纤维多孔介质介观尺度结构对其真空绝热性能的影响

Effect of Mesoscopic Scale Structure on Vacuum Adiabatic Performance of Fibrous Porous Material

纤维多孔介质在绝热材料领域的应用广受关注,真空工艺是提升材料绝热性能最为有效的方法。本文研究了真空条件下介观结构对纤维多孔介质的有效导热系数的影响,改进了已有纤维随机结构生成方法,运用D_(3)Q_(19)格子Boltzmann方法对其有效导热系数进行求解。改进的生成方法可明显改善纤维分布,穿插率可降低至3.1%。模拟结果与实验及理论数据具有良好的一致性。结果表明,在1~8μm的区间内,纤维直径越小,纤维多孔介质在真空下的绝热性能越好,对内部真空度的依赖性越低;纤维长度方向与传热方向越不一致,绝热性能越好;在方向角到达90°时,绝热性能最佳。研究工作对真空绝热板纤维芯材的结构设计及优化具有重要意义。

The application of fibrous porous material(FPM)in the field of thermal insulation materials is widely concerned,and vacuum process is one of the most effective methods to improve the thermal insulation performance.The effect of microstructure of FPM on its effective thermal conductivity under vacuum is studied.The existing random structure generation method is improved and D_(3)Q_(19) lattice-Boltzmann method is used to solve the thermal conductivity.The modified generation method can significantly optimize fiber distribution and reduce the interpenetration rate to 3.1%.The simulation results are in good agreement with experimental and theoretical data.Results indicate that FPM with finer diameter leads to smaller pore size and has a more excellent ability to maintain the lower effective thermal conductivity under higher pressure in the range of 1—8μm.Besides,the more the length direction of fiber is inconsistent with the heat transfer direction,the better the insulation performance is.And the insulation performance reaches the peak when the direction angle reaches 90°.These results are of great significance to the structural design and optimization of the fiber core material of vacuum insulation panel.