Relationship between air temperature and mean radiant temperature in thermal comfort.

Abstract

GROUPS of 6–8 apparently healthy persons were exposed to three environmental conditions in a room previously described1. The test subjects were lightly dressed (about 343 g/m2 surface area, excluding shoes), seated and engaged in reading and writing. Though the subjects noted their comfort responses every half-hour, only the last votes of a 3-h session were considered. The conditions were: (a) air temperature approximately equal to mean radiant temperature ; (b) air temperature higher than mean radiant temperature (up to 17.9° F) ; (c) air temperature lower than mean radiant temperature (down to 15.3° F). Humidity was arbitrarily kept at 50 per cent, and air velocity was less than 20 ft./min. Dry bulb and wet bulb temperatures were measured with aspirated and shielded mercury-in-glass thermometers; radiant temperature with the globe thermometer2, a two-sphere radiometer3,4 and a modified thermopile5 ; and air velocity with a rhodium-plated kata thermometer6. All six room surfaces were kept at approximately the same temperature. The combinations of air temperature and mean radiant temperature were adjusted to yield a mean vote of ‘comfortable’ (‘4’) on a seven-point thermal comfort scale1. Mean votes, above and below ‘4’ which did not differ by more than 0.5 sensory units, were used as bases for finding, by linear interpolation, the air temperature and mean radiant temperature, which evoke a ‘comfortable’ vote.