纳米孔超级绝热材料声子热输运模拟研究

Study on Phonon Heat Transport Simulation of Nanoporous Super Thermal Insulation Material

为研究纳米超级绝热材料中声子输运,采用一维声子热输运的格子玻尔兹曼方法(LBM),建立纳米薄膜内声子热输运的数学模型。在稳态条件下,对LBM方法获得的纳米薄膜内声子能量密度特性曲线、纳米薄膜有效热导率的有效性进行验证。基于LBM方法,对克努森数Kn(纳米薄膜声子平均自由程与薄膜厚度之比,特定纳米材料有一定的声子平均自由程)对纳米薄膜内声子能量密度的影响进行模拟分析。由LBM方法获得的纳米薄膜内声子能量密度特性曲线、纳米薄膜有效热导率与对比方法获得的计算结果基本吻合,证明LBM方法有效。随着克努森数Kn的增大,界面效应(纳米薄膜界面处声子能量密度的跳跃)越明显,说明尺度效应(克努森数Kn对声子能量密度、有效热导率的影响)是纳米材料的明显特征。

In order to study the phonon trans-port in nano super thermal insulation material, the mathematical model of phonon heat transport in nano- film is established by the Lattice Boltzmann Method （LBM） of one-dimensional phonon heat transport. The effectivenesses of the phonon energy density character- istic curve in nanofilm and the effective thermal con-ductivity in nanofilm obtained by LBM are verified un- der steady-state conditions. Based on the LBM meth- od, the effect of Knudsen number Kn （ the ratio of pho- non mean free path in nanofilm to film thickness, a particular nano-material has a certain phonon mean free path） on the phonon energy density in nanofilm is simulated and analyzed. The phonon energy density characteristic curve in nanofilm and the effective ther- mal conductivity in nanofilm obtained by LBM are basi- cally consistent with the calculation results obtained by a comparative method, proving that the LBM method is effective. The interracial effect, namely the jump of phonon energy density at the interface of nanofilm is more obvious with addition of the Knudsen number Kn, showing that the scale effect, namely the effect of Knudsen number Kn on the phonon energy density and the effective thermal conductivity, is an obvious feature of nano-material.