Document VjoBeLMp8E0np9VdE3kYXvd64

528 CHAPTER 22 1951 Guide ing line may not be indicative of the actual heating effect of a radiator in the room. The comfort-indicating temperature Bhould be taken below the breathing line level. 5. High column radiators placed at the sides of. window openings do not produce as comfortable heating effects as long, low, direct radiators placed beneath windows. HEATING THE RADIATOR AND CONVECTOR The maximum condensation occurs in a heating unit when the steam is first turned on. Tests19 on an old-style column-type cast-iron radiator indicated that in the first 10 min the condensation rate reached a'peak of 0.95 lb per sq ft of radiator per hour and 10 to 15 min later dropped to a rate of 0.24 lb. In one-pipe gravity systems the rate of steam supply to the heating unit, while heating up, is frequently retarded by controlled elimination of air through air valves or traps. In two-pipe systems auto- Fig. 4. Steam Consumption of Exposed and Concealed Radiators matic control valves may also retard the supply of steam. Vacuum types of air venting valves may be used to reduce the length of the venting periods. ENCLOSED RADIATORS The general effect of an enclosure placed about a direct radiator is to restrict the air flow, diminish the radiation and, when properly, designed, improve the heat distribution within the heated space. . Investigations13 indicate that in the design of the enclosure three things should be considered: i Sis!i 1. There should be better distribution of the heat below the breathing line level to produce greater heating comfort and lowered ceiling temperatures. 2. The lessened Bteam consumption may not materially change the radiator heat ing performance. 3. The enclosed radiator may inadequately heat the space. A comparison between a bare or exposed radiator (A) and the same radi ator with a well-designed enclosure (B), with a poorly-designed enclosure (C)j and with a cloth cover (D) will illustrate the relative heating character istics. In Fig. 4 the curve (B) reveals that- the enclosed radiator used'less steam than the exposed radiator, but gave a satisfactory heating perform- Radiators and Convectors 529 ance. A well-designed shield placed over a radiator gives about the same result. Curve (C) shows the unsatisfactory effects produced by improperlydesigned enclosures. Curve (D) shows that the effect of a cloth cover extending downward 6 in. from the top of the radiator was to make the performance unsatisfactory and inadequate. Some commercial enclosures and shields for use on direct radiators are equipped with water pans for the purpose of adding moisture to the air in the room. Tests20 show that an average evaporative rate of about 0.235 lb per square foot of water surface per hour may be obtained from such pans, when a radiator is steam heated and the relative humidity in the room is between 25 and 40 percent. This source of supply of moisture alone is not adequate to maintain a relative humidity above 25 percent on a zero day. REFERENCES 1 I=B=R Installation Guide No. 5, Baseboard Heating Systems, Institute of Boiler and Radiator Manufacturers, New York. A Study of Radiant Baseboard Heating in the I=B=R Research Home, by Alonzo P. Kratz and Warren S. Harris (University of Illinois, Engineering Experi ment Station Bulletin No. 358, 1945). I I=B=R Testing and Rating Code for Baseboard Type of Radiation (Institute of Boiler and Radiator Manufacturers, First Edition, July 1950). `A.S.H.V.E. Code for Testing Radiators (A.S.H.V.E. Transactions, Vol. 33, 1927, p. 18). ' A.S.H.V.E. Standard Code for Testing and Rating Concealed Gravity Type Radiation (Steam), (A.S.H.V.E. Transactions, Vol. 37,1931, p. 367): (Hot Water), (A.S.H.V.E. Transactions, Vol. 39, 1933, p. 237). (See also A.S.H.V.E. Trans actions, Vol. 41,1935, p. 38, and Vol. 42,1936, p. 29). A.S.H.V.E. Research Report No. 998--Factors Affecting the Heat Output of Convectors, by A. P. Kratz, M. K. Fahnestock, and E. L. Broderick (A.S.H.V.E. Transactions, Vol. 40,1934, p. 443). 7 Factors Influencing the Heat Output ofRadiators, by A. C. Davis, W. M. Sawdon and David Dropkin (A.S.H.V.E. Transactions, Vol. 42, 1942, p. 185) and (Cornell University, Engineering Experiment Station Bulletin No. 29, April, 1942). Heat Emission from Radiators, by K. F. Hubert (Cornell University, Engineering Experiment Station Bulletin No. 24,1937). Comparative Tests of Radiator Finishes, by W. H. Severns (A.S.H.V.E. Trans actions, Vol. 33,1927, p. 41). 19 Heat Loss from Direct Radiation, by J. R. Allen (A.S.H.V.E. Transactions, Vol. 26,1920, p. 11). II Heat Output of Concealed Radiators, by E. A. Allcut (University of Toronto, School of Engineering Research Bulletin No. 140,1933). 17 The Heating Effect of Radiators, by Charles Brabble (A.S.H.V.E. Transac tions, Vol. 33, 1927, p. 33). u Investigation of Heating Rooms with Direct Steam Radiators Equipped with Enclosures and Shields, by A. C. Willard, A. P. Kratz, M. K. Fahnestock and S. Konzo (A.S.H.V.E. Transactions, Vol. 35, 1929", p. 77 or University of Illinois, Engineering Experiment Station Bulletin No. 19i) . Investigation of Various Factors Affecting the Heating of Rooms with Direct Steam Radiators, by A. C. Willard, A. P. Kratz, M. K. Fahnestock and S. Konzo (University of Illinois, Engineering Exper iment Station Bulletin No. 223). 14 A.S.H.V.E. Research Report No. 962--The Application of the Eupatheoscope for Measuring the Performance of Direct Radiators and Convectors in Terms of Equivalent Temperature, by A. C. Willard, A. P. Kratz and M. K. Fahnestock (A.S.H.V.E. Transactions, Vol. 39,1933, p. 303). " The Kata Thermometer--Its Value and Defects, by W. J. McConnell and C. PYagloglou. (Reprint No. 953 from U. S. Public Health Service Report, pp. 2293-2337, September 5,1924)..