多孔介质有效导热系数的实验与模拟

应用实验与数值模拟相结合的方法研究了多孔介质的有效导热系数.将分形理论与孔道网络模型相结合的分形孔道网络模型用于研究多孔介质的有效导热系数,为太阳池储热、地源热泵传热、食品干燥等方面打下了基础.模拟计算结果与实验结果吻合较好,证明了分形孔道网络模型适用于计算多孔介质的有效导热系数.研究了孔喉比、配位数、垂直热流方向喉道比例、喉道长度、孔隙率、固体骨架导热系数(K.)及流体导热系数(Kf)等多方面对多孔介质有效导热系数的影响.结果表明,垂直热流方向喉道会增大多孔介质的热阻,降低多孔介质的有效导热系数.当K8大于Kf时,随着孔喉比的增大以及喉道长度的减小,多孔介质的有效导热系数越大.当平行热流方向喉道数目相等时,多孔介质的有效导热系数随着配位数的减小而增大;当垂直热流方向喉道数目相等时,多孔介质的有效导热系数随着配位数的增大而增大.

Experiment and Numerical Simulation of Effective Thermal Conductivity of Porous Media

Effective thermal conductivity of porous media was investigated by experimental and numerical approaches. Fractal pore network model (combination of fractal theory and pore network model) was used to research effective thermal conductivity of porous media. This research has laid a foundation for thermal storage of solar pond, heat transfer of ground source heat pump and food drying. The numerical results of fractal pore network model agree well with experimental ones, which indicated that the fractal pore network model is suitable for researching effective thermal conductivity of porous media. The effects of pore-throat ratio, coordination number, vertical throat proportion, throat length, porosity, thermal conductivity of matrix and fluid on effective thermal conductivity of porous media were studied. It was revealed that vertical throat proportion can enlarge the thermo-resistance of porous media and decrease its effective thermal conductivity. If thermal conductivity of matrix is larger than that of fluid, effective thermal conductivity of porous media increases with of pore-throat ratio and the decrease of throat length. When the number of parallel throat is fixed, effective thermal conductivity of porous media increases the decrease of coordination number. On the contrary, when the number of vertical throat is fixed, effective thermal conductivity of porous media increases with the increase of coordination number.