H ILL INO S UNIVERSITY OF ILLINOIS AT URBANA-CHAMPAIGN PRODUCTION NOTE University of Illinois at Urbana-Champaign Library Large-scale Digitization Project, 2007. UNIVERSITY OF ILLINOIS BULLETIN ISSUED WEEKLYI Vol. XXV October 25, 1927 No. 8 [Entered as second-class matter December 11, 1912, at the post office at Urbana, Illinois, under the Act of August 24, 1912. Acceptance for mailing at the special rate of postage provided for in section 1103, Act of October 3, 1917, authorized July 31, 1918.] EFFECT OF ENCLOSURES ON DIRECT STEAM RADIATOR PERFORMANCE BY MAURICE K. FAHNESTOCK BULLETIN NO. 169 ENGINEERING EXPERIMENT STATION PtBLISHEB BY THE UNIVERSITY OF ILLINOIS, URBANA PRICE: TWENTY CENTS HE Engineering Experiment Station was established by act of the Board of Trustees of the University of Illinois on December 8, 1903. It is the purpose of the Station to conduct investigations and make studies of importance to the engineering, manufacturing, railway, mining, and other industrial interests of the State. The management of the Engineering Experiment Station is vested in an Executive Staff composed of the Director and his Assistant, the Heads of the several Departments in the College of Engineering, and the Professor of Industrial Chemistry. This Staff is responsible for the establishment of general policies gov- erning the' work of the Station, including the approval of material for publication. All members of the teaching staff of the College are encouraged to engage in scientific research, either directly or in cooperation with the Research Corps composed of full-time research assistants, research graduate assistants, and special investigators. To render the results of its scientific investigations available to the public, the Engineering Experiment Station publishes and distributes aseries of bulletins. Occasionally it publishes circu- lars of timely interest, presenting information of importance, compiled from various sources which may not readily be acces- sible to the clientele of the Station. The volume and number at the top of the front-cover page are merely arbitrary numbers and refer to the general publica- tions of the University. Either above the title or below the seal is given the number of the Engineering Experiment Station bul- letin or circular which should be used in referring to these pub- lications. For copies of bulletins or circulars or for other information address THE ENGINEERING EXPERIMENT STATION, UNIVERSITY OF ILLINOIS, UBANA, ILLINOIS UNIVERSITY OF ILLINOIS ENGINEERING EXPERIMENT STATION EFFECT OF ENCLOSURES ON DIRECT STEAM RADIATOR PERFORMANCE BY MAURICE K. FAHNESTOCK SPECIAL RESEARCH ASSISTANT IN MECHANICAL ENGINEERING ENGINEERING EXPERIMENT STATION PUBLISHED BY THE UNIVERSITY OF ILLINOIS, URBANA BULLETIN No. 169 OCTOBER, 1927 CONTENTS I. INTRODUCTION ........ 1. Preliminary Statement . . . . 2. Object of Investigation . 3. Scope of Investigation . . . . 4. Acknowledgments . . . . . II. DESCRIPTION OF APPARATUS . . 5. Description of Unenclosed Radiator 6. Arrangement of Plant . . . . 7. Description of Enclosures . . . 8. Description of Shield and Cover III. TEST PROCEDURE . . . . . . . 9. Test Procedure . . . . . . IV. RESULTS . . . . . . . . . . . . . . 10. General Statement . . . . . . . . . . 11. Performance of Unenclosed Radiator . . . . 12. Effect of Character of Air Outlet . . . . . . 13. Effect of Height of Enclosure . . . . . . . 14. Effect of Size of Air Inlet . . . . . . . . 15. Performance of Enclosures with Grilled Construction 16. Performance of Metal Shield and Cloth Cover V. CONCLUSIONS . . . . . . . . . . . . . 17. Conclusions . . . . . . . . . ... PAGE 5 5 6 6 6 6 6 6 9 . . . . . . . . . . . . . . . . . . 6 . . . . . . 6 . . . . . . 6 . . . . . . 6 . . . . . . 11 12 S12 . 13 S20 S 21 S22 26 31 S33 S33 LIST OF FIGURES NO. PAGE 1. Unenclosed Radiator in Test Booth . . . . . ... . . . . . 7 2. Diagram of Test Plant . . . .. . . . . . . . . . . 8 3. Minimum Height Sheet Iron Enclosure . . . . . . . . .. 9 4. Maximum Height Sheet Iron Enclosure . . . . . . . . . . 10 5. Enclosures Used in Series I, II, and III Tests . . .. . . . . . 11 6. Performance Curves for Various Outlets with Minimum Height Enclosure . 14 7. Performance Curves for Various Outlets with Medium Height Enclosure . 14 8. Performance Curves for Various Outlets with Maximum Height Enclosure .15 9. Effect of Height of Enclosure on Steam Condensed . . . . .. . 15 10. Enclosures Used in Series IV-a, IV-b, and IV-c Tests . ....... .16 11. Performance Curves for Various Inlets with Minimum Height Enclosure .17 12. Performance Curves for Various Inlets with Medium Height Enclosure .17 13. Performance Curves for Various Inlets with Maximum Height Enclosure . 18 14. Enclosures Used in Series V Tests . . . ... . . . . . .26 15. Enclosure with Woven Metal Grille Construction . . . . . . .. .27 16. Sections of Metal Grilles, Actual Size . . . . . . . . . .. . 28 17. Performance Curves for Enclosures with Various Grilled Constructions . 29 18. Metal Radiator Shield . .. . . . . . . . . . .. .30 19. Radiator with Cloth Cover . . . . . . . . . . . . .. . 31 20. Performance Curves for Metal Shield and Cloth Cover . . . . .. .32 21. Graphical Table of Results . . . . . . . . . . . . .. .34 21-a. Continuation of Graphical Table of Results . . . . . . .. .36 LIST OF TABLES 1. Heat Transmission Coefficients for Various Temperature Ranges . .. 19 2. Relative Steam Condensing Capacities of Enclosures of Different Heights . 23 EFFECT OF ENCLOSURES ON DIRECT STEAM RADIATOR PERFORMANCE I. INTRODUCTION 1. Preliminary Statement.-This bulletin is a report of the results of the first year's work under the terms of a coSperative agreement between the National Boiler and Radiator Manufacturers' Association, the Illinois Master Plumbers' Association, and the University of Illi- nois, providing for an investigation of steam and hot-water heating systems. The agreement was formally approved March 9, 1926, and became operative on April 10, 1926. The results presented in this bulletin are based upon the work done between April 1926, and April 1927. The two co6perating associations have been represented during the first year by an advisory committee, the membership of which is as follows: C. D. BROWNELL, Chairman, representing the Illinois Master Plumbers' Association, Champaign, Illinois. C. K. FOSTER, representing the National Boiler and Radiator Man- ufacturers' Association, Chicago, Illinois. O. J. PRENTICE, representing the Steam Specialties Manufacturers, Chicago, Illinois. F. W. HERENDEEN, representing the National Boiler and Radiator Manufacturers' Association, Geneva, New York. H. S. ASHENHURST, representing the Insulation Manufacturers, Chicago, Illinois. SEWARD BEST, representing the Heating Contractors, Quincy, Illi- nois. J. M. ROBB, representing the Heating Contractors, Moline, Illinois. I. H. COGLEY, representing the Heating and Piping Contractors' Association of Chicago, Chicago, Illinois. It is the function of this committee to propose such problems for investigation as are of the greatest interest to the installer of small direct steam and hot-water heating systems, operating on gravity cir- culation. Of these problems, the Engineering Experiment Station staff selects for study those which can best be investigated with the facilities and equipment available at the University. The co6perating associa- tions provide funds for defraying a major part of the expense of this research work. For the first year the Chicago Master Steam Fitters' Association also assisted by contributing materially to the funds for the prosecution of the work. ILLINOIS ENGINEERING EXPERIMENT STATION 2. Object of Investigation.