Research On Heat And Moisture Transfer Under Impermeable Chemical Protective Clothing

Chemical protective clothing is designed to prevent damage to the body and fatalities from the effects of chemical and biological substances.Impermeable chemical protective clothing is one of the kinds of chemical protective clothing.The ability to transfer heat can be greatly affected due to the large size and limited air permeability of the impermeable chemical protective clothing.Work efficiency and thermal comfort are consequently affected because a large amount of heat is stored in human body.Some studies have investigated impermeable chemical clothing,but the majority of them are focused on material level.Therefore,in this study,heat and moisture transfer under impermeable chemical protective clothing will be investigated from garment levelIn the study,temperature and relative humidity at waist and thigh were measured in different ambient temperatures(0℃,20℃)through the comfort control mode of the thermal manikin.Afterwards,thermal resistance and moisture resistance of the impermeable chemical clothing were measured,and heat losses from skin in different ambient temperatures(0℃,20℃,34℃).Finally,PHS(Predicted Heat Strain)model was improved for the impermeable chemical protective clothing.This model was verified through a thermal manikin test under temperature of 20℃ and a human trial from literature under temperature of 40℃.It was found that:(1)Thermal resistance and moisture resistance of the impermeable chemical clothing are 0.208℃.m2/W and 180.35 Pa.m2/W,respectively.(2)In comfort control mode,both temperature and relative humidity in the microclimate increased and reached a stable state gradually.Apparent temperature gradient and humidity gradient were formed under impermeable chemical protective clothing.(3)When ambient temperature is below skin temperature,heat is transported by vapor and released further by condensation,which is referred to as the "heat pipe" effect.Heat pipe effect exists in microclimate under impermeable chemical protective clothing.Heat losses from thermal manikin due to heat pipe effect were about 190 W/m2 at 0℃.and 80 W/m2 at 20℃,respectively.Therefore,the lower the ambient temperature,the more obvious the heat pipe effect.(4)Core temperature predicted by the PHS model is similar to core temperatures measured in the manikin test and the human trial.PHS model can be used to predict the exposure time.However,skin temperature predicted by PHS model increased slower than the manikin test and the human trial.Change of skin temperature in human trial delayed significantly when the ambient temperature decreased,while skin temperature predicted by PHS model did not show the similar trend.This discrepancy might because that the heat pipe effect under impermeable chemical protective clothing was not taken into consideration while designing the model.