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 lm or larger particles has a significant mechanical collection compensation to the loss in electrostatic efficiency; while for 0.4 lm particles such compensation is slow and insignificant.

On the importance of fibers' cross-sectional shape for air filters operating in the slip flow regime

“…There are many analytical, numerical, and empirical correlations that have been developed for filters made up of circular fibers. There are also a few studies dealing with non-circular microfibers (i.e., fibers with diameters greater than a few micrometers), such as the work of Lamb and Costanze [12], Sanches et al [13], Raynor [14], Fotovati et al [15], Cheung et al [16], Dhaniyala and Liu [17]. However, despite the abundant number of studies dealing with microfibers, no work has been dedicated to exploring the performance of media made of non-circular nanofibers.…”

Effect of particle-fiber friction coefficient on ultrafine aerosol particles clogging in nanofiber based filter

“…In this work, the fully sticking (single touching point) boundary condition was applied for the particle-particle interaction modeling (similarly to other theoretical studies [13,[15][16][17][18][19][20][32][33][34]) which can be justified for the 10 nm -5 μm particle size range as showed experimentally by Wang and Kasper [35] and Pawu and Braaten [36]. Under this condition, dendrites (formed by the accumulated particles during the filtration process) cannot bend or break down in this model.…”

“…A number of theoretical studies considering the above described filter clogging mechanism [12][13][14][15][16][17][18][19][20][21][22] have already been performed for micro-fibrous filters.…”

Novel Formulae for Deposition Efficiency of Electrically Neutral, Submicron Aerosol Particles in Bipolarly Charged Fibrous Filters Derived Using Brownian Dynamics Approach

“…More common are the filters with bipolarly charged fibers; however, there are not many information in the literature concerning the calculation of aerosol particle deposition onto such fibers. The simulations for bipolarly charged fibers of rectangular cross-section were done, e.g., by Cao et al (2004) and Cheung et al (2005), while the deposition on a cylindrical fiber with a line dipole charge distribution was investigated theoretically, e.g., by Brown (1981). The experimental data of filtration efficiency of neutral aerosol particles in electret filters were reported, e.g., by Lee et al (2002), Kim et al (2005), and Ba lazy et al (2006).…”