-The immediate object of the series of tests reported in this bulletin was to determine the effect of various types of present-day commercial radiator enclosures, shields, and cov- ers on the steam condensing capacity of a direct cast-iron radiator. 3. Scope of Investigation.-The effect of an enclosure, shield, or cover upon the steam condensing capacity of a radiator depends upon many factors. The tests made in connection with the present in- vestigation were planned to determine the influence of a number of these factors in the case of radiator enclosures, and those studied were air inlets, air outlets, heights, and grilles. In conjunction with the work on enclosures, tests were run on an unenclosed radiator, a commercial type of shield, and a cloth cover. 4. Acknowledgments.-This investigation has been carried on un- der the personal supervision of A. C. WILLARD, Professor of Heating and Ventilation and Head of the Department of Mechanical Engineer- ing, and A. P. KRATZ, Research Professor in the Department of Me- chanical Engineering. Particular credit is due Professor A. C. Willard for his original layout of the test program and his support and advice during the investigation. Credit is due Professor A. P. Kratz for his personal supervision of the work, and his aid in presenting and inter- preting the test results. The investigation has been carried on as a part of the work of the Engineering Experiment Station of the University of Illinois, of which Dean M. S. Ketchum is the director, and of the Department of Me- chanical Engineering, of which Professor A. C. Willard is the head. II. DESCRIPTION OF APPARATUS 5. Description of Unenclosed Radiator.-The radiator used for these tests was a standard 20-section, 38-inch, 3-column, cast-iron water type radiator having a nominal area of 100 sq. ft. The surface was brushed and painted (not dipped) with two coats of flat black paint. 6. Arrangement of Plant.-The general arrangement of the plant is shown in Fig. 2. The radiator stood on the main floor of the Mechanical Engineering Laboratory and was partly surrounded by the test booth shown in Figs. 1, 2, 3, and 4. The back of the booth was placed 21/2 inches from the radiator, and, together with the sides, served to shield the latter from transverse air currents. The overall dimensions of the booth are given in Fig. 2. The top of the booth EFFECT OF ENCLOSURES ON DIRECT STEAM RADIATOR PERFORMANCE 7 FIG. 1. UNENCLOSED RADIATOR IN TEST BOOTH served to deflect the vertical air currents in approximately the same manner as the ceiling of a room. The whole inside of the booth pre- sented surfaces similar to papered walls for receiving radiation. These conditions, while not exactly duplicating those of actual service, where the radiator is often set under a window which is in an exposed wall, did duplicate standard conditions under which practically all radiator tests have been conducted, and certainly afforded means of obtaining valid comparative data. As shown in Fig. 2, the piping, separator, receiver, and weighing tank were placed in the basement of the laboratory, directly beneath the radiator. A separator was used to remove all entrained moisture from the steam, and a mercury manometer and thermometer indicated the steam pressure and temperature. A glass section was installed in the 2-inch vertical riser to the lower tapping of the radiator. The condensate left the radiator through this same connection, and was ILLINOIS ENGINEERING EXPERIMENT STATION FIG. 2. DIAGRAM OF TEST PLANT collected in a receiver having a gage glass. The weighing tank was connected through a water seal to the receiver, and the minimum sub- division of the scales used was 0.01 pound. The separator, receiver, and piping were heavily lagged, and the glass section in the vertical riser was enclosed in a triangular glass observation box for the pur- pose of protection and for the prevention of heat loss. The %-inch air vent tapping on the last radiator section was fitted with a short length of piping and a hand controlled globe valve. All thermometers in the test booth, Fig. 2, were shielded to protect them against the EFFECT OF ENCLOSURES ON DIRECT STEAM RADIATOR PERFORMANCE 9 FIG. 3. MINIMUM HEIGHT SHEET IRON ENCLOSURE effect of direct radiation. A thermometer was placed near the piping in the basement, and one was also placed at breathing line level on the main floor of the laboratory. 7. Description of Enclosures.-No commercial enclosures were used, but all enclosures were constructed so as to be adapted to limiting the effect to the particular factor being studied, and at the same time to avoid presenting features that were commercially im- possible. All enclosures were painted inside and outside with two coats of flat black paint. In all cases there was a clearance of 22 inches between the back of the radiator and the back of the enclosure, and of one inch between the radiator and the enclosure at the front. The end clearances were 8 inches and 4 inches, the larger clearance being at the steam inlet end. The effects of height, and of sizes and types of openings were determined with enclosures having the sides and ends ILLINOIS ENGINEERING EXPERIMENT STATION FIG. 4. MAXIMUM HEIGHT SHEET IRON ENCLOSURE made of solid sheet iron. The minimum height of enclosure for this type is shown in Fig. 3, and the one of maximum height is shown in Fig. 4. The various arrangements of these enclosures are indicated in Fig. 5. They are also shown corresponding to the curves in Figs. 6, 7, and 8. The type and dimensions of the enclosures used to study the effect of different grille constructions are shown in Figs. 14 and 15. The three types of grilles tested are shown to actual scale in Fig. 16. 8. Description of Shield and Cover.-The shield tested is shown in Fig. 18 and in Fig. 20 corresponding to the result curve. It was a metal shield of a common commercial type without a humidifier. The top was insulated and extended 2 inches in front of the radiator. The clearance between the shield and the top of the radiator was approxi- mately /2 inch, and the back, which extended to within 3% inches of the floor, was in contact with the radiator. The cloth cover shown in Fig. 19 was 6% inches deep, the same width and length as the radiator, and was made of a closely woven crash cloth. EFFECT OF ENCLOSURES ON DIRECT STEAM RADIATOR PERFORMANCE 11 77-*, - ^/9 - A>>^ ^/c/^ ^?/ _ ^ ~^" ^/^ /^/ anda gr///d The gr///e use w/h a per cen'7 fr-ee area = encl/osure 6 wa.s ru/ opt Top of En'7c/asures A, B, for Ser/'e.s Top of E-nc/osures A, B, for 5er/5s 27 Tej Top of Enc/osures A, B 8 for Ser/les Z Tes Enc/osu/res made of '2Q s5hee/ iron paine/ed wMi / coa/s of b/ack Pecora 2ra Enc/osures /Vos. ZL 2 , P, /, /5, 1/, 0, Z, 22 , , , , SM30, as descr/ied /,, F/s. 2/ cVa'd 2/-a. FIa. 5. ENCLOSURES USED IN SERIES I, II, and III TESTS III. TEST PROCEDURE 9. Test Procedure.