Filtration efficiencies in electrostatically augmented granular beds

Abstract

Fine particle filtration efficiencies of electrically enhanced granular beds are computed and compared with available experimental data. Collection efficiencies of a single bed sphere in a gaseous flow are first calculated by numerically solving the equations of particle motion. The collection mechanisms incorporated here are inertial impaction, interception, and charged fine particle-imposed electric field interaction. The approach is based upon a “unit cell” model which enables one to include the effects of surrounding bed particles on the collection process. Stokes' flow and potential flow are used to model the gas flow around the bed particle. Total efficiency is computed by integrating the single-sphere collection efficiency over the bed volume. These calculated total bed efficiencies compare satisfactorily with data obtained from an existing granular bed facility over a range of parameter values. Both theory and experimental data show that the electrical force significantly enhances particulate collection in granular beds.