Analysis and evaluation of permeability techniques for characterizing fine particles Part I. Diffusion and flow through porous media

The specific surface area and particle size can be deduced with speed and simplicity from appropriate measurements and calculations of fluid flow and diffusion in porous media. The interdependence of these two processes is developed in a series of two articles.In Part I, models are presented for molecular and Knudsen diffusion during flow through aggregates of solid particles at both atmospheric and low pressure permeametric conditions. For a randomly packed bed of granular particles, a cell model is developed that takes into account the tortuosity and variations in the cross-sectional area. A new analytical expression for the Kozeny constant is derived in terms of the bed porosity and particle shape. The effect of porosity on surface area measurements using permeability methods is explained.