多孔介质内部热质传递的等效耦合扩散模型

The Equivalent Coupled Diffusional Model for Heat and Mass Transfer inside the Porous Media

基于Whitaker的体积平均方程,在不附加任何新的假设的基础上,寻出一组关于液体饱和度、温度和气相压力的新支配方程,应用该方程组对微孔硅酸钙保温制品干燥过程进行了数值分析.在蒸发速率、平均含湿饱和度及温度变化方面,数值解与实验结果十分吻合.文中还提出了表面质流和表面局部蒸发的概念,根据这两者与外部传质的平衡与转换可以解释临界点出现的机理.

A new set of governing equations for liquid-saturation,temperatureand gaseous phase pressure inside the unsaturated porous media is deducted inthis paper based on the volumetric average equations proposed by Whitaker without any additional assumptions.The physical significance of this set of equa-tions is very clear which can be recognized as the mathematical expression of thephysical phenomenon applying the equivalent coupled diffusional model.Thedrying process of the porous calcium-silicate products is numerically simulated byusing this model.Concerning about the variation of the evaporating rate,ave-rage liquid-saturation as well as the temperature field,the numerical analysis ofthis model is consistent with the experimental results.In this paper the differentconcept of surface mass flux and local surface evaporation are proposed.The me-chanism of occurrence of the critical point can be explained from these conceptsas well as the equilibrium and transpost between the surface and external masstransfer.