maximum readings were, it is true, again recorded at 60° north, but the maxima were not sharply defined, the in- tensity of radiation altering little between 80° north and 20° south. With grates “A” and “B” the oy, intensity of radiation through the o° plane was little Disacram 13.—Grate “ D.” DiacraM 14.—Distribution of the radiation from coal fires in grate ‘““D’”’ over the surface of an imaginary hemisphere of radius 34°4”, with its centre at the centre front of the fire. Cu — i istributi rve 1.—Vertical distribution, Curve 2.—Horizontal distribution. THE COAL FIRE 19 more than half that recorded at 60° north (the maximum) ; but with grate “C”’ it was nearly nine-tenths as much. TABLE VII DISTRIBUTION OF RADIATION FROM COAL FIRES IN GRATE ‘*D”’ | Thermopile Readings. ; gos otreclion Total To “West.” To ‘‘East.” Total. ashe Garrected. - yr of Area. 80°. | 60°. | 40% | 20° oO. 20°. | 40°. | 60.° | 80°. ee North. . 22 53 70 76 80 a7 74 54 24 530 0-174 92 6G" North . 37 73 83 93 95 gI 89 80 41 6B2 0°50 341 40° North 34 69 84 93 96 98 84 68 34 660 0-766 506 20° North ‘ 26 57 81 96 | 103 98 84 62 23 630 0°94 592 0° e 4 22 | 54 77 93 |-100 99 82 55 20 602 I-00 602 20° South . 20!) 46 | 66 80 86 | 80] 68] 49] 20 515 0-94 484 ae" South. . 17 33 47 59 66 62 50 37 20 391 0-766 300 60° South .- I4 27 38 44 47 44 39 30 14 297 0-50 148 80° South. . Io 15 19 20 22 21 | 20 15 Io 152 0-174 26 Totals », | 202 | 427 | 565 | 654 | 695 | 670 | 590 | 450 | 206 3090 Distribution Factor= 309° 100 = 30°9. The mean values of the distribution factor resulting from several determinations were 32°3, 31-9, 31°3, 30°2, 31:2, 31-4, 30°2, 30°9, 29°5 respectively ; a mean value of 31 was adopted. For the purpose of ensuring that no appreciable variation of this factor occurred with time, measurements were made separately over successive hours after lighting the fire ; the resulting mean values for the first, second, third, fourth and fifth hours after lighting were, for a fire fed every hour, 30-8, 30-2, 30-9, 30-3, 31-4 respectively. Over the first hours after lighting the fire, although the distribution factor showed no deviation, there was relatively more radiation thrown upwards and less downwards. For a dying-out fire, there was again a greater intensity of radiation at upward and a less at downward directions, but the dis- tribution factor was rather increased—about 33. Measurements of Radiation falling on One Square Foot Area 34:4" from Front of Grate ‘‘ D.’’—A number of experiments were first undertaken without any restriction of the flue area, and with the doors in the fender below the fire wide open and allow- ing free access to air. The curves given in Diagram 15 show the variation with time of the heat absorbed by the radiometer 344" from the centre front of the fire under these conditions. The fires were lighted with 5 lbs., and fed hourly with 24 lbs., of coal; Curves I, 2 and 4 refer to fires made with a first-class house coal of calorific value 14,600 B.Th.U. per lb., and resembling the coal from the well-known Arley seam at Wigan; Curve 3 to fires made with selected tops from the Haighmore seam at Pontefract, calorific value 13,900 B.Th.U. per Ib.; and Curves 5 and 6 to fires made with Arley washed cobbles, calorific waine 14,500 B.Th.U. per lb. The residues amounted to 14 to 2 lbs. These curves differ ‘somewhat from those corresponding with grates ‘“‘ A” and 20 THE COAL FIRE “B,” but remittent cycles are again exhibited, with less marked and slightly delayed maxima. Radiant Efficiency of Grate “‘ D.”—In Table VIII. the calculations of radiant efficiency resulting from the data given in these experiments are shown. it will be seen that the radiant efficiency, as indicated by the individual experiments, 1s remarkably constant, varying from 23-7 to 25-1 per cent, or a mean value of 24 per cent. No dependence on the coal used is to be detected, but the three samples were all high-class coals of high calorific value and low ash content. TABLE VIII RapIANtT EFFICIENCY OF CoaL Fires IN GRATE “D.” (Unrestricted Draught) Fires lighted with 5 lbs. of coal and 3 lb. of wood. Heat absorbed by Radiometer 34-4 inches from centre front of fire, in B.Th.U. per square foot per hour. EXPERIMENT EXPERIMENT EXPERIMENT EXPERIMENT EXPERIMENT ExPERIMENT Time. I, II. III. IV. Vv. VI. (Oct. 9, 1917.) | (Ort. rx, 1917.)| (Dec. 7, 1917.) |(Dec. 27, 1917.) | (Feb. 12, 1918.) | (Feb. 21, 1918.) 23 Ibs. of coal | 2} Ibs. of coal | 2} Ibs. of coal | 2% lbs. of coal | 2} lbs. of cnal | 23 lbs. of coal added at 60, added at 60, added at 60, added at 60, added at 60, added at 60, 120, 180, 240, | 120, 180, 240, | 120, 180, 240 120, 180, 240, | 120, 180, 240, | 120, 180, 240, 300, 360 mins. | 300, 360 mins. Tins, 300 mins. 300 mins. 300 mins, Hour 1 95 81 70 IIl 94 68 Hour 2 200 290 202 307 169 " 182 Hour 3 306 320 348 280 279 349 Hour 4 348 371 306 345 278 328 Hour 5.- ri 7 324 315 312 367 290 275 Hour 6. i : 310 306 182 337 300 315 Hour 7- . 314 291 52 I7r 220 179 Hour 8 171 154 16 20 85 63 Hour 9 20 31 - 2 62 16 Hour 10 3 6 sie tie II 2 Total Heatin B.Th.U. per Square foot ab- sorbed by Radio- meter from lighting to dying out of fire. “eR? : . 2091 2165 1490 1940 1788 1777 Total Calorific Value in B.Th.U. of Fuel burned. ‘‘C. 3 273,000 273,000 193,000 240,000 234,000 234,000 Radiant Efficiency R x 31 G * 100 * 23°8 24'5 23°9 25°1 23°7 23°7 Mean Air Flow | through Room from end of hour 1 to one hour after last mending. Cubic feet per hour 18,500 16,900 16,900 Effect of Variation of Draught, and consequent Variation in the Rate of Burning on the Radiant Efficiency of Grate ‘“‘ D.’”’—A series of experiments was undertaken THE COAL FIRE 21 CurRVE I Heat absorbed by Radiometor 34 4 ches trom centive fram of B Th U persq ft per hour 340 360 380 400 420 Time in minutes since fire was lighted CuRVE 2 Heat absorbed by Radiometer 344 inches from centre front of fire B Th. U. per sq ft. per hour. 2 340 360 380 400 499 430 480 500 620 640 Tima in minutes since fire was lighted. CURVE 3 Heat absorbed by Radiometer 34 4. inches from centre front of fire B. Th. U. per aq. fi. per hour 380 400 420 440 400 480 820 640 320 ime in minutes since fire was lighted. =e 3€ B35 3 8 Bae. & i? ES O bee aS? gis ff Time in minutes since fire was lighted. menes from centre front of fire B Th U. per sq ft per hour CURVE 5 Heal abscrved by Radiometer a4 4 Time in minutes since fire was lighted 5 8 2 & e Curve 6 inches fram cantre front of fire Heat absorbed oy Radiometer 34°3 B.Th OU. 220 240 340 Time in minutes since fire was ighted DiacraM 15.—Variation with time of the heat absorbed by the radiometer 34°4” from the centre front of coal fire in grate ‘‘ D.”” Unrestricted draught. Curves 1 and 2.—Fire lighted with 5 Ibs. coal and fed with 2} Ibs. coal at 60, 120, 180, 240, 300, and 360 minutes after lighting. , Curve 3.—Fire lighted with 5 lbs. coal and fed with 24 lbs. coal at 60, 120, 180, and 240 minutes after lighting. Curves 4, 5 and 6.—Fire lighted with 5 Ibs. coal and fed with 24 Ibs. coal at 60, 120, 180, 240, and 300 minutes after lighting. 22 THE COAL FIRE with a view to ascertaining the influence of draught restriction, and consequent diminution in the rate of burning, on the radiation emitted by coal fires burning in grate “ D.” oy eee In the previously described experiments, with free access to air benea e€ ire 'y Radiometer 34 4 contre front of fi 39% por hour al 2] a 2 B des 5 Oo 385 Poy Ha = 5a ® 140 160 200__ 220 280 300 320 340 6360 Timo in minutes since fire was lighted. a8 ge ee Bes ze2 a $85 Bee foocte hemes ed 5 35k O 845 Be Bee rtd 2 240 280 340 420 440 460 460 ae Timo in minutes since fire was lighted #2 gé Bes om £2 sis Hf 3.c o ete & 2 & Sts Bes O $88 Be3 ee 367 mrtg 180. 200-220 240 320 380 400 420 440 a60 z 620 Time in minutes since fire was lighted ve ee Be Bos gee eee S383 B éfe a & 5 & o > Heat absorped by § & E 2 i 2 e § 2 « o £20 40 60 86 109 120 140 160 180 220 240 200 300 320 340 360 389 400 420 ao 480 600 620 640 Tume in minutes since fire was lighted D1IaGRAM 16.—Variation with time of the heat absorbed by the radiometer 34:4” from the centre front of coal fires in grate “D.”” Draught restriction. Curve 1.—Fire lighted with 5 lbs. coal and fed with 24 lbs. coal at 60, 150, 240, and 300 minutes after lighting. Damper pushed in slightly. Curve 2.—Fire lighted with 5 lbs. coal and fed with 24 Ibs. at 60, 180, and 300 minutes after lighting. Damper pushed in as far as possible and fender below hearth cemented in. Curve 3.—Fire lighted with 5 lbs. coal and fed with 2% Ibs. coal at 60, 180, and 300 minutes after lighting. Bars removed from fire and hearth cemented up. Curve 4.—Fire lighted with 5 lbs. coal and fed with 2% lbs. coal at 60, 180, and 300 minutes after lighting. Bars removed from fire and hearth cemented up. Damper pushed in as far as possible. grate and no flue regulation, it was found that the fires consumed about 24 Ibs. of coal per hour, and had a radiant efficiency of 24-1 per cent, the mean air flow through the room (as determined by methods to be described later) when approximately steady conditions had been reached being about 18,000 cubic feet, or about nine complete changes, per hour (see p. 47). When resistance to the flow of air was introduced by closing the doors in the THE COAL FIRE 23 fender below the grate or reducing the effective flue area by pushing in the damper, or both, the rate of burning of the fires was decreased, and it became necessary for the maintenance of a fire of about equal size to supply coal only at the rate of 2} lbs. every hour anda half, or every two hours, according to the conditions of experiment. The residue of cinder and ash remaining in the grate was about 2% lbs. or rather higher than for fires with unrestricted draught. The results are shown graphically in Diagram 16, Curves 1, 2, 3 and 4, the calculation of the radiant efficiency being given in Table IX. All fires were lighted with 5 Ibs. of coal (Arley washed cobbles of calorific value 14,500 B.Th.U. per lb.) and 4 lb. wood. Curve 1 refers to a fire which was fed with 24 lbs. of coal 60, 150, 240 and 300 minutes after lighting, the draught through the room being reduced to about 14,000 cubic feet, or about seven changes, per hour by pushing in the plate damper slightly. Curve 2 refers to a fire which was fed with 23 lbs. of coal 60, 180, 300 minutes after lighting, the mean draught through the room being reduced to less than one change per hour by pushing in the damper as far as was possible consistent with the fire not smoking into the room. The fender below the grate was also entirely closed. Curve 3 refers to a fire which was fed with 23 lbs. of coal 60, 180, 300 minutes after lighting. The bars of the grate were removed and the grid hearth covered with a layer of cement; the fender below the grate was entirely closed, but there was no restriction of the flue area. The mean draught through the room was about 15,000 cubic feet, or about eight changes, per hour. Curve 4 is for conditions similar to Curve 3, but the flue damper was also pushed in as far as was practicable, the air-flow through the room being only 3000 cubic feet, or rather more than one complete change, per hour. The mean radiation emitted over the successive hours after lighting the fires, and the calculations of the radiant efficiencies are shown in Table IX. It will be observed that the radiant efficiency is approximately the same in all four cases, the mean value being 24-1 per cent, or exactly the same as that recorded for fires with no draught restriction (see Table VIII). It must be concluded, therefore, that within the limits likely to be met with in practice, the radiant efficiency of coal fires is independent of the draught and rate of burning. The effect of removing the bars from the fire, moreover, resulted in only 0-5 increase on the mean radiant efficiency, an amount within the error of experiment. Effect of Variation in the Intervals between successive Stokings on the Radiant Efficiency of Grate “‘ D.’”,—Two tests were made with grate ‘‘ D,” in both of which the fire was lighted with 5 lbs. of coal and } lb. of wood, but in one of which coal was added every six minutes, } Ib. at a time, that is at the same average rate as before ; whilst in the other the fire was stoked twice only, 64 lbs. of coal being added 1 hour 50 minutes after lighting, and 74 lbs. 24 hours later. The total weights of coal added in the,two experiments were 17} and 19 lbs. respectively ; in the first experi- ment the pieces of coal used were smaller than usual, about five pieces to each mending, so that they could each time be spread evenly over the surface of the fire which could thus be kept fairly symmetrical ; in the second experiment the pieces of coal used were larger than usual. THE COAL FIRE 24 TABLE IX RADIANT EFFICIENCY OF COAL FIRES IN GRATE “D.” (Restricted Draught.) Fires lighted with 5 Ibs. of coal and 4 Ib. of wood. 2¢ Ibs. of coal added every 14 or 2 hours. Heat absorbed by Radiometer 34-4 inches from centre front of fire in B.Th.U. per square foot per hour. E ane LIL EXPERIMENT IV. ExperRIMent I. Exresniens 11: Gane %. 1918) : cha oa 19) Time. Mi 8). M. i; 2 i 2] up Danone Be atepee Slaked a as ee. from fire and base inslightly. 2}1bs.| far as possible and éemerited \u: cemented up. of coal added yonder oes ine 2} Ibs. of eel ae to at 60, , 240, 24 Ibs. of coal adde 5 = an atte | at 60, 180, 300 mins. se iat Bo, pe added are ae, a ee Hour 1 . : 3 85 66 52 48 Hour 2 < . 244 169 IoI 137 Hour 3 304 182 147 137 Hour 4 265 227 107 203 Hour 5 131 192 188 166 Hour 6 255 147 188 179 Hour 7 : é 5 . 122 132 174 167 Hour 8 : 2 : zs 32 74 106 92 Hour 9 ‘i : ‘ 3s 12 30 60 53 Hour 10 Fi ‘ ‘ 3 13 24 28 Hour I1 3 2 12 Total Heat in B.Th.U. per square foot absorbed by Radiometer from lighting to dying out of fire. “R.” , 1453 1235 1209 I222 Total Calorific Value in B.Th.U. of Fuel burned. “CC.” . ‘ 196,000 159,000 152,000 154,000 Radiant Efficiency Rx 31 C x 100 23°0 24° 24°7 24°6 Mean Draught through Room from end of hour 1 to two hours after last mending. Cubic feet per hour 13,700 Less than 2,500 15,100 2,800 Curves showing the radiation received in the central position are shown in Diagram 17, Curves 1 and 2, the heat absorbed by the radiometer being expressed in B.Th.U. per square foot per hour. For the more frequent mendings it may be seen that the radiation in the successive intervals between stoking at first increased continuously until a stage was reached in which the coal was burning away at a quicker rate than it was being supplied ; in consequence the fire sank a little and the radiation over successive intervals decreased steadily for a time, afterwards increasing again ; a similar cycle of changes was repeated, the individual readings oscillating about the steadier variation. A slight instantaneous fall in radiation generally accompanied the addition of a fresh supply of coal. The fire, when stoked at the wider intervals, showed two decided though rather = Se A ae THE COAL FIRE 25 flat maxima, one about three-quarters of an hour after the first stoking, the other TOE ax a1 Heal absorbed by Radiometer 34 4 inches from centre front of fire B Th. U. per sq fA per hour. 40 140 Time in minutes since fire was hghled DiacGraM 17.—Variation with time of the heat absorbed by the radiometer 34:4” from the centre front of coal fires in grate ‘'D.’’ Variation in frequency of stoking. No draught restriction. Curve 1.—Fire lighted with 5 Ibs. coal and fed with } Ib. coal at 60, 66, 72, . . . 348 minutes after lighting. Curve 2.—Fire lighted with 5 Ibs. coal and fed with 6} Ibs. coal 108 minutes after lighting and 7} Ibs. coal 258 minutes after lighting. about an hour after the second stoking ; the minimum values were found immediately after the addition of fresh charges of coal. TABLE X RADIANT EFFICIENCY OF COAL FIRES IN GRATE ‘“D” (Irregular Mending. No Draught Restriction.) Fires lighted with 5 lbs. of coal and 4 lb. of wood. Heat absorbed by Radiometer 34-4 inches from centre front of fire in B.Th.U. per square foot per hour. i E I. E ENT II. moe (Dec. 12, 1917). | (Dee. 10, 1917). 4 lb. coal added 64 Ibs. coal added every 6 minutes at | at 108 minutes and 60, 66,72... 7} Ibs. coal at 348 mins. 258 mins. Hour 1 : 75 " 102 Hour 2 ‘ 254 133 Hour 3 328 348 Hour 4 260 276 Hour 5. 3 ‘ : : : 298 225 Hour 6. ‘ a : ‘ . ‘ 292 443 Hour 7 . é 179 226 Hour 8 52 65 Hour 9 8 I2 Hour 10 2 3 Total Heat in B.Th.U. per square foot absorbed by Radiometer from lighting to dying out of fire. “RR.” . ‘i ns > a . ‘ 1748 1833 Total Calorific Value in B.Th.U. of Fuel burned. Ge : 4 é ‘ : ‘ 222,000 243,000 Radiant Efficiency “ Exes x 100 24°4 23°4 Cc Mean Air Flow through Room from one hour after lighting to one hour after last mending. Cubic feet per hour. 7 . : _ é 19,400 26 THE COAL FIRE The average values of the heat received by the radiometer over the i hours and the working out of the radiant efficiencies are given 1n Table X.; the values of the radiant efficiency obtained in the two runs were 24-4 and 23°4 per es respectively, showing a slight excess in favour of the six-minute mending, = : slight deficit in the less frequent mending, as compared with the ara ue : 24°I per cent observed in many experiments for hourly mendings of 2 Ibs. each. These differences, however, are within the errors of experiment. ee Effect upon the Radiant Efficiency of Grate ‘* D i of crushing the Coal into a A quantity of Arley washed cobbles was crushed into slack which was burned in grate“ D.” The fires were lighted with 5 Ibs. of coal, and at the end of the first hour 5 Ibs. of the slack was added; owing to the diminution of the rate of combustion resulting it was not found practicable to add any further supplies of slack to the fires, which continued to burn for some ten or twelve hours. The air-flow through the room in the two experiments averaged, when approximately steady conditions had been reached, 11,300 and 13,300 cubic feet respectively. In Diagram 18, oe ea a | S pep xa yo i % Ko {Lat pL o 2040 60 89 100 120 140 180 180 200 920 240 260 200 300 320 340 Gud 380 400 420 440 480 480 6Cb 510680 cho 680 ‘Time in minuted since fire wan lighted. bol ze oF te Bos 3-8 i s7 a ese, a 2i¢ a Beet Leo oe = ~ & gf S10 at Po —< — m Se. ~~ [~~ aL P fon o si 0-340 380 380 400 420 440 460 480 600 620 640 660 68Q zo 40 60 80 '00 120 140 180 180 200 220 240 260 280 300 3: Tima in minutes ainco fire was lighted Diacram 18.—Variation with time of the heat absorbed by the radiometer 34'4” from the centre front of slack fires in grate “‘ D.” Curves 1 and 2.—Fire lighted with 5 Ibs. coal and fed with 5 lbs. slack 60 minutes after lighting. Curves I and 2, the variation with time of the radiation emitted is illustrated as given by the readings of the radiometer. It will be observed that the fluctuations are comparatively slight, and that for some hours after the addition of the slack the fires threw out nearly constant radiation, except for temporary increases (as at 441 minutes Curve 1, and 418 minutes Curve 2) caused by occasionally stirring the fires in order to prevent their burning hollow and going out. Distribution of Radiation from Slack Fires.—The distribution of the radiation from these fires was considerably modified as compared with that from lump coal fires, the relative amount of radiation thrown upwards at high angles being con- siderably decreased, especially at first, and the maximum readings being found at 0° (see Table XI.). The resulting distribution factor was decidedly low, averaging 28, the radiant efficiency working out at 20 per cent of the total calorific value of the coal burned as compared with 24 per cent for uncrushed coal in this grate (Table XII.). ; THE COAL FIRE 27 TABLE XI DISTRIBUTION OF RADIATION FROM SLACK FIRES IN GRATE “D” Thermopile Readings. Cosine C ti To “ West.” To “Bast.” Totals. tet Pea 80°. | 60° | 40% 20°. °°. 20°. | 40°. 60°. 80°. obras: 80° North 16 39 52 56 59 | 57 55 40 18 392 O'l74 68 60° North . 25 49 56 63 64 61 60 54 28 460 0°50 230 40° North . 27 55 67 74 76 78 66 54 27 524 0°766 402 20° North 23 51 72 85 92 87 74 55 21 560 0'94 525 0° ‘ 22 55 80 93 | Ioo 99 82 55 22 608 I'00 608 20° South . 20 46 | 65 79 85 79 67 48 20 509 0°94 478 40° South . 16 31 45 56 62 58 47 35 19 369 0'766 283 60° South 10 18 26 30 32 30 26 20 Io 202 0°50 IOI 80° South... 5 8| ro} ro] «1 Io | I0 8 5 77 O'l74 13 | Totals 164 | 352 | 472 | 546 | 581 | 559 | 487 | 369 | I70 | 2708 2708 Distribution Factor = ee =27°1. TABLE XII RADIANT EFFICIENCY OF SLACK FIRES IN GRATE “D” after lighting. (Fires lighted with 5 lbs. coal and 4 Ib. wood. 5 lbs. slack added 60 minutes Heat absorbed by Radiometer 34.4 inches from centre front of fire in B.Tb.U. per square foot per hour, Time. ExrERIMENT I, EXPERIMENT II. Aug. 5, 1919. Sept. 29, 1919. Hour 1 gI 99 Hour 2 57 II4 Hour 3 65 104 Hour 4 72 125 Hour 5 65 143 Hour 6 82 II2 Hour 7 80 68 Hour 8 94 68 Hour 9 139 59° Hour ro 81 25 Hour 11 40 13 Hour 12. 20 5 Hour 13. x 5 Total Heat absorbed by Radiometer in B.Th.U. per square foot from lighting to dying out of fire. eR? 5 i 891 926 Total Calorific Value in B.Th.U. of Fuel burned. Ce f . 123,000 127,000 Radiant Efficiency. Per cent Eemee x 100 20°3 20°4 Mean Air Flow through Room from one hour after lighting to one hour after last mending 11,300 12,300 28 THE COAL FIRE . Effect of certain advertised Patent Preparations on the Radiation emitted by C . Fires in Grate “ D.’”’—During the past few years wide advertisement, by means 0 notices displayed in ironmongers’ and other shops, and also by occasional pear in the advertising press, has been given to certain patent preparations genera. y in the form of crystalline salts of a yellowish or brownish colour, solutions of whic are claimed, when previously sprayed upon the coal, greatly to increase the efficiency ofafire. The assertions made are variously—(r) increase in brightness, (2) increase in temperature, and (3) increase in the duration of burning, of a fire, and a usual statement is that the heating value of the coal is doubled. It would follow directly from (2) and (3) that the total radiation emitted would be increased. Samples of two of the salts referred to were procured and analysed, and a quantity of coal treated according to the instructions was used for making test fires in grate “ D.” 2 The salts were found to consist mainly of common salt with small quantities of other sodium and magnesium salts and of ferric oxide. The analyses, which are given below, were found to be typical of other similar preparations : Sat “X.” Sart “Y.” Sodium Chloride. é 3 - 87-7 Sodium Chloride . i ; + 93°0 Water . ; . : » 28 Water . A é ‘ : ; 6-0 Ferric Oxide . : : : - 36 Ferric Oxide. . : : . o9 Sodium Carbonate . : 3 - OF Magnesium Chloride . : - O72 The amount of salt deposited on the coal was about 0-05 per cent by weight. The procedure of working was exactly as before, the fires being lighted with 5 lbs. of the treated coal and } lb. wood, and fed hourly with 24 Ibs. of the treated coal (Arley washed cobbles of calorific value 14,500 B.Th.U. per lb.) for six hours, being then allowed to die out. Observations were, as usual, continued over the complete period of burning. The results are shown graphically in Diagram 19, Curves I, 2, 3, 4 and 5, the mean values over successive hours, and the resulting radiant efficiencies being given in Table XIII. It will be seen that the radiometer curves are of essentially similar type to those obtained under similar conditions with untreated coal (see Diagram 15), while the radiant efficiencies found, viz. 23-5 for salt ““X” and 23'4 for salt ‘‘ Y,”’ do not differ appreciably from the mean value of 24-1 per cent for untreated coal (Table VIII.). The preparations in question, therefore, had no effect either upon the radiation thrown into the room by the fire or upon its duration of burning. Moreover, as will be shown later, the rise of temperature produced in the air of the reom was found to be similar to that resulting from fires of the same size and in the same grate made with untreated coal. It was thus concluded that the claims made for these preparations are not confirmed in practice.} 1 See Filandean on “Coal Economizers,”’ Annales des Falsifications, 1917; also Garelli on ‘Coal Saving Preparations,” Ind. Chim. Min. Met., 1917; also “ Aroxa, the Great Coal Sa = Expt. Sins. in Austria. ver,”’ Soc. of Agr. [TasBre XIII. : THE COAL FIRE 29 TABLE XIII RADIANT EFFICIENCY OF COAL FIRES IN GRATE “D.’”’ (Unrestricted Draught.) Special treatment of Coal with advertised Salts “ X” and “ Y.” Fires lighted with 5 Ibs. of treated coal and 4 Ib. of wood. Heat absorbed by Radiometer 34-4 inches from centre front of fire in B.Th.U. per square foot per hour. Salt “x.” Salt “ ¥.” Time. EXPERIMENT ee ae EXPERIMENT | EXPERIMENT a II. a Iv. Vi. (Jan. 30, 1918).| (Feb. 1, 1918). | (Feb. 13, r918).| (Feb. 27, 1918).|(March 4, 1918). 2h Ibs. of 24 Ibs. of 24 Ibs. of 24 Ibs. of 2h lbs. of treated coal treated coal treated coal treated coal treated coal added at 60, added at 60, added at 60, added at 60, added at 60, 120, 180, 240, | 120, 180, 240, | 120, 180, 240, | 120, 180, 240, 120, 180, 240, 300 mins. 300 mins. 300 mins. 300 Mins. 300 mins. Hour 1 87 76 96 41 86 Hour 2 261 224 205 153 235 Hour 3 295 353 263 376 340 Hour 4 282 360 300 341 265 Hour 5 . ‘ % . 273 238 317 306 276 Hour 6 . ‘5 é 233 264 301 321 313 Hour 7 . 5 5 184 152 193 156 174 Hour 8 80 122 73 63 59 Hour 9 20 28 12 20 28 Hour 10 6 8 3 4 12 ‘Total Heat in B.Th.U. per square foot absorbed by Radiometer from lighting to dying out of fire. RRR ‘: . = 1721 1825 1763 1781 1788 Total Calorific Value in B.Th.U. of Fuel burned. a sg 3 . : 231,000 237,000 231,000 235,000 241,006 Radiant Efficiency XS! x 100 3 : 23°1 23°9 23°7 23°5 23°0 Mean Air Flow through Room from one hour after light- ing to one hour after last mending. Cubic feet per hour : 7 7 ‘ 17,600 19,100 19,600 18,600 19,400 RADIATION FROM ANTHRACITE FIRES A quantity of typical good Welsh anthracite of calorific value 14,400 B.Th.U. per lb. and ash content 3-7 per cent was procured for these tests, which were made in grate “‘D.” The fires were lighted with 24 Ibs. each of coal and anthracite and 4 lb. wood, and subsequently were fed at hourly intervals with 2} lbs. of anthracite alone. The flue damper was opened wide, and a 3” aperture was left in the fender beneath the fire. Under these conditions the fires lighted fairly easily, and quite a pleasant slow steady fire was maintained, which, however, was rather dull in 30 THE COAL FIRE , appearance, and which died out slowly at the end of the runs leaving a residue of unburned fuel, cinder and ash which amounted to about 7 lbs., or three times as S 3 3 inches fram centre front of tire CurvE I Heat absorbed by Radiometer 34 4 B Th U. per sq ft per hour 220 250 260 280 300 Time in minules sonce fire was lighted 100 tag 160 22 3é Bos e238 Eso aa Sat [coy ete > FSe ees 5 £68 oO £5 oe S32 Bor Zed ED 700 230 340 380 360 ano 440 450 480 500 Time in minutes since fire was lighted we 3 es foe z2 om BSE f@ @£e e BSe et ee ges 3 See age Zia Time in minutes since fire was lighted CuRVE 4 Heat absorbed by Radioma inchew from c B.Th U. pers 80 100 120 149 180 180 200 220 940 280 230 300 320 sad 420 440 469 480 §00 S20 Time in minutes since fire was lighted. m5 a B See B 23¢ 5 258 oO Bes Ber Iso 220 130160 : Timo in minutes zines fire was lighted. aii a Ss eae te a of the heat absorbed by the radiometer 34:4” from the centre ront of coal fires in grate “D.” Nod icti i i eee g o draught restriction. Coal treated with patent preparations Curves 1, 2 and 3.—Fire lighted with 5 Ibs. treated coal and f i and 300 minutes after lighting. Preparation ‘‘ X.” peer eR treated Goes ee ena Ae Curves 4 and 5.—Fire lighted with 5 lbs. treated coal and fed wi and 300 minutes after lighting. Preparation ‘“ Y.” Se Meg Tee teeclsel opal Sk as, much as usually remained from coal fires burning under similar conditions in this grate. The variation with time of the heat absorbed by the radiometer 34:4” from the THE COAL FIRE zi centre front of these fires is shown graphically in Diagram 20, Curves 1, 2 and 3. For the first two hours after lighting the fire there was, but for a slight interruption at 60 minutes when the fire was fed, a continuous increase in the intensity of radiation emitted, slow in the first hour and more rapid in the second e ze 3c H 2 = q F > Bes m EEE D> 345 O 8. gor zid 300 320. 620 640 g:nco fire was lighted | ze gt 33 Ze Eo a 258 é 5 25s 3 © ge mw 38% O 232 £32 sor ae 600 520 540 Tune in minutes since fire was a8 soi 33 ee om §2 gé g ¢f: 28g m 35 se O gé 28 a6 es BTU 20 #0 160 160 220 300 320 340 400 420 440 460 430 640 560 260 ‘Time in minules since fire was lighted DiacraM 20.—Variation with time of the heat absorbed by the radiometer 34°4” from the centre front of anthracite fires in grate ‘“‘ D.” Curve 1.—Fire lighted with 2} Ibs. each of coal and anthracite and fed with 24 lbs. anthracite at 60, 120, 180, 240, 300 minutes after lighting. Curve 2.—Fire lighted with 24 lbs. each of coal and anthracite and fed with 24 lbs. anthracite at 60, 120, 180, 240, and 300 minutes after lighting. Curve 3.—Fire lighted with 24 Ibs. each of coal and anthracite and fed with 2} Ibs. anthracite at 60, 120, 180, 240, and 300 minutes after lighting. hour. Over the subsequent hours there was little variation, the intensity of radia- tion remaining nearly uniform except for a short period immediately after each stoking, when a slight drop followed by an increase was generally noticed. RADIANT EFFICIENCY OF ANTHRACITE Fires IN GRATE “ D.’’