-As the tests were made in a large laboratory where it was impossible to maintain a constant temperature from day to day it was necessary to run a number of tests on each set-up and determine a performance curve for the different temperature ranges. Since the laboratory was large, the heat given off by the radiator at no time materially affected the breathing line temperature in the test booth, and this temperature was used as the air temperature base in connection with all performance curves. The large number of tests ILLINOIS ENGINEERING EXPERIMENT STATION made on the different enclosures,the shield, and the cover extended over a long period of time, and as the tests were conducted in a laboratory where other work was in progress simultaneously, it was necessary to make check tests from time to time in order to make certain that no factors aside from those being studied were affecting the results. These check tests were usually made on the unenclosed radiator, and although the investigation was carried on during summer and winter months it was always possible to duplicate results. During every test the steam pressure was maintained constant by a combination of an automatic pressure reducing valve and a manually controlled throttle valve. A constant water level was maintained in the receiver. In all cases, the temperature of the steam in the radiator was 216 deg. F. The separator through which the steam passed just before entering the riser to the radiator was allowed to blow contin- uously, and similarly the air vent on the radiator was partly open during each test. The condensate left the radiator through the same connection by which the steam entered, was collected in the receiver, passed into the weighing tank, and was weighed every 10 minutes. No test was accepted that showed a variation of more than 22 per cent in these successive increments of weight. With such constant conditions, an hour was considered as sufficient duration for a test. During this time all temperature and pressure readings were taken every ten minutes and the average values used in the computations of results. By means of the glass section installed in the vertical riser to the radiator the flow of condensate could be observed, thus insuring that the critical velocity was never exceeded, and that no condensate was carried back into the radiator. This arrangement had the further ad- vantage, that, since the condensate leaving the radiator had no chance to accumulate at one end and was always in intimate contact with live steam, the temperature of the condensate was unquestionably the same as that of the steam. This method has proven unusually satis- factory and no record has been found in which it has been previously reported in connection with radiator tests. The heat loss from the piping at various basement temperatures was determined by running a series of tests on the piping alone, with the radiator disconnected. Correction of all condensation weights was made to allow for the steam equivalent of this loss. IV. RESULTS 10. General Statement.-The results of all the tests are presented in the form of curves shown in Figs. 6-9, 11-13, 17, and 20, using the EFFECT OF ENCLOSURES ON DIRECT STEAM RADIATOR PERFORMANCE 13 temperatures at the breathing line in deg. F. as abscissas and net pounds of steam condensed in the radiator per hour as ordinates. For direct comparative purposes the result of each test for a breathing line temperature of 80 deg. F. is given in the graphical table, Figs. 21 and 21-a. The heavy black bars present a graphical representation of the net pounds of steam condensed in the radiator per hour, using the particular enclosure, shield or cover indicated, with the steam temper- ature at 216 deg. F. The columns on the left page of this table give data covering the controlling factors of each enclosure, shield, and cover tested. The number assigned to each enclosure is given in the extreme left column, and for a more detailed description of any par- ticular enclosure reference may be made to Figs. 5, 10, or 14. The rela- tive steam condensing capacity of each arrangement, based upon the performance of the unenclosed radiator, is given in the third from the last column on the right-hand page. The last two columns give the amount of radiation, in per cent, to be added or subtracted when using the particular enclosure, shield, or cover indicated, in order to obtain the same amount of steam condensed as would be obtained with the bare radiator. 11. Performance of Unenclosed Radiator.-In all cases, the performance was defined by a curve with room temperatures at the breathing line used as abscissas and net pounds of steam condensed in radiator per hour as ordinates. On each of the curve sheets shown in Figs. 6-8, 11-13, 17, and 20, the performance of the unenclosed radiator is shown as a base curve for the purpose of making compari- sons, and all direct comparisons are made with a room temperature of 80 deg. F. at the breathing line. The curves for the unenclosed radiator in Figs. 11-13, 17, and 20 were transferred directly from the ones in Figs. 6, 7, and 8 on which the experimental points are shown. It may be noted from Fig. 8, curve A, that at a room temperature of 70 deg. F. at the breathing line, and with steam at 216 deg. F., the unenclosed radiator condensed 24.25 lb. of steam per hour. Using a value of 969.3 B.t.u., taken from Goodenough's Steam Tables, as the latent heat of steam, this weight represents a total heat transmission of 23 500 B.t.u. per hour. Since the temperature difference from steam to air is 146 deg. F., a value of Ko, = 1.610 is obtained, where Ko is the coefficient of heat transmission, or the heat transmitted per square foot of radiation per degree temperature difference per hour for room temperature at the breathing line of 70 deg. F. ILLINOIS ENGINEERING EXPERIMENT STATION s^ i. u"^ 7:- j-T - 's ~· -tI;' '' t.' ^ /l -s l Z I 7 /7 4 1'~ -Cr 2 2 *I t; _-h *$ -^ g t L 7 7 -< 7 7 1I 2L f7 N0Lt *NO~~tC XP Lc3~~ L~3/ jN K. K x '\ s: a 8. spunod /a/V 2 -f ~- 7' / ^ ^ m l z i/ /' Y s / i /\ zI I t el~-J~ h I f i/ i I L-- sI ·-- . I~ 9: - "i 11 EFFECT OF ENCLOSURES ON DIRECT STEAM RADIATOR PERFORMANCE 15 ILLINOIS ENGINEERING EXPERIMENT STATION Series Z(a)-Enc/osures A wadB tested w/#h opeo otlets, us/ nl/ets / and 4, and w/#/7 punched me/a/ gr///e Ou/le/s usig /n/ets / 3, and4. The grille used had 2 "s. ho/es w/i1h per cent Free Area = 44. Ser/es 27(b)-and If(c)- Enc/osure A tested w/ih open /ut/et us/ng /n/ets /2, 2 , and4. Enc/osures made of pa/2t/ed w///7 Z coats Top of Enc/osure A for Ser/es Z7(c) Too of Enclosure , for Serles Y7(6 Top or Enc/osures Z for Series I(Va) Inlet No. /n/eP Aa. /own on Irı_ A// adimens/ons not 2, 53 are s1owaw are the same ... 1-/41 the sawe as In/et 4 as Enc/osure A. Various /n/les used ia Series 7 Tests. Enclosures o s. 3,4, 8,9, ,/ /, /9, 6, & 27 (See Fs. l/and'2/a) FIG. 10. ENCLOSURES USED IN SERIES IV-a, IV-b, AND IV-c TESTS Reference to the table on page 37 of the Heating and Ventilating Guide for 1926-27 indicates that the rating of a 20-section, 38-inch, 3-column radiator with steam at 215 deg. F. and air at 70 deg. F. is 21 990 B.t.u. per hour. From the table on page 42 of the Guide, a cor- rection factor of 0.993 may be obtained by interpolation. Making use of this factor, the 21 990 B.t.u. per hour may be corrected to terms of steam at 216 deg. F. and air at 70 deg. F. If this is done, a value of 22 140 B.t.u. per hour is obtained, and for the temperature differ- EFFECT OF ENCLOSURES ON DIRECT STEAM RADIATOR PERFORMANCE 17 % NZ ~z % IN FN Ilk I- az x z N 'IQ k B) al'as"Il-9,4102 4",G-_,1 J 04 b90, 1- Q -'- K "I *1. ~j) ILLINOIS ENGINEERING EXPERIMENT STATION Top of Eac/osure 34'7a0ove 7 - Top of Rad/rat'/- eam Co 26 -- -- - - -- -- - - Z/6°^- - - 24 \ - - o---- - - - - S(-9"X50o Open Top lo,/e, e3 4.