| High-temperature operations widely exists in many industrial fields such as construction,shipbuilding,metallurgy,and mining.High-temperature operating environments can cause a series of high-temperature adverse reactions to the physical and psychological aspects of workers,bringing great security risks to workers'occupational health and the production processes.Wearing a cooling suit can effectively improve the working comfort of workers under high-temperature operating conditions,reduce occupational health hazards and accident rates caused by high temperatures.This is one of the most effective methods for human body high-temperature protection.Among them,the temperature-reducing material made of phase change material has obvious advantages compared with other types of temperature-restraining clothing,and it is also a research focus of high-temperature personal protective materials.This paper is based on the previous research on the performance of phase change materials and meet the requirements of human thermal comfort and cooling effect.The main phase change material with paraffin wax as the cooling clothing and the composite phase change material with expanded graphite as additive were selected.The expansive graphite/paraffin composite was optimized for compounding and a series of experimental studies were carried out on its thermal properties.A mathematical model describing the thermal resistance of garments for cooling and the heat storage of garment cooling materials was established.Based on this,a thermal protection software system for evaluate the cooling clothing was developed.The main work and conclusions are as follows:Expanded graphite was subjected to high-temperature expansion experiments under different conditions using a muffle furnace and other equipments,and the conditions for preparation with the best expanding effect were determined;the mixture of n-hexadecane,n-octadecane,and n-icosane was mixed.DSC 2500 differential scanning calorimeter was used to analyze the thermal characteristics of mixed alkanes,and the phase transition temperature and latent heat of phase change were calculated.The paraffin ratio of paraffin phase change materials in temperature-decreasing clothes was determined based on the human thermal comfort requirements.DSC test was conducted on the composites to analyze the effect of expanded graphite on the phase transition temperature and phase change of the composites.The phase transition temperature of composites increased slightly with the increase of expanded graphite,and the temperature increase range was within 0.5°C.However,the expanded graphite has a great influence on the phase change of the composites.The solid-liquid phase change of the composites shows a linear relationship with the paraffin content,the correlation coefficient R~2 is 0.9745.Experimental investigation on the adsorption saturation of composite phase change materials was conduct.It was found that the addition of expanded graphite can improve the leakage of paraffin in composites well,and expands when the graphite content is11%(based on paraffins).Graphite completely adsorbs paraffin and reaches saturation.At the same time,by analyzing the heat storage temperature,it was found that after adding the expanded graphite to the paraffin,the heating time of the material was reduced and the heat storage rate was significantly increased,which fully demonstrated that the expanded graphite has a positive effect on improving the thermal conductivity of the paraffin.The optimal scheme for the composition of composite phase change materials was determined.Based on the theory of human thermal balance and clothing thermal resistance test methods,a mathematical model was established between the thermal resistance of the thermal protective clothing and the thermal storage power of the composite phase change material.The Predicted Heat Strain(PHS)model was used to improve the model,and Thermal protection effectiveness evaluation software for a cooling suit was developed. |
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