—In Table XIV. the average values of the heat absorbed by the radiometer over successive hours are shown and the radiant efficiency obtained in each run. This, it will be observed, was about 27 per cent of the total calorific value of the fuel burned as compared with 24 per cent for coal fires in the same grate. [TABLE XIV. 32 THE COAL FIRE TABLE XIV RapDIANT EFFICIENCY OF ANTHRACITE Frres IN GRATE ‘“ D” Fires lighted with 2} lbs. each of coal and anthracite and 3 lb. wood, and fed with 24 Ibs. anthracite at 60, 120, 180, 240, and 300 minutes after lighting. Heat absorbed by Radiometer 34-4 inches from centre front of fire. B.Th.U. per square foot per hour, Time, FF ° Experiment I. EXPERIMENT II. EXPERIMENT III, September 18, 1919. September 22, 1919. October 13, 1919. Hour 1 25 60 gI Hour 2 145 182 168 Hour 3 207 17t 152 Hour 4 212 166 139 Hour 5 183 186 163 Hour 6 190 159 173 Hour 7 155 166 183 Hour 8 ‘ 4 r 136 129 139 Hour 9 : . 84 83 104 Hour 10 7 ‘ 40 80 53 Hour 11 7 z 3 16 44 30 Hour 12 : : 2 4 20 17 Hour 13 : . ‘ ae 5 8 Total Heat in B.Th.U. per square foot absorbed by Radiometer from light- ing to dying out of fire. wR” 7 : é 1397 1451 1420 Total Calorific Value in B.Th.U. of Fuel burned. Gy? x ¢ 167,000 158,000 156,000 Radiant Efficiency per cent R x 31 Eq * 100 . 2°59 28+4 28-2 Mean Air Flow through Room from one hour after lighting to one hour after last mending 16,000 13,900 16,300 RADIATION FROM COKE FIRES Comparative experiments were carried out with grates “B” and “D” using coke instead of coal as a fuel. For high temperature cokes the fires were for con- venience lighted with 23 lbs. each of coal and coke and } Ib. wood, and subsequently coke was added at the rate of 24 Ibs. per hour. It was found that the coke as taken from the college cellars contained as much as 15 to 20 percent of moisture. A quantity of the fuel was therefore dried artificially and runs were made with coke of varying moisture content. The calorific value of the dry coke was about 13,000 B.Th.U. per lb. RADIANT EFFICIENCY OF COKE FrRes IN GraTE “ B.”—In Diagram ar “THE COAL FIRE ae Curves I, 2, 3 and 4, the variation with time of the heat absorbed by the radiometer exposed to the radiation from coke fires burning in grate ‘““B” (Diagram 6). is illustrated.. In all cases the fires were lighted with 5 lbs. of mixed coal and coke and were afterwards fed hourly with 24 lbs. of coke, dried in the cases of Curves 1 and 2, and with 5 per cent and 16 per cent moisture in Curves 3 and 4 respectively. CurRVE I Ss s inches from centre front of fire Heat absorbes by Radiometer 34°4 B. Th U. per aq. ft. per hour. Time in minutes since fire was lighted, CURVE 2 inches from centre front of fire Heat absorbed by Radiometer 34°4 B. Th. U. per sa. fl per hour 300. 320 Time in minutes since fire was lighted. Curve 3 inches from centre front of fire Heat absorbed by Radiometer 34° B. Th_U. per eq. fe per Time In minutes since fire was lighted. CuRVE 4 Heal absorbed by Radiomater 34'4 Inches from centre front of fire B. Th. U. por sq. ft. per hour 100 240 Teme in minutes since fire was lighted. Dr1aGRAM 21.—Variation with time of the heat absorbed by the radiometer 34°4” from the centre front. of coke fires in grate “‘B.’’ No draught restriction. Curve 1.—Fire lighted with 2} lbs. each of coal and coke and fed with 2} lbs dried coke at 60, 120, 180, 240, 300, and 360 minutes after lighting. Curve 2.—Fire lighted with 2} Ibs. each of coal and coke and fed with 2} lbs. dried coke at 60, 120, 180, 240, and 300 minutes after lighting. Curve 3.—Fire lighted with 24 lbs. each of coal and coke and fed with 2} lbs. of coke containing 5 per cent moisture at 60, 120, 180, 240, and 300 minutes after lighting. Curve 4.—Fire lighted with 2} Ibs. each of coal and coke and fed with 2} lbs. coke containing 16 per cent moisture at 60, 120, 180, 240, and 300 minutes after lighting. For the run represented by Curve 3 the draught was slightly restricted by reducing the aperture in the fender (5” in the other experiments) to 2”. The residue of cinder and ash left unburned in the grate was considerably larger than for coal fires, amounting to about 34 lbs. as compared with under 2 lbs. from coal fires in the same grate. D THE COAL FIRE Measurements of Radiation falling on One Square Foot Area 34:4” from Grate “B” Coke Fires.—The shape of the curves differs considerably from those given in Diagram 8 for coal fires burning in the same grate under similar conditions and fed at the same rate. The radiation, as in the case of a coal fire, falls to a minimum when a fresh charge of fuel is added, but rises less rapidly to its maximum, and does not exhibit the sudden peak which in the coal fires corresponded with the increase and dying away of flame. With a diminished draught (Curve 3) the maximum becomes still less pronounced, the radiation increasing slowly to an almost steady state, which is interrupted by the addition of more coke, again to drop to a minimum and increase steadily to an almost flat maximum. Distribution of Radiation from Coke Fires in Grate ‘ B.”—The distribution factor was found to be slightly less for coke than for coal fires, and a value of 36 was adopted for this grate. 34 TABLE XV RADIANT EFFICIENCY OF COKE FIRES IN GRATE “B” Fires lighted with 24 Ibs. of coke, 24 Ibs. of coal, and $ Ib. of wood. Firebrick back of grate vertical. 5-inch aperture in ash-guard beneath grate. Heat absorbed by Radiometer 34-4 inches from centre front of fire in B.Th.U. per square foot per-hour. i Experiment I. Experiment II. ExpeRiMENT ITI. EXPERIMENT IV. Time. (Dec. 11, 1916). (Jan. 4, 1917). (Nev. 2, 1916). (Nov. 3, 1916). Dried coke. Dried coke. Coke with 5 per Coke with 16 per 2k Ibs. of coke 24 Ibs. of coke cent. moisture. cent. moisture, added at 60, 120, | addcd at 60, 120, 2} Ibs. of coke 2% Ibs. of coke 180, 240, 300, 180, 240, 300 added at 60, 120, added at 60, 120, 360 mins. mins. 180, 240, 300 mins. | 180, 240, 300 mins. Hour 1 20 52 254 38 Hour 2 46 93 59 80 Hour 3 182 210 107 147 Hour 4 254 230 144 I51 Hour 5 301 226 199 131 Hour 6 264 270 209 161 Hour 7 258 143 197 11g Hour 8 176 32 154 60 Hour 9 103 5 68 20 Hour 10 44 ave 16 2 Hour 11 8 2 Total Heat in B.Th.U. per square foot absorbed by Radiometer from lighting to dying out of fire. ‘R.” 1656 1261 1181 909 Total Calorific Valuein B.Th.U. ” of Fuelburned. “C.” .. . 235,000 202,000 200,000 171,000 Radiant Efficiency R x 36 MELON 25°4 22+4 21°2 19-2 The average value of the radiant efficiency was 23-9’ per cent for dry coke, 21-2 for coke with 5 per cent moisture, and Ig'2 per cent for coke with 16 THE COAL FIRE 35 a « per cent of moisture content (see Table XV.). That is to say, the dry coke of calorific value 13,000 B.Th.U. per Ib. gave, weight for weight, some 3 per cent more’ radiation than coal of calorific value 14,500 B.Th.U. per lb.; while with 16 per cent of moisture content the radiation emitted by the coke was about 30 per cent less than that thrown out from the same weight of coal. One pound of this coke would only equal in calorific value 0-84 lb. of dry coke, and this accounts for some 13 per cent of the deficit ; heat is also wasted in vaporising the moisture present, but this amounts only to about 1 per cent of the total calorific value, and if it were assumed that the whole of it were lost from radiation, would account only for a further 4 or 5 per cent of the deficit. It appears, therefore, that the water present introduces some modification in the chemical reactions which take place. RADIANT EFFICIENCY OF COKE FIRES IN GRATE “‘ D.’”’"—A number of experi- ments were made with grate “D” burning ordinary gas coke of calorific value 12,800 B.Th.U. per Ib., in which the moisture varied from 2 to 21 per cent by weight. The fires were lighted with 24 lbs. each of coal and coke and 3 lb. wood, and were fed hourly with 24 lbs. of coke. The weight of cinder and ash left in the cold grate was about 4 lbs. as compared with about 2 lbs. residue from coal fires in this grate. TABLE XVI DISTRIBUTION OF RADIATION FROM COKE FIRES IN GRATE “D” Thermopile Readings. Gsiue : Correction Total To “West.” To ‘‘East.”” Total. sees Corrected. of 80°. | 60%. | 40°. | 20°. °°. 20°. 40°. | 60°. | 80°. Area. 80° North . 18 54 75 81 86 78 “| 51 17 531 0-174 92 60° North. 34 75 81 87 90 86 33 717 38 651 0*500 326 40° North. 35 81 95 | IOI | I0o 98 92 a7, 33 712 0-766 545 20° North. 18 64 88 99 | 102 99 88 64 18 640 0*940 602 o° ‘ 20 62 89 99 | 100 96 89 66 16 637 1-000 637 20° South. I5 43 64 79 88 80 66 44 15 494 0940 464 40° South. I2 29 46 58 65 59 47 30 12 358 0-766 274 60° South. 9 19 28 36 39 35 28 19 9 222 0-500 IIL 80° South. 6} 11 16] 19 2{ 19/ 16} «1 7 127 0-174 22 Totals i 167 | 438 | 582 | 659 |-692 650 | 580 | 439 | 165 | 3073 = 3°73 Distribution Factor =—~ = 30-73. Distribution of Radiation from Coke Fires in Grate “‘ D.’’—Determinations of the distribution factor resulted in a value of 304 being taken for these runs, as compared with 31 for coal fires in the same grate. The mean values of the individual readings obtained over the hours after the first, and before the dying out of the fire, are shown in Table XVI. The value over the first hour after lighting was rather low—29-6—and over the dying-out period of the fire rather high—31-8. 36 THE COAL FIRE . : 4" ke Measurements of Radiation falling on One Square Foot Area 34-4" f ae oe Fives in Grate “ D.”—Diagram 22, Curves 1, 2 and 3, show the aig = fee time of the radiometer determinations, Table XVII. the mean values ov successive hours and the radiant efficiency values. ; aeons As was found to be the case when burning coke in grate “ B pages ene oo show less marked maxima than coal fires burning in the same grate. HEE ey CURVE I Heat absorbed by Radiometer 34'4 mches from centre front of fire & Th U per eq A per hour 80 G00 140 160 180 200 220 280 340 360 i 480 6! Time in minutes since firo was lighted inches from centre front of fire CURVE 2 Heat absorbed by Radiometer 34 4 B Th. U. per'sq A per hour 286 280 320 340 360 380 400 Time in minutes since fire was hghted eo 3 3 CuRVE 3 S 3 S Heat absorbed by Radiometer 34 4. Inches from centre front of fire 8 Th. U per ag f per how 140 to in minules since fire was lighted DiaGRAM 22.—Variation with time of the heat absorbed by the radiometer 34°4” from the centre front of coke fires in grate “ D.” Curve 1.—Fire lighted with 24 lbs. each of coal and coke and fed at 60, 120, 180, 240, and 300 minutes after lighting with 2} lbs. coke containing 2 per cent moisture. Curve 2.—Fire lighted with 2} lbs. each of coal and coke and fed with 2} lbs. coke containing 8 per cent moisture at 60, 120, 180, 240, and 300 minutes after lighting. : Curve 3.—Fire lighted with 2} Ibs. each of coal and coke and fed with 2} lbs. coke containing 21 per cent moisture at 60, 120, 180, 240, and 300 minutes after lighting. and 3 are for coke with 2, 8 and 2x per cent of moisture respectively, the corresponding radiant efficiencies being 28-7, 26-0 and 24°4 per cent as compared with an average of 24:1 per cent for coal fires in the same grate (Table VIII), results very:similar to those already recorded for grate “B.” That is to say, weight for weight, the dry coke of calorific value 12,800. B.Th.U. per Ib. gave Some 5 per cent greater radiation than coal of calorific value 14,500 B.Th.U. per Ib., while with 21 per cent of moisture it gave some 28 per cent less. [TaBLrE XVII. RADIANT EFFICIENCY OF COKE FIRES IN GRATE “D” THE COAL FIRE TABLE XVII 37 (No Draught Restriction.) Fires lighted with 2} lbs. of coal, 24 lbs. of coke, and 4 Ib. of wood. Heat absorbed by Radiometer 34-4 inches from centre front of fire in B.Th.U. per square foot per hour. Time EXPERIMENT I, EXPERIMENT II, EXPERIMENT III. . (November 13, 1917). (January 21, 1918). (November 20, 1917). Coke with 2 per cent Coke with 8 per cent Coke with 21 per cent moisture. 2} Ibs. of coke moisture. 24 lbs. of coke moisture. 23 lbs. of coke added at 60, 120, 180, 240, | added at 60, 120, 180, 240, | added at 60, 120, 180, 240, 300 mins. 300 mins. 300 mins. Hour 1 84 75 28 Hour 2 134 155 58 Hour 3 242 198 113 Hour 4 258 233 107 Hour 5 300 270 167 Hour 6 307 , 271 197 Hour 7 240 200 195 Hour 8 165 92 155 Hour 9 84 30 96 Hour ro ‘ 26 8 52 Hour 11 a 3 4 2 8 Total Heatin B.Th.U. per square foot absorbed by Radiometer from light- ing to dying out of fire. eR : 2 1844 1534 1176 Total Calorific Value in B.Th.U. of Fuel burned. “Ee” ‘ - : 196,000 180,000 147,000 Radiant Efficiency Reka x 100 28-7 per cent 26:0 per cent 24°4 per cent TABLE XVIII DISTRIBUTION OF RADIATION FROM FIRES OF Low TEMPERATURE CARBONISATION COKE IN GRATE “D” Tbermopile Readings. Cosine Correction Total: To ‘ West.” To “East.” Totals. asian Gorrmected: of Area. 80° 60° 40° 20° 0 20° 40° 60° 80° 80° North t7| 56} 70] 74) 77} 75 | 70) 58| 18 | 515 | 0174 go 60° North 35 68 81 83 83 82 80 76 36 624 0*500 312 40° North 31 | 62] 75) 83] 90] 83] 74| 61r/| 29 588 0+766 450 20° North . 19] 59| 82) 93| 100] 96] 81} 57] 19 606 0°940 579 0° . 19 | 59 81 94 | 100 93 80 57 17 600 1-000 600 20° South. 14| 45! 66] 79] 84] 80] 66] 46) 14 494 0*940 464 40° South. 12| 29] 42] 56] 62] 58] 47] 31) 12 349 0+766 267 60° South. 8] ar 27 | 36] 40] 38 32 | 22 8 232 0°500 116 80° South. © 4{ ro} 12] 16} 18] 17] 14 | 10 4 106 O'174 18 Totals . 159 | 409 | 536 | 614 | 654 | 622 | 544 | 418 | 157 2887 288 Distribution Factor= =! = 28-9. 38 THE COAL FIRE TABLE XIX £¥ a2 RADIANT EFFICIENCY OF FirES OF Low TEMPERATURE CARBONISATION COKE ‘X IN GRATE ““D” (No Draught Restriction.) Fires lighted with 5 lbs. low temperature carbonisation coke ‘“‘X”’ and 4 Ib. wood. Heat absorbed by Radiometer 34-4 inches from centre front of fire in B.Tb.U. per square foot per hour. ] .| ExpermmMent IV. | Expermment V. Gert one ar Fae eh, (June 25, 1918). Nee i. eer 2h Ibs. fuel added | 24 Ibs. fuel added | 24 Ibs. fuel added | 2} Ibs. fuel added | 24 Ibs. fuel at 60, 120, 180, at 60,120, 180, | at 60, 120, 180, at 60, 120, 180, at 60, 150, 240, 240 mins. 240, 330 mins. | 240 mins. 240, 300 mins. 300 mine 2 % moisture. 5 % moisture. | 7 % moisture. 11 ¥% moisture. 4 4 mois 5 4 Hour t 59 930 50 120 47 Hour 2 243 241 ; 157 245 108 Hour 3 232 246 | 239 235 219 Hour 4 273 295 262 263 280 Hour 5 273 261 284 | 244 262 Hour 6 280 217 211 203 310 cio 175 244 159 | 190 204 Hour 8 83 139 106 132 97 Hour 9 : : 22 60 | 84 89 35 Hour 10 . : II 16 ‘ 41 75 12 Hour 11 : 4 3 14 36 : Hour 12 ‘ 3 I ese 8 5 +. Total Heat absorbed by Radiometer from lighting to dying out of fire. B.Th.U. persquare foot. “R.” ‘ 1656 1815 1615 1837 1575 Totai Calorific Value in B.Th.U. of Fuel burned. ‘“‘C.” . 148,000 158,000 147,000 172,000 144,000 Radiant Efficiency \ Rx 30 | EX 100 33°5 per cent | 34°5 per cent | 33-0 per cent 32-0 per cent | 32-8 per cent Mean Air Flow | through Room from one hour after lighting to | onehour after last mending. Cubic sere Ber por 12,200 | 22,500 | 13,900 16,400 19,700 RADIATION FROM Low TEMPERATURE CARBONISATION COKE FIRES A series of experiments was carried out with grate “‘ D” burning low temperature carbonisation cokes, which will be denoted by ““X” and “Y.” These fuels were found to light easily without the help of coal; the fires therefore were started with 5 ibs. of the coke and 4 Ib. of wood, and were fed hourly with 24 Ibs. of coke. Distribution Factor—The mean distribution factor was lower than for coal fires in the same grate, showing a value of 28-9 in the intermediate hours and of THE COAL FIRE 39 . CurvE 1 Heat absorbed by Ri inches from centre B Th U per sg “120 140 320 Time in minutes since fire was lighted. CuRVE 2 Heat absorbed by inches from ce: 260 gec 380 Time in minutes since fire was lighted. by Radiometer 34°4 Inches from centre front of fire B, Th U. por si Curve ‘3 Heat absorbed q. fl per hour. 220 389 400 10 260 ime in minutes since fire was 400 CurRVE 4 ‘Heat absorbed by Radiometer'34"4 inchea from centre front of fir B.Th U per sq ft. per hour. o 40 80 80 100 1a0 220 300 340 gan 440 Time in minutes aince fire was lighted. CuRVE 5 jeat absorbed by Radiometer 94°4 ches from centre front of fire 8. Th. U. per aq. fU per hour. 60 100 180 200 220 : 340 oi 440 460 480 600 620 640 Time in minutes since firo was lighted. Diacram 23.—Variation with time of the heat absorbed by the radiometer 34-4” from the centre front of fires of low temperature carbonisation coke “‘ X ” in grate “‘D.” No draught restriction. Curve 1.—Fire lighted with 5 Ibs. coke and fed with 2} Ibs. coke at 60, 120, 180, and 240 minutes after lighting. Moisture content 2 per cent. Curve 2.—Fire lighted with 5 Ibs. coke and fed with 2} Ibs. coke at 60, 120, 180, 240, and 330 minutes after lighting. Moisture content 5 per cent. Curve 3.—Fire lighted with 5 Ibs.’ coke and fed with 24 lbs. coke at 60, 120, 180, and 240 minutes after lighting. Moisture content 7 per cent. Curve 4.—Fire lighted with 5 Ibs. coke and fed at 60, 120, 180, 240, and 300 minutes with 2$]bs.coke. Moisture content 11 per cent. 2, Curve 5.—Fire lighted with 5 lbs. coke and fed with 24 Ibs. coke at 60, 150, 240, and 300 minutes after lighting. Moisture content 4 per cent. 40 THE COAL FIRE 32°6 and 32-9 in the first hour after lighting and in the dying-out period respectively. A value of 30 was adopted, having been found to yield the same results as were given by applying the above values separately to the times to which they correspond (Table XVIII.). TABLE XX »” RADIANT EFFICIENCY OF FIRES OF LOW TEMPERATURE CARBONISATION CoKE “Y IN Grate “D” (No Draught Restriction.) Fires lighted with 5 Ibs. low temperature carbonisation coke “ Y ” and 4 Ib. wood. Heat absorbed by Radiometer 34-4 inches from centre front of fire. B.Th.U. per square foot per hour. : PERIMENT II. EXPERIMENT IV, tered toy 5, 1918). a oe z aoe ; 24 Ibs, fuel added at | 2} lbs, fuel added at 2} ibs, fuel added at 2% Ibs. uel a ed at 60, 120, 180, 240, 60, 120, 180, 240 | “85 150, 180 mins. 60, 120, 180, 240, 300. mins. ne "4 % moisture. Sco mins: 2 % moisture. 4 % moisture, 5 % moisture, Hour 1 144 138 145 93 Hour 2 209 140 II5 215 Hour 3 255 259 155 255 Hour 4 282 280 | 152 258 Hour 5 272 278 156 317 Hour 6 264 228 104 252 Hour 7 226 145 54 I9I Hour 8 113 75 24 88 Hour 9 48 29 4 33 | Hourio . ‘ 28 4 a 16 Hour 11 : ‘ ‘ é 8 aa site 4 Total Heat in B.Th.U. per square foot absorbed by Radiometer from lighting to dying out of fire. ‘‘R.” 1849 1576 909 1722 Total Calorific Valuein B.Th. U. of Fuel burned. ‘‘C.” 187,000 142,000 100,000 182,000 Radiant Efficiency | R x 30 | ee 100 29'7 per cent | 33:3 per cent | 27-3 per cent | 28-4 per cent Mean Air Flow through Room from one hour after lighting to one hour after last mend- ing. Cubic feet per hour . 13,600 16,200 13,200 17,400 Radiant Efficiency of Fires of Low Temperature Carbonisation Coke “ X” in Grate “ D.””—Coke “ X”’ was of calorific value 13,200 B.Th.U. per lb. dry, coke “Y ” 13,300 B.Th.U. per lb. dry. The fuels as supplied were found to contain as much as Io per cent of moisture : runs for varying amounts were therefore made in each case. Curves 1, 2, 3 and 4, Diagram 23, show graphically the results from fires of fuel “X” with 2, 5, 7 and 11 per cent of water content respectively. The fires were lighted with 5 lbs. of fuel and were fed hourly with 2} Ibs. fuel. Curve 5 refers to a fire which was THE COAL FIRE 4t lighted with 5 Ibs. and fed at 13-hour intervals with fuel containing 4 per cent of moisture. The mean heat absorbed by the radiometer over the successive hours and the calculation of the radiant efficiency are given in Table XIX. It will be seen that the curves are similar in general shape to those illustrating ‘Ge “ge gos a3 HESS Ta A date o Fe “ai 6 48h i #32 220 Tima in minutes since firo was lighted. 32 gee a &3e gtk @ogse 2 g 23 2 $62. Oo £83 Sse ger rsa ‘Time in minutes since fire wee lighted. sg tc im 36 E52 m 3tk fSe fm Bs Dan 5 R g25 a 346 zee 200 220 e240 300 Times in minutes since fire woa lighted se gé $35 w fe Bi She 3 Pe 5 48 3 si¢ £25 im minutes since firo was tight D1aGRAM 24.—Variation with time of the heat absorbed by the radiometer 34°4” from the centre front of fires of low temperature carbonisation coke ‘‘ Y”’ in grate ‘‘D.’”” No draught restriction. Curve 1.—Fire lighted with 5 lbs. coke and fed with 2} lbs. coke at 60, 120, 180, 240, and 300 minutes after lighting. Moisture content 2 per cent. Curve 2.—Fire lighted with 5 Ibs. coke and fed with 2} lbs. coke at 60, 120, 180, and 240 minutes after lighting. Moisture content 4 pet cent. Curve 3.—Fire lighted with 5 lbs. coke and fed with 24 lbs. coke at 60, 120, 180 minutes after lighting. Moisture content 4 per cent. Curve 4.—Fire lighted with 5 lbs. coke and fed with 2} lbs. coke at 60, 120, 180, 240, and 300 minutes after lighting. Moisture content 5 per cent. the radiation emitted by ordinary gas coke burning in the same grate (see Diagram 22). The radiant efficiencies, however, 33'5, 32°8, 34°5, 33°0, 32°0 respectively, or a mean value of 33-1 for average water content of 6 per cent, are much higher than those given either by coke or coal fires, low temperature carbonisation coke ““X” being seen to yield as much as 30 per cent more radiation than the same weight of coal burning in the same grate. 42 THE COAL FIRE Radiant Efficiency of Fires of Low Temperature Carbonisation Coke “ Y i in Grate “‘ D.’—The results of similar experiments with low temperature carbonisa- tion coke “ Y” are shown in Diagram 24, Curves 1, 2, 3 and 4, and in Table XX. The average values of the radiant efficiency for the separate runs are 29:7, 33°3, 27-3 and 28-4 for moisture contents 2, 4, 4 and 5 per cent, an average of 30°6 per cent (excluding the third experiment which was made with the powdery fuel remaining at the bottom of a sack of which the calorific value was probably low ; this run also was short, and a violent hailstorm which occurred during its progress quenched it a little). This figure, while not so high as that for coke “ X,” still shows an excess radiation of about 19 per cent over that thrown into the room from the same weight of coal burned in the same grate. The fires made with these fuels were extremely bright and pleasant and were free both from smoke and smell. The results are of considerable interest, and suggest that low temperature carbonisation cokes, if put on the retail market at front of fire ed by Radiometer 34°4 centre CuRVE I s z . i é i §& re e Bz fe fo é 3 £ Tima in minutes sinco fire was hghted CuRVE 2 Heat absorbed by Radiomater 34°4 inches from centra front of fire B, Th. U. par aq ft per hour. 480 Time in minutes since fire was lighted. DiaGrRaM 25.—Variation with time of the heat received by the radiometer 34°4” from the centre front of fires of briquettes in grate “‘D.”” No draught restriction. Curve 1.—Fire lighted with 5 Ibs. coal and fed with two whole briquettes (weight 4 Ibs.) at 60 and 180 minutes after lighting. Curve 2.—Fire lighted with 5 Ibs. coal and fed with 24 Ibs. broken briquette at 60, 120, lighting. a reasonable price, should quickly become a popular and efficient fuel. The explanation of the high radiant efficiency which they show is possibly due to the peculiar structure of these fuels, in which, owing to their porous nature, the area of exposed surface is large. ; 180 minutes after RADIATION FROM BRIQUETTE FIRES Radiant Efficiency of Fires of Briquettes in Grate “ D.”’—Two runs were made for the measurement of the radiation emitted from briquettes burning in grate “ D.” The calorific value of the briquettes was 11,200 B.Th.U. per lb., with a moisture content 7 per cent. The results obtained are shown graphically in Di and the calculations of radiant efficiency are given in Te ce y lagram 25, THE COAL FIRE 43 TABLE XXI RaApDIANT EFFICIENCY OF BRIQUETTE FIRES IN GRATE “D” (No Draught Restriction.) Fires lighted with 5 lbs. coal and 4 lb. wood. Heat absorbed by Radiometer 34-4 inches from centre front of fire. B.Th.U. per square foot per hour, EXPERIMENT I, Experiment II. . (January 14, 1918). (January 16, 1918). Two whole briquettes 2} Ibs. broken (4 Ibs.) added at 60, | briquette added at 60, 1809 minutes. 120, 180 minutes. Hour 1 132 73 Hour 2 178 : 167 Hour 3 127 202 Hour 4 195 189 Hour 5. : ‘ 2 4 q 103 109 Hour 6. 3 . , _ é 67 59 Hour 7 73 34 Hour 8 37 21 Hour 9 , 3 : 18 114 Hour 10 ie 4 f 3 Total Heat in B.Th.U. per square foot absorbed by Radiometer from Highting to ane out: of fires “RY: 933 871 Total Calorific Value of Fuel burned. B.Th.U. Ces 148,000 150,000 ~ Radiant Efficiency Raat xI0o. i 3 * 196 per cent 18-0 per cent Mean Air Flow through Room from one hour after lighting to one or two hours after last mending. Cubic feet per hour . ‘ ‘i : < 12,300 18,700 In both cases the fires were lighted with 5 lbs. of coal. Curve 1 refers to a run in which two whole briquettes (weight 4 lbs.) were added to the fire 60 and 180 minutes after lighting. Curve z refers to a run in which 23 lbs. of broken briquette was added 60, 120, and 180 minutes after lighting. It will be seen that the variations in the intensity of the radiation emitted are less extreme than for coal fires, but that the efficiency, I9 per cent as compared with 24 per cent for coal fires burning in the same grate, was decidedly low. HEAT ABSORBED BY THE AIR PASSING UP THE CHIMNEY FLUE ABOVE COAL OR COKE FrrEs.—The experiments to be described were carried out upon grate “ D,” which was installed in the small experimental room (Diagram 7). The quantity of heat which is required to heat the air passing through the room from its initial temperature to the temperature at which it passes the level of the ceiling in the flue, must be supplied by the combustion of the fuel in the grate and represents a loss of heat so far as the particular room in question is concerned ; 44 THE COAL FIRE it should, however, be borne in mind that the hot flue acts as a source of heat to upper adjacent rooms, which, especially if the flue is an inner one, may be of con- siderable importance. : . Methods of Measurement.—Preliminary attempts which were made to estimate the volume of the gases passing up the chimney flue above coal fires in grate D showed that with unrestricted draught, owing to the excessive dilution by air of the products of combustion, the method of calculating the flow from an analysis of the products in an Orsat apparatus was unsuitable, the content of carbon-dioxide being generally below 1 per cent. Moreover, the instantaneous rate of burning of the coal could not be determined. The following method was therefore sub- stituted : One of the lower panels of the door was removed, and the velocity of the entering air was directly measured by an anemometer, all other possible air inlets being carefully blocked up. A thermometer hung in the panel space gave the temperature of the entering air, the corresponding temperatures in the flue at the level of the ceiling being taken from the readings of a Whipple indicator attached to a platinum thermometer in the flue. These measurements were carried out concurrently with the determinations of radiation described previously, readings of all instruments being taken every few minutes over the whole period of burning of the fire. With diminished draughts it became possible to obtain approximate check measurements by means of the Orsat apparatus, although the percentage of carbon-dioxide in the flue gases never rose above 2'5 percent. The air flows indicated varied from some 3000 to 25,000 cubic feet per hour as compared with values ranging from about 2000 to 20,000 cubic feet per hour as measured by the anemometer. The recognised slightly low values for carbon-dioxide given by the Orsat apparatus are sufficient to account for this discrepancy. Relation between Radiation, Air Flow and Flue Temperature.—The simultaneous values of radiation, air flow and flue temperature recorded on any day showed a marked correspondence ; that is to say, when the intensity of the radiation was high the flue temperature and rate of air flow through the room were also high. These results of course find their explanation in the fact that the current of air through the room is maintained by the force due to the temperature difference between flue and outside air. Typical examples to illustrate the correlation between the time variation of radiation, flue temperature and quantity of air passing through the room for fires in grate “ D” lighted with 5 Ibs. of fuel and fed hourly with 23 lbs. of fuel— (a) coal, (6) coke, (c) low temperature coke—are shown in Diagram 26, Curve 2, Diagram 30, Curve 1, Diagram 28, Curve 3. There was no draught restric- tion in any case. The heat absorbed by the radiometer is expressed in B.Th.U. per square foot per hour and the flue temperatures in degrees F. The relation between the curves is plainly defined, the maxima and minima following one another closely. The maximum points on the radiometer curves occur rather later than those for the air flow and flue temperature. Quantity of Heat absorbed by the Air and Gases passing up the Flue.—The product of the volume of air passing through the room (measured at N.T.P.), its specific heat and the temperature difference between the air in the flue at the THE COAL FIRE 45 ceiling level and the air entering the room at the door, is a rough measure of the heat supplied by the fire and passing away above this level. The effects due to moisture in the air were neglected. The curves given in Diagram 26 show the variation of flue temperature “g0,000 Fs Te anjy OF amyeodies Curve I Air Flow through Room in cubio feat per hour - 3 8 Qrequosyey) oro7 in minutos since fire was lighted ‘emperature in x = o feot per hour. CurRVE 2 4 Air Flow through Room in cubic leupoo Time in minutes since fire was lighted Curve 3 Buipeg ye any uF ounposodwosl -Air Flow through Room in eubic feet per hour. 320 300 380 420 460 480 600 620 Time in minules since fire was lighted. CurvE 4 (Qoyuesyey) [ea07 2uijog 1 onig“Us sumesadue, Air Flow through Room in cubi- feet per hour. 60 a 140 160 180 200 220 240 260 260 300 320 340 su 280 Timo in minules since fire vas lighted D1aGRAM 26.