^ ! ,?z1r' L_^ _4 ____//7/_, 2 - r\ Ao/ - 111osec /8-- 70 75 90 9f 9z 7empera/ure an Sreal/ivg ,./ 7e it dee /f FIG. 13. PERFORMANCE CURVES FOR VARIOUS INLETS WITH MAXIMUM HEIGHT ENCLOSURE ence of 146 deg. F., K,, = 1.517. Comparing this with the 1.610 ob- tained from curve A in Fig. 8, a difference of 6.1 per cent is indicated. This is considered a satisfactory agreement, particularly since the radiator tested was painted flat black, which would have a tendency to increase the heat transmission over that for an enameled or bare radiator. Several rules have been proposed for correcting the heat trans- mission or the coefficient K to terms of a temperature range deviating from the standard range of 145 deg. F. A rule proposed by Charles A. Fuller* is that K, the coefficient of heat transmission, varies by 0.2 per cent per degree above or below the standard range. In order to examine the application of this rule to the data obtained on the tests reported in this bulletin, the value Kr = 1.610, with a temperature *Harding, L. A., and Willard, A. C., "Mechanical Equipment of Buildings," Vol. I, First Edition, p. 78. EFFECT OF ENCLOSURES ON DIRECT STEAM RADIATOR PERFORMANCE 19 TABLE 1 HEAT TRANSMISSION COEFFICIENTS FOR VARIOUS TEMPERATURE RANGES Coefficient K Room Steam Temp. Temp. Temp. Range Difference Per cent deg. F deg. F deg. F. Calculated Corrected Difference from Curve from Base A, Fig. 8 Value 1.610 70 216 146 1.610 1.610 0.000 0.000 75 216 141 1.584 1.584 0.000 0.000 80 216 136 1.563 1.578 +0.015 0.959 85 216 131 1.546 1.562 +0.016 1.035 90 216 126 1.542 1.546 +0.004 0.259 range of from 216 deg. F. to 70 deg. F., was chosen as a base. This was then corrected to several temperature ranges by applying the 0.2 per cent rule, and the results compared with those obtained by direct calculation from the curve for the unenclosed radiator shown in Fig. 8. The results are given in Table 1. From the table it may be noted that the corrected values of the coefficient K agree within one per cent with those obtained by direct calculation from the curve in Fig. 8. Over the temperature range and at the actual temperatures used, the 0.2 per cent rule, therefore, seems to be well adapted to the data obtained. A second rule, proposed by Dr. Dietz,* is that the total heat transmission varies as the 1.3 power of the temperature range. That is Vtl - t2, where H - total heat transmission, B.t.u. per hour W, = weight of steam condensed at standard range, lb. rs = latent heat of steam at standard steam temperature, deg. F. tla = actual steam temperature, deg. F. t2a = actual room temperature, deg. F. tl, = standard steam temperature, deg. F. t2, = standard room temperature, deg. F. In order to compare the results of the application of these two rules to the actual test data, the following values have been calculated *Brabb6e, C. W., "Heating Effect of Radiation," Jour. A. S. H. and V. E., Vol. 31, No. 11, November, 1925, page 502. ILLINOIS ENGINEERING EXPERIMENT STATION for the heat transmission at a room temperature of 80 deg. F. with steam at 216 deg. F.: (1) From Curve A, Fig. 8 Hso = 21.93 X 969.3 = 21 250 B.t.u. per hour. (2) From the coefficient, K, corrected by the 0.2 per cent rule Hso = 100 X 1.578 (216 - 80) = 21 460 B.t.u. per hour. (3) From the exponential rule /216 - 80\1'3 Ho = 24.25 X 969.3216 - 70 = 21 450 B.t.u. per hour. From these values it may be seen that the agreement between the two rules is very close and that both rules are applicable to the test data within one per cent, over the temperature range actually used in these tests. 12. Effect of Character of Air Outlet.-The group of tests desig- nated as Series I were made for the purpose of determining the effect of the location, size, and type of the air outlet, using an enclosure of the same height as that of the radiator. The general details of the solid sheet iron enclosures used in these tests are given in Figs. 3 and 5, and also in Fig. 6, together with the corresponding result curves. The comparative data are based upon the performance of the enclos- ures with the temperature of the steam in the radiator at 216 deg. F. and the temperature at the breathing line at 80 deg. F. These data are tabulated graphically in Fig. 21 under enclosure Nos. 1, 2, 6, 7, and 11. In all cases the top of the enclosure practically touched the top of the radiator, and the air inlet consisted of a 4-inch by 50-inch open slot at the bottom of the front of the enclosure. The best com- bination in this series was obtained with a 91/-inch by 50-inch hori- zontal opening in the top of the enclosure. The area of the outlet was 462.5 sq. in. compared with 200 sq. in. for the inlet. The performance of this combination is shown in curve B, Fig. 6, and the relative capacity was 89.1 per cent, using the steam condensing capacity of the unenclosed radiator at the 80-deg. F. room temperature at the breathing line as 100 per cent. A grille having a ratio of free to gross area of 44 per cent, or a total free area of 209.4 sq. in., was then placed in the outlet, and the performance is shown by curve C. The relative capacity was reduced to 86.5 per cent. Hence adding the grille re- duced the performance of the same enclosure 2.9 per cent. Curve D, Fig. 6, shows the performance when a 12/2-inch by 50-inch vertical outlet having an area of 625.0 sq. in. was used at the top of the front of the enclosure. The relative capacity of this combi- EFFECT OF ENCLOSURES ON DIRECT STEAM RADIATOR PERFORMANCE 21 nation was 83.5 per cent. When the area of this outlet was reduced to 4 inches by 50 inches, or 200 sq. in., as shown by curve E, the relative capacity was reduced to 77.0 per cent. The addition of a grille, see curve F, reduced the relative capacity to 69.2 per cent. In this case the effect of the grille on the same combination was to reduce the performance 10.1 per cent. From these results it is apparent that the use of an enclosure materially affects the steam condensing capacity of a radiator, and that the use of a front vertical outlet, even with a comparatively large area, is less advantageous than the use of a top outlet. A grille causes more serious reduction when used with a front outlet than with a top outlet. Referring to Fig. 6 it may be noted that the performance curves are all practically parallel to each other and to the base curve of the unenclosed radiator. Therefore, although all of the values used in the discussion were based upon the performance with a breathing line temperature of 80 deg. F., the relative percentages quoted are approximately the same over the entire range of temperatures included in the tests, and may be used for all practical purposes. This is not true for any other series of tests. 13. Effect of Height of Enclosure.-The two groups of tests made in addition to those of Series I, for the purpose of determining the effect of the height of the enclosure, were known as Series II and III. This work was also continued under Series IV-a, IV-b, and IV-c tests, in connection with the tests made for studying the effect of size of air inlet. The general arrangements of the enclosures used are shown in Figs. 5 and 10 and in Figs. 6, 7, and 8 corresponding to the perform- ance curves. In every case the enclosures had solid ends and front, and in the tests of Series I, II, and III a 4-inch by 50-inch open inlet at the bottom of the front. In the tests made under Series IV-a, IV-b, and IV-c the inlet was 4 inches by 82% inches, extending across the entire bottom of the front and ends. The results obtained in Series I are shown in Fig. 6 and were dis- cussed in Section 12. Figure 7 shows the results of the tests included in Series II made with enclosures 55% inches high, and having a clear- ance of 17% inches between the top of the radiator and the top of the enclosure. Figure 8 shows the results of the third series of tests made with enclosures 72 inches high, and having a clearance of 34 inches between the top of the radiator and the top of the enclosure. With the exception of the increase in height, these enclosures were exactly