A synthesis of tortuosity and dispersion in effective thermal conductivity of porous media
A synthesis of tortuosity and dispersion in effective thermal conductivity of porous media
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DOI：
10.1016/j.ijheatmasstransfer.2010.03.004
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发表时间：
2010-07
影响因子：
5.2
通讯作者：
Chen Yang;A. Nakayama
中科院分区：
文献类型：
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作者：
Chen Yang;A. Nakayama
利用体积平均理论，研究了弯曲度和分散度对饱和多孔介质有效导热系数的影响。首先，利用单元胞模型推导了有效滞热导率的一般表达式，单元胞模型由具有连通臂的矩形实体组成。将所得结果与已有的充填床、多孔泡沫和丝网筛网的实验和理论数据进行比较，证实了滞热系数表达式的有效性。其次，利用基于体积平均理论的固相和液相两个能量方程，求出了导热系数的一般表达式。研究表明，固、流两相间的间隙换热与热分散密切相关。所得的纵向和横向导热系数表达式与现有的实验数据和经验关系式吻合较好。
Effects of tortuosity and dispersion on the effective thermal conductivity of fluid-saturated porous media are investigated analytically with help of a volume averaging theory. Firstly, a general expression for the effective stagnant thermal conductivity has been derived using a unit cell model, which consists of rectangular solids with connecting arms in an in-line arrangement. The validity of the expression for the stagnant thermal conductivity has been confirmed comparing the present results with available experimental and theoretical data for packed beds, porous foams and wire screens. Secondly, an general expression for the thermal dispersion conductivity has been sought with help of the two energy equations for solid and fluid phases, derived on the basis of a volume averaging theory. It has been shown that the interstitial heat transfer between the solid and fluid phases is closely associated with the thermal dispersion. The resulting expressions for the longitudinal and transverse thermal dispersion conductivities agree well with available experimental data and empirical correlations.