Modeling at Pore-Scale Isothermal Drying of Porous Materials: Liquid and Vapor Diffusivity

摘要

Numerical simulations of isothermal drying of non-hygroscopic liquid-wet rigid porous media are performed. Two- and three-dimensional pore networks represent pore spaces. Two types of mechanisms are considered: evaporation and hydraulic flow. The drying is considered to be a modified form of invasion percolation. Liquid in pore corners allows for a hydraulic connection throughout the network at all times. As drying progresses, liquid is replaced by vapor by two fundamental mechanisms: evaporation and pressure gradient-driven liquid flow. Using a Monte Carlo simulation, evaporation and drainage times are computed. The controlling mechanism is indicated by the shorter calculated time. Initially, the drying is governed by liquid flow, then by a combination of liquid flow and evaporation and finally by local evaporation. Reported here are the distributions of liquid and vapor with drying time, capillary pressure curves, liquid film saturation curves, and liquid diffusivity and vapor diffusivity as a function of liquid saturation.