similar in every respect to those used in Series I. The difference in relative capacity between the enclosures having similar inlet and outlet ILLINOIS ENGINEERING EXPERIMENT STATION characteristics was therefore due directly to the variation in height. In order to facilitate comparison, the results of the tests involving different heights have been grouped and are shown in Table 2. The relative capacities are based on the performance of both the enclosed and the unenclosed radiator at a breathing line temperature of 80 deg. F., and for other performances not at the given temperature range just stated direct reference may be made to the curves shown in Figs. 6, 7, 8, 11, 12, and 13. The results of the six groups of tests given in Table 2 show the consistent increase in capacity with height. The results of all of these tests are shown in slightly different form in Fig. 9 in order to permit interpolation for heights other than the ones tested. These curves indicate that the steam condensing capacity of an enclosed radiator is appreciably increased by increasing the height of the enclosure, but that the height increases at a greater rate than the performance. The last group of tests given in Table 2 shows that with the best combination of inlets and outlets the capacity of the enclosed radiator was greater than that of the unenclosed radiator for both the 55%-inch and the 72-inch heights. It may be noted by comparing the three groups of curves in Figs. 6, 7, and 8 that as the height of enclosure is increased the total spread of the curves becomes less, thus indicating that disadvantageous outlets have less effect when used with high enclosures than when used with lower ones. In conjunction with the tests in Series II and III, six groups of tests were made to determine whether a deflector in the top of the en- closure had any effect on the steam condensing capacity of the radi- ator. The same metal deflector, extending the full length of the enclosure, was used with each of the three front outlets shown corre- sponding to the performance curves D-l, E-l, and F-l, Figs. 7 and 8. The results obtained when the deflector was used are shown together with those obtained when it was not used, and it may be seen that the deflector did not have any appreciable effect. It was possible, there- fore, in every case to represent the performance of the enclosure with and without the deflector by means of a single curve. 14. Effect of Size of Air Inlet.-The greater portion of the work done for the purpose of determining the effect of size of air inlet was included in the tests of Series IV-a with enclosures 38 inches high, but some additional tests were also made in Series IV-b and IV-c in con- nection with the study of effect of height of enclosure. The enclosures used in Series IV-b were 55% inches high and those used in Series IV-c were 72 inches high. In all cases the enclosures with solid ends and fronts were used. By referring to Fig. 11, which shows the results of EFFECT OF ENCLOSURES ON DIRECT STEAM RADIATOR PERFORMANCE 23 TABLE 2 RELATIVE STEAM CONDENSING CAPACITIES OF ENCLOSURES OF DIFFERENT HEIGHTS Height of Relative Inlet Outlet Enclosure Tests Enclosure Capacity Number' in. per cent 1 Series I 38 89.1 9% in. x 50 in. 15 Series 11 55% 94.4 Open Top 23 Series III 72 99.3 2 Series I 38 86.5 g 9h in. x 50 in. 16 Series II 55% 89.9 Grilled Top 24 Series III 72 92.5 11 Series I 38 83.5 " 12% in. x 50 in. 22 Series II 55% 89.0 S Open Front O 30 Series III 72 91.7 S 6 Series I 38 77.0 4 in. x 50 in. 20 Series II 55Y 86.2 SOpen Front S28 Series III 72 90.2 7 Series I 38 69.2 4 in. x 50 in. 21 Series II 55% 78.3 Grilled Front 29 Series III 72 85.6 S3 Series IV-a 38 93.6 c.i 9% in. x 50 in. S17 Series IV-b 55% 104.0 M 0-g Open Top . o25 Series IV-e 72 109.1 *These numbers refer to the enclosure numbers given in Figs. 21 and 21-a, and the performances are shown there diagrammatically. Series IV-a tests, it may be noted that several different inlets were used in conjunction with four types of outlets. Two different inlets were used with the 9%-inch by 50-inch open top outlet and the 4-inch by 50-inch open front outlet. Three inlets were used with the 9%-inch by 50-inch grilled top outlet and the 4-inch by 50-inch grilled front outlet. The performances of these enclosures with the various combi- nations of inlets and outlets for a room temperature at the breathing line of 80 deg. F. are shown in Fig. 21 under enclosures Nos. 1 to 10. Figures 12 and 13 show the results obtained with enclosures 55% inches and 72 inches high, using four different inlets with a 9¼-inch by 50-inch open top outlet, and the capacities for a breathing line tem- perature of 80 deg. F. are given in Fig. 21-a, under enclosures Nos. 15, ILLINOIS ENGINEERING EXPERIMENT STATION 17, 18, 19, 23, 25, 26, and 27. Since the slopes of the performance curves in Series IV-a, IV-b, and IV-c vary considerably, the relative capacities given in Figs. 21 and 21-a are applicable only to the tem- perature ranges indicated, and in order, to determine the capacities at other ranges, direct reference must be made to the original curves given in Figs. 11, 12, and 13. Again referring to Fig. 11, and considering any group of curves for an enclosure with a given outlet, it may be noted that the relative positions and the slopes of the curves vary for different inlets. To point out and explain this fact the second group of curves may be used as an example. In all of the three cases, the enclosure had a grilled top outlet 91 inches by 50 inches. This outlet had a total free area of 209.4 sq. in. Three types of inlets were used. The first consisted of a 4-inch by 601/-inch slot across the bottom of the front and a 4-inch by 11-inch slot across the bottom of each end of the enclosure. This inlet had a total free area of 330 sq. in. and a total perimeter of 189 inches. The second was 4 inches by 50 inches, with an area of 200 sq. in., and a perimeter of 108 inches. The third was similar to the first except that the slots were two inches wide instead of four inches. This inlet had a total free area of 165 sq. in. and a total peri- meter of 177 inches. Since the outlet was always the same, the inlet was the determining factor and the relative capacities obtained with a breathing line temperature of 80 deg. F., for enclosures 2, 4, and 5, as shown in Fig. 21, were 86.5 per cent, 88.6 per cent, and 82.5 per cent, respectively. It may be noted that these relative capacities were in the order of the areas of inlet, with the maximum relative capacity corresponding to the maximum area. It may also be noted that the slope of the curve for the enclosure with the 4-inch by 50-inch inlet was greater than that for those with the 4-inch by 82%-inch and the 2-inch by 82%-inch inlets, which had practically the same slope. The following may serve as a possible explanation for this difference in performance. The difference in performance for the three enclosures is undoubt- edly caused by a difference in the frictional resistances and free areas 'of the inlets. The expression for head lost due to friction may be assumed to be of the form: f V2 L P 2gA EFFECT OF ENCLOSURES ON DIRECT STEAM RADIATOR PERFORMANCE 25 where h = the head lost in feet of fluid flowing f = the coefficient of friction V = the velocity in ft. per sec. L = the length of duct (or thickness of plate in this case) in feet P = the perimeter in feet A = the area in sq. ft. g = the acceleration due to gravity - 32.2 feet per sec. per sec. Assuming the same motive head, or temperature difference between air and steam, the area of the inlet orifice would