Influence of thermal gradients on the invasion patterns during drying of porous media: A lattice Boltzmann method

Abstract

Drying of porous media sounds simple yet complicated to study the multiphase flow counterparts in porous media with intricate pore geometries. In the past, we have discussed the Lattice Boltzmann Model (LBM) as a powerful multiphase solver for the drying of porous media. In this study, we extend our previous work on the Shan Chen representation of the multiphase LBM to drying of porous media with imposed thermal gradients. A linearly varied stationary temperature profile is imposed concerning the depth of the porous medium, i.e., free evolution of temperatures due to the phase change is neglected. The preferential heating is divided into two kinds of gradients: First, the positive thermal gradient where temperatures varies linearly on an increasing order from top to bottom (e.g., the contact heating mode of drying). Second, the negative thermal gradient opposite the former (e.g., convective mode of heating). It is observed that the thermal gradient can lead to stabilizing and destabilizing drying fronts, where the latter situation incurs two drying fronts in a later period of drying. The novelty of this work is the establishment of thermal aspects to the previously discussed LBM and introduces the concepts of evaporation–condensation of trapped clusters and liquid bridges. The characteristics of thermal drying for stabilized and destabilized drying fronts is re-established at a magnified level of study using the developed LBM.