多孔介质孔隙结构重构及水蒸气传递特性

Reconstruction of Pore Structures and Water Vapor Transfer Properties of Porous Medium

采用随机生长法分别构造了各向同性、各向异性的孔隙率相同,孔径分布和孔隙表面分形维数不同的多孔介质,探索了在多孔介质孔隙率相同的情况下,微观孔隙结构对孔隙内湿传递过程的影响。结果表明:决定多孔介质内部输运特性的孔隙结构参数,除孔隙率以外,孔径分布和孔隙表面分形维数等参数对多孔介质孔隙中水蒸气扩散过程的影响显著;孔隙率相同,孔径分布和孔隙表面分形维数不同的3种各向同性和3种各向异性多孔介质的水蒸气扩散浓度最大差别分别为30.6%和23.3%;各向同性多孔介质的小孔分布率越大,孔隙表面分形维数越大,说明孔隙的连通性和水蒸气在多孔介质孔隙中的扩散性能越好;各向异性多孔介质(水蒸气扩散的方向垂直于其生长率较大的方向)的大孔分布率越大,孔隙表面分形维数越小,水蒸气在多孔介质孔隙中的传递性能越好。

Isotropic and anisotropic porous medium with the same porosity, different pore size distributions and pore surface fractal dimensions were constructed by random growth method, and the impact of microscopic pore structure on moisture migration process in pores of porous medium was theoretically studied. The results show that the internal transport properties of porous medium are not only determinded by porosity, but also greatly influenced by pore size distribution and pore surface fractal dimension. The biggest water vapor diffusion concentration differences of three kinds of isotropic and three kinds of anisotropic porous medium with the same porosity, different pore size distributions and pore surface fractal dimensions are 30. 6 ~ and 23.3 ~, respectively. Better water vapor diffusion properties in pores of isotropic porous medium demands for bigger tiny pore size distribution rate and larger pore surface fractal dimension, which means the pore connectivity is better. While better water vapor diffusion properties in pores of anisotropic porous medium（water vapor diffusion direction is perpendicular to the direction of larger growth rate of anisotropic porous medium） demands for more big pore size distribution and smaller pore surface fractal dimension. The method lays a theoretical foundation for preparing indoor humidity control of building materials.