determine the actual velocity through the inlet. As the area increased, the velocity would V2P V2 decrease. Since the head lost varies as and the fraction - would A A decrease at a greater rate than P increased, it is reasonable to pre- V2 P sume that , - and hence the friction loss, h, would decrease as A A is increased. Therefore A would be the factor that determines the relative positions of the three curves under discussion. This reasoning is substantiated by the fact that the maximum relative capacity was obtained with the maximum area of inlet, and the other relative capaci- ties were also in the same order as the inlet areas. In considering any one curve alone, it is evident that since A is constant, the head lost varies as V2P. As the room temperature de- creases, the available motive head, and hence the velocity, increases, and the condensation becomes greater. But the product V2P also in- creases with the velocity, thus tending to increase the head lost and to reduce the condensation below what would be obtained if friction did not exist. Therefore the product V2P determines the slope of the curves, and the smaller slopes correspond to the greater values of V2P. It is evident that if P is large, the slope will be small. This reasoning is substantiated also by the curves, since the 4-inch by 50-inch inlet with a perimeter of 108 inches gave a curve having the greatest slope, while the two others with perimeters of 189 inches and 177 inches, respectively, gave curves with practically the same slope, and less than that for the 4-inch by 50-inch inlet. The results of these tests indicate that the air inlet is an impor- tant factor in the performance of an enclosure, and that it should extend across the entire front and ends. This is shown by comparing the performance of any one of the enclosures, using first a 4-inch by 50- inch inlet, and then a 4-inch by 821/-inch inlet, all other factors re- maining the same. The ratio of the perimeter to the area is also of importance, and long narrow inlets are not desirable. ILLINOIS ENGINEERING EXPERIMENT STATION Enc/osure A was tested:- Us/nge punced mean / gr///e ron/t/ and so//a End7s. Per Cent Free Area' of 6rl/le =44. ( "js. /ol/es). Enc/losures A and s wer ,'es/ed-- (1)-(/s/[ipunch/d 7ear/ 4r// ,/ /7l ar73nd Ends. Pr Cent/ Free Area, of Sr,//e = 44. ( "s'. hol/es) (2)-/s/ng woven met/ gr//e' Fron/ t and Ends. Per -e enl/ Free Area, of 6r//i/e= 42. (3)-/s/kng voven w 'meta/ grlle F/ron and E'nds-. Per Cent Freen H-iea or crru/e AlPe e Peco, as 4nclosu/re Ri. Punched mei ga/'r// a/ways usedin, top o/,enm,, per cen/ Free Arear= 44. Enc/osures /Vos. /Z, /2~ , 1/3, /53, / 4, X /4a. (See F,5 . 2/e FIG. 14. ENCLOSURES USED IN SERIES V TESTS 15. Performance of Enclosures With Grilled Construction.-The group of tests made to show the effect of enclosing the radiator with enclosures having full grilled construction is designated as Series V, and the general arrangements of the enclosures may be seen in Figs. 14 and 15. The grilles used were: a woven metal grille having a ratio of free area to gross area of 53 per cent, a woven metal grille having a free area ratio of 42 per cent, and a punched metal grille having a free area ratio of 44 per cent. In computing the free areas of the various grilles, all the openings, both large and small, were included in the total free areas. Figure 16 shows the actual size and construction of the different grilles. Each grille was tested on two types of enclosures. One type had a 9/4-inch by 50-inch grilled opening in the top, while the other type had a solid top. One enclosure was constructed with solid ends and top, with the punched metal grille covering the front. Both the sheet iron and the grille work extended to within 4 inches of the floor. On all other enclosures the grille work began 4 inches above the floor and extended over the entire front and ends. EFFECT OF ENCLOSURES ON DIRECT STEAM RADIATOR PERFORMANCE 27 FIG. 15. ENCLOSURE WITH WOVEN METAL GRILLE CONSTRUCTION The results of the various tests are given by the curves in Fig. 17, and the tabulated values for enclosure Nos. 12, 12-a, 12-b, 13, 13-a, 14, and 14-a, in Fig. 21. The enclosure with the outlet in the top, and covered with the woven metal grille having a free area ratio of 53 per cent, gave a relative capacity of 93.1 per cent for a room temper- ature at the breathing line of 80 deg. F. This same enclosure with a solid top gave a relative capacity of 85.5 per cent, the solid top reducing the capacity approximately 8.2 per cent. Retaining the same general construction, a woven metal grille with 42 per cent free area ratio was substituted in place of the woven metal grille with 53 per cent free area. In the case of the enclosure with the outlet in the top, a relative capacity of 91.8 per cent was obtained, and with the solid top the relative capacity was 84.2 per cent. In this case the substitution of the solid top in place of the top with the grilled opening caused a re- duction in capacity of 8.3 per cent, which is approximately the same reduction as obtained when the enclosures were covered with the woven metal grille having a free area ratio of 53 per cent. The third construc- tion tested was similar to the first two with the exception that a punched metal grille having a free area ratio of 44 per cent was used in place of the woven metal grilles. Referring to Fig. 17, it may be noted that there was no appreciable difference between the perform- ILLINOIS ENGINEERING EXPERIMENT STATION FIG. 16. SECTIONS OF METAL GRILLES, ACTUAL SIZE EFFECT OF ENCLOSURES ON DIRECT STEAM RADIATOR PERFORMANCE 29 /ep7,oerat/re at -reaft//ng A/_"1e //2 d4eg. -. FIG. 17. PERFORMANCE CURVES FOR ENCLOSURES WITH VARIOUS GRILLED CONSTRUCTIONS ance of this enclosure and the one covered with the woven grille having a 42 per cent free area ratio. This was true of both the enclosure having an outlet in the top and the one with a solid top, and in each case the same curve served to represent the performance of the en- closure covered with either grille. The fourth construction tested was the one in which the enclosure had solid ends, with a punched grille front having a free area ratio of 44 per cent. This combination of front and ends was used with the solid top only and the results obtained are shown in Fig. 17 by the curve having the least slope. This curve indicates that for low motive heads, or small temperature differences between the radiator and the surrounding air, the enclosure with solid ends has a greater capacity than similar enclosures with ends of grilled construction. However, since the slope of this curve is much less than the slope of the performance curves for similar enclosures ILLINOIS ENGINEERING EXPERIMENT STATION Fio. 18. METAL RADIATOR SHIELD having grilled ends, the results obtained over the whole temperature range at which the tests were made show that for the motive heads found in common practice the grilled ends have a small advantage. For a room temperature at the breathing line of 80 deg. F. the relative capacity of the enclosure with the grilled construction having a 53 per cent free area ratio was only 1.3 per cent more than it was with the grilles having either 42 or 44 per cent free area ratio. This was true for both types of enclosures, the one with the outlet in the top and the one with the solid top. Thus it may be seen that, although the difference in the free area ratios of the grilles used was as great as 11 per cent, the difference in the relative capacities was only 1.3 per cent. This is very small in comparison with the effects of other factors, such as height, air outlets, and air inlets. EFFECT OF ENCLOSURES ON DIRECT STEAM RADIATOR PERFORMANCE 31 FIG. 19. RADIATOR WITH CLOTH COVER The enclosures used in this series of tests were very close approx- imations to the usual type of commercial enclosures, and while some improvement over the types having solid front and sides with slotted inlets and outlets was indicated, it is evident that any enclosure, unless extended to a considerable height above the top of the radiator, will reduce the condensation that would normally be expected from the bare radiator. 