Knudsen's permeability correction for gas flow in tight porous media using the R26 moment method

Gas in microchannels and tight porous media is often in a nonequilibrium state. The conventional thermodynamic models for fluid flow and heat transfer fail, i.e., the classical Navier-Stokes-Fourier equations, are no longer accurate or valid. In this situation, the pressure-driven gas flows in parallel microchannels, circular micropipes, and tight porous media are solved based on the regularized 26 moment equations in this paper. A higher-order approximation of more general correlation for rarefied gas flow called higher-order Knudsen's permeability is presented in both microchannels and tight porous media. In addition, the Klinkenberg's first- and second-order equations are proposed according to Taylor series' expansion of higher-order Knudsen's permeability. The comparisons are implemented between the present model and available experimental data.