| For firefighters and soldiers exposed to thermal hazardous environments,flame resistant clothing provides essential protection for them from the high temperature and flames on the field of fire.The thermal protection performance of clothing directly affects the rescue efficiency and the safety of firefighters.At present,there are many methods for evaluating the thermal protection performance of fire-fighting fabric,which are aimed at different types of heat exposure.However,there is no a unified comprehensive standard for the evaluation of thermal protection performance.The common standard testers,such as,TPP(Thermal Protective Performance)and RPP(Radiant Protective Performance),only consider the effect of heat transfer on thermal protection performance during continuous exposure,ignoring the effect of heat-storage release on skin burn.Although SET(Stored Energy Test)for the evaluation of the heat storage-release property is relatively complete,it mostly focuses on the testing under low-intensity radiation exposure.In this paper,TPP and RPP test equipment were successfully improved to provide accurate fabric heat storage evaluation function,which was not available in the original test equipment,and became the equipment platform support for the systematic study of thermal protection performance evaluation under the comprehensive influence of heat transfer and heat release of fabrics in the whole process of heat exposure and cooling stage.Based on the modified equipment,this paper carried out a comparative analysis of the evaluation results of TPP and RPP experiments under high heat flux density,and explored the effects of heat source type,heat exposure intensity,heat exposure time,air layer setting,heat storage and release conditions,etc.on the influence law of the difference between TPP and RPP evaluation results,and at the same time study the different mechanism of the above-mentioned many influence factors in the two different research scopes of heat exposure and heat storage release.The main research contents and conclusions of this study include the following aspects:(1)Influence of the types of heat sources on the evaluation of thermal protective performanceUnder 84k W/m~2 heat exposure intensity,the second degree burn time of the fabric under TPP heat source was significantly higher than that under RPP heat source(P=0.007<0.05),after considering the heat storage release,the thermal protection performance evaluation results of the two heat sources decreased and the results were opposite,and the difference range increased.In the heat exposure stage,the heat exposure intensity significantly affected the difference of second degree burn time between the two heat sources(P=0.003<0.05).In other words,it is limited to use a single evaluation method to evaluate the thermal protection performance of fabrics under the same thermal exposure intensity.Therefore,the thermal protection ability of fabrics should be comprehensively considered by considering various heat source types and thermal exposure intensity and heat storage release conditions.(2)Influence of exposure time on the evaluation of thermal protective performanceIn the heat exposure stage,MAF value and skin heat absorption under RPP were significantly higher than TPP at 84k W/m~2,and the degree of difference did not change with the increase of heat exposure time.At 50k W/m~2,MAF value and skin heat absorption under TPP were significantly higher than that under RPP,and the degree of difference increased with the increase of heat exposure time.When considering heat storage release,the MAF value and skin heat absorption under TPP were significantly higher than those under RPP under the two heat exposure intensities,and the degree of difference did not change with the increase of heat exposure time.The smaller the heat exposure intensity,the greater the difference between the two heat sources.The heat storage release of TPP at 84 k W/m~2 was significantly higher than that of RPP,and there was no significant difference between the two heat sources at 50k W/m~2(P=0.493>0.05),the heat exposure time increased,and the overall trend was firstly increased and then decreased,but it did not show a strong regularity.(3)Influence of air gap thickness on the evaluation of thermal protective performanceWith the thermal exposure intensity of 84k W/m~2,the second degree burn time under TPP heat source was higher than that under RPP in two air layer states,and the difference of thermal protection performance between the two heat sources under 6.4mm air layer was significantly greater than that under 0mm air layer(P=0.006<0.05),the result is opposite when considering heat storage release.When the air layer is6.4mm,the higher the heat exposure intensity is,the greater the difference of thermal protection performance between the two heat sources is.The opposite is true when heat storage is considered.(4)Influence of heat storage release on evaluation of thermal protective performanceThe Certification Exposure Time of TPP is less than that of RPP under the two heat storage release conditions.Under the heat exposure intensity of 84k W/m~2,the difference of thermal protection performance between the two heat sources in the natural release state was higher than that in the heat release state under pressure(P=0.025<0.05).Under 50 k W/m~2 thermal exposure intensity,there is no significant difference in the effect of two heat storage release states on the thermal protection performance evaluation results of the two heat source fabrics.(P=0.896>0.05)... |
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