Enhanced Simulation for Electrostatic Effects in Electret Filter Media

The filtration process in electret filter media can result in non-monotonic penetration curves due to the changing effect of filtration over time. The graphs in Figure 1 depict this phenomenon in the orange curve (experiment) that demonstrates a low penetration rate initially, followed by an increase and eventually a decrease. Initially, the high charges in the media capture most particles, but as more mass accumulates, the charges weaken, resulting in fewer particles being trapped. As mass continues to accumulate, captured particles contribute to the capture efficiency, leading to an increase in the number of trapped particles.

Our previous attempts to simulate this behavior did not take into account the decreasing charges, as shown in the simulation results on the left side of Figure 1. However, by accounting for the dependence of electrical charges on the deposited dust, digital filtration experiments accurately reproduce the behavior observed in physical experiments, as shown in the simulation results on the right side of Figure 1.

To improve the agreement between digital and physical filter experiments, we developed a general modeling framework that can account for the dependency of electrical charges on the deposited mass. Since the exact relationship between charge reduction and deposited mass is not entirely understood, our model allows for detailed modeling of electrical charges.