Modeling and prediction of loading characteristics of electret filter media for charged PM2.5

Abstract

The filtration performance degradation of electret filter media during usage poses a significant challenge. Aerosol pre-charging has been identified as an effective method to address this problem. Nonetheless, the performance evolution of electret filter media during charged particle loading still need a comprehensive understanding. In this study, a novel loading model was developed to estimate and predict the efficiency and pressure drop evolution of electret media during its loading with charged particles. The model considered the charge screening effect, the charge redistribution among electret fibers, and the particle deposition morphology. In the model, the electret fiber surface is divided into particle attraction and repulsion zones. Based on the experimental observation, the deposited particles on the attraction and repulsion zones are regarded as dendritic-deposition particles and homogeneous-deposition particles, and the two can be transformed into each other depending on environment humidity and particle hygroscopicity. In addition, the charge redistribution among the electret fibers during loading process is calculated according to Kirchhoff’s current law, considering the conductivity and electric neutralization effects induced by the deposition of charged particles. Furthermore, a new calculation method of Coulombic capture efficiency considering deposition distance is proposed to describe the screening effect. The developed simple and efficient model demonstrated satisfactory predictive ability under various particle loading conditions in comparison with the results of experiments. It is expected to become a powerful tool for rapid design and optimized operation of electret filtration media.