有机相变蓄热复合材料导热性能的实验研究

Experimental Study on Thermal Conductivity of Organic Phase Change Composites

摘要:

以膨胀多孔石墨(EG)和硅藻土(DI)这2种多孔矿物介质与硬脂酸丁酯(BS)有机相变材料制备了有机相变蓄热复合材料,并采用调制差示扫描量热方法(MDSC)测试了复合材料的导热系数,借助层状复合材料热传导模型分析了多孔矿物介质内部结构特征对复合材料导热性能的影响.结果表明:采用EG和BS制备的有机相变蓄热复合材料具有明显的层状结构,其压制方向的导热系数更接近于层状复合材料热传导模型c轴方向的导热系数;采用DI和BS制备的有机相变蓄热复合材料的导热系数接近层状复合材料热传导模型a-b平面方向的导热系数,即该复合材料内部具有非常好的连通性.多孔矿物介质对有机相变复合材料导热性能的增强效果不仅受多孔矿物介质导热系数的作用,而且还受到复合材料内部结构特征的影响.当复合材料在热传导方向上形成连通性结构时有利于上述增强效果;而当复合材料形成与热传导方向垂直的层状结构时则不利于上述增强效果,即使多孔矿物介质具有很高的导热系数也是如此.

Abstract:

The thermal conductivity of organic phase change composites made of porous mineral(expanded porous graphite(EG),diatomite(DI)) and butyl stearate(BS) was tested by means of temperature modulated differential scanning calorimetry(MDSC).The effect of the structure of porous minerals on thermal conductivity of the composites was analyzed based on the model of thermal conductivity of layered composite.It is found that the composite made with EG and BS has an obvious multilayered structure,the thermal conductivity in the compressive direction matches well with the thermal conductivity of c axis of the layered model.While the thermal conductivity of the composite made with DI and BS coincides with the thermal conductivity in the direction parallel to the a-b plane of the layered model,which means that the skeleton of the composite made with DI and BS is well interconnected.The enhancement of the thermal conductivity of composite by porous minerals is not only controlled by the thermal conductivity of the porous minerals,but it is also influenced remarkably by the skeleton of composites,which results from the structures of the porous minerals.The interconnectivity is very helpful for the enhancement of the thermal conductivity of the composite in the same direction.In the condition of layered structure perpendicular to the direction of the thermal conductivity,the enhancement is very (limited) by the perpendicular layers,even if the thermal conductivity of the porous minerals is high.