Diffusivity of simple fluid mixtures in porous media: Molecular dynamic simulations and correlation models

It is well know that molecular dynamics simulations can provide an insight into the microscopic characters and relate them to the microscopic properties, and MD simulations are widely used to study the microscopic flows in porous media. The diffusivity of Lennard-Jones liquid argon, krypton and their binary mixtures in the macrovolumen systems has been calculated by equilibrium molecular dynamic (EMD) simulations in order to prove this program's validity. In addition, the diffusivity of liquid mixtures of argon and krypton in slit porous media has been obtained by EMD simulations at different reduced temperatures, densities and pore widths. The result shows that the diffusivity of fluids will increase sharply in narrow pores. Based on the Chapman-Enskog theory and Heyes equations, two correlation models, which can describe the diffusivity of simple fluid mixtures in porous media, are proposed as functions of the reduced temperature, density and pore width.. The results calculated from the models are in good agreement with the data from MD simulations.