16. Performance of Metal Shield and Cloth Cover.-Tests of Series VI were made for the purpose of determining the effect of a common commercial type of metal radiator shield and a cloth radiator cover. The shield and cover tested are shown in Figs. 18 and 19, and again in Fig. 20 corresponding to the result curves. A general descrip- tion of both shield and cover was given in Section 8. Curve B, Fig. 20, shows the results of the tests made on the shield, and curve C the results of those made on the cloth cover. With a room temperature at the breathing line of 80 deg. F., the relative capacity ILLINOIS ENGINEERING EXPERIMENT STATION i '3 1 Tempera'/ure at B6rea'/h/'n2 LZi e /1? de. F FIG. 20. PERFORMANCE CURVES FOR METAL SHIELD AND CLOTH COVER of the radiator with the shield was 91.9 per cent, comparing favorably with the relative capacities of 91.8, 91.8, and 93.1 per cent for the enclosures with grilled construction having grilled openings in the top. However, when this is compared with the relative capacities of 84.2, 84.2, and 85.5 per cent for the enclosures with grilled construction hav- ing solid tops, the effect of the shield is seen to be less disadvantageous than the effects of enclosures which are very close approximations to the commercial types. The relative capacity of the radiator with a cloth cover for a room temperature at the breathing line of 80 deg. F. was 88.0 per cent. These values are tabulated in Fig. 21-a, under shield No. 1, and cover No. 1. EFFECT OF ENCLOSURES ON DIRECT STEAM RADIATOR PERFORMANCE 33 V. CONCLUSIONS 17. Conclusions.-As a result of this investigation the following conclusions were drawn: (1) The one-pipe connection to the radiator, in which the steam enters and the condensate leaves through the same connec- tion, gives very consistent and satisfactory results when used for the determination of the steam condensing capacity of radiators. (2) The coefficient of heat transmission K, or the heat trans- mitted per sq. ft. of radiation per degree temperature difference per hour, may be corrected to terms of a temperature range devi- ating (within reasonable limits) from the standard range of 145 deg. F., either by the 0.2 per cent rule proposed by Charles A. Fuller* or by the exponential rule proposed by Dr. Dietz.t (3) The type of air outlet used materially affects the per- formance of a radiator enclosure, and a front outlet, even with a comparatively large area, is less advantageous than a top outlet. (4) The capacity of an enclosed radiator is appreciably in- creased by increasing the height of the enclosure, but, for a given radiator, an increase in height with low enclosures results in a greater gain in steam condensing capacity than a corresponding increase in height with high enclosures. (5) By using the proper combination of inlets and outlets and increasing the height of the enclosure a sufficient amount, it is possible to increase the steam condensing capacity of the enclosed radiator above that of the unenclosed radiator. (6) Disadvantageous outlets have less effect when used with high enclosures than when used with lower ones. (7) The frictional resistance in the air inlet is an important factor in the design of an enclosure, and long narrow inlets having large ratios of perimeter to area are undesirable. (8) Enclosures which were very close approximations of common commercial types reduced the relative capacity of the radiator approximately 15 per cent. (9) The common commercial shield tested reduced the rela- tive capacity of the radiator about 8 per cent. (10) The cloth cover tested reduced the relative capacity about 12 per cent. *Harding, L. A., and Willard, A. C., "Mechanical Equipment of Buildings," Vol. I, First Edition, page 78. tBrabbhe, C. W., "Heating Effect of Radiation," Journal of the A. S. H. and V. E., Vol. 31, No. 11, November, 1925, page 502. ILLINOIS ENGINEERING EXPERIMENT STATION Descript/fon of Enc/osure Enclosure He/'1ht of Top of Free Area /Frw Area mer closure Above /n/t Out/et of/n/et of Ou/le Top of 4ad,/or sq in sq. J Radiator not enclosed-Pa/'aed w/Y1 two coats blac- Pfcoa p/ia,/ (/Nofa peled / ~ 450''Aross iI50Oet O0 46.s S 0.0 fronst top 2a0 46> 2 4" 4'iS~6'Across 9~50'r/7/edw _ _t freonmi top we00 0o 0 3 . 4 I'Ac2mross 1g'SO ope S" front anden fop .0 462 4 0.0, 4'i'Acrioss 4'r50'"Gr//e/ _ o front fn ns top 3ao 5 0,0 4'r82j 'Across 4) 0'iSOr///Pe Sf ront and ends top /6s0 204 6 00" 4O"r Across 4'i50 "Open e S _ _front_ fr fronot t 200.0 7 00" 4r'0iAcross 450"'Gr///ea z fro'nt froli/t00 19 "9.. s40Open 30 2 front o l: froot 330a0 4. 06Zj'Acoss d6'50Gril/ed 3300 / front and ends front / // 4', 4x'SO'cross /I2'fX5Open front front IO 0 tro .Z Punch/edgri/q fron,, so/dl ends and oop GrI/-w3ork beg/7- q/ng 4"abow floo Fnre wa0 gri, 44 ,. 's. ho/es. /Za 00' Some as I/ wfih punched gri// en's /2h 0.0 Same as /ta iyvh 9/Sb O gfri/d tofp out/et (f sq ho/es) /3 00, Woven meta/l r//l front and etms, soll iop. Gril-work hbegimnny 4'aIve /oo: /-ree are gr/i// 42 %. /3as a" Sa7me as /3 wi/ 9SfI 'yrl//e/fd(i;ok.) top of/// /4 00, Woven meta/ r / fl roan/ nd enfa, sol/d' to Gri// w 00iy/k m 4 awi' floor ree arrea gr/// 5 /4a 00o" Sme as /4 with .fi;SOr///led(f4Apo/es pO out/et A/ole." O-Secfhon, 3 Col, C., Water Type Road'/tor (Direct) /lsed /,' a// rTess. 2/-/ FIa. 21. GRAPHICAL TABLE OF REBULTS I EFFECT OF ENCLOSURES ON DIRECT STEAM RADIATOR PERFORMANCE 35 Ne/ Pounds of Steam Condensedn Roadra/or per Hour % o o o o % % % N "I %O 16 %, IN V "IS "I ı ı \ k% %W /9.53 R'e/a//ive Condens/'ng Capacity/ Per Ceno, /oao WheMn g.i'/7 Elc/osure, TO adtion To To Add Sub/t /8.98 665 /6 20.53 93.6 7 /9.43 88.6 /3 /8.09 82.5 2/ /689 77.0 30 /5/? 69.2 45 /7.50 79.8 25 /£/7 69.2 45 /487 678 47 /83/ 83.5 20 /8.67 85./ /7 /8.47 84.2 /9 20./4 9/.8 9 /8.47 84.2 /9 20./4 9/.8 9 /8.74 85.5 /7 20.42 93./ 7 Steaz' Tpera/fwre Cons/tant/ 2/6E Brealhbin L,/ Tep. = ILLINOIS ENGINEERING EXPERIMENT STATION Description of Enco/asure Enc/osure Y/'gh aof Top of /Fre Area Free Arew Numb/er Enc/osure Aboe /n/et Out//e/ of /n/e of Ou'//e Top of Radio/ar s7.m . sq //i. a/flr/aor no/ enc/osead- Pa1tred w/b two coats b/ack Pecorar pain'// /Vo dopped) /s /7" 4'XSO'Across 9w'50" Opvn Z 465 front lop 16 /7" 4X~I"Across 9 SOr//led ZO0. 209.4 front top /7 7f 4'Zj Across 9ı'ISaope 3366 462.5 front' andenods topo /6 17J" ZlZj"Across 9SS50Ope4; 2663 462.5 front andends top /9Z ,7d Across 197SOOpenm 1/5 462.5 front and ends top /54"r!"Across 2 pde nro 4 with andw//hout 2O6O 260,6 front de/ecf or ,, 4"'50'Across 4'rSO'5nw//frona 2/ /7a wih andwi;hout 2066 92./ Front def/ec/or 22 /7w 4' th"Across whan ho 2a 9. front deF/ector  34 4aSO 'Aross '050O "Open 2000 462.5 front top 24 344~ 6"Across A o'61r#/led 2600. 26~.4 front top Z5 4'XSri'Acros 94s550'pe/; 33a.0 462.5 front mon ends top 26 34' Z e'i'Across 94'50'0pen 26. 462 front nd ends top 7 34" ~*x2 ' 'Across 9;F'5"Omen /65. 462.5 front and ends top 4'50" 'Across 450"Open front, with aondwihout 20.6 2600.6 front def/ector 34 450 Across 06e/ 2root 29 34 with and wihot 200.0 92.1 front deflector 4"X50s 'Across ithZY'fOe Pat, 3 34" with andwithou 200.0 625.0 front deflector d Meta/ Sht/a: w/ih /nsu//aed Top; No //aum/o'/er. Vote . ZO-Sec/ion, 3 Co, C,, Water Type Roa'/tor (Direc/) ./sed /i a// Tests. 