—Variation with time of the volume of air passing through the room and the temperature in the flue at the ceiling level for coal fires in grate ‘‘ D.’”” No draught restriction. Curve 1.—Fire lighted with 5 lbs. coal and fed with 2} lbs. coal at 60, 120, 180, and 240 minutes after lighting. Curve 2.—Fire lighted with 5 lbs. coal and fed with ae lbs. coal at 60, 120, 180, and 240 minutes after lighting. Curve 3.—Fire lighted with 5 lbs. coal and fed with 23 lbs. coal at 60, 120, 180, 240, and 300 minutes after lighting. Curve 4.—Fire lighted with 5 lbs. coal and fed at 60, tae, 180, 240, and 300 minutes after lighting with 2} Ibs. coal. and air flow with time for coal fires in grate ‘‘ D”’ lighted with 5 lbs. and fed hourly with 2} Ibs. of coal. From these the mean excess heat in the air passing the ceiling level over that of the entering air may be calculated for each successive hour. The flue temperature remained above that of the entering air for some time after the dying out of the fire, and a small addition (obtained by extrapolation) was made for this. In Table XXII. the mean values of the air flow, flue temperature and entering air temperature are shown for each successive hour ; readings taken just before the THE COAL FIRE lighting of the fire are alsoincluded. It will be observed that even without fire there was a considerable movement of air through the room, which varied from day to day, but averaged some 7,000 cubic feet, or three complete changes of air, per hour, the flue being, as already stated, go feet high, and passing through a warmed building six .stories high. On lighting the fire, the air flow at once increased, the average flow over successive hours being nearly 18,000 cubic feet per hour when approximately steady conditions had been established, the average flue temperature I10° F ., OF 56 degrees in excess of the entering air temperature of 54° F. The excess temperature of the air passing up the flue at the ceiling level over that of the entering air represented a mean absorption of heat equal to 56, 54, 55 and 46 per cent respectively of the total calorific value of the fuel consumed in the four experiments, or an average value of 52 per cent. Effect of Treatment of the Coal by Patent Preparations.—Corresponding results are illustrated in Diagram 27, Curves I, 2, 3, 4, 5, and in Table XXIII. for similar runs, but in which the coal used has been treated with the patent advertised pre- parations referred to on page 28. Here the average air flow was nearly 20,000 cubic feet per hour, the flue temperature 102” F. or 50 degrees above the entering air temperature when conditions had become fairly steady ; the corresponding mean absorption of heat over the whole periods worked out at 48, 48, 54, 53 and 56 for the five separate runs, or an average of 52 per cent of the total calorific value, a result similar to that obtained with untreated coal, and which shows that the salts were without effect. Conditions in Flue with Low Temperature Carbonisation Coke Fires —In Diagrams 28 and 29°and Tables XXIV. and XXV. the volume of air passing through the room and the mean flue temperatures are given for low temperature carbonisa- tion cokes ““X” and “ Y.”” The fires were lighted with 5 lbs. of fuel and 3 Ib. of wood, and were fed hourly with 24 lbs. of fuel—there was no draught restriction. The air flow as represented by Curves 1 and 4, Diagram 29, was very erratic, probably due to the continual opening and shutting of the outer door. The mean flue temperatures over the intermediate hours were about 89° F. and 92° F. respectively for entering air temperatures of 58° F. and 56° F., and air flows 17,000 and 15,000 cubic feet per hour, the excess of flue over entering air temperature being rather less than for coal fires. It will be seen that the heat carried away in the hot air passing the ceiling level of the flue varied from 373 per cent of the calorific value of the fuel burned on May 31 to 70} per cent on October 21. The rates of burning and-excess temperature of flue over entering air varied little, but the air flows on the two days were, after steady conditions were approximated, about 11,000 and 23,000 cubic feet respectively, the air flow before lighting the fire having been very low on the former date. The sum of the heat carried away in the hot flue air and of the radiation emitted amounts on October 16 and 21 to ror and 105 per cent respectively of the total ay value of - fuel burned. This result, though possibly at first sight eer - 7 ee by the fact that a part of the radiant energy is L g the air which passes up the flue, and this proportion is therefore counted twice over if the two factors are added. 46 47 THE COAL FIRE yuso ied Soh yuso rod $rS yuso red ¥e¢ yuso rad $¢¢ 2 “* pauainq jenyz 2q} JO onjfea oy10eo 1e10} 94} jo o8e -yusor1ed @ se passoid -Xq ‘[eA9] SUTTIE0 9y3 ye ong oy} Ur on} -erad U9} 91} 03 Te Sut -I0}U9 Jo a1nze10dm19} aster 0} pormbear zeazy g-9S Sg oob‘br S.cob to ool br z.GG S9 oob‘z1 is ae ee : : : g Inoy ols L6 006‘SI zor 98 oor‘St 9-SS gl 00g‘ te Se os : : z Z inoyy L-9S gor oor‘Lr L.Gv 601 oor‘Zt 0-95 £6 006‘9I SS 6g 00S ‘gr 9 Imo}y{ o-LS gor 009‘9I 6.S¢h 601 000‘61 gSS ZII 00z‘gI 0-6S bzI 009‘0z ¢ mop g-L¢ €or 00g‘9I o-Sh 601 009‘91 g-SS Tir 009‘g1 0-6¢ bz 00661 ; F m0 g-9S gor | oo09‘Z1 v.br gor | oor‘Sr 0.G$S gor 009‘61 0-6S gIL 00261 ; ‘ € mop o-LS L6 oov‘gt oh 601 00S ‘gI 6.¢¢ For oog‘Z1 0-66 ZIl 00S ‘gr : @ Inox I-9S 26 ool ‘Gr v.1b 1g oo1‘Z1 L.4¢ zg 009‘€1 0-6S Lg oo€‘€1 , I Inopy{ ¥.G¢ €.9¢ 002'9 Zev gb oo1'g €.bs g-€S 000‘ 0-6S ot oob‘g9 ait Suryysry s1oyag s “TaAa y "[2A0' . *JaART “‘Taaa sunosta stm ‘moy sad guusiwo sam99 moq sod Bapsoya Bamte9 *moy sod “w0Oy sumo “moq Jad *V | contro | Wthocg? | AY | ante | "moog | YY | onion | Satooge? | “iy? | sour or | hook? qsnoiq} ysnoiq} ysnoiq} ysnomq} Ef dura, i : a iL ‘amjeradmeaL Sagnias ‘anjersduray, se Tow sainqexadulay, It es a I Ty ura meet y ueaW wea r neOW Ty dea “surur o0€ ‘obz ‘ogr ‘oz1 ‘og ye peppe [eoo “sq fz *(g16r ‘zz Areniqa.q) ‘AI INaWINaaX *sutur O0€ ‘obz ‘ogr ‘oz1 ‘og ye poppe [e0o “sq] Fz *(2161 ‘Zz Jaquiadaq) “III INaNIMaaX A “sual oz ‘ogr ‘ozI ‘og 78 pappe [eoo “sqy Fz "(2161 ‘Z 1equiedeq) “II INaWIaadX | “sulul OFZ ‘OgI “OzI ‘09 je pappe eoo “sqi Fz “(2161 ‘of JaquiaAON) ‘| INAWIaaaX | (‘uorjoE}sey WYSNeIG ON) ‘poom “q] $ pure yeoo jo ‘sqy S YIM poyyST] sarny ITXX ATAVL «QM» GLVED NI STAY IVOD FAOMV ANTY AANWIHD dA ONISSVd LVAH 48 THE COAL FIRE odwe iiseielteas Bumeo ie onjy ul sanyor CurvE I Air Flow through Room! in cubic feet per hour ime in minutes eince fire was lighted. = 2 i 4 3 5 Ne as m Ey os > 83 3 m ee a? p $ gs ¢ 3 “ee O £3 ‘Se = g a - = z a a a "220 Tre in minutes since fire was lighted. a g 3 3 3 a om § a Ea 3 5 és 5 £s E ew fs 5 D 32 5 a3 O £28 z o 2 & z = 3 = a a Time in minuten smce fire was lighted XN feel per baur 6 CuRVE 4 Aur Flow 4frough Room in cube (ueyuesye 4) 10407 Auyeg je eng ur oumesodwoy Time in minutes since fire was lighted ‘emperature in CuRVE 5 jawianraioe Bulag Ww arg Ur ounessdway Air Flow through Room in cubic feet per hour 240 Time in monies since fire was hghieo DiaGRaM 27.—Variation with time of the volume of air passing through the room and the tempera- ture in the flue at the ceiling level for coal fires in grate ‘“D.”” Coal treated with patent salts. No draught restriction. Curves 1, 2) 3, 4, 5.—Fire lighted with 5 lbs. coal and fed with 24 lbs. coal at 60, 120, 180, 240, and 300 minutes after lighting. 2 THE COAL FIRE f oO CurvE 1 Air Flow througn Hoom in cubic feat per hour Temperature in Flue at Ceiling Level (° Fahrenheit) «Time in minutes since fire was lighted. CurRvVE 2 Temperature in Flue at Ceiling Level (° Fahrenheit) Air Flow through Room in cutie feet por hour. 200 Timo in minutes since fire was lighted at Ceiling Level (° Fahrenheit). CURVE 3 Air Flow through Room in cubic feel per hour. Temperature in Flue oO 60 Time in minutes since fire was lighted Temperature in = Flow feat per hour, CurRVE 4 Temperature in Flue at Ceiling Level (° Fahrenheit) Aur Flow through Room in cubic Time in minutes aince fire was lighted Temperature in ‘Air Flow Ne feet per hour CuRVE 5 Air Flow through Room in cubic Temperature in Flue at Ceiling Level (° Fahrenheit), . 340 Time in minutes since fire was lighted. Diacram 28.—Variation with time of the volume of air passing through the room and the tempera- ture in the flue at the ceiling level for fires of low temperature carbonisation coke ‘‘ X ”’ in grate “D7 Curve 1.—Fire lighted with 5 lbs. coke and fed with 2} lbs. coke at 60, 120, 180, 240 minutes after lighting. Curve 2.—Fire lighted with 5 lbs. coke and fed with 2} lbs. coke at 60, 120, 180, 240, and 330 minutes after lighting. Curve 3.—Fire lighted with 5 Ibs. coke and fed with 24 lbs. coke at 60, 120, 180, and 240 minutes after lighting. Curve 4.—Fire lighted with 5 lbs. coke and fed with 24 lbs. coke at 60, 120, 180, 240, and 300 minutes after lighting. Curve 5.—Fire lighted with 5 Ibs. coke and fed with 24 Ibs. coke at 60, 150, 201, and 300 minutes after lighting. THE COAL FIRE 50 yueo rad 9S yuao red €S yuso sod +S yuso rod lb ques 10d $Lb | - * peuing fant ayy Fo onjea ogT10[e9 [@}0} 9q3 Jo a8eqUI9 -iod @ se possoidxq ‘eas, Buried 93 | ze ong oy} ur oin3 i -erodure, 0} We S8ur -19}19 JO ammyeredurey | astel 0} pormnbar zeaxy 1-64 bL | oor‘L1 | g.rS Sg | oo€'Sr] +.S¢ og | cog’gr |] +.6¢ €g | ooz‘gr get G9 | 006‘S1 | - * g inoyy 1-60 6g | 006'61| g.1S gL | o06'Z1| +.S¢ €6 | oob’zz} £.96 te | ooz‘l1) z.€S 62 o0o0S‘gI | : * £ moy z.gh vor | oor'1z| g-1S 16 | ooS‘61r|] ¥.S¢ bor | ooL'1z| €.9¢ ZOI] ool‘61)| 9-€S 06 oor‘gt : ‘9 nox Z-Qv Tor | o0S‘oz | geIS, o1rt | oo€‘gr | S.bS For | oof'oz | €.9¢ g6 | oog’gr| 1-€S +6 oQo£‘gr | - : : ¢ mop 1.67 G6 | oco9‘oz) gS g6 | oof 61} S.FS gor | oof'61 | z-L¢ Lor} oo1fo0z | 6.06 66 | oof ‘Zr + moy cL? 1or | 00061 | g.1S ZII | o0S‘gr} 9-€S -goI | o0g‘gr | €.96 vor| o0S$‘61 | 9.64% oor; ooS‘Z1 | - € mop v.oF 96 | 006'Sr| g.rS. gor | ooz‘Zr} 9-€S oor | 00S‘Z1 | S.bS S6 | o06‘Z1| 9-gh L6 Oo€ ‘gr z Inoy L.€b 1g | ooS‘Z1] g.1S gg | oog’Sr]} 9-€S Lg | oorgr| 2.26 6£ | oob'Sr} zgr gL | oog‘F1 | - I im0y #2 gor | 0046 geIS | b-zg e ve€S | 1.gS |oor'g | €-2S | L.zG | oorfor| zgh | bezS | oog’g | - aitg Butyysry e10jogq | ; ‘TRAST . ‘TadaT s ‘TeAaT é “TaAaT : "TaAaa iste 4 yer euapet ae Baris ae ‘moy sed sur ee *“moy sed gute; Sau smoy sed Suess aud ‘moy sod mV ant Uy cao ay anyty Ul Pero av an{gq Uy Paueee iv an{y uy Tao ay anry uy oo ap qgnons ysnoiyy qgnoryy : ysnoiqy ysno1qy ‘amyeiadma t, nv ene ‘amyjesaduray re Te ‘ainqerodmay ny on ‘ainjeraduay, a ae ‘amyjeraduiay, se en ueayl uveyl * uesyl uel ues “suiu O0€ ‘obz ‘ogr ‘oz1 ‘09 7e pappe [e0o pazeer} ‘sqI ~ “(9167 ‘b qorey]) ‘A LNGHINGAX “sutur O0€ ‘obz ‘ogr ‘oz1 ‘09 ye pappe [e0d payeary “sq] fz “(g161 ‘4z Areniqa,q) ‘AT INGNINGEX | “sulur Oo€ ‘obz ‘ogI ‘ozz ‘og 7 pappe [e090 pozeex} ‘sq] fz *(g16r ‘€x Areniqa.f) “II INaWIasak suru 00€ ‘obz ‘ogi ‘oz1 ‘09 ye poppe [209 poyees} ‘sql fz *(g161 ‘1 Areniqayq) “TJ INININaaX “sural 00€ ‘obz ‘ogi ‘ozr ‘og ye poppe [eoo payeas} ‘sqy Fz *(gr61 ‘o€ Arenue[) ‘T INANINTAX A» 10, X » SHes uoyed YIM pozeer} Teod (uoTPOLIsOY PYsNeI” ON) ‘poom “q] § pure [eos jo ‘sq] $ YIM porysy sory «Us» ALVUY NI SAMI TVOD aAOaV FATA AUNWIHD dN ONISSVd LVEH TWIXx WIAVL 51 THE COAL FIRE ques red gq yueo rad +S queso red gt zuso rod ¥od yueo rod $l€ : : + pouinqg Teng oy} jo onjea OpoTeo [e}0} sy} jo osezueo1od e se pessoidxy “[OAoT But -[199 ye ONG Ur ony -e1oduie} 0} Ite S8ut -10}U9 Jo 91nzeI19duI94 aster 0} parmber eazy aie ne * €.96 og | ooL‘Er| z-€9 zg | oog‘z1| L.2S ace oo0g'Si | g.1Z 0g | ooo'g | - 7: * Of mnoxy 22S SL | oob‘g1| ¥.S¢ Ig | ooS'hr] z.bo 8g | oo6‘E1| z-€¢ bl ooSt£r | xzl Sg | 0096 | - ‘ ‘ 6 «INO ZS ZB | 00961 | ¥.S¢ Ig | oo€ Sr] ¥.¥9g gg | ool'hr} z-€S £g 00961] 1.22 $6 | oog‘or | - : * g ImoP g-€S 6g | oo9‘oz} z.S¢ bg | o09‘S1 | 9-49 £6 | ooz‘Sr] g.€S 88 o000'Iz | 9.12 €or | oor‘z1 | - - * L mop I-b¢ £6 | oof‘1z| ¥.€¢ zg | oog'St}] o.b9 96 | oog‘'Sr| +¥.€¢ 1g o00z‘'zz | b.12 gor | oog‘z1| - * 9g Imo I-bS g4 | oorfoz} g.€S 9g | oor‘Z1} o0-€9 L6 | ooG‘F1} 9.€¢ zg o00g9'zz| ¥-oL IOI | oo€‘11| - " * ¢ IO £.6S 06 | oof‘oz| 6.S¢ 88 | 006‘91 | 9-19 G6 | oohF1}] G.1S £g oor'hz| z-ol Gor | ool‘z1 | - . ‘ - Imo g-E$ tg | 000'61} 1-09 €6 | o06‘SI}] z-19 €6 | ooS‘€r}] €.1¢ zg ooL‘'1z| 6.99 $6 | ooz‘z1 5 * € InoF, Z-€S 94 | oo0‘Z1| 9-09 9g | oo€'91| 9-65 4g | oo1'€r| 6.06 bg o0S‘bz} 9.9 g6 | oorzr ? ‘ % In0oy z.€G TZ | oo€'S1] g.gS Sg | o06‘€1] z-gS SZ | oorf1r] L.o0S eZ 006'IzZ] S.S9 €g | 006‘g | - : ‘ I anoy L-zG | €.99 | oo€‘or}] 0-6 | o-€9 | o0g‘Z zl | L.19 | o0S‘9 os i ne 6.49 | g-bg | BoS'z | + omg Suq8rqZ o10;og ® “PRATT : *[aAaT eae “JaAaT “ano ‘PAST ai65 *[RAaT auponto | FHP | ors geo | Boasts | PHUPD | snog sed | suspen | MAIR | anon ed | aoumyun | FPulPO | sven ed | aouayue | SUD | mou zed iW any uy | ‘mo00y IV anpg uy | ‘woOy av any up | “wWooy av onpy uy | ‘wooy aW ony Ul | ‘woo qsnomq} qsno1q} qsno1q} qsnoiq} qsnoiyqy MOLT MOLT MOLT MOLT MOLT ‘amyerodurey, Iry ues ‘anyeraduay, Iry ueayy samnyerodulay, ITy wea ‘amyeredulay, Iry ueayy ‘amjeroduey, Iry weayy weal uel wea weap wea “saynurur oo£ ‘10z ‘oSr ‘og ye poppe fang ‘sq fz *(g16x ‘91 1aq0}00) ‘A INDWINGdX A *saynural oo€ ‘obz ‘ogr ‘ozz ‘og 18 poppe [any ‘sql $z *(gr6r ‘Sz aun{) ‘Al INGWINaaxX *soynurur oFz ‘ogr ‘ovr ‘og 3e pappe Jeng ‘sq fz *(g16z ‘Zz Avy) “III INaWINaaEX | *saynulur O£€ ‘obz ‘ogi ‘ozz ‘og 4e pappe fans “sqy Fz *(gr6z ‘12 13q0}90) “II INaAWINaaX | “sopnulu oFz ‘ogr ‘ozz ‘og ye puppe Janj ‘sqy fz “(gr61 ‘1€ Aeyy) *] INAWIaaaxX | ‘poom ‘q] } pue yong Jo ‘sq S$ YIM pozYysy sem (‘woonysoy yySnvIq ON) «d» ALVA) NI ,.X>,, THOD AWNLVAAMWA]L MOT AO -SHaly AAOMV ANTY AANWIHD dN ONISSVd Iva AIXX ATAVL 52 THE COAL FIRE * 2 i 3 ig ‘emperature in j = 8 Air Flow 4 = : i 5 i Hes i : s eo 2. m £3 i se 2 . z oO & , : 4 Time in minutes sinca fire was lighted. ‘ ei g ‘amperature in i = oy Aur Flow A cSt § z a BR 8 oo i : - & 3 2 a- : ; © if # : ° : = ; & Time in minutes since fire was lighted P 5 2 sf a i : 33 a A e i eh oa m 83 Rp 5 if Oo § a : £ a Time In minutes since fire was lighted 3 z £ 4 mR Ps b E8 Fa 6 is : : a 100 +120 160 Time in minuteg since fire was lighted DraGRaM 29.—Variation with time of the volume of air passing through the room and the tempera- ture in the flue at the ceiling level for fires of low temperature carbonisation coke ‘‘ Y ” in grate “Dp” Curve 1.—Fire lighted with 5 lbs. coke and fed with 2} Ibs. coke at 60, 120, 180, 240, and 300 minutes after lighting. Curve 2.—Fire lighted with 5 lbs. coke and fed at 60, 120, 180, 240 minutes after lighting. Curve 3.—Fire lighted with 5 lbs, coke and fed with 2} Ibs. coke at 60, 120, and 180 minutes after lighting. Curve 4.—Fire lighted with 5 lbs. coke and fed with 2} Ibs. coke at 60, 120, 180, 240, and 300 minutes after lighting. aaa omy uf oanyeredurey feet per hour CurvE I Air Flaw through Room in cubic BuyseD 220 240 Timo in minutes since fre was hghtod DiaGRam 30.—Variation with time of the volume of air passing through the room and the tempera- ture in the flue at the ceiling level for fires of gas coke in grate ‘ D.” Curve 1.—Fire lighted with 23 Ibs. each of coal and coke and f : or with 2} lbs. coke. ed at 60, 120, 180, 240 minutes after lighting re, THE COAL FIRE yuas sed Sb yuss rad 9S yuss sod 9S yuao sod S¢ ‘ a peuing jen} aq} JO oN[RA ogTIOTe [e}0} 24} Jo o8ezUI0 -iod @ se possoidxq ‘[QAQ] SuTIO. ye ONY Ut ainzerodure, 07 Ire But ; -10}U9 Jo 9Inze1odu19} este 0} poitnber yeapT 0-0S 99 oog‘€I 8-9 al 00z'6 0:99 £g ooS‘€r-7~ €.24 zl 00'S ° : : 6 ino 0-0S LL ooG‘St g-¥9 0g oof ‘or 0-99 06 oog ‘hr 0-0$ 3 oor‘e1 : g m0 0-0 16 ool ‘Fr 6.£9 +g oo£ ‘11 4.99 36 oob‘gr 0-0 L6 oo0z‘Z1 é 4 moy 0-0S 6g 00g‘gI I-€9 Lg oo1‘er 0-99 ZOL ooS‘L1 €.LP €or oor ‘or : 9g mn0oy z-gh £6 000‘0z €.z9 68 oob‘€r 9-99 IOI 006‘9I €.Ly z6 00S ‘QI s ¢ mop 0-0S 98 ooz‘Lt I-Z9Q Sg 009‘Z1 b.19 ZOL ooz'LZ1 €.Lb 16 oob‘Zr ; : : + oy z-gh 06 009‘SI +.6S tg oof‘€1 g-S9 g6 00z‘91 €.Ly oor 00z‘or € mnoy z.gh 88 oor ‘Sr I-09 Sg ooS ‘Ex 1-S9 06 009‘F1 v.ob 06 ooL€I : z Inox Z-Qh cL oof ‘gt 0-19 06 oor‘FI £.€9 €6 009‘ST L.€v 0g 00291 “ : I Inoy{ b.gh 1-gh 000‘'ST ZO €.G9 0009 o€g 4.99 oor‘ g-zb LLY 000‘gI * aly sunysry sloyog ‘4 ‘aAaT s “PRATT P *TaAaT “GOS ‘jaAaTy™ soynyee | MONRO | auogand | sonore | PPO | sessed | stunts | FHF | srtany | Panam | PO | Jeans av eng Uy “WOO ™ ony Uy wont nv ontg Uy ee Tv any uy og pater s NO. mod ee si ry u are “e u ies a ‘amjzeisdurey, ITy weap ‘anjesodua ary ue ‘ainzereduray, ity weeyy ‘amyzerodulay, Iny uesyy ure uray weal weap ‘suru Oof ‘ove ‘ogi ‘oz1 ‘Sg 38 pappe oH00 ‘sqy fz “(gr6x ‘4 yore) ‘AL LNAaWIaaaxg “sult OgI ‘ozI ‘og 3 pappe ayo sq] Fz *(g16r ‘6 ang) ‘JI INaWIaaaxg “sulm OFz ‘ogr ‘ozI ‘og ye pappe ax00 ‘sq] fz *(g16x ‘S Aqn{) ‘TI INIWINaaxXy “suIt Oo€ ‘obz ‘ogi ‘ozI ‘og ye pappe ayo ‘sqy {z “(gr6r ‘g yore) ‘I INAWINadX “poom “q] § pue jon} jo ‘sq] S YIM pozYsy serpy (“worOEseY FYSNeIC] ON) dU», FLVAD NI ,, A» AHOD AMNLVAAIWAL MOT 40 SAULT TAOMV ANTY AANWIHD don ONISSVd LVaH AXX FTAVL 54 THE COAL FIRE Conditions in Flue for Coke Fires.—A run made with coke but otherwise under the same conditions gave a mean flue temperature of 92° F. for entering air tempera- ture 534° F. and air flow about 17,000 cubic feet per hour. The heat supplied to the air passing above the ceiling level was 55 per cent of the calorific value of the fuel burned (Diagram 30). Conditions in Flue for Briquette Fives—The results of two experiments in which the fires were lighted with 5 lbs. coal, but afterwards fed with briquettes, are illus- trated in Diagram 31. Curve 1 refers to a fire which was supplied with two whole briquettes (weight 4 Ibs.) 60 minutes and 180 minutes after lighting, Curve 2 to a fire fed with 24 lbs. broken briquette 60, 120, and 180 minutes after lighting. The heat supplied to the air passing through the room between its entrance and the ceiling level in the flue was respectively 51, 52 per cent of the calorific value of the fuel burned (Table XXVI.). The erratic draught in Experiment I. was due to the frequent opening and shutting of the outer door. TABLE XXVI HEAT PASSING UP CHIMNEY FLUE ABOVE BRIQUETTE FIRES IN GRATE “ D.” (No Draught Restriction.) Fires lighted with 5 lbs. of coal and } Ib. of wood. Experiment I. EXPERIMENT II. (January 14, 1918). (January 16, 1918). 2 briquettes weighing 4 Ibs. added at 2 Ibs. broken briquettes added at 60, 180 mins. 60, 120, 180 mins. Mean Air Mean Temperature. Mean Air Mean Temperature. Flow Ss Flow cue In Flue Air pea In Flue Air Cubic feet | at Ceiling Entering Cubic feet | at Ceiling Entering per hour. Level. Room. per hour. Level. Room. Before Lighting Fire . 9,100 42°8 i * 9,600 45°O | 40°6 Hour 1 : ‘ 15,100 83°2 37°4 16,600 73°8 40°6 Hour2 . ; 15,500 74°2 38°5 17,500 75°6 41°4 Hour 3 : : 13,500 74°3 30°4 18,000 85°5 42°1 Hour 4 10,800 88°2 40°5 18,100 83°3 42°6 Hour 5 : ; 9,400 80°6 41°2 16,000 73°6 42°8 Hour 6 : 15,800 67°7 42°6 14,000 64°6 42°4 Hour7 . ; ; 9,000 71°6 42°8 13,100 59°4 42° Hour 8 13,300 63°2 43°0 12,900 55°8 41°4 Hourgo . ; ‘ 16,400 55°4 44°1 II,500 53°6 41°4 Heat required to raise tem- perature of entering air to temperature in flue at ceiling level. Expressed as a percentage of the total calorific value of the fuel burned a 51 per cent 5 52 per cent EFFECT OF DRAUGHT RESTRICTION UPON THE HEAT ABSORBED BY THE AIR PASSING UP THE CHIMNEY FLUE.—Resistance to the free access of air to the fire could be introduced either by pushing in the damper and so diminishing the effective flue area, or by reducing the aperture in the fender below the grate, or both. A series of experiments was carried out in which, by means of flue regulation alone, the mean air flow through the room was cut down from about 20,000 cubic feet per hour to less than 2,000 cubic feet per hour; the corresponding rate of burning of THE COAL FIRE 55 the fire was reduced only to about one half, the greater proportion of the air for high rates of flow passing directly up the throat of the flue and taking no part in the com- bustion of the fuel. Flue restriction therefore resulted in increased flue temperatures. _ When draught restriction was introduced in the fender below the grate a more marked diminution ’in the rate of ‘burning was caused, the air entering this inlet passing through the fuel and being actually utilised in its combustion. In Diagram 32, Curves I, 2, 3, 4,5, 6 and 7, and Table XXVII. the actual results obtained are given. All fires were lighted with 5 lbs. of coal and } Ib. of wood, and no draught restriction was inserted until the end of the first hour. In the runs illustrated by Curves I, 2, 3 and 4 there was free access to air beneath the fire, but the flue damper was pushed in, slightly in Experiment I. and successively 2 in Air Flow esadwioy yh Room in cubi 3 = zo) es £2) siideaiet eoer Are Flow the Bumog 1 enjg wh ony ao Time in minutes since fire was lighted cubie ye redeso ugh Room in (uaquosyes ) 19409 ue gun Buyeg ie ang feet per hour Air Flow thro 2 B S$ 240 Time in minutes since fire was lighted D1aGRam 31.—Briquettes. farther in the subsequent experiments until, for Experiment IV., it was pushed in as far as was possible consistently with the fire not smoking into the room. Curve 5 is for a run in which not only was the damper pushed in as far as was practicable, but also the fender below the grate was cemented in to prevent air entering through this source. After the first hour the draught was too low to be recorded by the anemometer. In the runs represented by Curves 6 and 7 the bars were removed from the fire, and the grid base was covered with a layer of cement, the fender below the grate, with closed doors, also being cemented in position ; the flue damper was left fully open in Experiment VI. but was pushed in in Experiment VII., when, after the fourth hour, the anemometer ceased to turn. The fires were mended one-and-a-half hourly or two-hourly, as suitable, accord- ing to the rate at which the coal burned away. The mean air flow through the room varied from 13,700 cubic feet per hour in Experiment I. to less than 2000 cubic feet per hour in Experiment V., the correspond- ing flue temperatures averaging 111° F. and 136° F. ; the entering air temperatures were 564° F. and 604° F. respectively. The corresponding mean loss of heat over the whole period of burning of the fire worked out at 544 per cent and 13 per cent respectively of the total calorific value of the coal burned. THE COAL FIRE on oO ‘emperature in Aur Flow CuRVE I Am How through Roum in cubic feat per hour at Ceiling Level ( Fahrenheit) Temperature in Flue Timo in minutes since, fire was lighted CuRVE 2 Au. Flaw through Room cue Temperature in Flue at Ceiling Level ( Fahrenkeit). Time in minutes since fire was lighted. int Air Flow CurVE 3 Au Flow through Room in cube feet per hour Temperature in Flue at Ceiling Level (° Fabrenheit). Time in minutes since fire was lighted Temperature in —-| Air Flow ~ cubic - CuRVE 4 feet por hour. Temperature in Flue at Ceiling Level (° Fahrenheit). Air Flow through Room in Time in minutes since fire was lighted. DiacramM 32.—Variation with time of the volume of air passing through the room and the temperature in the flue at the ceiling level for coal fires in grate “ D.” Draught restriction. Curve 1.—Fire lighted with 5 lbs. coal and fed with 2} Ibs. coal at 60, 150, 240, and 300 minutes after lighting. Damper pushed in slightly at end of first hour. Curve 2.—Fire lighted with 5 lbs. coal and fed with 2} lbs. coal at 60, 150, 240, and 330 minutes after lighting. Damper pushed in partly*at end of first hour. Curve 3.—Fire lighted with 5 Ibs. coal and fed with 2} Ibs. coal at 60, 180, 300 minutes after lighting. Damper pushed in at end of first hour. Cur ve 4.——Fire lighted with 5 lbs. coal and fed with 2} lbs. coal at 60, 180, 270 minutes after lighting. Damper pushed in at end of first hour. THE COAL FIRE 57 DIAGRAM 32—(continued). g 2 = E 3 : 3 mm EL ce 83 gt (a 23 zak 5 mp ge ? (Oa . 2 28 = 9 a ce «8 Tima in minutes sinco fire was lighted. 4 ee i Aur i = gs - g3 ad i a fe ae > 32 2s SM 8% sz Pp «¢ 26 O x 2e § ee a 9° g ; 320 a Time in minutes sinca fire was lighted ‘ ‘omperature. in 3 ——] Aw 3 = z a 3 3 3 n #2 si & z Si 33 fm 3s 2. > =£3 25 % Fy a 3 i? Ore ze a < g & Time in minutes since fire was lighted. Curve 5.—Fire lighted with 5 Ibs. coal and fed with 24 lbs. coal at 60, 180, and 300 minutes after lighting. Fender below hearth cemented in position. Damper pushed in at end of first hour. Curve 6.—Fire lighted with 5 Ibs. coal and fed with 2} Ibs. coal at 60, 180, and 300 minutes after lighting. Bars removed from grate and fender cemented in position. No damper restriction. Curve 7.—Fire lighted with 5 lbs. coal and fed with 24 lbs. coal at 60, 180, and 300 minutes after lighting. Bars removed from grate and fender cemented in position. Damper pushed in. In Experiments VI. and VII., when the bars were removed from the front of the fire, the mean air flow when approximately steady conditions had been reached was 15,000 and 3000 cubic feet per hour respectively with open and closed flue damper, the corresponding flue and entering air temperatures being 92° F., 103° F., and 634° F., 63° F., with mean heat absorption over the whole time of burning, equal to 51 and 18 per ‘cent of the total calorific value of the coal respectively. A comparison of Curves 1 and 6 shows how much less was the rate of burning for the same air flow when the restriction was inserted below the fire than when it was produced by restriction of the flue area. Relation between Air Flow and Heat passing up Flue.—Diagram 33 illus- trates the correlation between the percentages of the total heat of combustion of the fuel which are carried away up the flue above the ceiling level, with the volumes of air passing. For zero air flow the heat loss must obviously be zero; the curve THE COAL FIRE 58 quay radg1 quoo rod 1 yuao Jod €1 quao sed 2z quao Jad of yuss red $gt ques rad $+S 3 ° * pening jeny ay} jo anyfea ogiioyeo §=[e}0} ay} jo oseyusoiod e& se passeidx ‘TeAaT sulpieo ye ang Ul any -eraduie} 0} Ire sur ‘ -Jo}Ua Jo anyeradu1az asteI 0} pammnbai jeazy |. £9 | 6 | , ss 6.19 | 96 : " o0$'z | 9.66 | +g | oo9'€ | S.gS'| g6 ; ooh | r-95 | 99 | Oorer | + + 6mozy Sg t uy} ssor_T zg | €or 3 Ey 0-99 16 oe i Lez Zor & 9-49 zg ao 6.66 oor | oo1'b $.9S orr| 00g‘9 | z-Z¢ | €g | oo€'€r g oy @ ; SoT S.+9 211 5 9-S9 96 | oof'br | z.z9 611 9-49 €11| oort €.09 1z1 | ooby £.9¢ gzr| 0089 | 6.25 | €or oof ZI £moy 1.49 zz1 | oos‘ztt| 1-9 g6 | ooo'Sr | 6.19 €€r 5 gg 6€1 | o00'S 0.19 z€1 | oog’s 9-8S S€1 | 0069 | g-Z¢ 4z1 | oov‘er * g mow g-£9 zz | oo€‘z | +-¢9 v6 | oog’Sr | g.19 zbr b 9-49 gfx} oog'h £-19 1br | 00'S £.g¢ ZE1 | o0g’9 | g.9S | OoI | OOf ‘Fr S$ moy 0-€9 | -9zx | oo1r'€;!| S.€9 z6 | o0Z'S1 | S.09 €g1 a 0.49 S€1} oor's z.66 1g1 | 00£'9 1.gS C€x1 | oa0'4 | €.9$ | z11r | COLI b mop ge) | eee | ee) ee ee) ee eee ee | eae | deel cere | eee | eal come | Gre) oer | ours ae ‘ ‘ cl 8 = zEx +19 ZI “8 Ir 1-9 oor Z : 1.gS 62 ooz‘zr | 6.66 Sg |*oo6bzr | Z2.4S 76 | oor'Sr | 0.19 66 oo4‘1r | 0.26 Ig | ooz‘zr | £.96 83 oorh1 | Z.zS gf o000'bz I moy 6.25 | 9-z9 oob‘é g-zg | 2-99 | ooz‘or | 0.bS | 0.66 | 006'9 ¥-09 | z-I9 | 00S‘z z.Z& | z.99 | o00S‘z $.SS | z.09 Ook E s+ | g.96 | oozgr amy su qsrT a1oyaq: uey}ssay ueq}ssay >1Si1o >| Pi.) o oa] >| Sila Pu) o 1 OL Pie) Be [LO A) BB |e. A [EB | ea B BB | ee A) Ge | e. E ES | fe S|) BR | fe Ro) BS | 2a. Pol Bm | SHS | Pe | By | SES | Pe | Fu | SES | Pe lem | SEE) Ps Ea | SES | ee | Ba | SER | Fe Ba | SEP oe > os | o8 > oe | sR ]R ob | oR | Re ob | 9 a 3 S68 = on |oB 8S ras) Bs |r& | pee | BS B)/efb | ss | ee | sen | 8s | ek | p25 | BS | oe | ee8 | os & | wes | §¢s 2 mes PE | Sa Be | SR Paid Sea Pe|d Baa : b SR Bs | he | ea Ba fo | Sa B] ss = B | <8 ae Bp | <2 oe Bp | ge | Soe ge ary oe "ee ge | aoe Bpige | So3 Be Veet | ee ee) Se eee |e Gee TE eee |e |e aoe oR (eels so ao 40 ° ° Go ix So om peo os os os os os ‘omyerodmsay, 5B g ‘omjeroduay, | & B 2 |-amzerzedua 3B 4 |-emjeredua 6B 4 fj-oinzeradue, 5 B 4 |-emnjzeradma, 8B 3 -amyeredu 5 Ba a c L L L Li 2 3 L ued A uray a ure 5 uve 5 ue i 5 ueay A uveyl A *EINOY JO Pus *uomtsod ut payuaurso | je U1 paysnd sedureq | ‘worrsod uF paywewtes | 5059 wojaq Japuag +I oq jo pus “1 moq Jo pus “1 mmoq Jo pua ney wol}Isod ur pojzueuIed Iapuey pue 93019 P 39: PI O pua je AT} q3TS aaOuS Ay “93013 aoe Bees ere ‘I moy jo pua }e Ul peysnd rodueq | je ur peysnd redwmeq | ie ur paysnd sadureq 30 p as ny 1 ae POS ee aoe Pee ‘oor ae ze ul pegsnd radmeq “surur OZz ‘og ‘09 “smu OO£ ‘ogr ‘09 “surur O€€ ‘obz ‘oS ‘0g |, we ee ore eee SUPT OO “ogi ‘ow | 4e poppe eoosay 4z | . “SUM OOE ‘ogy ‘og | 4x pappe Teco ‘sql fe | 38 peppe eco ‘sql fz | 4 peppe [eo ‘sql fz oe Mee oe qe poppe Teoo “sq te Uguor % aunty 7© poppe Teoo “sql fz *(g16r ‘gt *ydas) “(g161 ‘Ex ydas) *(g161 ‘z1 “ydas) + vlurer ue cent 1 -(g16r ‘zi ounf) “TA INARTIREX | A igentaeek A] INSNINRaX III INIWIaaaX | ‘T] INANINSIX “T INaNINDax ‘ILA INSNIURAX | (‘yysneIq peonpeyy) ‘poom ‘q] % pure yeoo Jo “sq S WM pozysy sorry TIAXX ATaVL «€d» FLVA NI SAMI IVOD AAOGV ANT] AUNWIHD dO ONISSVd LVAH THE COAL FIRE 59 therefore passes through the origin. For 2,200 cubic feet, or one complete change per hour, the loss was 13 per cent, becoming respectively about 25, 35, 42, 46, 49, 52, 53 and 54 per cent for air flows, equivalent to two, three, four, five, six, seven, eight, nine and ten changes per hour. It appears, therefore, that the heat carried away by the air passing up the flue increases, rapidly for low draughts, but more slowly as the draughts become greater, until for air flows above 15,000 cubic feet per hour little systematic variation in the heat carried away is shown. Now it has already been demonstrated that, over the limits investigated, the radiant -efficiency of the fires in these runs remained independent of the volume of air passing through the room. What therefore becomes of the heat which is pre- vented from passing up the flue when draught restriction is introduced? It will be shown later that this is not spent in warming the air of the room, which, although maintained at as high temperatures by the slowly burning fires of low draught as by the more rapidly burning fires, actually, owing to the greatly reduced volume of the air passing, absorbs a less proportion of the total heat of combustion than in the former case. 8 g Level in ° e B bed 60 50. 