Flow and Diffusion of Gases in Porous Media

Abstract

A generalized treatment of gas transport in porous media is presented as developed on the basis of the ``dusty‐gas'' model, a model in which a porous medium is described as consisting of uniformly distributed, giant molecules (dust) held stationary in space. The problem is broken down into a series of special cases which involve the various combinations of gradients in composition, pressure, and temperature. Equations are given for the description of several well‐known phenomena. These include isobaric, isothermal diffusion; diffusion under the influence of a pressure gradient; Poiseuille's flow equation, including the Knudsen minimum; the Kramers—Kistemaker effect; thermal transpiration; and the effect of pressure on the thermal‐diffusion factor. The results are likewise applicable to capillaries by a suitable substitution for geometric parameters.