关键词: 多孔介质, 泡沫金属, 热传导, 等效热导率, 预测, 导热形状因子

Abstract:

The conduction form factor (m), which is used to calculate the equivalent thermal conductivity of foam metal, is introduced through theoretical analysis, and m is calculated and analyzed based on a large number of experimental data reported in the literature. It is shown that m fluctuates with materials, porosities as well as pore densities of metal foams randomly and erratically. In other words, the directional deformation effect of porous foam structure should be taken into account sufficiently to accurately predict the effective thermal conductivity. Accordingly, by direct numerical simulation, a dimensionless criterion correlation characterizing the variation of m with directional deformation parameters which are defined as the ratio of cell diameter between the macro heat transfer direction of metal foam and its orthogonal direction was obtained. A new method for predicting directional effective thermal conductivity was further proposed by employing the conduction form factor, which was verified through literature reported experimental data. It is found that the effective thermal conductivity can be accurately calculated by the prediction method proposed in present study, with a small prediction deviation of 0.77%. Compared with previous theoretical prediction models derived on a basis of isotropic porous structure assumption whose prediction deviations from experimental data are more than 14%, our method can significantly improve the prediction accuracy of effective thermal conductivity.

Key words: porous media, metal foam, heat conduction, effective thermal conductivity, prediction, conduction form factor