Method

Heat from sources such as the rock, autocompression in the intake airway machinery, the air temperature of the available ventilation and the heat released when coal is broken away contribute to the thermal load of the mine atmosphere in underground coal mining. Water required for dust control collects and together with ground water increases the level of humidity. Methods for the assessment of hot environments can be generally divided into three types. These are direct measurements, empirical methods and rational indices2). The most commonly used heat stress indices, based on direct measurement of climatic parameters, for the assessment of the thermal environment in mines do not consider the personnel parameters “work rate” and “clothing”. The Wet Globe Temperature and the Wet Bulb Globe Temperature (WBGT) are examples of indices used in this type of method4, 5). The climate indices in the second group are based on empirical studies demonstrating a direct correlation between various climatic conditions and the strain they cause. The best known indices in this group are the Effective Temperature Index and the Predicted Four Hour Sweat Rate Index5). Rational methods for measuring hot environments are based upon a calculation of the heat exchanges between the human body and the environment. A physiological heat strain prediction model was developed by McPherson to calculate the inequality between net heat transfer and a known or estimated metabolic rate. A transient period will occur when the body temporarily accumulates or loses heat at a rate Ac (W/m2), given by equation [1] 2). Ac= M-(Br+ Rad+ Con+ Evap)[1] Where; M: Metabolic energy production, W/m2 Br: Respiratory heat loss, W/m2 Rad: Radiant heat loss, W/m2 Con: Convective heat loss, W/m2 Evap: Evaporative heat loss, W/m2 Br+ Rad+ Con+ Evap is named Air Cooling Power (ACP) and is used for the determination of the heat transfer between the human body and the environment.