Effects of solid particles with various charging states and oil aerosols on the filtration characteristics of electret media

Abstract

In this study, electret media were loaded with neutralized and charged potassium chloride (KCl) to examine the effect of charged solid particles on loading behaviour. The media were then loaded with diethylhexyl sebacate (DEHS), dipropylene glycol (DPG) and glycerol to obtain a correlation between the efficiency degradation and liquid aerosol. The results indicated that the efficiency of electret media decreased from 72% to 46% under the neutralized KCl loading whilst the efficiency decreased from 96% to 82% under the positively charged KCl loading. Particle charging increased the initial efficiency and also effectively minimized the efficiency degradation. Given the increase in efficiency via chargers, the deposition morphology of the solid particles on the fibres was changed to mitigate the efficiency degradation. With respect to electret media loaded with DEHS, DPG and glycerol, the decrease in efficiency was associated with the solubility difference between the fibres and oil aerosols. Given sufficient affinity between the oil particles and fibres, oil molecules permeated the chain segments of the fibres and produced swelling that damaged the charge traps and decreased efficiency. The results of this study can guide practical electret filter operations and provide a better indoor environment.