30. FA 20 ue YY the Flue, Percentage of Total Heat of Combustion of Fuel absorbed by the Air between its enterin; the Room and its passing the Ceilin 2,000 4,000 6,000 8,000 10,000 12,000 14,000 16,000 18,000 20,000 22,000 24,000 Air Flow through Room in cubic feet per hour. Diacram 33.—Relation between the volume of air passing through the room and the heat passing up the flue. Let us consider two examples, one a rapidly burning fire consuming 2} lbs. of coal per hour with radiant efficiency 25 per cent and flue loss 50 per cent, the volume of air passing through the room being, say, 20,000 cubic feet per hour; the other a slowly burning fire consuming 2 Ibs. of coal every two hours with radiant efficiency again 25 per cent, but air flow 5,000 cubic feet per hour and flue loss 25 per cent. Let the total weight of coal burned by the two fires be the same—that is to say, the second fire burns for about twice as long as the first. But the heat absorbed by the air passing up the flue cannot be considered as independent of radiation, as part of the radiant energy thrown into the room goes to warm the contents of the room and indirectly to warm the current of air on its way to the flue ; and it will be shown later that a considerable temperature rise in the air may have been attained before it entered the fire, having been supplied by energy which originally appeared as radiation or conducted heat. Let it be supposed, however, that some 30 per cent of the total heat of combustion has still to be accounted for after allowing for radiant 60 THE COAL FIRE energy emitted and heat absorbed by the flue air; the greater part of this must make its escape by conduction through the walls to the outside. In the two examples cited above, the total radiation emitted is the same, but the heat passing up the flue above the ceiling level is less in case (2) by an amount equal to 25 per cent of the total calorific value of the fuel consumed, and this deficit is not accompanied by any extra radiation or heating of the room air. It has, on the other hand, been shown that the flue temperatures are increased when the draught is reduced, and in example (2), therefore, not only was the flue maintained at a higher temperature than in example (1), but for about twice the time. That is to say, the total conduction losses would be more than doubled, and this would be sufficient to account for the extra 25 per cent of the calorific value as compared with example (I). With restricted draught it would follow that the heating of upper rooms due to the proximity of the flue would be augmented, and for an inner flue the quantity of heat thus utilised might be considerable. (Professor C. V. Boys, experimenting in his home with a register grate, found that a reduction in draught produced by pushing in the register was accompanied by a rise in the temperature of thermo- meters hung against the flue wall in the room above.) WARMING OF THE Room Arr.—Measurements of the warming of the room air were made for grates ‘‘B” and “ D,” which are installed in the smaller experimental room (Diagram 7). For the fires in the large experimental room no measurements . of air temperature were made. Determinations were first carried out with grate “‘ B,” lighted with 5 Ibs. and fed hourly with 24 lbs. of coal. Readings of a delicate mercury thermometer, hung up in the middle of the room, with its bulb 5 feet above the level of the floor, and shielded from direct radiation by a piece of bright metal foil, were taken every few minutes. Except for slight checks when fresh coal was added to the fire the temperatures recorded rose steadily for the first four or five hours, at first quickly and later more slowly. After the fifth hour there was generally little further systematic rise in the average temperatures over the hour, the readings oscillating about a nearly steady value and showing flat maxima and minima, the former considerably, the latter slightly, later than the corresponding maxima and minima of the radiometer readings. When the fire was lighted there was sometimes a fall in the temperature of the room air owing to the sudden increase in the cool current entering ; this was soon replaced by a rise as the fire burned up. Typical examples of the temperature variation in the middle of the room are shown in Diagram 34, while Table XXVIII. gives the mean values of the temperatures over the successive hours for coal fires in grate ‘“B.’’ Even when steady conditions had been reached the mean rise over the initial temperature amounted only to about 8 degrees F., while for the first three hours after lighting the fire it averaged little more than 3 degrees F. For coke fires the figures were slightly lower, but the temperatures continued to increase to the sixth hour (after which the fires were allowed to die out). Distribution of Temperature over the Room.—In order to get some idea of the ¥ tik COAL FIRE 61 distribution of temperature over the room, pairs of mercury thermometers (one of each pair with silvered, the other with blackened bulb) were hung up in different positions in the room, with their bulbs 5 feet above the floor level. Readings of these thermometers were taken every few minutes, and the variation of temperature Temperature = qraquasye4) Wooy JO ayjuad ui ounjes2dwoy Heal absorbed by Radiometer 34 4 aches from centre front of Gre B Th U per sq ft per hour Tima in minutes since fire waa Radiometer 200 B Th U. per sq. per hour “weoy Jo asjuos ur sunjmicdwe ‘Heat absorbed by Radiometer 34 4 daches from contre front of fire 160 Time im minutes aince fire was hghted DiaGRAM 34.—Variation of the temperature in the middle of the small experimental room with time after lighting coal fires in grates ‘‘B” and “ D.” with time as recorded by both blackened and silvered thermometers is shown in Diagram 35. Comparison with Diagram 8 at once discloses a remarkable resemblance between the curves for the black bulb readings in the position nearest the fire and the radiometer readings. TABLE XXVIII Fires in Grate “ B’’ lighted with 5 lbs. coal and 4 Ib. wood and fed hourly with 2% Ibs. coal. Mean of Temperature recorded by a Mercury Thermometer hung up with its bulb in the middle of the room, and shielded from direct radiation. °F, Time, Nov. 1, 1916. | Nov. 8, r916. | Dec, 10, 1916. | Dec. 13, 1916. | Dec. 15, 1916. | Jan. 10, 1917.| Jan. 15, 1917. Before Lighting Fire 53°7 54°5 462 - 478 | 47°7 | 462 47°7 Hour 1 : 55°4 558 46°9 48-0 484 46°9 48-4 Hour 2 : 57°4 59°2 49°5 50°4 50°0 49°5 59°0 Hour 3 z 4 59°9 62°1 51°2 53°3 52°0 514 53°71 Hour 4 ‘ ‘ 62°7 63°5 - 52°5 55°0 53°8 53°1 55°9 Hour 5 & 9 64°4 63°4 522 56°1 559 52°2 56°5 Hour 6 ‘ 3 65°6 62°7 53°2 55°6 56°5 534. a6 In position (1)—2 feet from the fire—the mean excess of the blackened over the silvered bulb thermometer reading was, when steady conditions had been reached, 7°4 degrees, in positions (2) and (3)—4 feet and 8 feet from the fire— respectively 3°4 degrees, 3°4 degrees. Corresponding determinations for a similar run, in which the silvered thermo- 62 THE COAL FIRE meters were additionally protected from direct radiation by means of bright metal foil shields, are shown in Diagram 36. Here the excess of the blackened over the silvered bulb readings was, in positions 1, 2, and 3 respectively, 17:8 degrees, 13-0 degrees, and 2-2 degrees, the silvered bulbs in the positions near the fire giving lower readings than previously. Readings in position (3)—centre of the room—at different levels above the floor showed little variation between the floor level and 5 feet, though the former were slightly the higher. These results, though difficult of exact interpretation, show how misleading may be the indications of a thermometer as a measure of the temperature of the air in a room heated by an open fire. Taking the readings of the silvered and shielded thermometers in the second trial as a rough measure of air temperature, however, it seems by extrapolation that the air may enter the fire at a temperature considerably above that of the entering air to the room. Here the difference amounted to some 25 degrees F., or about one-half the average excess found in the flue at the ceiling level. It was observed, however, that the increase in the temperature of the room air varied con- Time in minutes since fire was lighted. Time in minutes since fire was ighted DiacRams 35 and 36.—Variation with time of the indications of pairs of thermometers (a) with blackened and (b) with silvered bulbs at different positions in the experimental room (5’ above the floor and 2’, 4’, 8’ from the fire). The heavy lines are for blackened bulbs, the fine lines for silvered bulbs. siderably with weather conditions, being much greater on cold days. On this occasion the entering air was at 43°-3 F., and the warming of the room air con- sequently much greater than usual. Measurements carried out on a day of enter- ing air temperature 65° F. showed an excess of only 5:9 degrees F. in the middle of the room and little farther gradient towards the fire. A third experiment showed that the temperatures on the flue wall varied from 64°:5 F. (blackened) or 62°-8 F. (shielded) just above the throat of the flue to 49°-3 F. (blackened) or 46°-7 F. (shielded) in the extreme left-hand corner of the wall at the same height. The air entered the room at a temperature of about 39°5 F. ; Room Aiv Temperatures with Grate ‘‘ D.”—A delicate mercury thermometer was hung up in the middle of the room with its bulb protected from radiation by a shield of-bright metal foil. Fires were lighted in grate ‘‘ D” with 5 Ibs. of coal and were fed hourly with 24 lbs. of coal for six hours, after which they were allowed to die out ; there was no draught restriction. Readings of the thermometer were taken at frequent intervals, and the average values over the successive hours calculated; these are shown in Table XXIX., the mean temperature of the air entering the room being also included. In Diagram 37 the mean temperatures of room and incoming air over successive hours THE COAL FIRE 63 are shown graphically, the curves being arranged in order according to the value of the entering air temperature ; the temperatures recorded just before lighting the fire are included. Curves 2, 3, 4, 5 refer to experiments in which the coal used had been treated with the patent preparations referred to on pp. 28, 29, but as the - (° Fahrenheit.) (° Fahrenheit.) aS a a z i m Time in hours since fire was tgntea in hours since fire was N (° Fahrenheit,) (° Fahrenheit.) on Time in hours was WwW (° Fahrenheit.) (° Fahrenheit.) n ; z Time in hours N ( Fahrenheit.) (° Fahrenheit.) © (° Fahrenheit.) J " in since was DiacRam 37.—Mean hourly temperatures of the incoming air and the air in the middle of the small experimental room. Fires in grate ‘‘ D ”’ lighted with 5 Ibs. coal and fed hourly with 2} Ibs. coal. results exhibited no divergence from those obtained with untreated coal, they have been included with the latter. . Corresponding results are given in Table XXX. and Diagram 38 for fires of low temperature carbonisation cokes. Before lighting the fire, the temperature of the air in the middle of the room was generally several degrees above that of the incoming air, the mean excess being THE COAL FIRE 64 bl | G.9£ 0.99 r.bL o.bg 02d v.ES 6.99 1.bS b.49 ¥.€¢ g-z9 1.6¢ z.6¢ €.Lb G.6S |° * 9g m0 £.0L z.GL 9.99 g-EZ 0.£€9 L2l g.€S £4.99 1.bS 1.€9 g.€¢ 9-29 z.gh z.6$ E.Lb z.6S | * * ¢§ mo z.oL r.bL +.99 6.22 8-19 3.69 6.S¢ 6.99 €.bS 6.19 G.1¢ 4.19 1.6b 6.25 €.Lb 0.65 | ° * bv moy 6.89 Lael g.S9 6.04 Z.19 0.89 1.09 £49 gES 6.66 €.1¢ 9.09 Z.Qh 6.55 €.LP LLG |° * € mnozy 9.L9 +.69 1.9 £.69 g-6S ¢.S9 9.09 0.99 zZ.€S LLG 6.06 g.gS Z.Qv Lvs F.gh €.b¢ |° * @ inoy g-S9 g.S9 £.€9 G.lg | z.g¢ 1.€9 9-8S TQ ZES g-9S | L.of 1.96 z.gh €.1¢ Lev | 6.05 | °* * I ano0y omy 6.49 9.49 0.€9 6.49 z.l¢ ¥.z9 0.6¢ F.09 L2G 1.9¢ S.0S Z.GS t.oh 6.94 9.zh z.gb | 8unYsry] s10joq “uy |‘Wooy jo| “MY = |"Wooy jo] “my |‘mwooy jo} ‘ary |'mooyjo| “my |"mooy jo; ‘ary |*mooy jo} ‘ay |"WooYy jo) “TW | "MOON 70 Supojugq | app | sumayug} appy | 8amez0q | appr | 8uneq0q | arppy | Sulsajuq | efppyN | SuLe}0q| eppIN | SuejUq |) eIPPIN | 8uUITeIUq | eTPPIA “(g161 ‘IE Avy) *(gr6x ‘S Aqnf) *(g161 ‘Zz Sey) *(g16x ‘Sz ounf) “(9161 ‘gz 1aqQ0300) | *(g16r ‘tz 1aqoq9Q) | *(gz61 ‘Z yore) *(gr61 ‘g yorey) “aun, ‘IIIA INGWINaaxg | “TIA INGWIaadxXY | “TA LINaWIaaax] “A INGNIMAEX | “AI INGWINRAX A "TI INaWIagax | *T] INANIAaAX *‘y INSWIAGdX A ‘A. ‘WOTLIPEY Joosp wo papperys sisyomMoureyT Amore Aq popslooed se soinjertaduey, uceyl ‘MOTJOLIJSAI JYSNeIP ON , ‘aumes ‘sqy $z yyIM Apnoy poy pue 9x09 woryestuogies omnyerodure, MoT ‘sqy S YM pes ,, ,, WeIH Ul sary XXX HTAVL & 4.96 9.¢9 6.S¢ 0.99 ¥.GS b.99 €.96 Q-z9 9.€S Z.19 z.gh PLS L.Gb 1.9S : * 9 inoy 0.L¢ 0.b9 g.SS g.49 G.bS L.G9 £.9¢ $.z9 1.€S g-09 Z.gh €.9¢ 6.SP 0.S¢ * ¢ In0y | 9.Z¢ 9.29 9.GS I.€9 G.PS 0.h9 ZL 1.z9\ | 6.06 v.66 1.6¢ B.S o.Sh 9.€S * - moRT g-9S Z.I9 0,SS G.19 g.€S Z.Z9 £.9S 8-09 9.60 6.L5 | €.Lb E.bS bby g.€¢ . 2 € mop 0.L§ 3-8S 6.bS €.g¢ g.€S 1.09 G.bS 8-09 9.9h 9.GS b.gr €.2¢ o.€h 0.0¢ : ‘ @ ImoPyT 1.9S g-9S LYS 1.9& 9.€S S.g¢ L.zS 8-09 z.gh Z.€S Leb €.60 v.1b Se : ‘Tmo $.6¢ ¥.L¢ C.rS 0.6¢ FES S.gS €.2¢ 8-09 Z.Qh €.2¢ S.Eb L.L¥ Z.Ib Lbr | * ang 8ujysry e10jag | “mV “WOO jo “IV “mIOOY jo “ITV *m00y jo “ny *m00y JO “Ty “moo y Jo “IIV ‘mIOOY jo “rv *uI00Y JO Buyeyug | eTppIW | Saoyng | ePPAA | Sueyug| erppra | SuseT_] eIPPIW | SupEUq| oIPPHA | FUMeIWA) eIPPHW | SulelUM | eTPPIAL “(zr Areniqaq) “(4 Jaquiadeq) *(€z Areniqa,q) *(1 Areniqay) *(o€ Arenuef) *( gore) *(Ze Jaquisssq) ‘ou, TIA LNANINadX A ‘IA LNAWINBax YT ‘A INGWINGaX ‘AT INSWIaadxX | “IIT INANINaaX | *T] LNAWINaax | *yT INaWIaaax A “a. ‘doMelpey perp mow peprerys sioyomOTIey TL, AinoJopy Aq popsodar se sommjeraduley, ues ‘MOTPTIJSeI }YSNeIP ON ‘Teoo ‘sqy $z YM ApINoY pey pue poom ‘q] F pue Teoo ‘sq, S YIM powysy ., 7 ,, 2}e14) Ul soITy XIxxk FTAVL THE COAL FIRE 65 nearly 4 degrees; over the sixth hour after lighting, the mean excess was 9-3 degrees for coal and g-o degrees for low temperature coke fires ; the corresponding rises over the initial room temperature were 8-6 degrees, 9:3 degrees respectively, or about the same as for fires in grate “ B.” The excess of the temperature of the air in the middle of the room (as recorded by the shielded thermometer) over that of the entering air, as will be observed in the diagrams, varies with the latter, being greater the colder the incoming air. It depends also upon the difference existing between room and incoming air temperature H (° Fahrenheit.) (° Fahrenheit.) aS “Time in since fire was lighted N (° Fahrenheit.) (° Fahrenheit.) on Tirae in hours since fire was ow (° Fahrenheit.) (° Fahrenheit.) a in hours since was lighted Time in hours since fire was lighted N (° Fabrenheit,) 1 Time in hours was D1acRam 38.—Mean hourly temperatures of incoming air and of the air in the middle of the small experimental room. Fires in grate ‘‘D” lighted with 5 Ibs. and fed hourly with 23 lbs. of low temperature carbonisation coke. prior to lighting the fire, being greater when this difference is great, which is likely to be on days of low entering air temperature. For on cold days the temperature has generally fallen, that is to say, the walls and contents of the room, which lag behind, would be comparatively warm. Room Temperatures with Draught Restriction.—The results obtained on days on which the draught was reduced artificially are given in Table XXXL, Diagram 39. The mean excess of the temperature recorded in the middle of the room over that of the incoming air at the start was nearly 3 degrees ; over the sixth hour after the lighting of the fire it was 8 degrees for mean entering air temperature 62° F., a : F 66 THE COAL FIRE result similar to that for unrestricted draught. As in the previous experiments, it will be seen that the rise is greater the colder the entering air. These results are very striking ; on June 7 and June 12, for example, the mean air flow through the room was respectively about 16,000 and 4,500 cubic feet per hour, the rate of burning and the mean radiometer readings were about the same, yet the temperature in the middle of the room was no higher on the latter date than on the former. All the experiments lead to the same conclusion, that is, that the temperature of the air in the middle of the room is independent of the air flow. a Ce) 2 E 3 g 4 I q o 5 B 2 & & was lighted? en <3 Z = g > E 2% 8 5 é é a & In hours a 3% E 6 : E fy = x L since fire waa lighted fire was lighted N (° Fahrenheit.) ° in fire D1aGRAM 39.—Mean hourly temperatures of incoming air and of the air in the middle of the small experimental room. Fires in grate ‘“‘ D ”’ lighted with 5 Ibs. coal and fed one-and-a-half-hourly or two-hourly with 24 Ibs. coal. Draught restriction. It seems, therefore, that increased air flow means not increase of velocity in the central current, but spreading. Measurements of shielded thermometers only, hung against the walls in various positions, were made on May 27 and May 31 for low temperature carbonisation coke, and on May 3 and May 9g for coal fires with restricted draught, burning in grate ‘D.” On all occasions the temperatures recorded in the middle of the room were higher than on any of the walls, the flue wall being the warmest of the latter. 67 THE COAL FIRE 1.$9 6.2L g.Fo 6.04 z.bo S.oL 0.19 f.1Z | . 9.96 0.0L 6.19 9.69 g.L¢ 1.S9 $49 0.2L 9.49 1.69 g.£9 0.04 L.19 6.2L £.9¢ 1.69 g.19 0.0L g-9S 6.£9 G.€9 €.02 o.b9 |, -9.L9 1.€9 C.89 z.6S rid 1.96 €.69 S.09 £.69 £.9S 6.S9 S.19 £.69 L.€9 9-99 1.29 4.99 G.6S 1.49 o.L¢ 6.49 g.6S 6.99 g.SS | L.£€9 €.09 9.49 6.19 6.%9 €.19 6.49 G.g¢ g-b9 1.9S Z.z9 I.gS g-z9 LVS 9.09 6.6S 9-99 0.19 Z.29 1.gS $.z9 o0.2¢ $.z9 £.96 8.09 L.4S $.6S L.zS G.9S Q-z9 0.99 $.09 9.09 6.26 €.19 z.LG 9.z9 G6 ¥.6S o.bS 6.66 es 6.56 soba | oene | soaetos | pene | Sablon | SIPDIN | 2uusvug | aIpIN Sauer | ‘IPP | Sousa | arppIN | Sausiog | sfppIe Axoao “sal £2 krona “sat fz Axand "sal f2 Axoao sat fe ons ot Sxono "sql i ora ears *(g16r ‘Z aun{) ‘LIA INaNIMadx |] -(g16x ‘91 “3dag) ‘LA INAWIaTaX A *(g16x ‘z1 oun{) "A LNANIYIIX | *(g161 ‘€1 ‘ydas) ‘Al LNAWINaEX | *(g161 ‘z1 *ydas) ‘TI INTNINTdX | *(g161 ‘6 Ae) “‘T INAWINaaX | "(gr161 ‘€ Ae) ‘T INaWINaaX A ‘uONLIPEY Wop Wor paplarys ssojoMoweyy Amore Aq popsodar se samnjesaduay ues - 9 S . . + nop inoy nop nop inoy{ ImoyH * omy Buryysry e10yoq “ou ‘TYSNeIp popU}soy ‘sInoy om} ArsAo IO yey & pue mmoy Arosa [vod “sqy $z YPM poy pue ‘poom ‘q] § pue Teoo ‘sq & YM pers] ., d,, e215 Ur soln IXXX HIEVL 68 THE COAL FIRE On May 31 the entering air was very warm (65° F. to 72° F.), and except on the flue wall and in the middle of the room the temperature of the walls of the room over the first hours after lighting the fire remained below the entering air temperature ; in positions near the door the walls remained cooler than the entering air through- out the whole run. The greatest rise over the entering air temperature was in the middle of the room over hours five and six, and amounted to 5 degrees. On May 27 the entering air temperature varied from 57° F. to 643° F., and the room wall temperatures were, in all positions, warmer than the incoming air from the beginning of the experiment ; the greatest excess was in the middle of the room over the fifth hour and amounted to 9 degrees. On both May 3 and May 9 the maximum excess of the temperature recorded in the middle of the room was g degrees over the fourth hour. SUMMARY TOTAL RADIATION EMITTED BY COAL AND COKE FIRES BURNING IN VARIOUS TYPES OF OPEN GRATES Radiant Efficiency of Coal Fires—The total amount of radiant energy thrown into a room from coal or coke fires burning in open grates was found to vary com- paratively little with the type of grate employed. The radiant efficiency, or the percentage of the total energy of combustion of the fuel consumed which entered the room as radiation from fires of high-class house coals (calorific value from 13,900 to 14,500 B.Th.U. per lb.), varied, in different grates, from 194 to 24 per cent, and showed no advantage in favour of the modern grate, the figures referring to old-fashioned grates with bars in front being actually slightly higher than those obtained from modern barless grates. Moreover, the effect of removing the front bars from a grate was found to have only a negligibly slight effect upon the radiation emitted into the room. The effect, however, of crushing the coal into slack was to reduce the radiant efficiency to about 20 per cent as compared with 24 per cent for uncrushed coal burning in the same grate. Effect of Variation of Draught—Diminution of the draught through the room from 20,000 to 2,000 cubic feet (or from nine to one complete changes) per hour, and a consequent reduction of one-half in the rate of burning of the coal did not alter the value of the radiant efficiency. In other words, over the limits investigated, the aggregate radiation emitted by equal weights of coal was independent of the rate of combustion, slower burning resulting in proportionately reduced emission of radiant energy. It seems, therefore, that for practical purposes the average quantity of radiant energy thrown into a room by high-grade coal burning in open grates (built with their fronts flush with the wall) may be taken as approximately equivalent to 22 per cent of the total calorific value of the coal burned. Radiant Efficiency of Anthracite Fires —A Welsh anthracite of calorific value 14,400 B.Th.U. per lb. gave a radiant efficiency of 27 per cent in a grate which showed 24 per cent radiant efficiency for coal fires. THE COAL FIRE 69 Radiant Efficiency of Gas Coke Fives.—Dried gas coke of calorific value about 13,000 B.Th.U. per lb. was found to emit radiation equivalent to 244, 284 per cent of the total energy of combustion as compared with 21, 24 per cent for coal fires in the same grate and burning under similar conditions. Weight for weight, then, dry coke of calorific value 13,000 B.Th.U. per lb. gave some 4 or 5 per cent more radiation than coal of calorific value 14,500 B.Th.U. per lb. As the moisture content of the coke increased, however, the radiant efficiency decreased, the diminution in the aggregate quantity of radiation being more than the equivalent of the amount of heat required to vaporise the water present ; and for contents of more than, say, Io per cent of water the radiation emitted by the coke was less than from an equal weight of coal. Radiant Efficiency of Low Temperature Carbonisation Coke Fires.—Low tempera- ture carbonisation cokes were remarkably efficient as radiating sources, two samples giving when dry respectively 34 and 31 per cent radiant efficiency as compared with 24 per cent for coal in the same grate. The calorific value of these fuels was about 13,200 B.Th.U. per lb., and the radiation emitted was therefore some 25 per cent in excess of that produced from an equal weight of coal of calorific value 14,500 B.Th.U. per lb. As in the case of coke, the radiant efficiency of course diminished as the moisture content of the fuel increased, but for the highest proportions of water found (11 per cent by weight) the aggregate radiation emitted was still considerably in excess of that thrown out by an equal weight of coal. The fires made from these fuels were bright and pleasant and were free from both smoke and smell ; they were lighted easily by the usual methods, and without the addition of any coal. Radiant Efficiency of Briquette Fires——Briquettes of calorific value 11,200 B.Th.U. per lb. and moisture content 7} per cent gave a radiant efficiency of Ig per cent as compared with 24 per cent for coal when burned in the same grate. Distribution of Radiation from Coal and Coke Fires.—Although the total amount of energy thrown into the room as radiation from the combustion of equal weights ot the same fuel in different types of grate varied over a relatively small range, the design of the grate had a considerable bearing upon the distribution in space of the radiation emitted. The readings of greatest intensity of radiation were found for all the grates investigated, upwards at an angle of 60° to the horizontal through the approximate centre of the fire; but this maximum was most sharply defined for the flat-surfaced fires in the low, barless grates ‘‘ A”’ and “ B,” where its direction corresponded roughly to that of the normal to the surface of the fuel, and its intensity amounted to about twice that at 0°, while for the small register grate “‘ D”’ little variation in radiant intensity was met with between 80° “ north” and 20° “ south.” That is to say, persons situated at considerable distances from a fire, and therefore subtending reduced angles of emission of radiation, would receive a lesser proportion of the total energy emitted from flat-surfaced fires, where the quantity of radiation thrown upwards at high angles is relatively great, than from more nearly vertical- surfaced fires which emit relatively more horizontal radiation. Judged therefore by its value as a direct radiator, the vertical-surfaced fire from the point of view 70 THE COAL FIRE of an occupant at a distance has an advantage, as compared with a nearly horizontal- surfaced fire, which increases as his distance away increases. Or, to take an extreme example, it is clear that the horizontal radiation from a plane surface of emission would be much greater when that surface was vertical than when it was horizontal. Passing downwards from the maximum the radiation decreased steadily, rapidly in the case of fires in grates ‘‘ A’ and “ B,” more slowly for grate “C,” and at first almost imperceptibly for grate ‘“‘ D,” though afterwards the decrease was more rapid.’ A second increase was found with grate “‘C” below 40° “south,” the thermopile becoming gradually exposed’to radiation from the under side of the fire, and the intensity of radiation at 80° “ south” was more than half the maximum. The lowest values of downward radiation were given by grate “‘ A,” which was built up solidly from floor to hearth and in which the intensity of radiation downwards at 60° “south” was only about 5 per cent, that at 80° “ south ” 2 per cent, of the maximum. Passing “east ” or “ west ” from the vertical plane through the centre of the fire the radia- tion for all grates decreased continuously, but less quickly than would be indicated by a cosine law. The diminution was most rapid for the narrow grate “ B” and least rapid for the very wide grate “ C.” For fires of about the same size and burning in the same grate, but made from different fuels, there was little variation in the distribution of the radiation emitted. Flow of Air through the Room and its Heat Absorption.