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American Society of Heating and Ventilating Engineers Guide, 1924-25 the first column; divide the proportionate heat loss opposite this amount, in the second column, by the proportionate transmission opposite the difference in temperature between the radiator and the room, as given in the fourth column, and the result will be the proportionate amount of radiation required. Example.--What is the proportionate amount of radiation required to heat a room to 90 deg., with a temperature of 20 deg. below zero outside, and a steam temperature of 240 deg. Solution.--The difference in temperature between 20 deg. below outside, and 90 deg. inside, is 110 deg. Opposite 110, the propor tionate heat loss or 1.57 is found in the second column. The difference in temperature between the radiator and the room (steam 240 deg., room 90 deg.) is 150 deg. Opposite this, the Ambrican Society of Heating and Ventilating Engineers Guide, 1924-25 EFFECT OF AIR CIRCULATION The amount of heat given off by a radiator may also be increased by increasing the velocity of the air over the surface of the radiator. This increase in velocity will increase the amount of heat carried off by convection: No exact data are available on the effects that may be introduced by increasing these velocities over radiator surfaces, but in rooms with moving machinery the heat transmission is increased approximately 10 per cent. EFFECT OF PAINTING The effect of painting was originally determined by experiments made with a cast iron rectangle, and in applying these to radiators of standard type, corrections must be made to allow for the difference between the area of the radiating and converting surfaces. The effect of painting is to change the radiation constant of the radiating Fig. 6. Effect of Humidity on Heat Transmission proportionate transmission 1.09 is found in the fourth column. Divide 1.57 by 1.09 and the quotient, 1.44 is the proportionate amount of radiation required. The late John R. Allen, while Director of the Society's'Research Laboratory, submitted a paper as a report (A. S. H: V. E. Journal, January, 1920), which in addition to the treatise on the heat emitted by various types of radiation, from which the preceding tables were calcu lated gives other data from which the following is taken. EFFECT OF HUMIDITY Fig. 6 shows the effect of increasing the humidity upon the heat transmission. It will be noted that with extreme change of humidity there is a slight change in the heat transmission,.the heat transmission reducing slightly as the humidity increases. Humid ity can have very little, if any effect upon radiation, and the effect of humidity must therefore change the convected heat lost by the radiator. This change of converted heat is probably due to the change in the density of the air passing over the radiator. 34 Time elapsing after Steam is turned into Radiator (r Minutes) Fig. 7. Chart Shows Demand upon Boiler for Heating-Up Plant surface and has practically no effect upon the heat lost by convection. It is, therefore, a. surface effect and it makes no difference what paints are placed on the radiator as a priming coat, the results are always dependent upon the last coat of paint put upon the radiator. In radiators having a large proportion of radiating surface such as pipe coils or wall coils, the effect of painting will be more marked than in four-column radiators having a comparatively small radiating surface in proportion to converting surface. All finely ground materials have about the same radiation constant. Therefore all paints having finely ground pigments will give about the same effect. Metals have a poor radiating effect so that any paint involving flake metal, such as the bronze, will have a low radiating constant. The following Table 26 shows the heat loss from a two-column 38-in. radiator, 10 sections long, when painted with different kinds of paints: TABLE 26. EFFECT OF PAINTING ON TWO-COLUMN 38-IN. RADIATOR. STEAM TEM PERATURE 215 DEG., ROOM TEMPERATURE 70 DEG. FAHR. Condition op Surface Per Cent Condition of Surface Per Cent Cast iron bare........................................ 240 Painted with white enamel............ 242 Painted with aluminum bronze................200 tf " maroon Japan.......... 240 " " gold bronze..................... 205 u " white zinc paint....... 242 Painted with no-lustre green enamel 230 35