|
Nummerical modelling of heat exchange between a human body and the environment |
|
|
|
|
Nummerical modelling of heat exchange between a human body and the environment Authors: J. Wacławik, M. Branny
This paper outlines a mathematical model of the heat exchange between a human and environment inside a mine working. At low and moderate temperatures and air humidity, the body heat is transferred to the environment essentially by convection. In extreme climatic conditions heat exchange is accomplished by sweat evaporation. At temperatures exceeding the skin temperature heat loss by evaporation becomes the main temperature regulation mechanism. In our considerations we assumed the state of thermal equilibrium, when no heat is accumulated in the body. The heat balance for the human body is given as: M=C+R+B+E where: M - metabolic heat production, C - conductive heat, R - radiation heat exchange (long-wave radiation), E - evaporative heat transfer, B - respiratory heat loss. An assumption is made that the average skin temperature is a factor controlling the convective, radiant and evaporative modes of heat exchange. Several formulas come from the international standard ISO 7933 "Hot environments. Analytical determination and interpretation of thermal stress using calculation of required rate of sweat productions". Factors that affect the state of thermal stress include: -heat accumulation in a worker's body; -maximum rate of sweat productions emitted during work; -dehydration level; -level of skin wettedness. The heat balance of human body enables the estimation of these parameters.
|
2011