Effects of an external electric field on the collection efficiency of air filters: Filtration mechanisms with an external e-field

Abstract

An external electric field was applied on the filter to improve its collection efficiency, and the collection efficiencies of the different filters under various conditions were evaluated. Dominant electrical filtration mechanisms for each condition were investigated using experimental and theoretical approaches. Four types of air filters were used as test filters: a charged fiber filter, a lowgrade filter with 50% collection efficiency in the most penetration particle size (MPPS) zone, and two high-grade filters with more than 95% collection efficiency in the MPPS zone. Three different particle charge states-neutralized, single-charged and uncharged-were considered. For neutralized particles, the external electric field led to a 14.5%p. and 2.5%p. increase in the collection efficiencies of the low-grade filter and charged fiber filter, respectively. With the electric field, the collection efficiency of the low-grade filter increased by 30%p. for single-charged particles. The electric field also affected the collection efficiencies of the charged filter and high-grade filters, but the effect was not significant. For uncharged particles, the electric field did not lead to a remarkable increase in the collection efficiencies of any of the filters. Through experimental and theoretical analysis, it was found that the polarization force imposed on the charged fiber was the dominant factor for the charged fiber filter regardless of application of the external electric field. The Coulombic force imposed on the electric field was the dominant factor for the low-grade filter, while both the Coulombic and the polarization forces affected the collection efficiency of the highgrade filter.

Facile Functionalization via Plasma-Enhanced Chemical Vapor Deposition for the Effective Filtration of Oily Aerosol

“…Among the capture mechanisms, including interception, inertial impaction, diffusion, etc., the electrostatic attraction is most helpful in capturing particles of the most penetrating particle size (MPPS) in the diameter range of about 0.1–0.5 µm [6,7,8]. Thus, electrostatic charges are often imposed upon the filter media during manufacturing to better attract: (1) The oppositely-charged particles by the coulombic interaction, and (2) the neutral particles by induced polarization [9,10,11]. While the capture efficiency of different sized-particles varies depending on the air velocity, very fine particles smaller than MPPS are captured rather efficiently by the diffusion mechanism [12].…”

Tribo-charge enhanced hybrid air filter masks for efficient particulate matter capture with greatly extended service life

“…Accordingly, when this pulsed electric field was on, PMs passing through the PP/PAN underwent different electrostatic forces, namely Coulombic and polarization. The Coulombic force is due to the charged airborne particles within the electric field, while the polarization force stems from the charged PP/PAN fibers [50] , [51] . Given that the carrying charge of PMs depends on the environmental circumstances, which means PMs have the possibility of carrying positive, negative, or neutral charges.…”

Development of a rapid plasma decontamination system for decontamination and reuse of filtering facepiece respirators

“…The electrostatic attraction filter efficiencies for both charged and uncharged particles are governed by the electric field strength. 22 During the plasma decontamination process, respirator samples are exposed to an external AC electric field, about 2 MV/m. When an external AC electric field is applied to a polarized melt-blown non-woven polypropylene filter layer, the polarizability of the filter layer can be affected.…”