—All experiments upon air flow were carried out in the smaller experimental room, which was on the first floor of a six-story building with a flue go feet high. Even without a fire in the room there was a variable air flow through the room, generally of the order of some 6,000 cubic feet per hour, but which occasionally fell very low, and on one day reached the high figure of 10,000 cubic feet per hour. On lighting the fire, the air flow immediately increased, and an hour or two later, when approximately steady conditions had been reached, the average value over successive hours averaged, on different days, about 19,000 cubic feet per hour. The corresponding flue temperature at the level of the ceiling was 105° F. for mean entering air temperatures of 53° F. The quantity of heat absorbed during the day by the air between its entrance to the room and its passage above the ceiling level in the flue averaged, for the different runs made, about 52 per cent of the calorific value of the coal burned. When resistance to the flow of air was introduced by pushing in the damper and so reducing the effective flue area, the rate of burning of the coal was reduced, though relatively in smaller proportion than the air flow, a diminution of the mean draught for steady conditions from 20,000 to 5,000 cubic feet per hour resulting in only about a halved rate of burning. This is to be explained by the fact that for the larger draughts the amount of air passing through the room is greatly in excess of that required for the complete combustion of the fuel, and much of it passes directly under the canopy and up the flue without ever coming into contact with the coal or taking any part in its combustion. But when resistance to the air flow was introduced by diminishing the aperture in the ash-guard beneath the grate, the rate of burning of the fuel for the same reduction in draught was cut down much more rapidly ; and when this lower inlet was cut out altogether by entirely THE COAL FIRE 71 closing the doors and cementing the guard against the hearth, the rate of burning of the fuel was reduced to one-half for an air flow which still averaged 15,000 cubic feet per hour. By also pushing in the flue damper as far as was practicable, the draught was reduced to some 3,000 cubic feet per hour, but the rate of burning was not diminished further. The mean temperature of the air passing the ceiling level in the flue was higher on days when the draught was curtailed, especially when the reduced flow was brought about by means of the flue damper and without obstruction to the ingress of air beneath the fire being introduced. Under these conditions the mean difference between the temperature in the flue and that of the incoming air to the room from an hour or two after the lighting of the fire to an hour or two after the last mending varied from about 70 degrees F. for air flows of 4,000 cubic feet per hour to 50 degrees F. for air flows of 18,000 cubic feet per hour. With the metal grid hearth of the fire cemented up solid and the ash-guard cemented against the hearth the flue temperatures recorded for grate ‘‘ D” were comparatively low, both with and without further draught restriction, by means of the flue damper. For example, under these conditions, with ash-guard restriction alone, on June 7, 1918, with air flow 15,900 cubic feet per hour, the excess of flue over entering air temperature was, when steady conditions had been reached, about 29 degrees F. as compared with 57 degrees on May 3, 1918, when the draught was reduced to 14,600 cubic feet per hour by flue regulation alone; and again on June 12, 1918, with both flue damper and ash-guard doors closed, was only 52 degrees as compared with 75 degrees for similar conditions on May 9, 1918, except that on the latter date the metal grid hearth of the fire was not covered with cement. The absorption of heat by the air in its passage between door and ceiling level in the flue increased with the draught through the room, at first quickly and afterwards more slowly, being equivalent to only about 15 per cent of the heat of combustion of the fuel for draughts of 2,000 cubic feet per hour and about 41, 54 per cent respectively for draughts of 10,000, 20,000 cubic feet per hour. A series of experiments carried out with gas coke and various low temperature cokes burning with free access to air, showed flue temperatures averaging about 33 degrees above the incoming air to the room, and which, over the limits investi- gated, did not vary appreciably with the draught. This excess is considerably less than that associated with coal fires, but after the last stoking the flue temperatures fell less rapidly than with coal fires and the total absorption of heat over the entire run was not dissimilar, being equivalent to 45 or 55 per cent of the total calorific value of the fuel burned, for draughts between 12,000 and 18,000 cubic feet per hour. A comparatively low value—37} per cent—was obtained on May 31, 1918, for a low temperature coke, but on this date the air flow through the room before lighting the fire was very low—probably less than 2,000 cubic feet per hour. Very high values were obtained for the same fuel on October 16, 1918 and October 21, 1918— 68 and 70 per cent—but on these days the air flow through the room without fire was unusually high. Generally speaking, other conditions being similar, the heat carried up the flue by the air was greater on days when the air flow through the room without fire was high, and less when it was low. 72 THE COAL FIRE Heating of the Room Air.—The difference in temperature between the incoming air and the air at different positions in the room (as given by the readings of delicate mercury thermometers with their bulbs protected from radiation by shields of polished metal foil) was not uniform for similar fires, but varied with the outside weather conditions, being greater the colder the incoming air. On very warm days the temperatures inside the room before lighting the fire were little above that of the entering air—sometimes slightly below—but on very cold days they were as much as 6 degrees F. above. After lighting the fire a steady rise of temperature (some- times preceded by a slight fall following immediately upon the lighting of the fire and the consequent sudden increase in the velocity of the entering current of air) to about the fifth hour took place, after which there was little systematic increase, though slight fluctuations followed the variations of the fire. The average excess over the entering air was, at this stage, about 9 degrees F., but varied considerably from day to day, being higher on cold days than on warm. The wall tempera- tures, except near the flue, showed a still smaller rise. Extrapolation of readings taken at varying distances from the fire indicated that for coal fires in this small experimental room the air entering the flue throat was already considerably warmer than that entering the room, the actual temperature difference, however, varying over wide limits with the temperature of the entering air, being greater when the latter was low and smaller when it was high. The estimated differences varied from some 25 degrees F. for entering air temperature 43° F. to 6 degrees F. for entering air temperature 65° F. But this heat, although appearing in the room under test, cannot be regarded wholly as useful heat, as the occupants of a room do not generally approach within at least a foot or two of the fire ; and the rise in temperature of the incoming air in its passage to the middle of the room averaged only about 9 degrees F., or an absorption equivalent to less than Lo per cent of the total calorific value of the fuel burned. Perhaps an intermediate estimate represents an approximation to the useful heat, but part of this, it must be borne in mind, has appeared originally as radiation. It must, however, be remem- bered in dealing with the effective heating value of fires, that the air passing through the room is always considerably below body temperature, and that even though it were warmed to temperatures which for still air might be excessive, yet a feeling of coldness and discomfort might be produced if the draught velocity were very great. Draught regulation, therefore, becomes a question of paramount importance, for it is useless and wasteful to maintain a large, rapidly-burning fire if the sensation of warmth thus produced is to be counterbalanced by the effects of excessive draught. It is, for this reason, advisable that all fires should be provided with suitable regulating apparatus, in order that, when combustion is well established, the draught may be cut down so far as is consistent with a feeling of freshness and comfort. It is doubtless rather to diminution of draught than increase in radiation that the popularity of some modern grates is due. Taking the case of a coal fire burning with a high draught, it would appear that about 22 per cent of the energy of combustion of the fuel appears as radiation (a part of which, owing to its high angle of emission, is projected to the upper portions of the room and there partly dissipated), while the heating of the air THE COAL FIRE 73 in its passage through the room and up the flue to the ceiling level is equivalent to about 52 per cent of the heat of combustion, some of this energy having appeared originally as radiation. There are further minor absorptions of heat, however, by the walls and furniture of the room, and a slight loss in unburned products. It seems probable, therefore, that the residue, of which the greater part must be absorbed by the brickwork surrounding the fire, does not amount to more than about 20 per cent. This, for an outer flue, is mainly waste, passing away by con- duction to the cold outside walls ; for inner flues, on the other hand, a proportion which depends upon the construction of the flue is utilised in warming adjacent rooms. When the draught to the fires is restricted, however, the proportion of the total available heat which appears as radiation is unaltered and may again be taken as 22 per cent. The flue loss for the lowest draughts was reduced to about 13 per cent, leaving some 40 per cent of the total heat of combustion as compared -with unrestricted draughts still to be accounted for. It appears likely that the greater part of this rather obscure proportion of energy is dissipated by conduction through the flue walls; for with the weakest draughts and the consequent halved rate of burning of the coal, the flue temperatures, owing to the much greater reduction in the air flow, were considerably increased. Not only, therefore, did the conduction for the same weight of coal burned extend over about twice the time, but the temperature difference also was increased ; that is to say, the conduction losses would be more than doubled. This fact could be taken advantage of if all flues were built along inner walls, the fires being provided, as suggested above, with means of draught regulation. In this way, without any loss in the heating of the actual room in question, a considerable proportion of the heat which would otherwise make its escape through the outer flue walls and the chimney would be transmitted through the flue walls to the adjacent rooms. In this respect attention is directed to experiments carried out by Professor C. V. Boys, in which a diminution of the draught to a fire (produced by partly closing the register) resulted in an increased temperature on the wall adjacent to the flue in the room above. A further point which is of radical importance in fire-grate design is that the grate should be as little recessed as possible. Open fires being so largely dependent upon radiation for their effect, any obstacle to the radiation acts as a screen and may result in a considerable loss of efficiency. It is particularly of importance, in view of the proposed erection of large numbers of-small houses in the immediate future, that attention should be directed “to such essentials of grate and flue construction. In their selection of heating apparatus it must be clearly borne in mind that householders will, almost without exception, be guided by considerations of financial economy. The foregoing experimental work has shown that the aggregate efficiency of the coal fire in heating the room in which it is placed is generally at least 30 per cent even for grates of supposedly inferior design ; that of the better modern gas fires is known to be in the neighbourhood of 60 per cent, whilst the efficiency of electric fires, in which there is no flue egress of heat, may be taken as 100 per cent. Adopting these values, it can readily be calculated that, with coal at 45s. per ton, gas at 4s. 6d. per thousand cubic feet, and electric power at 1d. per unit, the cost of a coal fire for continuous 74 THE COAL FIRE heating is only about one-third that of a good gas fire, and one-fifth that of an electric fire of equal heating capacity. These relative heating costs of course vary directly with the prices of the fuels or power, but on any scales likely to be met with solid fuel for continuous heating holds a decided economic advantage over gas and a more marked advantage over electricity. Under these circumstances, therefore, it follows that, regardless of the greater cleanliness of gas or electric fires and, owing to the fact that they can be turned on or off at will, their special suitability for heating rooms which are used for short periods only, the householder, guided by considerations of initial cost, will in the vast majority of cases continue to use coal fires until either legislation forbids him to do so or the prices of gas and electricity are substantially reduced. The importance of securing the greatest possible economy in the burning of solid fuel in ordinary open grates is therefore indicated. APPENDIX AN ACCOUNT OF THE WORK HITHERTO CARRIED OUT IN RELATION TO THE FOLLOWING DOMESTIC HEATING APPLIANCES—GAS FIRES AND OPEN FIREPLACES This brief account of the investigations which have been carried out up to date on this subject was prepared by the writer for the Air Pollution Advisory Board of the Corporation of Manchester, with the object of indicating what work has been undertaken in this direction up to the present time, so as to form a guide as to the future investigations and researches necessary. While the abstract cannot, in the nature of things, be complete, it is hoped that the account given does cover the principal work done, and will therefore be of service not only to the Air Pollution Board, but also to others intending to carry out similar researches. THE COMBUSTION OF COAL AND GAS IN HOUSE FIRES By J. B. Cohen, Ph.D., and G. H. Russell, AI.C. (Journ. Soc. Chem. Ind., 1896, p. 86) The average percentage of soot in 12 analyses, estimated by aspirating the ces gases through weighed and dried cotton-wool, was 64 per cent on the carbon urned. Comparisons of the heating effects of coal and gas fires were made with refer- ence to: (1) The rise of temperature of the air in different parts of the room. (2) The heating effect by radiation as determined from the readings of thermometers - suspended a yard away from the fires. (3) The dryness of the air. (4) The draught into the chimney. It was found that with a coal fire the heating was done mainly by radiation, the temperature of the room air being little increased. With old-fashioned gas fires the room air was rapidly heated, but a ‘“‘ modern ”’ fire heated by radiation. . It was thought that a coal fire produced a much more rapid exchange of air in the room than was generally necessary, disagreeable draught being caused near the ground, whilst ventilation was really needed at the ceiling. Gas STOVES: REPORT UPON AN EXPERIMENTAL ENQUIRY RELATING TO THEIR THERMAL EFFICIENCY AND TO HYGIENIC CONSIDERATIONS Carried out for the Coal Smoke Abatement Society by J. A. Owens (The Lancet, Nov. 17, 1906) The rooms in which the tests were carried out were all of approximately the same capacity, i.e. about 4,000 cubic feet, with unplastered brick walls, floors and 75 76 APPENDIX ceilings of coke breeze concrete, no flooring boards being in position. Each room had one window, which was kept closed, but half an inch clear space was left on the latch side of the doors. There was no furniture in the rooms. The flue was 69 feet high. ; Each stove was tested continuously for eight hours, the gas pressure being kept at I2/Io inch. : Thermal Efficiency of the Stoves.—The following data were obtained : (1) The number of cubic feet of gas burned. ) The composition and calorific value of the gas. : ; ) The temperature of the air in the corridor whence air was admitted to the room. ) The temperature produced in the rooms under test : . (a) 6 feet above the floor and 6 inches from the wall opposite the fire. (b) 18 inches below the ceiling in the centre of the rooms. . (c) 6 feet in front of the fire and 6 inches above the floor exposed to the radiant heat. (5) The temperature of the flue gases issuing from the top of the flue. (6) The percentage of carbonic acid in the flue gases. ; 7 x (7) The velocity of the upward current in the flue, as determined by the ‘‘ smoke ”* test. I (2 (3 (4 All temperatures were taken half-hourly, and analyses of the air of the room were also made. The majority of the stoves tested were those with clay ball fuel or Bunsen burners with glass chimneys. The efficiency of the stoves was expressed as the percentage of the total heat. of the gas burned which was given to the air of the room, and was calculated from the difference between the inlet temperature and the ‘‘ steady temperature of the room.” This efficiency varied from 0-6 to 3-6 per cent of the totalheat. The percentage heat lost in the flue gases varied from o-1 to 23-0 per cent of the total. The remaining heat, from 75 to 98 per cent, was supposed to be given to the walls, etc. of the building. The “ Smoke Test.” —The investigators did not rely much on the carbon dioxide test, but designed what they called the smoke test, which is really an experimental determination of the velocity of the gases in the flues. The test was carried out as follows : Packets of ten grains of gunpowder in tissue paper were inserted into the top of the stove on a wire and lighted. The time intervals between the lighting of the powder and the first and last appearance of the powder at the top of the flues were measured by means of a stop-watch, and the average of the two was taken to represent the time taken by the smoke to traverse the length of the flue. Tests of the volume of the flue gases passed were made on several stoves : (1) Under ordinary conditions, having no opening for admitting air to the main flue except through the stove; and (2) With the plate closing the main flue removed, admitting an induced draught round the stove flue. The results showed an enormous difference made by opening the main flue at the bottom. The volumes of the flue gases in cubic feet passed per hour in four stoves were: 1,952, 9,431} 4,031, 11,592; 3,817, 13,928; and 1,467, 9,780 ; under conditions (x) and (2) respectively. There was a tendency for a localised current of air to be established near the floor from the door or inlet to the stove, the surrounding air not being changed at anything like the same rate. This was demonstrated by igniting about ten grains of black gunpowder in the middle of the room ; as the smoke cleared away it was seen to linger in the parts of the room out of the way of this direct current. APPENDIX 77 It was concluded that a properly constructed gas fire, with a flue large enough to carry away all the products of combustion is quite satisfactory from a hygienic point of view, and does not in any way vitiate the air of the room nor does it produce any abnormal drying effect. THE TESTING AND HYGIENIC EFFICIENCY OF GAS FIRES By J. H. Brearley (Journal of Gas Lighting, June 25, 1907) Testing for Radiatton.—‘‘ As an improvement on thermometers pure and simple, rectangular vessels—termed radiation calorimeters—were used. The side facing the fire was blackened to assist absorption, and the calorimeters were filled with water, provision being made at the top for the insertion of a thermometer. These were placed 2 feet 6 inches away from the fire in several positions, and the tempera- tures were observed on lighting the fire and six hours afterwards, care being taken before the last reading to agitate the water thoroughly. Though fairly comparable results were obtained the method was crude, cumbersome, and open to the same objection as applies to the use of simple thermometers, namely, cold currents striking the reverse side. e “ Attention was then directed to the thermopile and galvanometer, which proved quite satisfactory. The thermopile used was of the Rubens linear type, and connected to one of Paul’s single-pivot moving coil galvanometers. “When considering the flue type of gas fire, one is chiefly concerned with the radiation which may be recorded in the half circle described by a number of people sitting round it. Such a half circle, radiating from the centre bunsen of each fire, was marked out on the floor three feet distant from the fire. On the line of this half circle seven readings were taken of each fire. In each of the positions care was exercised to obtain the maximum vertical reading by adjusting the thermopile. This point was invariably in the horizontal plane of the hottest part of the fire.” A number of comparative figures for the radiation from gas fires under different conditions were obtained, reduced to a common standard of 100 cubic feet consump- tion of gas with calorific value 600 B.Th.U. gross. GAS FIRE TESTS: RADIATION | _ Fire. Condition of Fire. enue % | | D_ | Bunsens only 50 D Iron frets 136 | D Fireclay balls | 125 H Air tubes at back. Fuel depth, 53 inch 44 H 3 inch tile at back. Fueldepth, 5inch | 59 H 44 inch tile at back. Fuel depth, 34 inch | 75 | H 6 inch tileat back. Fueldepth,2inch | g2 The tests on Fire ‘‘ H ” show the advantages of small depths of fuel. Testing for Heat carried away in the Waste Products.—‘‘ Attention was then directed to abstracting the heat from the products, and a Wilson’s circulating water-heater was adopted. Though the waste products when passed through the circulator were not brought down to the initial temperature, it was possible by calculation to estimate the heat remaining in the products at the outlet. The 78 APPENDIX highest temperature recorded at the inlet to the calorimeter was 737° F., and there was no difficulty in reducing this to 122° F. at the outlet. : “Consideration was given to three methods of ascertaining the units of heat remaining in the gases after passing through the calorimeter : (1) To measure the speed by an anemometer, and the temperature by a thermometer. (2) To analyse the products for carbon dioxide, and calculate therefrom the number of cubic feet passing per hour. . eet os (3) To calculate the number of cubic feet passing from the reduction in the temperature effected by the calorimeter, and the units of heat recovered thereby. It was concluded that (3) was the most reliable.” The total flue heat in various fires ranged from 8 to 33 per cent. ; Testing for Heat of Convection.— A hood was constructed of wood, ¢ inch thick, with joints carefully made tight, and the inside lined with } inch asbestos sheets. The flue pipe passed under a 6 inch slot at the back of the hood, the remaining space being made up with asbestos. An anemometer and thermometer were placed at the outlet of the hood.” ees The heat lost, expressed as a percentage of the total, varied in different tests from 18 to 50 per cent. . It was remarked, however, that in every case a considerable proportion of the products joined the stream of air up the hood, and it was suggested that “ either the hoods and canopies of gas fires are wrong‘in design or the flue outlet is too small, or both.” The fires tested were representative of most of the types in use. The possibility of carrying out tests for radiated heat, flue heat, and convected heat simultaneously was suggested by the experimenter. It was decided that gas fires when properly constructed and kept clean do not produce carbon monoxide. 7 In a note on Mr. Brearley’s paper, Messrs. H. A. Des Voeux, M.D., and J. A. Owens, M.D., A.M.I.C.E., write: . “We have come to the same conclusion as Mr. Brearley, that up to now the thermopile and galvanometer give the most reliable comparative results. In tests on solid smokeless fuels we find the maximum reading of the galvanometer was on a line at 45° to the horizontal, whereas Mr. Brearley found the maximum at the horizontal.” Mr. Brearley, replying, pointed out that the latter was due to the fact that the surface of the gas fire is vertical, while that of a solid fire varies, say from horizontal to 45°. REPORTS OF THE GAS HEATING RESEARCH COMMITTEE OF THE LEEDS UNIVERSITY, I9g09 AND IgIO The object of the work, which was carried out by Mr. E. W. Smith, M.Sc., was to make a scientific investigation of the efficiency of the gas-stove as a heating appliance. The measurements included the determination of : (a2) The total energy radiated from the stove. (0) The effect on the radiation of changes in the volume of air passing through the room and up the flue. - (c) The extent of the so-called “ drying ’’ of the room air where gas fires are used. (2) The extent of the vitiation of the air caused by open gas fires. (e) The amount of heat passing directly up the flue and not available for heating the room. (f) The amount of carbon dioxide found (z) in the room and (2) in the flue. APPENDIX 79 . The amount of heat used in warming the air of the room. h) The volume of air that might be raised from 45° to 60° Fahr. by the heat available in the stove. ‘(t) The effect of using a reflector. ) (j) The effect on the heat lost to the room, of changes in the volume of air passing up the flue. The experimental room was 9 feet by 9 feet, with an air capacity 710 cubic feet, Jo. nq 76° 50 : 50° 3Y 30 10) ' 10° ee ne t Tare ae = ‘|—- -& : - : E i. v ‘ Cc . {D \ 46 10° 30 30° 50 50° 7¢ 70° s ‘DIAGRAM 40. and was built with special non-conducting walls and floor. Air was admitted through movable panels ro inches square at the top and back of the room ; and the products of combustion were carried away through a sheet copper flue wrapped with asbestos board. The rate of air change in the room was determined from measurements of the carbon dioxide and carbon monoxide in the flue gases. ; The method for determining the percentage of energy radiated as heat con- sisted of two parts: (1) A 12 inch square radiometer was used to obtain a number of calories representing radiant energy falling on the face of the radiometer at a point 34:4 inches from the centre of the fire. : (2) By means of a thermopile attached to a delicate galvanometer, an observation was taken at the centre of this area and at 80 other points on the surface of an imaginary hemisphere of radius 34°4 inches, with its centre at the centre of the fire. The semi-circumference of a circle of radius 34:4 inches is 108 inches. This can be divided exactly into nine lengths of 12 inches, each of which subtends an 80 APPENDIX angle of 20° at the centre. The surface of the hemisphere was therefore divided into 8r areas by lines of “latitude”? and “longitude” at intervals of 20° (see Diagram 40), and thermopile readings taken at the centre of each area were assumed to represent the mean value of the radiation over that area. From these readings the ratio of the total radiation through the surface of the hemisphere to the central reading, the ‘‘ distribution factor,” was obtained. The centre reading, as given in absolute value by the radiometer determination, was then multiplied by this factor to obtain the total heat absorption in absolute value. This, expressed as a percentage of the total calorific value of the gas burned, is the “ radiant efficiency ”’ of the fire. It was concluded that the total radiation from a gas fire was about 32 per cent, and that this was unaffected by the amount of ventilation through the room, while about 30 per cent passed directly into the flue. The flue loss varied with the volume of the air passing. There was no necessity for the products of combustion to escape into the room. 1g10.—A further report was issued in IgIo. _ The radiant energy of different stoves was found to vary from 37 to-43 per cent. Meker and large Bunsen burners were found to radiate about 14 per cent of their total energy. Experiments also showed that for a given gas fire there was a gas consumption which gave a maximum radiation, and that increase or decrease in the consumption decreased the radiant efficiency. Increased efficiency was found to result where the fuels were dipped in copper nitrate solution, giving a deposit of copper oxide after baking. The Leeds method of measuring radiant efficiency has been subjected to con- siderable criticism. The radiometer used for the central reading was designed by Proféssor R. H. Smith, and consisted of a number of heat-absorbent tubes of rect- angular section which were coated with lampblack and packed closely together, giving an absorbent surface of 12 inches square. A blackened sheet of iron pro- jecting outwards for about 6 inches protected the face of the tubes from draughts. The heat absorption was determined from the rise of temperature of a steady stream of water which was circulated through the tubes. The thermopile used was of the Rubens type, and consisted of twenty junctions of iron and constantan wire. In order to obtain sufficiently large deflections the thermopile was used with a reflecting cone. The use of the latter, and the conse- quent narrowing of the angular aperture, throws some doubt upon the accuracy of the readings. The criticism of various workers is summed up in some remarks by Professor Bone :—+ (1) The R.H.S. radiometer is liable to various small indeterminate errors, inherent in all such water calorimeter radiometers, due principally to: (a) imperfect absorption of radiation by the blackened surface ; (b) the effects of lag, which, if the experimental conditions remain the same, may be disregarded ; (c) the difficulty of carrying out a satisfactory “ blank’ experiment to determine the allowance to be made in the actual test for heat gained by the instrument from the surrounding warmer atmosphere. (2) It is practically impossible, owing to the large surface of such a radiometer, to standardise its readings from a known absolute source of radiation, (3) The time taken to complete both the radiometer (‘‘ blank” and actual) tests, and the eighty-one thermopile readings required to establish the distribution factor, is considerable, and there is always a risk of some alteration in the experimental conditions during the test, which would affect its result. 1 Proceedings Royal Society, Feb. 15, IQI5. APPENDIX 81 (4) There is also perhaps a little uncertainty about the absolute value of the “ distribution factor ”’ as determined by the Rubens thermopile used in the Leeds method. Inefficient insulation of the framework of the instrument and the projecting draught screen also interfere with the utility of the R. H. Smith radiometer. SoME PRACTICAL ASPECTS OF RADIATION By J. G. Clark ~ (Journal of Gas Lighting, April 26, 1910) A Radiation Calorimeter.