Study On Human Thermal Responses And Modified Predicted Heat Strain Model For Deep Underground Environment

With the increase of mining depth,heat damage of work face in deep mine is becoming more and more serious.High temperature heat damage not only reduces the production efficiency of mining industry,but also endangers the physical and mental health of mine operators.In addition,miner protective clothing is the medium of heat and humidity exchange between miner and environment.Thermal insulation and moisture permeability characteristics of miner protective clothing under different environment conditions greatly affect heat dissipation efficiency of miners.Therefore,it is necessary to research human thermal responses under high temperature and humidity environment in underground mine and investigate the thermal properties of miner protective clothing under different conditions,so as to evaluate the heat stress level of miners under different thermal environments.The mian research work and results are as follows:Firstly,the influence of air temperature(29/32 ℃),air velocity(0.8/1.3/1.8 m/s)and labor intensity(moderate/heavy)on human thermal physiological responses(oral temperature,sweat loss and skin temperature,etc.)and subjective responses(thermal sensation,thermal comfort,sweat sensation and thermal satisfaction,etc.)were studied by climate chamber experiment.Results showed that with the increase of air velocity,oral temperature of subjects showed a decreasing trend,while the sweat loss increased first and then decreased.With the increase of labor intensity,the differences of skin temperature under different air velocity conditions was decreased.Subjects’subjective feelings basically reached a stable level after 40 min of the experiment.Thermal sensation and thermal comfort were positively correlated with air temperature and labor intensity,and increasing air velocity could alleviate the subjects’thermal discomfort to some extent.Thermal satisfaction of subject was inversely proportional to skin temperature.With the increase of thermal sensation,more and more subjects voted"not very satisfied"and"not satisfied",and more subjects hoped to increase air velocity.Secondly,human thermal physiological responses under different relative humidity(50%/60%/70%/80%)and air velocity(0.3/0.6/0.9/1.2 m/s)conditions were studied by climate chamber experiment.Clothing thermal insulation and vapor resistance were calculated according to human body method,and the differences between the thermal insulation and vapor resistance correction factors calculated according to ISO 7933,ISO 9920 and the experimental values was compared.Results showed that,when air temperature was 25 ℃,human skin temperature decreased with the increase of air velocity and showed a trend of decrease first and then increase with the increase of relative humidity.The evaporation heat flow of human skin was proportional to the air velocity,but the increase is less and less with the increase of air velocity.Thermal insulation of miner protective clothing decreased with the increase of air velocity.When relative humidity was 50%,thermal insulation decreased by 28.5%with air velocity increasing from 0.3 m/s to 1.2 m/s.The variation law of the thermal insulation of miner protective clothing with air velocity measured in this experiment was closer to the thermal insulation correction formula in ISO 7933,and the variation law of the vapor resistance of miner protective clothing with air velocity was closer to the vapor resistance correction formula given by ISO 9920.Finally,according to variation rules of thermal insulation and vapor resistance of clothing under different relative humidity and air velocity conditions,predicted heat stress model(PHS)was modified and verified.Based on the modified PHS model,the effects of different parameters(air temperature,relative humidity,wind speed,mean radiation temperature and metabolic rate)on the physiological responses and maximum allowable exposure time of miners were analyzed.In addition,environment conditions that could meet the requirements of miners to safely work for 8 hours were given.Results showed that,compared with other parameters,mean radiat temperature had less influence on miner physiological responses.With the increase of ambient heat strain,the physiological index that determines maximum allowable exposure time of miners changed from sweat loss to rectal temperature.Increasing air velocity had a great effect on decreasing rectal temperature and sweat loss of miner,especially under high labor intensity conditions.However,when air velocity exceeded 2.5 m/s,the effect of increasing air velocity was little.