Abstract
This paper deals with the features of WBGT, and made them clear in view of heat transfer theory.
The currently used WBGT is an equation obtained from the experiments using subjects. However, it has not been derived from heat balance concerning the human body. It is often said that WBGT is reliable because it is an equation based on the experimental data. Nevertheless, an experimental equation is not always correct. In general, it contains scattering of data and the bias in the conditions of experiments.
Humans produce metabolic heat in the body and release/receive heat to/from the environment. Therefore, the physical law of heat transfer can be correctly applied to the human body and it is probable to derive WBGT equations.
The authors derived two WBGT equations theoretically based on the heat balance equation between the man and the environment. As the results, the characteristics and physiological meaning of WBGT have become clearer. Further, the rational WBGT equations have also been derived. The new ones contain and offer the seven main parameters to be considered, such as air temperature, humidity, air movement, long and short wave radiations, clothing worn and metabolic rate, thus making the estimation of man’s heat stress more strictly.
