Document 10Y6VxZejMy6eL25Rk3M0E9YX

r vyfil American. Society q/Heating and Ventilating Engineers Guide, 1935 ICO--I -ao O Fig. 1. Thermometric or Effective Temperature Chart Showing Normal Scale OF Effective Temperature. Applicable to Inhabitants of thi ; UNITED STATES UnDER FoLLOWING CONDITIONS: 40 Chapter 2--Ventilation and Air Conditioning Standards 41I ' Definition of Effective Temperature Briefly, effective temperature may be defined as an. arbitrary index of the deeree of warmth or cold felt by the human body in response to tempera ture humidity, and movement of the air. Effective temperature is not a true'temperature of the air but an index which combines temperature, humidity and air motion in a single value. The numerical value of the effective temperature index for any given air condition is fixed by the temperature of saturated air which, at a velocity or turbulence of 15 to 25 fpm, induces a sensation of warmth or cold like that of the given condition. Thus, any air condition has an effective temperature of 65 deg when it induces a sensation of warmth like that experienced in practically still air at 65 F saturated with moisture. In all reports of the A.S.H.V.E. Research Laboratory, the term still air signifies the minimum air movement it was possible to obtain in the Laboratory's psychrometric chamber. Actually, the air motion was between 15 and 25 fpm in all experiments, without qualification, as measured by the Kata thermometer. This was not a linear movement of air but it represented the turbulence or eddy currents produced by the air change. Even in tightly sealed rooms, the natural air movement is not likely to fall below 10 fpm so long as there is a temperature or pressure difference between the air inside and that outside the room. Fig. 1 shows the results obtained at the A.S.H.V.E. Research Labora tory in a single chart, the so-called thermometric chart. The equivalent conditions or effective temperature lines are shown by the short crosslines. The difference between the effective temperature for still air and for moving air, of any velocity, represents the cooling resulting from that air velocity. This thermometric chart applies to average normal and healthy persons adapted to American living and working conditions. It is limited to sedentary or light muscular activity, and to rooms heated by the usual American convection methods (warm air, central fan and direct hot water and steam heating systems) in which the difference between the" air and wall surface temperatures may not be great. The chart does not apply to rooms heated by radiant methods such as the British panel system, open coal fires, and the like. It will probably not apply with adequate accuracy to races other than the white or perhaps to inhabi tants of other countries where the living conditions, climate, heating methods, and clothing, are ' materially different from those of the subjects employed in experiments at the Research Laboratory. . .r '. If an occupant of a room loses heat by radiation'to;large wall or glass surfaces at lower temperatures, the air within the room must' be main tained at a higher temperature to compensate for this effect in order-to give the same feeling of warmth. The results of a recent study18 by the A.S.H.V.E. Laboratory, shown in Fig. 2, indicate that in poorly-insulated buildings this effect may become of considerable importance. Thus an occupant of a room having inside waif surface temperatures of 55 Eton three sides will require an air temperature of 74 F to have the same feeling; of warmth he would experience in a warm-wall room with air at 70, F, A wall, consisting of 8-in. brick and plaster, with. 16 F outside air tempera- "Cold Walls and Their.Relation'tb the Feeling of Warmth, by F. C. Hoiightea and Paul -McDermott (A.S.H.V.E. Journal Section, Healing, Piping and Ai>.-C<miit/ibn*n^,'Jariiiary,'I933, p. 53).- I . V .W 4t