Direct numerical simulations of moisture transport in porous media by a multi-component/phase-change lattice Boltzmann method

Abstract

In this paper, simultaneous heat and mass transport in porous media is studied numerically using a 2D multicomponent/multiphase phase-change lattice Boltzmann scheme. This newly developed LB model requires no correlation equations as inputs for physical properties of the porous medium (such as relative permeability, heat capacity, thermal conductivity and mass diffusivity) that is filled with a multi-component fluid of air/vapor mixture. Natural convection and condensation of humid air in an enclosure filled with and without a porous medium that is heated differentially by vertical walls are compared. The same numerical scheme is applied to simulate capillary rise of liquid in semi-infinite packed hydrophilic beds with different structures that are filled initially with a mixture of unsaturated vapor and air above a water reservoir. It is shown that evaporation in the packed hydrophilic bed plays an important role in capillary rise of liquid. Effects of contact angles as well as the influence of the directionality and heterogeneity of the packed bed are investigated. The directional and the heterogeneous packed beds are shown to be able to suck a larger amount of liquid in a shorter time period compared to homogeneous packed beds with the same porosity under the same condition.