Document bBKY3jZ0OvERam5jEYyNBz2RD

132 . Am. Soc. of Heat.-Vent. Engineers Guide. 1922 Case No. 6. Radiators are often placed under seats as in Fig. 13. In this case the distance between the top of the radiator and the bottom of the seat becomes'very important and should be not less than 3 in. and if possible it should be made 6 in. Under favorable conditions, when D is at least 3 in. and A is equal to 6 in., the heat transmission will be reduced from 15 to 20 per cent. When D is small, however, say 2 in., and A is reduced to 4 in., this reduction may be 35 or 40 per cent. In tests1 by Prof. K. Brabbee will be found other cases than those cited above. EFFECT OF POSITION The effect of position on the heat transmission of a radiator is a subject that has been investigated only to a very limited extent. The experiments that are available show that the heat loss from a radiator is about the same whether it is placed at the floor, at the ceiling, cr in the center of the room. It seems to make very little difference whether it is placed close to the wall or in the middle of the room. Placing a radiator close to an outside wall heats the wall immediately behind the radiator and if no insulation is placed behind the radiator this may represent a loss of from 3 to 5 per cent. __ / - 1 Reported by George Stumpf, Jr., in Heating & Ventilating Magazine, May, 1914, page 23. HEAT LOSSES FROM BUILDINGS The following table from The Establishment, of Standard Methods of Proportioning Direct Radiation, by James A. Donnelly, (Vol. 21, A. S. H. V. E. Transactions, p. 535) gives the proportionate heat losses from buildings, the proportionate transmission from direct radiators, and the proportionate radiation required (with steam at 210 deg.) for various room temperatures, when the outside temperature is zero: Room Tempera ture 35 40 45 50 55 60 65 70f 75 80 85 90 95 100 105 110 115 120 Propor tionate Loss in B.t.u. 0.50 0.57 0.64 0.71 0.79 0.86 0.93 l.OOf 1.07 1.14 1.21 1.29 1.36 1.43 1.50 1.57 1.64 1.71 Difference in Temperature between Radiator and Room 175 170 165 160 155 150 145 140f 135 130 125 120 115 110 105 100 95 90 Propor tionate Trans mission in B.t.u. 1.34 1.29 1.24 1.19 1.14 1.09 1.05 l.OOf 0.95 0.91 0.87 0.82 0.78 0.74 0.70 0.66 0.62 0.58 Room Tempera ture 35 40 45 50 55 60 65 70f 75 80 85 90 95 100 105 110 115 120 Propor tionate Surface Required Sq. Ft. 0.37 0.44 0.52 0.60 0.69 0.78 0.89 l.OOf 1.12 1.26 1.40 1.56 1.74 1.93 2.15 2.39 2.66 2.95 f Standard Conditions. Assuming that the rate of heat loss from a build ing varies directly with the difference between the out side temperature and the building temperature, and considering the heat loss for zero outside, 70 deg. inside, as the standard, or 100 per cent.; the second column shows the propor tionate loss of heat from a building when the outside temperature is zero, and the inside temperature is as given in the first column. Assuming that the rate Assuming that under of transmission from a di standard conditions of out- rect radiator to the air of side temperature zero, a building is in proportion building temperature 70 to their difference in tem deg., and radiator tem perature, with a variation perature 210 deg. (or 140 in the rate of transmission degrees difference between of 2 per cent., greater or the radiator and room) less, for each 10 deg. in the amount of radiation crease or decrease in their necessary is 100 per cent., temperature difference, and the proportionate amounts considering 140 deg. differ of radiation given in the ence in temperature (steam second column are those 210 deg., building 70 deg.) necessary to heat a build as standard, or 100 per ing to the temperatures cent, transmission, the sec given in the first column, ond column shows the pro when the outside tempera portionate transmission ture is zero. when the difference in tem perature is as given in the first column. Note.--The amount of surface required for heating is always obtained by dividing the heat loss from the building by the amount of heat transmitted per .square foot of radiation. ^ Therefore, as may be seen from the above tables, the proportionate amount of surface required for heating is obtained by dividing .the proportionate heat loss from the building by the propor tionate transmission of the radiator, in each case. 133