—This calorimeter consisted of a thin tube of 30 gauge copper, 54 inches high and 2 inches by 3 inch internal section, suspended in a frame at the top of a stand in such a way as to prevent heat passing into it by conduction from the stand. Water was led into the tube at the bottom and passed out at the top into a funnel switch. Thermometers, graduated in tenths of a degree centigrade, were fitted at the top and bottom of the tube to indicate the temperature of the inlet and outlet water. The instrument was arranged so that one of the broad faces of the flat tube was turned towards the fire under measurement. This side was lamp- blacked in order to give a heat-absorbent surface, and the opposite side was polished. The instrument was placed successively in different positions on the surface of an imaginary semi-cylinder whose vertical axis passed through the centre of the fire, and readings were taken with the blackened surface alternately screened from and exposed to the source of radiation. HEATING BY RADIATION By M. Lucien Bertin Abstract of a Paper to the Société Techniques (Journal of Gas Lighting, July 19, 1912) The work done generally was discussed. It was mentioned that E. W. Smith obtained 18 per cent radiant efficiency for a batswing burner. M. Gueguen had showed that the amount of radiation from Bunsen flames was about 71 per cent of that from luminous flames. Von Helmholtz had found that 5 per cent of the total energy was radiated from Bunsen flames. Callendar with a Meker burner found 15 per cent radiation. M. Bertin with gas fires of various types had found radiant efficiencies varying from 24 to 53 per cent under best conditions ; the efficiencies varied with the gas rate. He concluded that reflectors increased the radiation from 2 to 6 per cent. The importance of the direction in which the radiation was thrown was pointed out. 1 See H. Hartley, Journal of Gas Lighting, Nov. 11, 1913. Vide also Feb. z, 1915. 82 APPENDIX Tue RADIATION FROM FLAMES AND THE WELSBACH MANTLE By E, J. Evans, B.Sc. A Lecture to the Manchester and District Junior Gas Association (Journal of Gas Lighting, Nov. 12, 1912) Temperature radiation laws and the distribution of energy in the spectra of various flames were discussed. COAL AND GAS FIRE RADIATION By W. H. Y. Webber (Gas World, February 15, 1913) The figures given by Mr. Darling with respect to the relative temperatures of coal and gas fires were criticised; it was thought that although coal fires might attain a maximum temperature of r000° C., yet on account of their often being dull the average temperature was probably lower than that of gas fires with upright radiants. Comparison of a coal fire burning about 2 lbs. of coal per hour and a gas fire with the cock at “half”? and burning about 25 cubic feet per hour was made by means of an instrument in front of the fire attached to a galvanometer. The two fires were in similar grates and the comparisons were made on days of similar meteorological conditions. It was found that after the first two hours the radiation from the gas fire was approximately uniform, but that from the coal fire was very irregular, showing minima immediately after mending. The radiation from the gas fire was considerably greater than that from the coal fire. From the point of view of air heating, Mr. Webber found that there was nothing to choose between the two fires. Gas FIRES By William Thomson, F.R.S.E., FI.C., F.C.S. Manchester and Salford Sanitary Association, May 26, 1913 Measurements of the radiant heat from gas fires were made with an ordinary circular tin box of 8% inches circumference by 2} inches deep. This was filled with water and placed one yard from the fire under test, the exposed surface of 12 square inches being coated with lampblack. The water was well stirred and its temperature taken with a delicate thermometer before being placed in position, and again fifteen minutes afterwards. _ The difference of the two readings was a measure of the heat absorbed. : Mr. Thomson found that a fire with upright trellis-work burners gave, for the same volume of gas burned, two or three times as much radiant energy as fires in which were fireclay lumps heaped up in such a way as to resemble coal fires. RECENT PRoGRESsS IN GAS FIRE SCIENCE H. James Yates, F.C.S., M.I.Mech.E. at the British Association, 1913 (Engineering, October 10, I9QI3) ___ The results of tests of gas fires made in Mr. Yates’ own laboratories by determina- tions of the radiant efficiency, using the Leeds method, and of the amount of heat APPENDIX 83 lost through the chimney flue were given. The difference between the total amount of heat developed by the combustion of the gas, and the sum of radiation and flue loss was attributed to convection. The fires were tested (1) with the canopy well raised above the radiants, and (2) with the canopy brought down to the top of the radiants. The lowering of the canopy resulted in a lower radiant efficiency and a lower total heating efficiency, due to the cooling effect exercised by the air drawn over the radiants on the latter. With the canopy normal the mean radiant efficiency, as determined by the experiments, was about 48 per cent, the flue loss 31 per cent, and convection by difference 21 per cent. A table was given showing the efficiency results obtained for different-sized modern gas fires attached to a chimney 30 feet high. In these tests the canopy of the fire was well above the radiants. The Table shows the efficiency results for different-sized modern gas fires attached to a chimney 30 feet .high, with canopy well above radiants. Percentage of Net Heat of Combustion. Fire Width. Consumption. Temp. of Flue. Inches. Cubic Feet, Cases in °C. | Radiated. Lost in Flue Gas. Convected. | 0 25°24 | 117 47°8 30°8 214 14 34°02 104 503, 30°7 190 17 42°62 Log 49°2 29°4 21°4 21 52°90 IOI 510 26°4 22°6 The radiation figures were corrected for convected heat absorbed by the radio- meter, which amounted to about 5 units. The assumptions adopted by Mr. Yates in his calculation of convection have, however, been criticised. THE GAS FIRE By H. Hartley, M.Sc. (Journal of Gas Lighting, November 11, 1913) In the Leeds method there are two assumptions : (t) That the thermopile readings taken at the centre of each of the areas represent the mean density of heat over the area. (2) That the radiant energy falling on the areas is proportional to the thermopile readings and to the size of the areas. Mr. Hartley found that thermopile and radiometer readings at the centre and at 40° east on the Equator were not strictly in the same ratio, the difference being about one per cent. : . He also found that owing to the warming up of the “cold’’ junction of the thermopile, the centre reading altered with time, and central readings taken at the beginning and end of a complete test gave distribution factors which varied by 3% per cent.. ; Mr. Hartley found, on examination of results which had been obtained from a large number of gas fires, that the distribution followed a cosine law so closely that results given by multiplying the observations along meridian o° (after the corrections 1 See H. Hartley, Journal of Gas Lighting, Nov. 25, 1913. 84 APPENDIX i ich i i ine different for area had been applied) by 5-76, which is the sum of the cosines of the nine angles pe to Vn points in the horizontal plane at which observations are generally taken, was accurate within one or two per cent. P : Some preliminary criticisms of the R. H. Smith radiometer were also advance Chimney Pull and Radiant Efficiency —Fires were tested by the Leeds method : 1) When subjected directly to the full chimney pull; and (3 When the products of fl baatien were passing away under a large hood connected to the chimney. A fire in which the distance from the bottom edge of the canopy to the top of the fuel was 42 inches showed a diminution of radiant efficiency of only 0°5 pet cent when the chimney pull was very largely increased ; with the canopy only 2} inches away from the fuel, however, a loss of nearly 5 per cent was shown. It was also stated that this high canopy fire was so constructed that all products of combustion passed through the flue outlet when the appliance was set burning in the middle of a room without the aid of any chimney pull, an advantage not obtainable hitherto with a high canopy fire. ay Mr. Hartley considered that the flue loss under average conditions would approximate to 25 per cent, but it varies with the chimney pull. Any increase should be at the expense of convected heat and not of radiant heat. a With a fire fitted as is done in many cases, that is, in front of an existing coal grate, without the surrounding space obstructed, the energy passing into the room as convected heat is considerably lower than would be calculated on the assumption that all the heat which was not radiated and did not pass away through the flue nozzle was given to the room as convected heat. . Effect of Copper Nitrate Solution on the Radiants.—‘‘ The Gas Heating Research Committee in their report indicated that the dipping of a clay radiant into certain solutions would increase the efficiency of the fire. We were unable to confirm their results, and found that on taking the radiants out of a given fire, immersing them in a strong solution of copper nitrate, drying, igniting, and then re-employing them, we did not in any way increase the efficiency of the fire.”’ ; Silent Gas Injector—An appliance designed to eliminate the hiss generally associated with the gas fire, and due to the passing of the gas from the supply pipe to the burner, was described. THE INFLUENCE OF FLAME ON THE HEATING EFFICIENCY OF COAL FIRES By G. E. Foxwell (Journal of Gas Lighting, Dec. 23, 1913) The variation with time of the radiation from a coal fire burning in an ordinary house grate was obtained from the readings of two thermometers suspended about 2 feet away from the front of the fire. One of the thermometers passed through the cork, and was enclosed in the bulb, of a glass flask, and so protected from draughts and convection currents but exposed to radiation; the other was entirely un- protected. The thermometers were both found to give their maximum readings while the volatile matter in the coal was burning ; the minimum readings occurred just after stoking. The thermometer in the flask read from 2° to 6° C. above the unprotected one. APPENDIX 85 TENTH REPORT OF HAMBURG VEREIN FUR FEUERUNGSBETRIEB UND RAUCHKAMPFUNG, IQI5 This included a report of investigations upon domestic heating appliances. A NEW RADIOMETER FOR GAS FIRE TESTING (Journal of Gas Lighting, February 9 and March 30, 1915) This communication from the Richmond Gas Stove Company was divided into two parts. Part I. consisted of a detailed examination of the R. H. Smith radiometer, as the result of which it was concluded that the instrument is not suitable for use in the Leeds method of gas fire testing. Part II. contained a description and examination of a radiometer suitable for the Leeds test. 7 The radiometer designed by Mr. H. Hartley, M.Sc., con- f sists of a rectangular block of brass, one face of which is cor- : rugated and coated with lampblack. This absorbing block is suspended in the enclosure formed by a double polished metal case, and maintained at a steady temperature by the circulation of a stream of water through the latter. The case is provided with an opening 6 inches by 6 inches, through which the blackened face of the brass block is exposed to the source of radiation. A small hole drilled in the block along a vertical axis and filled with mercury to ensure sufficient heat contact, contains the thermometer bulb, the projecting stem of the | |' thermometer being shielded by a vertical strip of polished metal. (See Diagram 41, in which A is the metal block, B the thermometer in mercury, D the water jacket, E the opening 6 inches by 6 inches, F a double screen, and I the thermometer shield.) The apparatus is placed in position opposite the centre of the fire under examination, the absorbing block being protected by means of a double screen of polished metal. Temperature readings are taken at suitable intervals, alternately with the screen in position and removed. - The latter readings give the rise of temperature of the block due to the radiant energy | absorbed from the fire, the former the correction which must 5. oo. ay —The be applied to compensate for the transmission of heat from Richmond eae the block to the cooler surroundings. In such an instrument there will be a slight lag depending upon the thickness of the block, its mass and specific heat, its conductivity, and the rate and mise of temperature. A slight lag may also be present in the thermometer. Central readings from a gas fire, taken with varying times of exposure and increasing temperature of the block (and therefore increasing cooling correction) did not vary by 1 per cent from the mean, nor did large variations in the rate ot water-flow through the enclosure affect the results. In a later paper, ‘‘ Gas Fire Development, 1913-1915,” Mr. Hartley gives as the radiant efficiency of a 10-inch Bow Fire obtained by the above method, 44-8 per cent. For other gas fires he obtained values ranging from 44 to 53 per cent. The gross heating effect of the majority of the gas fires in use he considers to be less than 60 per cent, the amount of convected heat being in the majority of cases less than 10 per cent. 86 APPENDIX SCIENCE IN THE DEVELOPMENT OF GAS HEATING By W. R. Twigg (Institution of Heating and Ventilating Engineers, February 9, 191 5) Since rgro a test had been in use in the Davis laboratories in which no attempt was made to determine the total radiation thrown forward by a gas fire, but rather to measure a constant proportion of the whole, missing only those rays which are of least value when the fire is fitted and working under household conditions. A radiation calorimeter, consisting of a large blackened surface composed of a number of gilled copper tubes, was so arranged as to receive upon its surface a large and constant proportion of the radiation from a gas fire. The tubes, being placed vertically, were by virtue of their construction shielded from the effects of vertically moving convection currents. . A constant flow of water was passed through the tubes, the inlet and outlet temperatures being recorded. : The apparatus was placed centrally in front of the fire with the central burner 3 inches from the face of the gilled tubes, and the water-flow was so adjusted that the mean temperature of inlet and outlet was about equal to the room temperature. When steady conditions were reached readings were taken at frequent intervals. A very large number of tests showed that the results obtained by this method when multiplied by 1-27 gave a close approximation to the results from tests made with the thermopile and radiometer. A Hemispherical Water-flow Calorimeter.—This instrument, designed by Mr. T. Glover, consists of a hemispherical vessel made from two concentric copper hemi- spheres of diameters 18 inches and 184 inches respectively, each having a turned- over flange by means of which the two are bolted together and supported. Water is led into the radiometer at the bottom and leaves at the top, means being taken to ensure that it shall flow evenly over the whole surface before leaving by the outlet pipe at the top. Thermometers are provided at the water inlet and outlet, the heat absorption being determined in the same way as with other designs of water-flow radiometers. Mr. Glover found that a factor of from 1-28 to 1-32 was needed to correct the results to Leeds test equivalents. Work of Mr. John Bond, Engineer to the Southport Gas Undertaking.—Mr. Bond has been the originator of many forms of instrument for the measurement and comparison of the radiation from gas fires. Unfortunately, however, no complete account of his work has yet been published. In his laboratories Mr. Bond has used an ingenious method of determining the radiant efficiency of gas fires, which is based upon photometric principles. Having measured the radiation of one gas fire by other means, the latter is used as a standard, and is placed at one end of a long graduated horizontal bench. At the other end is placed the fire under test. A large, specially-constructed rect- angular thermopile, some 18 inches square, with exactly similar sets of junctions on the two sides, is placed between the two fires, and is adjusted until the galvano- meter deflection is zero. It follows then that each set of the thermopile junctions is ered heated, and that therefore the radiant heat received from the two fires is equal. Assuming this radiation to be inversely proportional to the squares of the relative distances of the fires from the thermopile, the amount received from one fire can easily be calculated in terms of that received from thé other. One being known, the other can be determined. APPENDIX 37 The accuracy of the results obtained by this method is directly dependent upon the validity of the ‘inverse square law” assumption. For a point source this latter is strictly obeyed, but for finite sources it holds only at distances beyond a certain point from the fire. Moreover, when as here, the measuring instrument intercepts a proportion only of the total heat radiation, the necessary distance depends also upon the relative areas of thermopile and radiating surface. The method, however, being differential, is not liable to errors due to incomplete absorp- tion by the thermopile surface. Another instrument, of the water-flow radiometer type, designed by Mr. Bond, takes the form of a segment of the surface of a hemispherical body, falling between two lines of “longitude ’’ 30° apart. The main absorbing surface is coated with dead black paint, the outer surface with lagging. The calorimeter is mounted with its axis vertical and with the centre of the hemisphere at the centre of the fire under test, and can be rotated from “ east” to “‘ west ”’ into different positions. -A constant flow of water is maintained through the calorimeter, the difference between its inlet and outlet temperatures, which is measured by means of a thermopile, giving, in conjunction with the rate of flow, a measure of the heat absorption. By taking readings in different positions the total heat emitted into the room is determined. A similar segment calorimeter has been used in the Davis Company’s labora- tories, but instead of taking separate readings in different positions the instrument was made to rotate slowly about a vertical axis. The water-flow was adjusted so as to bear a constant ratio to the volume of gas burned. A delicate thermocouple was used to measure the temperature difference between inlet and outlet streams, the “cold” junction being in the former, the “hot” junction in the latter. Arrangements were made to secure a photographic record of the galvanometer deflections in the form of a polar diagram showing the distribution of radiation around the fire in heat units per cubic foot of gas burned. From this the total radiation and radiant efficiency were calculated. It was proposed to take check readings with the axis of the apparatus horizontal. A BoLoMETRIC METHOD OF DETERMINING THE EFFICIENCY OF RADIATING BopIikEs By W. A. Bone, F.R.S., H. L. Callendar, F.R.S., and H. James Yates (Proceedings of the Royal Society, February 15, 1915) The method consists in substituting for the thermopile used in the Leeds method a simple bolometer in which the radiation falling from the fire upon a blackened coil of platinum wire was deduced from the increase of electrical resist- ance of the latter, the area of the bolometer being sufficiently small to allow of its being standardised directly from a source of radiation of known intensity. The constant of the bolometer, giving the intensity of radiation in terms of increase of resistance, was determined by comparison with a radio-balance. In the latter the radiation to be measured is admitted through a small circular aperture and received in a blackened copper cup, in which the absorption is practically complete. The heat received from the radiation is balanced by absorption of heat due to the Peltier effect in a thermo-junction through which a measured current is passed." The bolometer is constructed in the following manner: ‘‘ Two exactly similar coils of platinum wire, each 4 centimetres square and of 20 ohms resistance, are 1 See “A Radio-balance for the absolute Measure of Radiation,” by Professor H. L. Callendar, F. R.S., Proceedings Physical Society, Dec. 1910; The Electrician, March 17, I9It. 8g APPENDIX d back to back on either side of a circular gun-metal box provided with Sa and with suitable covers for the colls, so that either coil can be exposed to radiation or screened. When both coils are screened they - ea at the same temperature as the box; their resistances remain equal; an a ere is no deflection of the galvanometer however much the temperature of the a may change. But if one of the coils is exposed to radiation its temperature an a ance are increased by an amount depending upon the intensity of the radiation, and the galvanometer shows a proportional deflection. (See Diagram ) An advantage of this apparatus is the fact that by attachment to a Callendar Recorder an automatic record of the readings made can be kept for reference. | pe LT herman iter | Cele SS 4 Mabe Cham ber Water Infer —ELEVATIo N— —Sectrion— DiacRram 42.—The Bone-Callendar-Yates Bolometer. Distribution Factor.—For the distribution factor the central reading and four readings at 60° along the Equator and meridian were taken in place of the 81 of the Leeds test, the distribution factor being represented by the sum of the five readings 2 multiplied by "= and divided by the central reading, where R is the radius of the hemisphere. This “‘ short-cut’ method is applicable onl The “ distribution factor” as determined (x) Rubens thermopile, for the same 10-inch g y to certain types of fire. by the bolometer, and (2) by a APPENDIX 89 244 cubic feet per hour (at N.T.P.) gave a mean radiant efficiency of 45 per cent, the figures in individual determinations varying from 43-2 to 46-6 per cent. SECOND REPORT OF THE JOINT COMMITTEE ON VENTILATION RESEARCH OF THE INSTITUTION OF ENGINEERS AND THE UNIVERSITY OF LEEDS, JUNE I, I915 The Work was carried out by W. Harrison, M.Sc. The experimental room fitted up at the Leeds University was used for a series of experiments directed to ascertaining the volumes of air moved under the most favourable conditions by a gas fire. Numerous tests were made in the experimental room with various types of gas fires. The fires were joined to the flues by means of an adapter, and all joints were cemented up tight. The fires were adjusted to burn about 25 cubic feet of gas per hour, the makers having been requested to supply fires burning this amount. Determinations were made of the volumes of gases passing through the flue for several areas of inlet. Asa rule no tests were made until two hours after lighting a fire, this being the time required for the temperature conditions to become steady. Tests made with the door closed and the area of inlet increased showed that up to 12 inches by 12 inches increased ventilation was produced. This opening corresponds with 6 square inches of inlet per cubic foot of gas burned per hour in the fire. Greater inlets, such as obtained by opening the door, did not produce any increase in ventilation through the flue; in fact, in most cases the figures decreased. This is due to the fact that some of the radiant heat becomes effective in heating the air within the room, and some of the heated air escapes when the door is opened. In order to get the best ventilating effect from a gas fire it appeared to be necessary that the canopy and flue vent should offer as little resistance as possible to the flow of the flue gases. VENTILATION BY GAS FIRES Ventilation Volume in Cubic Feet per Hour, for Inlets. Gas Fire. 4 hae Bate a” Cabie’ Reet ; : Sq. Inches. per Hour, 12 in, x12 in, 6 in. x 6 in. 3 in.x3 in. No. I 8°5 30 24°3 2230 2040 1620 25°2 2259 2070 1620 No. 2 12'0 20 23°1 2290 2190 1720 24 24'1 2450 2180 I7IO No. 3 I2°5 18 23°6 2520 2280 1690 23°0 2480 2210 1680 No. 4 I4'l 22 26°1 2960 2560 1800 25°4 2810 2560 1760 No. 5 II'5 28 14°8 2950 2630 1860 48 24°4 2930 ee wae No. 6 17'4 15 24°L 3730 Bi 2020 20 24°0 3690 3240 1980 No. 16°8 24°0 090 3430 2070 oF aoe 4280 36050 2180 Experiments were made to increase the ventilating power of gas fires by making openings into the flue. In Fire No. 7 a hole was cut under the flue vent near the base of the fire. With a hole 113 inches by 9 inches the air moved was 10,000 go APPENDIX cubic feet per hour. With a hole 3 inches by 3 inches the air moved was 5,400 cubic feet per hour; with the fire without auxiliary opening, 4,100 cubic feet per hour. The gas rate was 24 cubic feet per hour. : In another case with the same fire a hole was cut from 6 to 18 inches above the centre of the entrance tube from the fire into the flue. With a hole 113 inches by 9 inches the volume of air moved was 8,300 cubic feet per hour. With a hole 6 inches by 6 inches the volume of air moved was 6,600 cubic feet perhour. With a hole 3 inches by 3 inches the volume of air moved was 4,700 cubic feet per hour. A similar experiment was made with Fire No. 1, which had the least flue vent area, and under ordinary conditions gave the least ventilating power. With the hole 113 inches by 9 inches above the flue vent the quantity of air moved was 8,100 cubic feet per hour, or nearly the same as moved by No. 7. It was pointed out that while the auxiliary opening allows comparatively fresh air to flow through it, the vent conveys products of combustion ; and since it is desirable to eject these first, the aim in the modern gas fire should be to reduce the resistance to the flow of these products. GAs HEATING AND SMOKE PREVENTION By H. J. Yates, British Association, 1915 (Engineering, October 15, 1915) In this country people had been accustomed to depend upon the open fire- grate and chimney for ventilation, but in some gas fires the flue vent and canopy were so designed as to draw a large volume of air up the flue. he ; Mr. Yates had produced a special contrivance, by which, in injector fashion, a very large amount of air was removed from the room. Briefly described, this provided two outlets to the chimney, so proportioned that by the under outlet the entire combustion products were carried off, while by the upper or ventilating outlet a large volume of ventilating air was removed. The tests on the new fires were made in an ordinary room with chimney 30 feet high, and the following results had been arrived at : The new ventilating gas fire, 11,800 cubic feet per hour. Ordinary gas fires: (a) 4,500 cubic feet per hour. (0) 4,850 cubic feet per hour. (c) 5,600 cubic feet per hour. (d) 5,000 cubic feet per hour. This shows an increase to over double the air removed by the nearest ordinary fire. One possible objection was that although the air is removed, it might take a path along the floor to the fire, the air at the breathing level remaining practically stagnant. To test this point samples of air were taken through pipes at points along three axes : (a) At right angles to the fire and 4 feet from the floor. (6) At 6 feet from the fire and vertical. (c) Parallel to the fire, 4 feet from the floor, 6 feet from the fire. Extra carbon dioxide was added to the air of the room, which was then mixed and analysed. After the lapse of a definite time, during which the fire was ventilating, three series of samples were taken. The results of the tests proved that ventilation extended along all the APPENDIX gI axes, and at least above the breathing level. Comparisons were made both with ordinary gas fires and with coal fires; the results plotted graphically showed that the ventilating fires greatly exceeded the ventilating capacity of the ordinary gas fire, and approached that of the coal fire as closely as was necessary. GaAs FIRE DEVELOPMENT, I913-I9QI5 By H. Hartley, M.Sc. (Journal of Gas Lighting, November 16, 1915) Gas Five Testing—This lecture was intended as a development of one given two years earlier. (See pages 83 and 835.) The testing of gas fires was again discussed, and reference made to the earlier criticisms of the R. H. Smith radiometer and to the introduction of the Richmond radiometer. Some results are quoted with a modified type of thermopile designed to overcome the faults of the Rubens thermopile when used for testing these appliances. It had been shown earlier that the deflection produced by the Rubens thermo- pile was affected by the length of the exposure to the fire. In this new Richmond thermopile this fault has been eliminated. A test was given showing that constant readings were obtained over a period of thirty minutes during which the instrument was exposed to the fire. The question of the effect of varying the position of the fire in the Leeds test had arisen in questions of recent discussions of a short-cut method of testing gas fires, and some experiments were cited to indicate that pro- vided that all the energy of the fire passed through the imaginary hemisphere explored by the thermopile the setting does not influence the results, although when the Rubens thermopile is used care has to be exercised in the adjustment of the range of vision of this instrument. Convected Heat and Gross Thermal Efficiency.