2/-a-/ FIG. 21-a. CONTINUATION OF GRAPHICAL TABLE OF RESULTS EFFECT OF ENCLOSURES ON DIRECT STEAM RADIATOR PERFORMANCE 37 Aet Ponads of Steam Condensed, i Raa/a/orrber /our o % o oo ^oo 14 N v % % ^ ! V 1% 2197 20.7/ '5.7/ 2/./4 20.23 /9.5/ 2/.78 20 28 23.92 ZZ. 52 2/.5/ /9.78S /8.77 20./0 2Od/'6 Re/af/'w Conlensin Per Cen, /000 894 9104 /040 89..3 99.3 92.5 /o0./ /02.7 98./ 90.2 856 9/.? 9/.9 k We4 U5,t7g To Add 6 // 4 /2 / 8 2 // /7 9 9 To Y^\htr W/^/ir^ 4 8 3 N/ote: Stram aTmperaturf Constant a 2/6' Breathina iLwe Temp. - 80 Z/-a-2 _ _ _ _ RECENT PUBLICATIONS OF THE ENGINEERING EXPERIMENT STATIONt Bulletin No. 129. An Investigation of the Properties of Chilled Iron Car Wheels. Part I. Wheel Fit and Static Load Strains, by J. M. Snodgrass and F. H. Guldner. 1922. Fifty-five cents. Bulletin No. 180. The Reheating of Compressed Air, by C. R. Richards and J. N. Vedder. 1922. Fifty cents. Bulletin No. 11. 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The Oiling of Earth Roads, by Wilbur M. Wilson. 1924 Fifteen cents. Bulletin No. 143. Tests on the Hydraulics and Pneumatics of House Plumb- ing, by H. E. Babbitt. 1924. Forty cents. Bulletin No. 144. Power Studies in Illinois Coal Mining, by A. J. Hoskin and Thomas Fraser. 1924. Forty-five cents. Circular No. 12. The Analysis of Fuel Gas, by S. W. Parr and F. E. Vanda- veer. 1925. Twenty cents. Bulletin No. 146. Non-Carrier Radio Telephone Transmission, by H. A. Brown and C. A. Keener. 1925. Fifteen cents. tOnly a partial list of the publications of the Engineering Experiment Station is published in this bulletin. For a complete list of the publications as far as Bulletin No. 134, see that bulletin or the publications previous to it. Copies of the complete list of publications can be ob- tained without charge by addressing the Engineering Experiment Station, Urbana, Ill. ILLINOIS ENGINEERING EXPERIMENT STATION Bulletin No. 146. Total and Partial Vapor Pressures of Aqueous Ammonia Solutions, by T. A. Wilson. 1925. Twenty-five cents. Bulletin No. 147. Investigation of Antennae by Means of Models, by J. T. Tykociner. 1925. Thirty-five cents. Bulletin No. 148. Radio Telephone Modulation, by H. A. Brown and C. A. Keener. 1925. Thirty cents. Bulletin No. 149. An Investigation of the Efficiency and Durability of Spur Gears, by C. W. Ham and J. W. Huckert. 1925. Fifty cents. Bulletin No. 150. A Thermodynamic Analysis of Gas Engine Tests, by C. Z. Rosecrans and G. T. Felbeck. 1925. Fifty cents. Bulletin No. 151. A Study of Skip Hoisting at Illinois Coal Mines, by Arthur J. Hoskin. 1925. Thirty-five cents. Bulletin No. 152. Investigation of the Fatigue of Metals; Series of 1925, by H. F. Moore and T. M. Jasper. 1925. Fifty cents. *Bulletin No.153. The Effect of Temperature on the Registration of Single Phase Induction Watthour Meters, by A. R. Knight and M. A. Faucett. 1926. Fifteen cents. *Bulletin No.154. An Investigation of the Translucency of Porcelains, by C. W. Parmelee and P. W. Ketchum. 1926. Fifteen cents. Bulletin No. 155. The Cause and Prevention of Embrittlement of Boiler Plate, by S. W. Parr and F. G. Straub. 1926. Thirty-five cents. Bulletin No.156. Tests of the Fatigue Strength of Cast Steel, by H. F. Moore. 1926. Ten cents. *Bulletin No.157. An Investigation of the Mechanism of Explosive Reac- tions, by C. Z. Rosecrans. 1926. Thirty-five cents. *Circular No. 13. The Density of Carbon Dioxide with a Table of Recalcu- lated Values, by S. W. Parr and W. R. King, Jr. 1926. Fifteen cents. *Circular No. 14. The Measurement of the Permeability of Ceramic Bodies, by P. W. Ketchum, A. E. R. Westman, and R. K. Hursh. 1926. Fifteen cents. *Bulletin No. 158. The Measurement of Air Quantities and Energy Losses in Mine Entries, by A. C. Callen and C. M. Smith. 1926. Forty-five cents. *Bulletin No. 159. An Investigation of Twist Drills. Part II, by B. W. Bene- dict and A. E. Hershey. 1926. Forty cents. *Bulletin No. 160. A Thermodynamic Analysis of Internal Combustion Engine Cycles, by G. A. Goodenough and J. B. Baker. 1927. Forty cents. *Bulletin No.161. Short Wave Transmitters and Methods of Tuning, by J. T. Tykociner. 1927. Thirty-five cents. Bulletin No. 16. Tests on the Bearing Value of Large Rollers, by W. M. Wilson. 1927. Forty cents. *Bulletin No. 163. A Study of Hard Finish Gypsum Plasters, by Thomas N. McVay. 1927. Twenty-five cents. Bulletin No.164. Tests of the Fatigue Strength of Cast Iron, by H. F. Moore, S. W. Lyon, and N. P. Inglis. 1927. Thirty cents. Bulletin No. 165. A Study of Fatigue Cracks in Car Axles, by H. F. Moore. 1927. Fifteen cents. Bulletin No.166. Investigation of Web Stresses in Reinforced Concrete Beams, by F. E. Richart. 1927. Sixty cents. *Bulletin No. 167. Freight Train Curve Resistance on a One-Degree Curve and a Three-Degree Curve, by Edward C. Schmidt. 1927. Twenty-five cents. *Bulletin No.168. Heat Transmission Through Boiler Tubes, by Huber O. Croft. 1927. Thirty cents. *Bulletin No.169. Effect of Enclosures on Direct Steam Radiator Perform- ance, by Maurice K. Fahnestock. 1927. Twenty cents. "A limited number of copies of bulletins starred are available for free distribution. THE UNIVERSITY OF ILLINOIS THE STATE UNIVERSITY Urbana DAVID KINLEY, Ph.D., LL.D., President THE UNIVERSITY INCLUDES THE FOLLOWING DEPARTMENTS: The (raduate School The College of Liberal Arts and Sciences (Curricula: General with majors, in the Humanities and the Sciences; Chemistry and Chemical Engineering; Pre-legal, Pre-medical, and Pre-dental; Pre-journalism, Home Economics, Economic Entomology, and Applied Optics) The College of Commerce and Business Administration (Curricula: General Business; Banking and Finance, Insurance, Accountancy, Railway Adminis- tration, Railway Transportation, Industrial Administration, Foreign Com- merce, Commercial Teachers, Trade and Civic Secretarial Service,-Public Utilities, C6mmerce and Law) The College of Engineering (Curricula: Architecture, Ceramics; Architectural, Ceramic, Civil, Electrical, Gas, General, Mechanical, Mining, and Railway Engineering; Engineering Physics) The College of Agriculture (Curricula: General Agriculture; Floriculture; Home Economics; Landscape Architecture; Smith-Hughes-in conjunction with the College of Education) The College of Education (Curricula: Two year, prescribing junior standing for admission-General Education, Smith-Hughes Agriculture, Smith-Hughes Home Economics, Public School Music; Four year, admitting from the high school-Industrial Education, Athletic Coaching, Physical Education The University -'igh School is the practice sbhool of the College of Education) The School of Music (four-year curriculum) The College of Law (three-year curriculum based on two years of'college work; For requirements after January 1, 1929 address the Registrar) The Library School (two-year curriouluin for college graduates) The School of Journalism (two-year curriculum based on two years of college work) The College of Medicine (in Chicago) The College of Dentistry (in Chicago) The School of Pharmacy (in Chicago) The Summer Session (eight weeks) Experiment Stations-and Scientific Bureaus: U. S. Agricultural Experiment Station; Engineering Experiment Station; State Natural History 7Survey; State Water Survey; State Geological Survey; Bureau of Educational Research. The Library collections contain (June 1, 1926) 711,753 volumes and 155,331 pamphlets. Far catalogs and information address -THE REGISTRAR Urbana, Illinois h i-- *y>^ -c: