Abstract

The gas transport mechanism in nanopores mainly includes bulk gas transport, gas adsorption/desorption, and surface diffusion. The bulk gas transport is comprised of viscous flow, slip flow and transition flow.  The apparent permeability model was established by considering the effects of slip flow, Knudsen diffusion, adsorption/desorption and surface diffusion. At high pressure, slip flow contributes significantly to the gas flux in macropores.  Surface diffusion contributes significantly to the gas flux in micropores and mesopores.  At low pressure, Knudsen diffusion contributes significantly to the gas flux in mesopores and macropores.