Effects of droplet deposition on aerosol capture efficiency of bipolarly charged fibers†

Aerosol filters composed of electrostatically charged bipolar fibers are referred to as electret filters. A novel computational model is developed in this work to study the impact of droplet deposition on aerosol capture efficiency of electret fibers. The electret fibers were assumed to have a dipole orientation that was either parallel or perpendicular to the airflow direction. The simulations were conducted using the ANSYS CFD code after it was enhanced with a series of in-house subroutines. Our simulations revealed that droplet deposition on electret fibers decreases their ability to capture airborne particles. More specifically, the simulations were devised to isolate droplet's physical and electrical properties (e.g., surface tension, electrical conductivity…) and quantify their impact on fiber capture efficiency. It was found, in particular, that droplet's electrical conductivity and permittivity have the most adverse impact on the performance of an electret fiber. This is perhaps because higher droplet conductivity results in severe fiber charge neutralization, and higher droplet permittivity leads to a stronger fiber charge shielding. In contrast, fiber wettability was found to have a negligible impact on fiber efficiency. The work presented in this paper offers valuable insights into the complex nature of electret filters used in different industrial and environmental applications.