Transient moisture transport in a cracked porous medium

Condensation under high relative humidity, imbibition under zero capillary pressure, and drying in a cracked mesoporous slab is numerically simulated. The porous medium is homogeneous, the crack lattice is periodic and has uniform aperture and transport properties. It is found that the crack lattice density and the crack hydraulic conductivity has minor influence on the global kinetics of condensation and drying, and a strong influence on the imbibition kinetics. The transient effects of the heterogeneity of the medium are examined from three view-points: the study of the spatial distribution of pressure head, the tentative definition of an effective diffusivity, and the comparison between the quasi-static and transient transport properties. The equivalent homogeneous medium approach is found to be relatively satisfactory to describe the global kinetics in the three processes. The transient effects appear in secondary features of the processes.