—It is stated that some 75 per cent of the thermal energy of the coal gas is available theoretically for conversion into radiant energy. The flue loss of a fire averages about 30 per cent, the radiant efficiency about 50 per cent, leaving a balance of about 20 per cent, which it has been usual to refer to as convected heat. Mr. Hartley draws attention to the fact that an appreciable amount of energy is transmitted through the back of the fire, probably 10 per cent of the whole available energy, and he does not think that more than Io per cent of the total energy is available as convected heat. The gross heating efficiency of the majority of gas fires in use he regards as not greater than 60 per cent, and it is suggested that it may be advisable to increase this by an increase— at the expense of the flue heat—of convected heat. Ventilation.—Observations had been made on the amount of ventilation produced by gas fires in the living room, and an empirical equation was advanced for calculating this quantity. The distribution of the ventilating air between the ventilation ports and the flue outlet is represented graphically for varying sizes of the former. The main factors affecting the ventilation are summarised : . Burners.—Mr. Hartley considers that in the existing type of gas fire high aeration is neither necessary nor advantageous; the degree of aeration at present necessary is that required to prevent the sooting up of the radiants. _ Flame silence would appear to be dependent upon the elimination of objec- tionable eddies from the gas stream ; this can be done by passing the mixture down a long tube, or by making the burner body of ample size; the latter, however, 92 APPENDIX causes an explosion when the flame is extinguished. To eliminate the eddies, and if necessary give flame silence at high aeration without the firing-back trouble, the Richmond Company have introduced in the gas burner a metal grid of plates +’; inch apart. This device produces the desired result. : Distribution of Radiant Energy.—Attention is drawn to the fact that fires which are practically flat-fronted have the disadvantage that the major portion of the radiant energy is emitted in a relatively narrow zone directly in front of the fire. It is argued to be an advantage to have a more or less uniform horizontal distribu- tion of radiant energy, so as to ensure that the portions of the room to the side of the fire shall receive their quota of the energy emitted, and an appliance is described which enables this object to be achieved. ; General Remarks.—It is shown that there is a marked conservation of the radiant energy emitted by a fire if it is ensured that projecting portions such as the fender and the canopy are protected by reflectors to prevent absorption of the energy emitted by the radiants. Swiss Tests oF Gas FIRES By Dr. E. Ott (Journal fiir Gasbeleuchtung, November 1915) This investigation took account of gas heating apparatus which acted mainly by convection as well as those which owed their heating effect mainly to radiation. The fires tested were of similar size, i.e. of gas consumption 25 to 26-5 cubic feet per hour. The middle of the burners was in all cases about 12 inches above the level of the floor of the experimental room, a laboratory basement of capacity 1,765 cubic feet, with adjacent rooms on three sides, external influences being insulated from the fourth side by means of puttied-in double windows and an iron roller shutter. Radiation was measured by means of a segment water-flow calorimeter almost exactly similar to that designed by Mr. J. Bond and described elsewhere. It was, however, used with its axis horizontal, and readings of radiation through the upper- most 30° were omitted on account of errors due to convected heat received in this region. Radiation from the lowest 30° was also neglected, as it was a very small’ proportion of the whole, and difficult to measure owing to the base of the fire. The results given below were obtained : | Radiation, expressed as a percentage of the Type of Stove. Net Calorific Value of the Gas Burned, Convection Stove | 1°5 Reflector Stove 8-6 Gas Radiator | I9°7 Radiation Fire 29'I \ | Radiation Fire | 19:2 | | Convection Stove | 3°6 The distribution of temperature over the room was ascertained by means of thermometers graduated in tenths of a degree centigrade, the bulbs of some being blackened and those of others protected with rolls of silver foil. Twelve thermo- meters In pairs were arranged in two circles with radii respectively 1 and 3 metres from the fire, the bulbs being } centimetre above the floor. Six thermometers APPENDIX 93 with polished shields were also placed 5 feet above the floor with their bulbs exactly over the middle line between each of the lower pairs. The efficiency was calculated by the following formula due to Dr. K. Bunte: ¢ (ta ine i) i, ? : a Efficiency percentage I00 - I00 x 5” where is the volume of carbon dioxide produced by the combustion of one volume of gas. is the percentage of carbon dioxide in the hot, humid flue gases. is the specific heat of the hot, humid flue gases. is the temperature of the escaping flue gases. is the temperature in the middle of the room. H, is the net calorific value of the gas in calories per cubic metre. (N.T.P.) soo os The thermometers were read several times an hour in the closed room prior to an experiment to ensure that there was equilibrium of temperature conditions. The fire was then lighted and kept burning at full consumption for 55 minutes, when the observer entered and quickly read the thermometers. Five minutes later the gas consumption was reduced to one-half and a sample of air taken from the middle of the room. Two hours and fifty-five minutes later the observer again entered and took temperatures and a sample of air. The fire was then turned out, but temperature readings were continued. In the tests of temperature distribu- tion the stoves were not connected to the chimney, their total efficiency therefore being Ioo per cent. Comparative tests, however, made with chimney draught showed similar distribution. The black bulb thermometers on the I metre circle with bulbs near the floor read about 50 per cent higher than the silvered ones. (Means 12:2°C.,81° C.) At 3 metres the difference was only Im per cent. (Means 4:2° C., 3°8° C.) The fall in temperature of the silvered thermometers at 5 feet height in the plane passing through the middle of the fire was from 15-1° C. at 1 metre to 12:0° C. at 3 metres.1 TRIALS OF GAS STOVES By Professor A. von Ihering, Journal fiir Gasbeleuchtung A room of 3,170 cubic feet capacity was selected, and eight different makes of stoves, sent out as suitable for heating a room of that size, were tested. The following data were obtained : ) The consumption of gas needed to make the room warm. ) The consumption of gas needed to keep the room at a given temperature. ) The composition of the gas used. ) The composition of the exit gases. ) The loss of heat in the exit gases. ) The heating value of the gas used. ) The amount of carbon dioxide in the air in the room. ) The temperature of the room at different points. ) The mean temperature of the room. ) The degree of moistness of the air. ) The relative quantities of heat radiated from the reflector. (I The stoves were placed in the middle of the east side of the room, and nineteen thermometers were placed at different positions; temperatures were also taken in the adjoining rooms. The spent gases were analysed in an Orsat apparatus. 1 The present writer, with a coal fire, when steady conditions were reached, found at the same height means of 16-8° C, and 13-4° C. at 2 feet and 8 feet from the fire, or nearly the same gradient. 94 APPENDIX An attempt to determine the absolute value of the heat radiation, by means of a calorimeter coated with lampblack, was not successful, as heat rays issued not only vertically to the plane of emission but also obliquely, and the latter did not strike the calorimeter. . The heat loss in the flue is given as from 4-3 to 29-2 per cent for various stoves, the difference, 95-7 to 70-8 per cent, being considered as available heat. PROBLEMS OF EFFICIENT MeTHops OF Domestic HEATING By A. H. Barker, B.A., B.Sc. (Nature, December 30, 1915) It is difficult to attach a precise meaning to the term “ efficiency ” in connec- tion with heating apparatus. If we regard all the heat which is delivered into the air of a room as utilised, then the low-temperature electric stove, the oil stove, or the gas radiator which deliver the products of combustion into the room may be regarded as having nearly 100 per cent efficiency. Heat is also delivered into a room, however, by the conversion of radiant energy into heat. The temperature condition of a room is very uncertain, and difficult to ascertain. A naked thermometer in a heated room indicates nothing but its own temperature, and it is possible to obtain from different kinds of correct thermometers at the same point in a heated room indications which vary by as much as I0° or 12°. The feeling of warmth is an exceedingly complex matter, and can only be measured by a different instrument altogether, a kind of electrical calorimeter which has to be proved by physiological experiments of the most difficult character to give a true criterion of the feeling of warmth.1 As a rough practical basis of comparison between different systems of heating, we may take the relative amounts of energy necessary to be employed in a room in order to produce the same feeling of warmth, as measured by a suitably calibrated instrument, while maintaining approximately the same interchange of air. The subjoined table is based on direct experiments in this sense. 1 See Dr. L. Hill on “ Healthy Atmospheres,’”’ Nature, April 22, 1915. [TABLE. APPENDIX 95 TABLE OF EFFICIENCIES FOR CONTINUOUS HEATING Approximate Equivalents. _inetmal e Tait, ae 1,000 B.O.T. units of electrical energy, utilised — — in best radiant stove of 60 per cent radiant 100 3 a eee efficiency, disposed in the best manner. a a 1°38 tons of best house coal, 14,000 B.Th.U. per \ 8 { eel 29 Ib., burned in bad grate, unsuitably disposed 35/- 39 0°52 tons best house coal burned in best one \ 21 { 20) ue modern grate sunk in wall J 35/- ce 0235 tons best anthracite, 14,500 B.Th. U, per f lb., burned in best modern slow combustion \ 45 { 40) 754 anthracite stove J Beir 9°42 18,300 cubic feet of gas at 520 B. Th.vU. per cubic 6 : foot, burned in medium old-fashioned gas \ 36 a a0 fire (not worst type) J 3/- 44° 10,700 cubic feet of gas burned i in best modern 1 2/6 21°3 ventilating gas stove f 62 { 3/- 25°6 0-198 tons of coke, 12,500 "B.Th.U. per Ib., burned in best provided modern water boiler { 20/- 3°17 with well-clothed circulation to radiators or &2 | 30/- 4°75 pipes. 0°306 tons coke ‘burned in usual “small house 20/- 4°9 hot-water installation } 4° { 30/- 7°36 19° 3 gallons petroleum 0:87 sp. gr., 20 249 B.Th.U. per lb., completely burned in any \ 8d. 10°4 kind of stove discharging products of com- | TQ0 rod. 130 bustion into the room _ . : ‘ a [4 H! Gas FIRES AND THE INJECTOR PRINCIPLE Third Report of the Joint Committee on Ventilation Research, June 1916. Experiments were made to determine how far the injector tube principle proved valid for the gas fire. An initial comparison made between the volumes of air moved up the main flue, firstly when burning the gas in a gas fire with a vent of 17 square inches and an auxiliary opening of Ioo square inches; and in the second case when burning the gas in a ring burner in the main flue with the same auxiliary opening, and draw- ing air through the vent of the unlighted gas fire. When the gas supplies were so adjusted that the temperature in the main flue was the same in the two cases, the volumes passing up the flue, determined by analysis, were also the same. This indicated that the head in the main flue resulting from the lower density of the hot gases was the moving force in both cases, and that the velocity of the gases ae from the vent of the lighted gas fire in the first experiment had a negligible effect. The actual volumes moved up the flue were 10,200 and 10,100 cubic feet respectively. Further experiments were made in different forms. “Summarising, we have not found in any of our tests that the injector principle, as applied by leading products of combustion at nearly normal pressure along a narrow tube, with a view to their inducing a flow of air along an encircling or apposed ‘air duct, and so increasing the volume moved, has any validity.” 96 APPENDIX Volumes of Air moved by different Consumptions of Gas up Flues of Various Stzes.—The flues used were 44, 6, 9, and 12 inches in diameter, 36, 70, and 106 inches long, and were fixed in the ceiling of the experimental room. The opening into the room was 12 inches square, which offered inappreciable resistance com- pared with the 44 and 6-inch tubes, but had a considerable influence when using a 13-inch tube, about 25 per cent less air being moved than when the door was wide open. | Flue 36 inches long. Flue 7o inches long. | Flue 108 inches long. Diameter of Flue, Volume of Air Volume of Air P Gas Rate. Inches, moved, e eee moved. | oe a Volume of Air moved, Cubic feet Cubic feet a Thee Cube feet per hour: Cubic feet per hour. per hour. per hour. Z per hour, 44 1060-1650 0°7-27°0 1660-2340 I'1-28'5 2260-2840 I+5-30°5 6 2120-3360 1°4-69'0 3170-4680 2°1-63°4 4230-5770 2:8-78-0 9 dusts iis ae 4% 6050-11950 4-175 12 nate wae rae A 10600-19800 7-138 Gas FIRE CONSTRUCTION By Harold Hartley, M.Sc. (Journal of Gas Lighting, October 24, 1916) Radiants.—The Richmond Company make their own radiants, and find them better than others on the market. They endeavour to obtain as much radiant energy as possible from the radiants themselves, and are not so dependent upon radiation from the firebrick back as are some other makers. Tests on several fires made by the Richmond Company showed an average radiant efficiency of 50 per cent with their own fuel and 46 per cent with other fuel by a different maker, A fire by another maker showed 49 per cent radiant efficiency with its own fuel and 51 per cent with the Richmond fuel. Radiant Efficiency.—The radiant efficiency for a gas fire is not constant, but varies with the consumption, and for each fire there is a consumption rate which gives a maximum efficiency. Results of this effect for a 12-inch fire at high and normal aeration are given below. 7 High Aeration. | Normal Aeration. Percentage Radiant Efficiency. Percentage Radiant Efficiency. Approximate Consumption. Cubic feet per hour. | | 18 | 44°5 48°3 22-5 48-9 50°5 27 | 49°9 527 31-5 53°0 53°6 36 53°1 51-0 41-5 | 52 ! 48-7 eerste a ee Ne | With a normal aeration the optimum consumption was 314 cubic feet per hour; at 36 cubic feet per hour flames were seen to come out at the top of the tadiants ; and at 41 cubic feet per hour it was obvious that too much gas was being passed through the fire. With the highly-aerated flame, however, flames did not appear above the radiants until 41 cubic feet per hour rate had been reached. APPENDIX 97 Gas HEATER EFFICIENCIES “An American Test (Journal of Gas Lighting, November 14, 1916) The following results are given in the report submitted by the Committee on the Utilization of Gas Fuel Appliances to last month’s meeting of the American Gas Institute of a series of tests to determine the relative distribution and quality of radiant heat emitted by certain types of blue and luminous flame heaters. The test was made in the appliance laboratory of the United Gas Improvement Com- pany, of Philadelphia. The object of the test was to compare the efficiencies of various types of heaters, considering only the radiation. Neither heat of convection nor heat of conduction was measured, nor was any examination made of the quality and composition of the products of combustion. The measuring apparatus used consisted of a modification of that designed by Mr. J. G. Clark and described on p. 81. Briefly it was a lune of blackened sheet-copper, maximum width 31 inches, the circle diameter being 58 inches. This lune was backed by a lune of heavier bright copper uniformly } inch narrower, and separated from it by about 4 inch. Top and bottom pieces completed the lune so as to allow water to flow through the space thus formed. Thermometers graduated to 1° C. were placed at the inlet and outlet connections of the lune. The heater to be tested was set in the centre of the sphere, and the blackened surface exposed to the radiation. The temperatures of ingoing and outgoing water were noted every two minutes for ten minutes, together with the amount of water flowing. Then a screen was placed in front of the heater and the readings repeated, the difference being taken as heat due to radiation absorbed. Readings were taken every 30° around the heater and a curve indicative of the relative distribution of the radiation produced. The appliances used for the test include heaters of foreign manufacture as well as those of domestic manufacture. Radiant Efficiency. Number. Make. Type. Front. Back. Total. I Domestic Portable 29°2 17°9 23°5 2 Foreign i 35'8 | 25°9 30°8 3 Domestic Fireplace |. 35°7 57 30°5 4 Foreign - 64°7 I12°7 38°7 5 Domestic Portable 14'7 6-7 I0'7 6 2 9 41°8 I2°7 2752 7 i Fireplace 33°8 23°6 28°7 8 55 Portable 60°5 19°3 39'9 9 Foreign Fireplace 67-7 18'5 43°1 Io Domestic Portable 20°7 21-2 | = -20°9 No. 1 contained three radiating elements, consisting of semi-cylindrical, vertical ground- glass shells, heated by a blue flame burner underneath. No. 2 was a blue flame, portable heater, containing six radiating elements in the shape of coarse fabric mantles. -No. 3 consisted of a refractory slab heated by blast burners. No. 4 contained radiating elements consisting of vertical ceramic grids. < ao 5 was a portable reflector heater, with yellow flame burners placed near the bottom of e heater. H 98 APPENDIX No. 6 consisted of an asbestos back heated by blue flame burners under atmospheric pressure. No. 7 consisted of ‘‘ Vitreosil ’’ cylinders heated by blue flame burners. No. 8 consisted of three vertical, perforated, refractory cylinders heated by blue flame burners. No. 9 was provided with a network of refractory substance heated by blue flame burners. No. Io was a cylindrical portable heater, whose radiating element consisted of a sheet metal drum heated by yellow flame burners. METHODS OF EcONOMISING HEAT By C. H. Darling, A.R.C.Sc.I., F.C. (Journal of the Royal Society of Arts, January 17, 1913) : One of the earliest British examples of a fireplace situated at the side fa room, and provided with’a chimney, is to be found at Conisboro’ Castle, which was erected in the Anglo-Saxon period. In this fireplace the chimney consists of an opening made through the wall—and it is probable that this construction was adopted owing to the impossibility of making a hole in the roof to serve as smoke exit, as other rooms were located above. The construction of special recesses for the hearth, with flues rising to the top of the building, dates from about two centuries after the Conquest. “The fuels universally employed until the beginning of the Tenth Century were charcoal and wood. The trade in coal for domestic use throughout Britain dates from 1561.1 “Dr. Pridgin Teale may be justly regarded as the pioreer of modern improvements. “Mr. A. H. Barker has recently devised a fireplace in which the escaping heat is used to produce hot-water circulation. A tubular boiler is located above the fire and communicates with a storage tank and set of radiators. ‘‘ Measurements made on a gas fire at the City and Guilds Technical College, Finsbury, showed temperatures varying from 940° C. at the hottest part to 650° C. in the colder regions, a fair average being 750° C., the escape gases being at 275° C. The temperature of a coal fire when burning brightly is of the average at least 100° hotter, or 800° C., the hottest portions often attaining Io00° C. The radiation from a surface increases as the fourth power of the absolute temperature, and taking temperature alone into account the quantities radiated at 850° C., 750° C. are in the ratio of 1-5 to 1-0. It is evident, therefore, that a comparatively small rise in temperature would greatly increase the radiating power of the fire.”’ Mr. Darling gave the following figures for the comparative values of different forms of heating appliances : Percentage | Method. Source of Heat. B.Th.U. per rd, wens ae Room. | | i in Open fire, bad design - | Coalat 26/-perton . - 110,000 | 20° 10 Open fire, good design - | Coalat 26/- perton ~. F 110,000 35. | O57 Closed anthracite stove . | Anthracite at 42/6 per ton . 75,000 75 | 0°45 Open gas fire, best design . | Gas at 2/6 per 1,000 cub. ft. 19,000 75 I°54 Open gas fire, poor design | Gas at 2/6 per 1,000 cub. ft. 19,000 60 I'g2 Electric radiator . . | Electricity at 1d. per unit . tee roo |; 65 Si See ‘* On the Anthracite Coal and Coal Fields of S. Wales.”? C. H. Perkins (British Association, 1880), APPENDIX 99 Tests OF DoMESTIC OPEN FIRE GRATES (The Lancet, May 10, 1902, Feb. 20, 1904, and May 19, 1906) A sitting-room on a ground floor in London was selected, its dimensions being 21% feet by 144 feet by 10} feet. The chimney measured 69 feet from hearth to top. The wood used in lighting the fire, and the total coal added were weighed, the number of times the fire was stoked was noted, and waste ashes at the end of the day also weighed. Directions were given to keep the fire up to the top bar of the grate. -) Temperatures were taken every half-hour: oe (1) 6 feet from the fire and 2 feet above the floor. (2) At the far end of the room, 5 feet above the floor. (3) In the hall outside the door. These were averaged each day, and the average of (3) subtracted from the mean of the average of (1) and (2) to give the temperature rise. The mean rise per pound of coal burned was then calculated. The results of further similar tests were published in 1906. The “‘ efficiency ” of the grates, expressed as the percentage of the total heat of the coal burned which was given to the air passed through the room, varied from about 3 to 7 per cent ; the loss in the flue gases from 9 to 16 per cent ; the remainder, from 76 to 88 per cent, being disposed of as “‘ heat which is given to the walls, etc., of the room, chiefly by radiation.” The amount of carbon dioxide in the flue gases was measured in the case of the grates in the final series of tests. The volume of flue gases passed up the chimney varied from 6,000 to II,000 cubic feet per hour. The mean rise of temperature of the flue gases over the room temperature varied from 30° F. to 41° F. ON THE MEASUREMENT OF THE EFFICIENCY OF DOMESTIC FIRES AND ON A SIMPLE FORM OF SMOKELESS GRATE By A. Vernon Harcourt, D.C.L., LL.D., D.Sc., F.R.S, (Journal of Royal Society of Arts, May 7, 1915) An instrument, the “ radio-thermometer,’ was designed by Mr. Harcourt to measure the amount of heat radiated into the room from the front of the fire under test. It consists of a small rectangular, water-filled copper box, 6 inches by 6 inches by 1 inch, with a small funnel-shaped inlet, enclosed in a wooden box 7 inches by 7 inches by 2 inches, with openings at the top, and 5 inches square in the middle of one side. The space between the two boxes is loosely packed with cotton-wool for insulation. The exposed side of the inner box is coated with dull black, and a thermometer having been inserted through a cork in the inlet, is placed facing the horizontal radiation from the fire. Readings of the thermometer are taken at suitable intervals, a cooling correction being avoided by using water of a lower initial temperature than that of the surrounding air, and continuing the 100 APPENDIX readings until its final temperature is as much in excess of that of the surroundings as the initial temperature was below. (See Diagram 43.) Mr. Harcourt’s experiments were made upon a special form of grate, which conformed to the following requirements : (I) That the face of a fire should be vertical so that the chief radiation should be horizontal. (2) That the bars should be as light as is compatible with sufficient strength, and wide apart, for they do not reach so high a temperature as the glowing fuel behind. (3) The fire should be narrow from back to front. (4) Air should pass in through bars in front, not through bars underneath, for the most vivid combustion occurs where the air and fuel meet. (5) It is well to put in at once all the fuel the fire will need and to light it at the top. — Lbarcrrovereier_ T real T _ ! poiawiony pee x | ta Pl | e ' i 4 Hot = 4 ' } : Pe | | 1 fl | 4 | 1 ! I | t | | ' _ hor Wo. Hah i Ly A, a{s | = Zeb IT I | |“ i} ry wt oly rot t I | i ! ti a Ae ty ‘ee | | ! : ie H | ty be 1 : | I ih ee : Sos Sls SSS 1 I 1 € as ee * — Elevation — — Section — D1aGRAM 43.—The Harcourt Radio-thermometer. Comparative figures for the radiation from coal and coke fires were as follows: Coke, 1-97; coal, 1-63; wet coke, 1-29. A set of observations generally extended over an hour, but although the pre- caution was taken of allowing the fire to burn for some time before measurements were begun the results obtained were submitted as rough approximations only. Mr. Harcourt was of the opinion that “ bulk for bulk coal is nearly twice as heavy as coke, burns for longer under the same conditions, produces more heat and from an open fire radiates rather more heat because it lasts longer.” “Weight for weight, coke has the advantage for domestic use, and would retain it even if the price of the two were the same.” ; The design of grate advised by Mr. Harcourt was, after the first hour or so practically smokeless, even when burning ordinary bituminous coal. By that time the top layer of coal had been converted into a glowing layer of coke, through which the soot and gases from the combustion of the lower layers had to pass on : APPENDIX IOI their way to the chimney. All combustible parts were therefore burned, and the fire was then smokeless. Such a result is, of course, only possible with a specially- designed deep fireplace. Note.—Later, in a letter to the Journal of Gas Lighting, Mr. Vernon Harcourt estimated that the proportion of the total energy of combustion of coke burned in his grate which appeared as radiation amounted to 44:5 per cent. FUEL ECONOMY IN COOKING APPARATUS A COURSE OF LECTURES DELIVERED AT THE UNIVERSITY OF LONDON, UNIVERSITY COLLEGE, SESSION Ig18 By A. H. Barker, B.A., B.Sc. (The Builder, March 16 to August 2, 1918) The general problems of efficiency in the kitchen range are discussed at length, attention being paid both to the various cooking operations and to the hot-water supply. The gross cost of heat obtained directly from solid fuel is shown to be the cheapest, but the additional labour in its use is pointed out, and the enormous waste involved in its burning. Gas also is a wasteful fuel owing to the loss of heat in the air and waste products passing up the flue. With electricity there is no need for the waste consequent upon a constant supply of fresh air, but it must be borne in mind that great waste takes place at the generating station, both in the com- bustion of the fuel and in the conversion of heat into electrical energy. The follow- ing approximate figures for the destruction of coal involved in the delivery of 1,000 B.Th.U. net to the food in an oven are given : Approximate Dest: 2 Fuel. Facet C4 et race Remarks, Coal. é ; : : ‘i -| 3 percent | 2:37 lbs. No other products Gas. Ir percent | 4:48 Ibs. Valuable by-products Electricity (best possible production : 14 lbs. coal destroyed per B.O.T. unit produced) er yh . : : Electricity (best ordinary production : 2% lbs. of coal destroyed per B.O.T.) . | 21 percent | 3:48 lbs. No other products 21 percent | 1°74 Ibs. No other products In roasting or toasting by a coal fire it is doubtful whether more than 2 per cent of the total heat of combustion is utilised, and with gas or electricity the result is little better. : ; For boiling also the coal fire is very inefficient ; the efficiency of an ordinary kettle placed on a gas-ring is some 20-25 per cent, but this figure could be consider- ably increased by attention to suitable design. ' Many other points are discussed, including the causes of the waste of heat, the loss involved in burning the fuel, the waste due to the design of the range, chimney draught, etc. A sketch of an economical combined cooking and hot-water apparatus designed on new lines by the author is included. 