Stochastic model development and simulation of agglomerative deposition of aerosol on an electret fiber

Abstract

Unlike ordinary filters, the initial high collection efficiency of the electret filter (E) might briefly fall as dust load increases. Here, the electrical enhancement factor of the electret fiber (lambda [subscript E] under dust-loaded condition for uncharged and charged particles is obtained from published experimental results. It is found that the collection efficiency of the electret fiber (eta) can be approximated as the sum of the electrical and mechanical collection efficiency. The predicted values of E are shown to agree well with reported experimental observations for both uncharged and charged particles. In addition, a three-dimensional stochastic model is extended to simulate collection and agglomeration of particles on the cylindrical electret fiber. Effect of interception, induced force (for uncharged particles) and coulombic force (for charged particles) parameters are studies. For both charged and uncharged particles, when the interception parameter is small, captured particles are densely packed. The effect of high electrical forces on the morphology makes the dendrites taller, straighter and more slender than those of small electrical forces. Next, the dust-loaded collection efficiencies of four identical electret filters with the same average packing density but different spatial distributions of packing density along the filter thickness are calculated and compared. The results show that we can significantly lengthen the filter service life by packing the filter loosely on the inlet side and progressively more densely towards the outlet side.