Effective Thermal Conductivity of a Wet Porous Medium—Presence of Hysteresis When Modeling the Spatial Water Distribution for the Pendular Regime

Abstract

This paper deals with the heat transfer between two spherical grains separated by a small gap; dry air is located around the grains and a liquid water meniscus is supposed to be present between them. This problem can be seen as a microscale cell of an assembly of solid grains, for which we are looking for the effective thermal conductivity. For a fixed contact angle and according to the volume of the liquid meniscus, two different shapes are possible for the meniscus, giving a “contactingâ€‌ state (when the liquid makes a true bridge between the two spheres) and a “noncontactingâ€‌ one (when the liquid is split in two different drops, separated by a thin air layer); the transition between these two states occurs at different times when increasing or decreasing the liquid volume, thus leading to a hysteresis behavior when computing the thermal flux across the domain.