Document x5qMppg2xZkgNyJy0kddo4pKy

HEATING VENTILATING AIR CONDITIONING CUIDE 1942 the radiator and the air in the room, and is expressed in Btu or Mb per hour. Standard test conditions specify either a steam pressure of 1 lb gage 15.6 lb per square inch absolute (215 F) or an average hot water tempera ture of 170 F and a room temperature of 70 F (5 ft above floor) for radiators, or an inlet air temperature of 65 F for convectors. The heating capacity of a steam radiator or steam convector is determined as follows: where Ht = tVshig Ht = Btu per hour under test conditions. ft's -- condensation in pounds per hour. hfg = latent heat in Btu per pound. (2) Table 5. Correction Factors for Direct Cast-Iron Radiators and Convectors ' $TBAM Proa. Heating Medium Factors tor Direct Cart-Iron Radiators Factors for Convectors Approx. Temp. F Gage Abs. Steam Room Temperature F AmInlet Temperature F - Vacuum Lb per oh Id. Hg. SqloL Wateb 80 75 70 65 60 55 50 80 75 70 65 60 55 50 22.4 20.3 17.7 14.6 10.9 6.S Lbper8qIo. 1 6 15 27 52 3.7 4.7 6.0 7.5 94 11.5 15.6 21 30 42 67 150 2.58 246 2.17 2.00 146 1.73 1.62 3.14 2.83 2.57 245 2.15 1.98 1.81 160 2.17 2.00 146 1.73 1.62 1.52 1.44 2.57 2.35 2.15 1.98 144 1.71 149 170 1.86 1.73 1.62 1.52 1.44 1.3S 1.28 2.1S 1.98 1.84 1.71 1.59 1.49 1.40 180 1.62 1.52 1.44 1.35 1.28 1.21 1.15 144 1.71 1.59 1.49 1.40 142 l.U 190 1.44 145 1.28 1.21 1.15 1.10 1.05 149 1.49 1.40 1.32 1.24 1.17 Ml 200 1.28 1.21 1.15 1.10 1.05 1.00 0.96 1.40 142 1.24 1.17 Ml 1.05 1.00 215 1.10 1.05 1.00 0.96 0.92 0.88 0.85 1.17 1.11 1.05 1.00 0.95 0.91 047 230 0.96 0.92 048 045 041 0.78 0.76 1.00 0.95 0.91 047 0.83 0.79 0.76 250 081 0.78 0.76 0.73 0.70 0.68 0.66 0.83 0.79 0.76 0.73 0.70 0.68 0.65 270 0.70 0.68 0.66 0.64 0.62 0.60 0.58 0.70 0.68 0.65 0.63 0.60 0.58 046 300 0.58 0.57 0.55 0.53 0.52 0.51 0.49 0.56 0.54 0.53 0.51 0.49 0.48 0.47 To determine the size of a radiator or a convector for a given space, divide the heat loss in Btu per hour by 240 and multiply the result by the proper factor from the above table. To determine the heating capacity of a radiator or a convector under conditions other than the basic ones with the heating medium at a temperature of 215 F. and the room temperature at 70 F in the case of a radiator, and the inlet air temperature at 65 F in the case of a convector, divide the heating capacities at the basic conditions by the proper factor from the above table. Ht may be converted to standard conditions of code ratings by using the proper correction factor from the following formulae: For radiators: /215 - 70\l-3 V la -- Tt / For convectors: /215 - 65\ V T, - T; ) (3) The output under standard conditions will be: where H3 = C Ht C8 = correction factor. Tb = steam temperature during test, degrees Fahrenheit. TV = room temperature during test, degrees Fahrenheit. Ti = inlet air temperature during test, degrees Fahrenheit. Ht = heat emission rating under standard conditions, Btu per hour. (4)- 264 CHAPTER 13. RADIATORS AND CONVECTORS Similarly, for hot water convectors, the output under test conditions may be determined as follows: H = w (fl. -- 0,) (5) where H = Btu per hour under test conditions. W = pounds of water handled during test. 0, = average temperature of inlet water, degrees Fahrenheit. 0, =s average temperature of outlet water, degrees Fahrenheit. t = duration of test, seconds. To convert test results to standard conditions, the following correction factor is used: /_ 170 - 65 \1- V -- ------TtJ j 105 V 8i + 6* 2 (6) It has been shown that when the exponent 1.5 is used the range of error is less than 3 per cent16 for convectors. "Loc. Cit. Note 12. 265