The impact of particle deposition on collection efficiency of electret fibers

This study presents a microscale simulation method that allows one to study the impact of particle loading on the aerosol capture efficiency of an electrostatically charged filter. This was done by considering a bipolarly charged fiber loaded with different amounts of neutral and charged particles with a diameter of 300 nm. The simulations predicted the deposition pattern of the aerosol particles as well as their impact on the electrostatic field of the bipolar fiber. The particle-loaded fiber was then challenged with aerosol particles in the range of 50 nm to 1 μm and with different charge polarities to study how the electrostatic field of the deposited particles interacts with that of the fiber to attract or repel the incoming airborne particles. More specifically, our simulations revealed that particle deposition can enhance the capture efficiency of a bipolar fiber when it is challenged with small particles (smaller than about 400 nm) regardless of the charge polarity of the airborne or deposited particles. The numerical simulations reported in this paper were conducted using the ANSYS CFD code enhanced with in-house subroutines to superimpose the electrostatic field of the deposited particles to that of the bipolar fiber and to include Brownian, polarization, and Coulomb forces in particle trajectory calculations.