低辐射热条件下附加相变材料织物的蓄放热双重特性

Thermal storage and discharge performance of fabrics with phase change material under low-level radiant heat exposure

为探究相变调温热防护服在热暴露阶段与冷却阶段的蓄热防护与放热危害双重特性,使用相变温度为28℃的微胶囊制备了用于多层热防护织物系统的涂层织物。利用模拟低辐射热条件下的织物热蓄积性能测试仪,探究了4种不同的空气层厚度及2种不同的热源强度对于附加相变材料织物系统蓄放热特性的影响,并考察了在自然放热与加压强制放热状态下织物系统放热特性的差异。实验结果表明:在热暴露阶段,空气层与相变材料的共同作用对于降低皮肤得热具有更加积极的作用;在蓄热自然释放状态下,相变涂层织物能够降低织物系统对皮肤的放热;然而在蓄热加压释放状态下,相变材料的使用反而显著提升了皮肤得热,尤其当空气层厚度较大时,相变涂层织物系统的皮肤得热量较未加压状态下提升了129%。

Objective Phase change materials(PCM)are a type of energy storage material,and the phase change layer attached to the thermal protective clothing fabric is able release heat when it solidifies.The release of heat under these two mechanisms may increase the potential danger of skin burns as a result of the heat exposure.Therefore,it is necessary to consider its thermal storage protective effect in the heat exposure stage and the hazardous effect in the cooling stage when exploring the comprehensive thermal protective performance of the thermal protective fabric assemblies incorporated with PCM on human skin.Method Temperature-regulating fabrics with phase-change materials that can absorb or release heat through phase transition were prepared by using a coating method and were then applied to a multilayer thermal protective fabric system.The heat storage protective performance of thermal protective clothing with PCM and the natural heat release performance and the compressed heat release properties in the cooling stage are quantitatively evaluated through parametric design,the parameters including the thickness of the air layer under the clothes,the intensity of the heat source,and whether the fabric is compressed after the heat exposure.Results In the stage of thermal exposure,the use of the PCM significantly reduced the skin heat gain during the heat exposure stage.At the same time,the phase change fabric systems significantly reduced the temperature inside the fabric system compared to the uncoated fabric system.In addition,the air layer had a more positive effect on reducing skin heat gain when it was incorporated with PCM.The skin heat gain decreased the most when the thickness of the air layer was increased from 0 mm to 6 mm,and the improvement in the thermal protection effect was not significant when the thickness of the air layer was continuously increased to 18 mm.In the process of natural thermal discharge,with the increase in air layer thickness,the CAE value(energy discharge amount or energy absorption during cooling)of the fabric system decreased.On the whole,the CAE value of PCM fabric system was smaller than that of the coated fabric system,but the heat release efficiency was slightly higher.Therefore,although the PCM fabric system could reduce skin heat gain in the natural heat release stage,more attention was paid to the influence of its heat release in the whole heat transfer process.It was noted that the CAE difference between the PCM fabric system and uncoated fabric system tended to decrease with the increase in the air layer thickness,which indicated that when the air layer thickness was larger,it played a leading role in the heat release of the fabric system,leading to the weakening of the positive role of PCM in the natural cooling process.In the process of forced thermal discharge,the skin heat absorption of the fabric systems increased significantly compared with the natural heat release stage.In particular,the application of compress aggravated the heat release in the PCM fabric systems if the fabric systems had an air layer in the heat exposure stage.When the thickness of air layer was 6 mm and 12 mm,the skin heat gain of the PCM fabric system was increased by 129%compared with that without pressure.Conclusion In the heat exposure stage,the comprehensive effect of the PCM fabric system and air layer plays a more positive role in reducing the heat reaching the skin surface.However,in the cooling stage,attention should also be paid to the complex effect of the combination of PCM fabric system and air layer on human skin,especially in the practical application of PCM,the air layer under clothing should be avoided squeezing and destroying as much as possible after the heat exposure stage to avoid causing accelerated release of heat storage and causing more serious heat damage to the skin.This significance of the research lies in the development of new clothing materials,the design of scientific thermal protective clothing systems,and the guidance of high-temperature operators to reduce skin burns by conducting basic research on the dual heat storage and release performance of PCM fabrics.