Study On Exergy Model And Thermal Comfort Of Workers In High Temperature And High Humidity Mines

Thermal comfort is the condition of mind which expresses satisfaction with the thermal environment.In high temperature and humidity mines,the heat and moisture dissipation of surrounding rock,water inflow and electromechanical equipment makes the mining workface a high-temperature and high humidity environment.Miners engaged in high-intensity labor were in a state of thermal discomfort for a long time,which was prone to symptoms such as inattention,massive dehydration,elevated body temperature and even heatstroke,which greatly increased the possibility of safe production accidents.At present,the studies on the thermal comfort of mine workers mainly adopted the thermal comfort index of atmosphere or building environment.These indexes were not applicable to mine environment and conditions,and there were certain limitations.Relevant laws and regulations at home and abroad only limit the air temperature.Relevant studies mainly focused on the tolerance and allowable working time of workers,and had not formed a unified model or index for the mine.Therefore,it is very necessary to study new theories and evaluation indexes and formulate relevant laws and regulations on safety production scientifically in high temperature and humidity mines.These are of great significance to ensure miners’ health,safe and efficient production.At present,some thermal comfort models and indexes were obtained based on the human heat balance equation,which reflects the conservation of human energy in "quantity".Exergy can reflect the energy balance from both "quantity" and "quality".Some recent studies believe that exergy loss and exergy transfer can express human thermal comfort,and the exergy method was more suitable for active human body than the predicted mean vote model(PMV)recommended by the ISO7730.Using the method of combining theoretical analysis and human test,this research study the human exergy balance model under the thermal environment of high temperature and humid mine,study the relationship between human exergy loss,exergy transfer,exergy efficiency,physiological parameters and thermal comfort,and study the cooling capacity of gas-cooling clothing according to the analysis of human exergy components.The main conclusions and achievements as follow:1.The transient exergy balance model of human labor process in mine hot and humid environment was established based on predicted heat stress model(PHS).To verify the rationality of the model,the calculation results of the model under different temperature and humidity were compared with the exergy model studied by previous researchers.It was found that the exergy loss of the human body was relatively small in relatively comfortable temperature and high temperature and high humidity environment.Exergy transfer and exergy efficiency change in a hump curve at different temperatures,their two peaks appear at relatively comfortable temperature and have a corresponding relationship,and become smaller at cold and high temperatures.Increasing wind speed was beneficial to improve exergy transfer and exergy efficiency.But it was the opposite in cold and extremely high temperature.2.In the high temperature and hight humidity mine thermal environment,with the increase in working time,the oral and skin temperature of the human body gradually increased;the higher the ambient temperature,the greater the rose.When the ambient temperature was constant,the human body’s subjective thermal sensation vote(TSV)increased gradually with the increase in working time.There was a strong correlation between sample entropy(Samp En)in heart rate variability index and TSV.3.When the ambient temperature was equal to or greater than 22℃,the exergy transfer and exergy efficiency of the human body had a strong correlation with oral temperature and TSV,but not with skin temperature.The maximum values of exergy transfer and exergy efficiency appeared in the environment where TSV were "slightly cold",and the exergy transfer and exergy efficiency become smaller in the uncomfortable environment such as "cold" or "hot" and "extremely hot".Exergy transfer had a strong correlation with the thermal comfort of the human body working in high-temperature mine,which was suitable to be used as the thermal comfort index of the human body working in high-temperature mine environment.The difference between the thermal neutral ambient temperature and that corresponding to the maximum exergy transfer was about 1 ℃.4.Based on the comparative analyzed of heat dissipation and exergy components of the human body working in mine environment,it was found that the evaporation efficiency and heat dissipation of sweat in mine environment were seriously limited.Gas cooling clothing was proposed as an optional scheme for personal protection in high temperature mine.The research shows that under the high-temperature and high humidity mine environment of 30 ℃ / 90%-34 ℃ / 90%,the evaporation heat transfer coefficient of trunk can be increased by 69-105%and the cooling power of air-cooling vest were 79.5 W ～ 97.6 W.The calculation model of cooling capacity of environmental ventilation clothing was established,the isoline diagram of cooling capacity of air-cooling clothing under different temperature,humidity,labor intensity and ventilation were drawn,and its variation characteristics were studied.5.The maximum exergy efficiency of the human body at different working hours were analyzed under constant temperature,humidity,and wind speed.It was found that the maximum exergy efficiency tends to be constant after working for more than 60 minutes.Based on the maximum exergy efficiency data in the 75 th minute,the calculation formula of the maximum exergy efficiency corresponding to the ambient temperature under certain labor intensity and different wind speed was fitted.Based on the relationship between maximum exergy efficiency corresponding temperature and thermal neutral temperature,the temperature control strategy of mining workface in high temperature mine was proposed.