Filtration Theory for Granular Beds

Abstract

Using "the method of isolated fibers," a semi-empirical equation for predicting the aerosol collection efficiency of a granular bed filter is presented. The equation is based on describing the theoretical deposition rate of particles on a single sphere (granule) in a flow field and expressing the influence of neighboring spheres in terms of empirical or semi-empirical corrections. The resulting calculation yields a predicted filtration efficiency for a bed of granules. Mechanisms for deposition by diffusion, impaction, gravity, and interception are considered. The influences of size of fitter media, packing density, bed thickness and superficial gas velocity on filter effectiveness are presented.