气凝胶及其纤维复合材料等效导热系数预测
Prediction of the Effective Thermal Conductivity of Aerogel and Its Fiber？？Loaded Composites

为了研究气凝胶及其纤维复合材料的隔热性能,分别数值重构了几种气凝胶及其纤维复合材料的微细观随机结构,采用格子Boltzmann方法数值求解了它们的等效导热系数,同时用基于瞬态平面热源法的Hot Disk热常数分析仪测量了它们在复杂环境下的等效导热系数。研究表明:骨架连续的开孔型微观结构比骨架不连续的颗粒型微观结构更符合气凝胶的实际结构,开孔型结构等效导热系数的数值预测值与实验值的偏差大部分在±10％内;气凝胶的密度值会影响它的隔热性能,且存在着最佳的密度使得气凝胶的等效导热系数最低;纤维复合气凝胶的等效导热系数随着纤维体积分数的增加而增加;纤维在垂直于热流方向的水平面内随机排布时对气凝胶的隔热性能影响最小。
Different random microstructures of aerogels and their fiber？？loaded composites were numerically reconstructed to investigate their insulation performances. The lattice Boltzmann method was adopted to calculate their effective thermal conductivities. Some experimental measurements based on the hot disk method were conducted to determine the effective thermal conductivities of the aerogels at different pressures. The results show that: the open？？cell microstructure with continuous skeleton is more suitable for the real structure of the aerogel than the granular microstructure with discontinuous skeleton; the predictions of the effective thermal conductivities based on the open？？cell structure agree well with the experimental data, and the deviations are within ±10％; the density of aerogels affects their effective thermal conductivities, and there exists an optimal density value to minimize the effective thermal conductivity of a aerogel; the effective thermal conductivities of the aerogel composites increase with the fiber doping concentration; the increment of the effective thermal conductivity of the fiber？？load aerogel is the lowest when the fibers are laid in the plane vertical to heat flux