Abstract
In this paper, we dealt with the outdoor environment in which occupants engaged in moderate intensity work (metabolic heat production at 174 W/m2) and wearing general vapor permeable clothing and clarified the characteristics of the Yaglou’s WBGT from view point of heat transfer theory. The following conclusions were obtained. 1) The weighting coefficients of WBGT coincide with the situation where skin wettedness is around 0.5. 2) WBGT for the outdoor environment evaluates the influence of solar radiation using the weighted average of globe temperature and air temperature while it neglects the influence of long wave radiation. 3) Human’s heat balance can be expressed by the same equation with WBGT and additional adjustment factor. 4) WBGT can be interpreted as an index expressing the weighted sum of skin temperature and body heat storage rate. And 5) WBGT becomes erroneous when it is applied to the situations with variations in air velocity, clothing thermal insulation, solar absorption factor of clothing, and radiant field. Based on these findings, we proposed the evaluation method of the adjustment factor of WBGT from heat transfer properties.
