大孔隙率多孔介质内热弥散现象数值模拟

Numerical simulation of thermal dispersion in porous media with large porosity

采用Surface Evolver泡沫演化动力学软件构建理想的大孔隙率多孔介质的几何模型:Weaire-Phelan模型。通过对有效热导率的计算,确定了该模型的适用范围。在此基础上优选两组几何参数作为计算依据,流体相分别采用空气和水,固体相为铝T-6201,通过数值模拟,研究了孔径、Darcy速度和流-固热扩散系数比的影响。数值计算结果表明:孔径越小,热弥散效应越强,流体本身的热物性对弥散的影响越明显;横向分量远小于纵向分量。当工质为气体时,横向分量可以忽略不计,最后得到了计算纵向与横向热弥散系数的经验关联式。

The structure of porous media with large porosity is described by a spatial periodic Weaire-Phelan model, which is built by the Surface Evolver software, and the application range of this model is determined by comparison of experimental data and simulation result for thermal effective conductivity. Based on the model, numerical computations on two specimens, with air and water as working fluids and aluminum T-6201 as solid matrix, are conducted. The effects of working parameters, such as pore size, Darcy velocity and ratio of thermal diffusion coefficient of fluid to solid, on the thermal dispersion are discussed. The simulation result shows that smaller diameter and stronger dispersion result in a more sensible dependency on thermal physical properties. In addition, the transversal component is far smaller than the longitudinal one. Empirical correlations for the longitudinal and transversal thermal dispersion are obtained in term of Peclet number.