102 APPENDIX First REPORT OF THE RESEARCH SUB-COMMITTEE OF THE INSTITUTION. OF GAS ENGINEERS ON THE EFFECTS OF GAS COMPOSITION. OCTOBER I918 The work was carried out by J. W. Wood, M.Sc., under the supervision of Professor J. W. Cobb, in the Nechells Laboratory of the Birmingham Corporation Gas Department. The investigation included the examination of the efficiency of different quali- ties of gas varying from coal-gas of calorific value 530 B.Th.U. gross (480 B.Th.U. net) and 18-7 per cent inerts to Mond gas slightly improved with coal-gas, calorific value 241 B.Th.U. gross (214 B.Th.U. net) and 51-7 per cent inerts : (1) for boiling the water in a copper kettle (contents 8 Ibs.). (2) for producing radiant energy from a gas fire. The efficiency was in both cases found to be independent of the quality of the gas used. For boiling the kettle on a gas-ring it was about 54 per cent, and did not vary with the time taken to boil the water; there was, however, a distance between the surface of the burner and the bottom of the kettle which gave a maxi- mum efficiency, flame contact being essential; xz inch was found to be a suitable distance in most cases. The results with gas fires were put forward as preliminary only, but within the limits of the investigation it appeared that, as stated, the efficiency of the fires for heating (as measured by the radiation emitted) was not dependent upon the quality of the gas used.if the fires gave a sufficient range of adjustment. A considerable drop in efficiency occurred when the fires were turned down so that less than half the radiants were heated. FuEL Economy IN PriIvATE HousEHOLDS By A. H. Barker, B.A., B.Sc. (The Builder, September 27, 1918 to February 7, 1919) The relative number of heat-units available in coal, gas, or electricity for the same cost, and the comparative efficiencies to be obtained in different types of heating apparatus, are discussed. Explanations of the different methods by which a room may be warmed are given, and considerations of the advantages of radiant energy or convected heat, both from the point of view of health and economy, are included. The following methods of heating are compared in respect to cost, rapidity of effect, uniformity, and hygienic value : (1) The ordinary open fire with modern grate. (2): The ordinary modern gas fire. (3) The anthracite stove. (4) The radiator. (5) Heating by naked gas flames, including what is called the gas radiator. (6) Heating by water or steam-heated radiator. The relative amounts of the total energy available which are radiated and convected are given for coal and gas fires, anthracite stoves, and water radiators : Coal Fire . . : - Radiated 25 per cent, convected 5 per cent. Gas Fire . . - Radiated 50 per cent, convected 1 5 per cent. Anthracite Stove Radiated 15 per cent, convected 3 5 per cent. Water Radiator “ - Radiated 12 per cent, convected 88 per cent. APPENDIX 103 SUMMARY Measurements of Radiation1—An absolute method for the measurement of the energy radiated from fires has been described by Professors Bone and Callendar and Mr. Yates (page 87), who used a bolometer which had been standardised by direct comparison with a source of radiation of known intensity.2_ The method, moreover, may be made differential by using the bolometer with both platinum coils uncovered, one being exposed to the source of radiation, the other to the room. The effects of convected currents of air should therefore be reduced. By attachment to a Callendar or other recorder automatic records can be obtained. Most other methods either (1) depend upon the assumption that a surface coated with lampblack or some other dead-black paint absorbs the whole of the radiant energy incident upon it; or (2) give comparative results only, as where a proportion only of the radiation, assumed constant, is absorbed; or (3) rely upon a radiation effect obtained from the difference of the sum of the measured flue loss and convected heat from the calorific value of the fuel consumed. Under the heading (x) are to be placed : (a2) The Leeds method (page 78),? when the central reading obtained by means of a radiometer with blackened absorbing surface is assumed to represent the whole energy falling upon that surface, and is multiplied by a factor, given by thermopile observations, to determine the total radiation emitted into the room. Any per- centage error in the centre reading is therefore reproduced unaltered into the final result. Further error may arise in the central reading if the condition that the mean temperature of inlet and outlet water shall be equal to that of the surround- ings is not accurately fulfilled.* ; There are also slight uncertainties in the value of the distribution factor due to the warming up of the ‘“‘ cold”’ junction of the thermopile, and to the limiting effect of the reflecting cone upon the area subtended by the thermopile at the source of radiation. Mr. H. Hartley found variations of 34 per cent in the dis- tribution factor due to the former cause (page 83).5 Another possible error in most radiation determinations, which apparently has sometimes been overlooked, and which certainly has sometimes been neglected, is that due to the readings, especially in upward directions, being affected to some extent by convection currents. Mr. Yates, using the Leeds method, found that a correction of about ro per cent was necessary to eliminate the effects of convection on the radiation result from a gas fire (page 83).6 Dr. E. Ott, using a segment water-flow calorimeter with horizontal axis, omitted readings through the top 30 on account of errors in that region due to convected heat received.’ (6) The work carried out under Mr. H. Hartley in the Richmond laboratory, which was intended to improve the appliances of the Leeds method. The weak- 1 See ‘ Instruments and Methods used in Radiometry,” W. W. Coblentz, Bulletin of American Bureau of Standards, vol. iv. No. 3; vol. ix. No. 1. : 7 2 See “ Studies of Instruments for Measuring Radiant Energy in Absolute Value,” W. W. Coblentz and W. B. Emerson, Bulletin of American Bureau of Standards, vol. xii., No. 4; A_Bolometric Method, etc.,” by W. A. Bone, H. L. Callendar, and H. J. Yates, Proceedings Royal Society, Feb. 15, 1915. ; : : Reports of the Gas Heating Research Committee of the Leeds University, 1909, 1910, . 4 “ Radiation Errors in Flow Calorimeters,” Coste and James, Journal Soctety Chemical Industries, IgII. 5 “ The Gas Fire, etc.,"’ H. Hartley, Journal of Gas Lighting, Nov. 8, 1913. 8 “ Progress in Gas Fire Science,” H. J. Yates, British Association, 1913. 7 “ Swiss Tests of Gas Fires,” E. Ott, Journal fir Gasbeleuchtung, Nov. 1915. or APPENDIX ness of the Rubens thermopile was indicated in a paper delivered to the Yorkshire Junior Gas Association in 1913. Later, in 1915, reference was made to a new. type of thermopile in which the faults of the Rubens instrument were eradicated. With regard to the radiometer, a preliminary criticism was made in 1913, and it was shown in the paper referred to on page 85 that the R. H. Smith water- flow instrument is unsatisfactory in gas fire testing. It was replaced by an instru- ment in which a metal block is employed as the heat absorbent instead of the water in the original appliance. The surface of the block is corrugated to minimise any small reflection which might occur; the loss due to imperfect absorption should therefore be small, and is compensated for in the dimensions of the block. The method also is free from possible error, inherent in water-flow calorimeters, due to differences between the mean temperature of the water in the instrument and the surrounding air (page 85). ; . (c) All methods, giving results other than comparative, which depend upon the readings of lampblack-coated calorimeters or radiometers, e.g. Mr. Clark’s radiation calorimeter (page 81), Mr. Glover’s hemispherical water-flow calorimeter (page 86), Mr. Bond’s segment water-flow radiometer (page 87), and Dr. Ott’s calorimeter (page 92). The water-flow instruments are also, as mentioned above, liable to “ cooling ”’ errors. Heading (2) includes : (a) Mr. Brearley’s method, in which gas fires were compared in terms of the radiation received through a horizontal semicircle with its centre at the centre of the fire, and measured by a thermopile connected to a Paul unipivot galvanometer (page 77).2. It is obvious that such a method, while possibly giving approximately comparable results for fires of the same size and shape, would be entirely unreliable under other conditions. If, for example, it were used to measure the radiation from a glowing rod, placed first vertically and then horizontally, it is clear that the results would be entirely at variance, although the radiation would remain for all practical purposes the same. (0) Mr. Thomson’s tin box calorimeter (page 82). This is subject to the same criticism as the above, and errors due to cooling would also arise. (c) Mr. Bond’s “ photometric’ method, which depends upon the assumption that the radiation from a gas fire at different distances along a horizontal line passing through the centre is inversely proportional to the square of the distance. With a as of radiation of finite size this depends upon the distances being large (page 86). (4) Mr. Vernon Harcourt’s radio-thermometer. This, again, may give approxi- mately comparative results for fires of exactly the same size and shape, but would be useless to compare, e.g. the radiation from a vertical gas fire with that from an open coal grate (page 99).4 Further, the heat absorbed by the calorimeter whilst the water is at temperatures below that of the room is less than that emitted whilst the temperature of the instrument is above that of the room, the period of duration of the latter half of the heating stage being appreciably greater than for the first half. Under the heading (3) must be classed : (a) The Coal Smoke Abatement Lancet tests of gas stoves, where the flue * “ Radiation Errors in Flow Calorimeters,” by Coste and James, Journal Society Chemical Industries, 1911. 2 “ The Testing of Gas Fires,” J. H. Brearley, Gas Engi ighti janes soe J y, Gas Engineer, June, 1907. Journal of Gas Lighting, 3 “ Gas Fires,’’ W. Thomson, Manchester and Salford Sanitary Association, May 26, 1913. 4 “' On the Measurement of the Efficiency of Domestic Grates.” Poisons ae ee y ic Grates,” A. Vernon Harcourt, Journal APPENDIX 105 loss was measured, the heat used in heating the air of the room calculated from the readings of thermometers—presumably unshielded—and the balance, amounting to from 75 to 95 per cent, was attributed to radiation. Results obtained in such a way are 2 uncertain that no importance can be attached to the radiation values (page 75).* . Measurements of Convected Heat——In The Lancet tests of gas stoves a value for the percentage heat used in warming the air of the room was given. This was calculated from the volume of air passing through the room, and the difference between its mean inlet temperature and the mean temperature of the room. The temperatures were obtained from the readings of ordinary mercury thermometers distributed at various points over the room, and it is doubtful, owing to the effects of radiation to and from the thermometer bulbs, whether they actually represent the air temperatures. The errors due to this cause may be considerable. There is also some doubt about the measurement of the volume of air passing through the room. The smoke test was used, in which the velocity of the flue gases was inferred from the rate at which the smoke from a charge of gunpowder burned in the stove passed up the flue. The quantity of heat utilised in raising the temperature of the air was given as from 0-6 to 3-6 per cent of the total. In 1907 Mr. Brearley published the results of some direct measurements of the heat of convection from a gas stove by placing a hood over the stove to catch the heated air, but not the products of combustion. Some of the latter, however, escaped into the hood. The results were therefore, as would be expected, high, and in different tests varied from 18 to 50 per cent, but it must be remembered that with the fire burning under normal conditions much of this would not be available for the warming of the air of the room (page 78).? A similar, but more accurate method, has been used by Mr. Barker in experi- ments on electric fires. Radiation measurements were also taken, and it was found possible to account for the total energy of the electric current within 3 or 4 per cent.® . Mr. Yates measured the flue loss and the radiant efficiency by the Leeds method, and obtained a balance, given as convected heat, of about 21 per cent from a modern 10-inch gas fire. This, however, probably includes the heat emitted from the back of the fire (page 83).4 | Heat lost in the Flue Gases——In The Lancet test the heat lost in the flue was determined for gas stoves by measurement of the temperature of the gases in the top of the flue, and by means of the smoke test, of the volume of gases passed. The loss varied from o to 23 per cent (page 76). Mr. Brearley gave consideration to three methods : (r) To measure the speed by an anemometer and the temperature by a thermo- meter; (2) to analyse the products for carbon dioxide and calculate therefrom the number of cubic feet passing per hour; and (3) to calculate the volume from the reduction in temperature effected by a Wilson’s circulating water-heater placed so as to abstract the heat from the flue gases. He concluded that (3) was the most reliable. The flue loss varied from 8 to 33 per cent (page 77).° 1 “ Gas Stoves, etc.,” The Lancet, Nov. 17, 1906. 7k 2“ The Testing and Hygienic Efficiency of Gas Fires,” Brearley, Journal of Gas Lighting, June 25, ee, “ ’ “On Electric Heating,” Barker, Electrical Review, Dec. 17, 1915; also “ A Laboratory for. Research on Heating,’’ ibid. Feb. 4, 1916. = ae 4 “ Recent Progress in Gas Fire Science,” by H. J. Yates, British Association, 1913. _ 5 “ The Testing and Hygienic Efficiency of Gas Fires,”” Brearley, Journal of Gas Lighting, June 25, 1907. 106 APPENDIX Mr. Yates, presumably by analysis and temperature measurements of the flue gases, obtained a flue loss of 31 per cent for a 10-inch gas fire (page 83). Dr. Ott measured the temperature in the middle of the room, and of the escaping flue gases, by means of thermometers, and calculated the flue loss as ne oy ot x 100, where ¢, is the temperature of the escaping flue gases, ¢, that in the middle of the room, a the volume of carbon dioxide produced by the com- bustion of one volume of gas, } the percentage of carbon dioxide in the hot flue gases, c the specific heat of the latter, and H, the net calorific value of the gas at N.T.P. (page 92).1 In The Lancet tests also analyses of the flue gases were made, but the smoke tests were rather relied upon. ; Professor von Ihering employed a similar method, and obtained results vary- ing from 4 to 29 per cent for gas fires (page 93). 2 Other methods are to measure the temperature of the flue gases with thermo- meters or thermocouples, and to measure their velocity directly by means of an anemometer or a Pitot tube connected to a microgauge.’ ; ; ‘It is clear from what has been said that the whole question of domestic heating is a difficult and complicated problem, and can be solved only by a complete analysis of the heating effects of the various appliances. The greater part of the available scientific investigations of the subject have been directed to the case of the gas fire. largely on account of the impetus given by the contributions of the Gas Heating Research Committee of the Leeds University ; and its importance has been demon- strated by the improvements in the gas fire which the last ten years have seen, and among which may be included (z) increase in radiant efficiency, (2) the adoption of hygienic standards, (3) the general adoption of high canopies, (4) the development of the silent gas fire. The latest types of gas fires provide ventilation ports in the cast-iron framework, intended to ensure adequate ventilation when the space surrounding the fire itself has been blocked up. Fires with curved surfaces, designed with a view to giving a more uniform horizontal distribution of radiation, have also been introduced. Unfortunately comparatively little specific information as to the heating effects of the various forms of electric heaters has been published, an aggregate heating effect of 100 per cent being generally assumed and ventilation being left out of the question ; but great improvements during the last few years have been introduced. The old so-called lamp radiators gave in practice a very low proportion of radiant energy, and owed their heating effect mainly to low temperature convection. The evolution of nickel-chrome resistance alloys, however, which can safely be run continuously at a bright red heat even when exposed to the air, made possible the development of the open type electric heater. Many of these are very pleasant and give a high radiant efficiency. On the other hand, many show fundamental errors of design, especially with regard to excess of ironwork in their framing, and much yet remains to be done upon the best arrangements of the radiating elements and their supports. With regard to the coal fire also, very incomplete systematic experimental conclusions have been available. Manufacturers have attempted to introduce improvements. Most modern grates are shallow, and wide from back to front: as little metal as possible is used in their construction, and the bars are thin or absent altogethér. The sides and back are made of firebrick, the back being inclined 1 Journal fiir Gasbeleuchtung, Nov. 1915. i * “Measurements of Air Velocities with Pitot Tubes,” Threlfall, Journal Electrical Engineering, an, 1904. APPENDIX 107 over the fire to minimise the passage of heat up the chimney. On the other hand, Mr. Harcourt and others have advocated the use of grates of essentially different design, in which the fire is narrow from back to front, the face of the fire being vertical so that the chief radiation is horizontal. The author’s experiments have shown that there is little difference between the aggregate heating effects of the two designs of grate, but differences in the distribution of the radiation must be considered. The necessity for the adoption of standardised methods of experiments of heating efficiencies and the publication of experimental data for the many different types of domestic heating appliances is strongly urged. Co-operation between the various workers is of the utmost importance, and it is hoped that manufacturers in general will follow the example of some of the gas fire makers in placing before the public results of trials upon their appliances, and so avoid possible duplication of effort. INDEX Aeration of gas flames, 91, 96 Aggregate heating effect of fires, 1, 59, 60, 73, 78, 91, 94, 95, 103, 106 Air flow through room. See Draught and Ventila- tion American tests of gas heaters, 97 Anemometers, 44, 78 Anthracite fires, diagram showing radiation from, 31 efficiency of, 31, 95, 98 radiation from, 29 table showing radiation from, 32 Arley cobbles, 4, 19, 23, 26, 28 Author’s experiments, 2-74 Author’s methods, 2, 3, 4 Barker, fireplace, 98 “ Fuel Economy in Cooking Apparatus,’ 101 “ Fuel Economy in Private Households,’ 102 “ On Efficient Methods of Domestic Heating,” 94 Barless grates, 4, 5, 9, 68, 95, 106 Bertin, ‘‘ Heating by Radiation,’ 81 Blackened thermometers, 61, 62, 92, 93 Bolometer, 2, 3, 87, 103 “ Bolometric Method of Determining the Efficiency of Radiating Bodies,’’ Bone, Callendar, Yates, 87 Bond, experiments, 86 segment calorimeter, 2, 3, 87 Bone, “‘ A Bolometric Method, etc.,’’ 87 criticism of Leeds tests, 80 Boys, Professor C. V., 60 Brearley, ‘‘ On the Testing of Gas Fires,’’ 77 Briquette fires, conditions in flue for, 54 diagram showing radiation from, 42 distribution of radiation from, 43 radiant efficiency of, 42, 69 table showing radiation from, 43 Bunte, 93 Burners, batswing, 81 Bunsen, 76, 80, 81 construction of gas fire, 91 Meker, 81 Callendar, ‘' A Bolometric Method, etc.,”’ 87 radiation from Meker burner, 81 recorder, 88, 103 Calorific values, 1, 2, 3, 4, 5, 9, II, 13, 17, 19, 20, 23, 26, 28, 29, 31, 32, 35, 36, 40, 42, 46, 54, 55,57) 60, 68, 69, 70, 71, 72, 76, 77, 80, 93, 95, 98, IOI, 102, 103, 106 Canopy, 83, 84, 106 Carbon dioxide, 44, 76, 78, 79, 90, 93, 99, 106 Carbon monoxide, 78 Chimney flue, heat passing up, 43-60, 70, 71, 76, 77) 78, 84, 94 height of, 4, 46, 76, 83, 90, 96, 99 inner, I, 44, 59, 60, 73 volume of gases passing up, 22, 23, 44-60, 76, 79, 89, 90, 91, 95, 96, 99 Cinder, 3, 6, II, 13, 19, 23, 30, 33, 35 Clark, radiation calorimeter, 81 “Some Practical Aspects of Radiation,” 81 “Coal and Gas Fire Radiation,’’ Webber, 82 Coal Fires. See Radiation from, Radiant effi- ciency of Cohen, ‘‘ On the Combustion of Coal and Gas in House Fires,’ 75 Coke fires, conditions in flue for, 54 diagrams showing radiation from, 33, 36, 39, I distribution of radiation from, 34, 35, 38, 40 radiant efficiency of, 32-42, 68, IOI tables showing distribution from, 35, 37 tables showing radiation from, 34, 37, 38, 40 Coke, low temperature carbonisation, 38-42, 63, 65, 66, 69 College of Technology, Manchester, 11, 18 Combustion, energy of, 1, 68 imperfect, 1, 73, 75 “Combustion of Coal and Gas in House Fires,” Cohen and Russell, 75 Comfort factors, 2, 72, 75, 78, 94 Conduction through flue walls, 1, 60, 73, 91 Convection, 1, 78, 83, 85, 91, 92 Cooking apparatus, IOI Cosine law, 11, 14, 70, 83 Cost of heating, 73, 74, 95, 98, 100, 102 Cyclic variations of radiation from open fires, 5, 10, 17, 20, 24, 31, 34, 36, 84 diagrams showing, 6, 10, 16, 21, 22, 25, 30, 31, 33, 36, 39% 41, 42 Damper, 18, 23, 54, 55, 57, 7° Darling, ‘‘ Methods of Economising Heat,’’ 98 relative temperatures of coal and gas fires, 82 Davis, laboratories, 86, 87 Distribution factor, for barless grates, 7, II for coal fires, 7, II, 14, 19, 26 for coke fires, 34, 35, 38 for slack fires, 26 for old-fashioned grates, 14, 19, 26 109 IIo Distribution factor—continued. methods of measurement of, 2, 4, 79, 83, 88 short-cut method for, 88 variation with time, 14, 19, 35, 38, 39, 4° Distribution of radiation, American measurements of, 97 author’s method of measurement of, 2, 4 Bertin on importance of, 81 Des Voeux and Owens on, 78 diagrams of, 7, 12, 15, 18 from barless grates, 6, 7, II, 12 from briquette fires, 43 from coal fires, 6, 11, 13, 18 from coke fires, 34, 35, 38 from gas fires, 92 from old-fashioned grates, 13, 14, 15, 18, 26 general discussion of, 69 Hartley on, 83 Leeds method of measurement of, 12, 79, 80, 83 1 Ott’s measurements of, 92 tables showing, 8, II, 14, 19, 27, 35 Distribution of temperature over room, 60, 61, 62 Draught, 5, 19, 20, 22, 23, 26, 34, 43-60, 65, 66, 68, 79, 72, 721 73: 75 76, 78, 84, 89, 90, 91, 93, 95, 96, 99 Draught restriction, 5, 18, 19, 20, 22, 23, 34, 44, 54, 55) 57, 59, 60, 65, 66, 68, 70, 71, 72, 73, 89 Drying of room air, 77, 78 Duration of burning, 11, 26, 28, 30, 59, 73 Efficiency of gas fires, 73, 76, 77, 78, 81, 83, 84, 85, 86, 87, 91, 92, 93, 95, 96, 98, Ior of ovens, Ior of solid fuel fires, 74, 75, 82, 84, 95, 99, I00. See also Heating Efficiency and Radiant Efficiency Electrical apparatus, 95, 98, 101, 106 Evans, ‘“‘ Radiation from Gas Fires,’’ 82 Flame, radiation from, 5, 10, 34, 81, 84 Flue gases, I, 2, 43-60, 70, 71, 75, 76, 77, 78, 79, 83, 84, 89, 90, 91, 93, 95, 96, 99, 105. See also Chimney flue Foxwell, “‘ Influence of Flame on Efficiency of Fires,’’ 84. Fuel, gas fire, 76, 77, 80, 84, 97, 98 Gas consumption, 76, 80, 82, 83, 89, 92, 93, 95, 96 Gas coke. See Coke Gas, Mond, 102 Gas ring, IOI, 102 Gas fires, and the injector principle, 95 construction of, 96 development of, 91 efficiency of. See Efficiency fuel, 76, 77, 80, 84, 97, 98 Hartley on, 83 science, 82 testing, 77 Thomson on, 82 INDEX Gas heating, and smoke prevention, 90 Reports of Research Committee, 78 “ Science in the Development of,’’ 86 Gas stoves, report upon, 75 trials of, 93 General considerations, 1 ; Glover, ‘‘ A Hemispherical Water Flow Calori- meter,’’ 86 Gueguen, radiation from batswing burner, 81 Haighmore seam, 9, 19 Hamburg, Verein fiir Feuerungsbetrieb und Rauch- kampfung, 1915, 85 Harcourt, ‘‘ On the Measurement of the Efficiency of Domestic Fires,’’ 99 radio-thermometer, 2, 3, 99, 104 Harrison, Second Report of Joint Committee on Ventilation, 89 Hartley, ‘‘ A New Radiometer,”’ 85 “The Gas Fire,” 83 “Gas Fire Construction,” 96 “Gas Fire Development,”’ 91 Heat, ‘‘ Methods of Economising,’’ Darling, 98 Heating efficiency, I, 2, 59, 60, 73, 75, 78, 84, 91, 93, 95, 97, 99, 101. See also Radiant effi- ciency and Efficiency of room air, 2, 59-68, 71, 72, 75, 76, 79, 93, 99 “Problems of Efficient Methods of, ’’94 Hey, 4 Hygienic considerations, 77, 78, 94, 106 Ihering, trials of gas stoves, 93 Introductory, 1 Lancet tests, 75, 99 Leeds tests, 2, 78, 83, 86, 103, 106 Low temperature carbonisation fuels, 38, 39, 40, 42, 46, 69 Manchester College of Technology, 11, 18 Measurements of radiation, American tests, 97 author’s experiments, 2-43 author’s methods, 2-4 Bertin on, 81 bolometric method for, 87 Bond on, 86 Brearley on, 77 Clark on, 81 Cohen on, 75 discussion of methods employed for, 103-105 Glover on, 86 Harcourt on, 99 Hartley on, 83, 96 Ihering on, 93 Leeds tests, 78 Ott on, 92 Thomson on, 82 Webber on, 82 Yates on, 82 Meker burner, 81 Modern grates. See Barless grates INDEX III Moisture in fuel, 4, 32, 33, 34, 35, 36, 40, 41 Mond gas, 102 Nickel-chrome alloys, 106 Old-fashioned grates, 13, 17, 95, 106 Orsat apparatus, 44, 93 Ott, Tests of Gas Fires, 92 Owens, “‘ On the Thermal Efficiency of Gas Fires,”’ 75 Patent preparations, 28, 46, 63 Peltier effect, 87 Philadelphia, United Gas Improvement Co., 97 Platinum thermometers, 44 Prescott, Ir Radiation, distribution of. See Distribution from Bunsen flames, 81 from gas flames, 82 ° maxima and minima of, for coal fires, 5,6, 10, 11, 14, 17, 18, 20, 25, 26, 34, 36, 44, 60, 69, 70, 78, 82, 84, 96 measurements of. See Measurement practical considerations, 81 up chimney flue, 1 variations of, with time, 5, 10, 17, 20, 24, 31, 34, 36, 84 Radiation from anthracite fires. See Anthracite fires Radiation from briquette fires. See Briquette fires Radiation from coal fires, author’s experiments on, 2-29 author’s methods of measurement of, 2-4 diagrams showing distribution of, 7, 12, 15, 18 diagrams showing variation of, 3, 6, Io, 16, 21, 22, 25, 26, 30 distribution of, 6, II, 13, 18 Foxwell on, 84 general effect upon a room of, 1 Harcourt on, 100 summary, 68 tables showing, 8, 13, 17, 20, 24, 25, 27, 29 tables showing distribution of, 8, 11, 14, 19 up chimney flue, Webber on, 82 Radiation from coke fires. See Coke fires Radiation from gas fires, an American test, 97 Barker on, 102 Bertin on, 81 Bone, Callendar, Yates on, 87 Brearley on, 77 Cohen on, 75 ° Hartley on, 83, 85, 96 Ihering on, 93 Ott on, 92 Smith on, 78 Thomson on, 82 Twigg on, 86 Webber on, 82 Yates on, 82 . Radiant efficiency, definition of, 2, 80 effect of aeration of flames upon, 91, 96 effect of bars upon, 23, 24 effect of dipping radiants into copper nitrate upon, 84 effect of height of canopy upon, 83 effect of methods of stoking upon, 23, 25 effect of radiants upon, 96 effect of reflectors upon, 81 effect of treating coal with patent preparations upon, 28, 29 effect of variation of draught upon, 20, 23, 24, 68 of anthracite fires, 31, 32 of batswing burner, 81 of briquette fires, 42, 43, 69 of Bunsen burners, 81 of coal fires, 4, 7, 8, 9, 10, 13, 17, 20 of gas fires, 80, 81, 83, 84, 85, 86, 89, 91, 92, 96, 97, 102 of gas coke fires, 32, 34, 35, 37, 68, Ior of low temperature coke fires, 38, 40, 41, 42, 69 of Meker burner, 81 of slack fires, 26, 27 summary, 68 Radiants, 96 Radiometers, 2, 3, 4, 5, 9, 10, 14-17, 19-43, 60, 66, 79, 80, 83, 84, 85, 87, 103, 104 Radio-thermometer, 99 Rate of burning of fuel, 4, 6, 10, 11, 13, 18, I9, 22, 23, 24, 26, 28, 29, 30, 32, 33, 35, 38, 40, 42, 43, 45, 46, 54, 55, 59, 60, 68, 70, 72, 73, 77, 82, 83, 89, 92, 93, 95, 96, 100 Residues, 3, 6, II, 13, 19, 23, 30, 33, 35, 99 Richmond radiometer. See Radiometers Rubens thermopile, 2, 3, 77, 80, 83, 91 Russell, ‘‘ On the Combustion of Coal and Gas in House Fires,’’ 75 Silent gas injector, 84, 91 Silvered thermometers, 61, 62, 92, 93 Size of coal, 9, 23, 26 Slack, 9, 26, 68 Sloping firebrick back, 4, 13 Smith, Report of Joint Committee, 78 Smith, R. H., radiometer, 80 Smoke, I, 23, 42, 55, 76, 98, 99, 100 Smoke test, 76 Soot, I, 75, 91 South Kirkby Colliery, 9, 13, 19 Teale, 98 _Temperature of air in flue, 43, 44, 45, 46, 54, 55,57) 59, 60, 70, 71, 76, 78, 83, 93, 99 of air in room, 2, 59, 60-68, 71, 72, 75, 79, 79, 93, 99 of entering air, 62, 63, 65, 66, 68; 735. 72; 76 of fires, 14, 28, 82, 98 of walls, 62, 66, 73 Tests of Domestic Open Fire-grates, 99 Thermopile, 2, 3, 4, 6, 18, 77, 79, 80, 83, 91, 103 Thomson, “ Gas Fires,” 82 112 INDEX United Gas Improvement Co., Philadelphia, 97 Weather conditions, 62, 64, 66, 82 Upper rooms. See Warming of = Webber, ‘“‘ Coal and Gas Fire Radiation,” 82 Whipple, indicator, 44 Ventilation, by gas fires, 75, 76, 89, 90, 91, 95 Wilson, circulating water heater, 77 Research committee, 89 Wood, First Report of Sub-committee of Institu- Volume of flue gases, 22, 23, 44-60, 76, 79, 89, 90, tion ot Gas Engineers, 102 ; 91, 95, 99 Von Helmholtz, radiation from Bunsen flames, 81 Von Ihering, trials of gas stoves, 93 Yates, ‘‘ A Bolometric Method, etc.,”’ 83 ‘Gas Heating and Smoke Prevention,’’ 90 Warming of upper rooms, I, 44, 59, 60, 73 “ Recent Progress in Gas Fire Science,’’ 82 THE END Printed under the authority of His MAJESTY’s STATIONERY OFFICE By R. & R. Clark, Limited, Efinburgh. 3 MISCELLANEOUS: REPORTS, ETC. Science ‘and Industry — Industrial Research in ‘the ‘ise States _ of America, by. Mr. A. P..M. Fleming, M.LE.E. 1916 (wath FOOD INVESTIGATION. BOARD. _ Report. for the year: 1918. Price 3d. 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TISSINGTON THORPE CLOUD \XHUCKNALL IDRIDGEHAY Hucknall N° 2 \\euTLers HILL BELPE) ( SHOTTLE ASHBOURNE HAZELWOOD MBERTEN INE @ OAKAMOOR CLIFTON abbington Cinderhille DUFFIELD Lf NORBURY & ELLASTONE nid | DENSTONE ae CROSSING > ; , RADFORD 3 English Miles nt bial a3 ch = rel K ROCESTER ) oO 1 2 3 = a : 10 BREADSALL NU pah ° Sie MAP SHOWING POSITION OF THE VARIOUS COLLIERIES. [Reproduced by permission of W. § A. K. Johnston, Ltd., and the Colliery Guardian Co. Ltd., from Map of the Coalfields of the North Midlands.)