Pore-Scale Studies of the Effective Gas Diffusivity in Microscale Porous Media: Model Development and Influencing Factors

The diffusion of gases in microscale porous media is a phenomenon of great importance in various engineering applications. Accurate prediction of gas diffusivity in these media is crucial for optimizing such processes. In this study, we conducted numerical studies using the Direct Monte Carlo simulation method (DSMC) to investigate the gas diffusion process in microscale porous media, in which the porous media was reconstructed by the quartet structure generation set (QGSG) method. We examined the influence of gas pressure, porosity, tortuosity, and porous microstructure on the effective gas diffusivity in microscale porous media. The results show that the dimensionless effective gas diffusivity is negatively correlated with the gas pressure, considering the same the same microstructure. The tortuosity, which depends on the microstructure, significantly influences the value of 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 gas diffusivity in a certain direction; however, it has almost no influence on the effective gas diffusivity. Finally, based on a large number of numerical results, we proposed a predictive model for effective gas diffusivity in microscale porous media. This model takes into account the the effects of Kn and tortuosity and is able to predict the gas diffusivity within isotropic and anisotropic porous accurately.