Expression of the radiative heat exchange for the human body and its application to modifying the original WBGT for outdoor environment

In order to calculate mean radiant temperature in an outdoor environment, we had to calculate a hypothetical sky temperature from directly measurement or an empirical formula of atmospheric radiation expressed as functions of daily mean air temperature, cloud amount, etc.
The aim of this research is to propose new expression for simply calculating the radiative heat exchange in an outdoor environment. In this paper, we defined the long-wave radiation coefficient based on the ratio of atmospheric radiation to long-wave radiation from the ground to the human body and derived linearized radiative heat exchange equation in an outdoor environment to be expressed only in the ground temperature and solar radiation. We qualitatively analyzed the long-wave radiation coefficient and the radiative heat transfer coefficient. Finally, based on measured data in an outdoor environment, we proposed the empirical formulae for calculating the long-wave radiation coefficient using solar radiation or the ground temperature.