Abstract

Based on the capillary hypothesis and fractal theory, a mathematical model for calculating the effective gas diffusion coefficient in porous media is established. By using fractal geometry theory, pore area fractal dimension, tortuosity fractal dimension and pore connectivity are introduced to quantitatively characterize the real internal structure in the porous media. An effective gas diffusion coefficient model for the fractal porous media is derived, and the influence of multi-scale porous media microstructure parameters on the effective gas diffusion coefficient is discussed. The results show that effective gas diffusion coefficient approximates to linearly increase with the increase of porosity, the pore area fractal dimension and the effective gas diffusion coefficient is positive correlation, but the tortuosity fractal dimension is negatively related to it. In the case of different porosities, the gas effective diffusion coefficient varies with the change of the pore diameter ratio, the effective gas diffusion coefficient increases with the increase of pore connectivity.

Highlights

  • Gas diffusion in porous media is a fundamental problem in many disciplines and engineering fields

  • The effective diffusion coefficient is very important for the heat and mass transfer process in porous media

  • The diffusion process of gas in the pores of porous media is mainly affected by the morphological characteristics of its internal pores

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Summary

Introduction

Gas diffusion in porous media is a fundamental problem in many disciplines and engineering fields. The effective diffusion coefficient is very important for the heat and mass transfer process in porous media. Gas effective diffusion coefficient models usually contain empirical and fitting constants, but few models provide detailed structural information of porous media [1]. The diffusion process of gas in the pores of porous media is mainly affected by the morphological characteristics of its internal pores. When studying the mass diffusion of gas in porous media, it is necessary to take full account of its morphological characteristics. A fractal model of the multi-scale pore structure of porous media is constructed. The gas diffusion process under different scale pores in porous media is studied, and the effective gas diffusion coefficient model of fractal porous media is derived.

Pore structure characteristics of porous media
Pore connectivity
Fractal characteristics of tunnel tortuosity
Mathematical model of effective gas diffusion coefficient
D f Dt max
Model validation
Conclusion

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