PORE-SCALE STUDIES OF THE EFFECTIVE GAS DIFFUSIVITY IN MICROSCALE POROUS MEDIA BY THE DIRECT SIMULATION MONTE CARLO (DSMC) METHOD

Abstract

The diffusion of gases in microscale porous media plays a pivotal role in multiple engineering applications. Accurate prediction of gas diffusivity in these media is crucial for optimizing such processes. In this research, we utilized the direct Monte Carlo simulation (DSMC) to analyze gas diffusion in microscale porous media, reconstructed using the quartet structure generation set (QSGS) method. We examined the influence of gas pressure, porosity, tortuosity, and porous microstructure on the effective gas diffusivity in microscale porous media. The findings indicate that the dimensionless effective gas diffusivity is inversely related to gas pressure, given a consistent microstructure. The tortuosity, which depends on the microstructure, significantly influences the gas diffusivity. Specifically, as the tortuosity increases, the effective gas diffusivity decreases at the same porosity. In addition, the anisotropy has a substantial effect on the gas diffusivity in a certain direction; however, it has almost no influence on the effective gas diffusivity. Finally, concluding from extensive numerical data, we introduce a predictive model for effective gas diffusivity in microscale porous media. This model considers the effects of Knudsen (Kn) and tortuosity and is able to predict the gas diffusivity in isotropic and anisotropic porous accurately with porosity ranging from 65% to 95% and Kn ranging from 0.1 to 10.