Cooling power of underground environments

摘要

The problem of heat stress underground in thegold mines is approached on the basis of the heat transferbetween the human body and the underground environment.Experimental measurements of radiant and convective heattransfer and a theoretical calculation of maximum evaporativeheat transfer enable the maximum cooling power of anenvironment to be calculated in terms of the dry-bulb and wet-bulb temperature, the mean radiant temperature, the wind speedand the barometric pressure. For most underground applicationsthe cooling power can be expressed as a function of wet-bulbtemperature and wind speed only The relative importance ofwind speed and wet-bulb temperature can be assessed. Inworking places where wind speed is low additional cooling ofworkmen can be achieved more effectively by increased windspeed than by decreased wet-bulb temperature. The wet katareading proves to be of limited value as an index of heat stressbecause environments with equal wet kata do not necessarilyhave the same cooling power: Finally, thermal equilibrium withthe environment is possible when cooling power equals orexceeds the rate of metabolic heat generation. The rates ofmetabolic heat generation for