Document 2joBE7rx3L3jzNmX7wbL4Nw47

HEATINC VENTILATING AIR CONDITIONING GUIDE 1944 environments in which the air and all surrounding surfaces are at the same temperature. The temperatures of the uniform environments are referred to as equivalent temperatures. Data given in Fig. 2 show that while the air temperature at the 30 in. level is the same for the three convectors and the one large-tube cast-iron radiator, in position No. 3 in the test room, the equivalent temperature is 1.5 F lower than the air temperature in the case of the three convectors, and the same as the air temperature in the case of the radiator. The difference between the minimum and the maximum amount of heat required to maintain the common air temperature at the 30 in. level is of the order of 13 per cent. In Fig. 3 are shown the results of tests made with the same three convectors and the one large-tube cast-iron radiator, so adjusted in size that each gave approximately the same equivalent temperature in the No. 3 position in the test room. The difference between the miminum and the maximum amount of heat required to maintain the common equivalent temperature is of the order of 7 per cent. The Kata thermometer11, the thermo-integrator12,13, and the globe14 thermometer are other instruments which have been used to measure the influence of air temperature, air movement and radiation in an environment. The following statements applying to the use of radiators are based on experience and test results: 1. The heating effect of a radiator cannot be judged solely by the amount of steam condensed within the radiator. 2. Smaller floor-to-eeiling temperature differentials can be maintained with long, low, thin, direct radiators, than is possible with high, direct radiators. 3. The larger portion of the floor-to-ceiling temperature differential in a room of average ceiling height heated with direct radiators occurs between the floor and the breathing level. 4. The comfort level (approximately 2 ft-6 in. above floor) is below the breathing line level (approximately' 5 ft-0 in. above floor), and temperatures taken at the breathing line may not be indicative of the actual heating effect of a radiator in the room. The comfort-indicating temperature should 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 window openings. HEATING UP THE RADIATOR AND CONVECTOR The maximum condensation occurs in a heating unit when the steam is first turned on. Tests15 on an old-style column-type cast-iron radiator indicated that in the first 10 min the condensation rate reached a peak of "The Kata Thermometer--Its Value and Defects, by W. J. McConnell and C. P. Yagloglou. (Reprint .No. 953 from U. S. Public Health Service Report, pp. 2293-2337, September 5, 1924). "The Thermo-Integrator--A New Instrument for the Observation of Thermal Interchanges, by C.-E. A. Winslow and Leonard Greenburg (A.S.H.V.E. Transactions, Vol. 41, 1935, p. 149), "The Calibration of the Thermo-Integrator, by C.-E. A. Winslow, A. P. Gagge. Leonard Greenburg, I. M. Moriyamaand E. J. Rodee. (The American Journal of Hygiene, Vol. 22, No. 1, July, 1935, pp. 137-156). "The Globe Thermometer in Studies of Heating and Ventilation, by T. Bedford and C. G. Warner. (The Journal of Hygiene, Vol. 34, No. 4). "A.S.H.V.E. Research Report No. 1067--The Cooling and Heating Rates of a Room with Different Types of Steam Radiators and Convectors, by A. P. Kratz, M. K. Fahnestock and E. L. Broderick (A.S.H.V.E. Transactions, Vol. 43. 1937, p. 389). 258 CHAPTER 13. RADIATORS AND CONVECTORS 0.95 lb per square foot of radiator per hour and 10 to 15 min later lowered to a rate of 0.24 lb. In practice 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. Automatic 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, Fig. 4.. Steam Consumption of Exposed and Concealed Radiators improve the heating effect. Investigations16 indicate that in the design of the enclosure three things should be considered: 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 steam consumption may not materially change the radiator heating performance. 3. The enclosed radiator may inadequately heat the space. A comparison between a bare or exposed radiator (A) and the same radiator with a well-designed enclosure (5), with a poorly-designed enclosure (C), and with a cloth cover (D) will illustrate the relative heating effects. In Fig. 4 the curve (5) reveals that the enclosed radiator used less steam than the exposed radiator, but gave a satisfactory heating performance. A well-designed shield placed over a radiator gives about the same heating effect. Curve (C) shows the unsatisfactory effects produced by improperly-designed enclosures. Curve (D) shows that the "University of Illinois, Engineering .Experiment Station Bulletins Nos. 192 and 223, and 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). 259