Estimation of collection efficiency enhancement factor for an electret fiber with dust load

In a previous study to investigate how the morphology of particles accumulating on an electret fiber evolves and affects the collection efficiency of the filter at dust-loaded condition, a three-dimensional stochastic model is utilized to simulate the deposition and agglomeration of particles on a cylindrical electret fiber via two different electrical effects, namely, induced force (for uncharged particles) and Coulombic force (for charged particles). In the present study, the additional effect of Brownian diffusion is incorporated in the model and the morphology of particle agglomerates obtained in the simulated results is found to agree well with experimental observations obtained by Hiragi and Kanaoka et al. for both uncharged and charged particles. In addition, the ratio of dust-loaded collection efficiency, η, to the clean-fiber collection efficiency, η₀, can still be approximated as linear function in the case of weak electrical effects. However, when the electrical parameters are large, the normalized collection efficiency has to be represented by two linear relations, i.e., at low dust load and high dust load. Estimates of the initial collection efficiency and efficiency enhancement factor are given graphically and tabulated as function of Peclet number, the interception parameter and the two electrical parameters.