Numerical Model for particle deposition and loading in electret filter with rectangular split-type fibers

Abstract

A simulation model for electret filter made of split type fibers has been developed to study the filtration efficiency as well as the particle loading process. The filter was assumed to be composed of rectangular fibers arranged in staggered array in which the flow field, the electrostatic field and the collection mechanisms were determined by numerical simulation. Single fiber efficiencies under various filtration conditions were calculated and compared with results obtained from semi-empirical expressions derived from experimental results. Influences of particle charge, fiber charge and orientation of fiber on the collection efficiency were evaluated. Finally the particle loading process was studied using the present model. Dendrite growth of particles in equilibrium charge state was simulated. The mechanical efficiency compensation effect was studied by a series of simulations. It is found that the loading of 1.5 μm or larger particles has a significant mechanical collection compensation to the loss in electrostatic efficiency; while for 0.4 μm particles such compensation is slow and insignificant.