Electrical Enhancement of Filters with Randomly Oriented Fibers

Abstract

A model is given for the interception deposition of an electrified filter whose fibers are randomly oriented to the mean direction of flow. A derivation is given for the field resulting from the fiber polarization when an external electrical field is present and when there is charge on a fiber. Analytical solutions are given for the single-fiber effective deposition rates and filter efficiencies in the case of no external forces and in the case of interaction of a charged particle (but no particle polarization) with a polarized or charged fiber. When the particle is polarized by a charged or polarized fiber, a fast numerical method for computing the efficiencies is presented. In the case of no electrical forces, the effective deposition rates due to interception and the corresponding filter efficiencies over a range of fiber orientations are computed. An average value is computed, assuming a uniform distribution of orientations. The results of similar computations are presented for cases when electrical forces are present.