Interaction between Brownian Diffusion and Coulombic Force in Electret Filtration

Abstract

In the electret filtration of charged ultrafine particles, Brownian diffusion and Coulombic force are the dominant collection mechanisms. In the present work, the interaction between Brownian diffusion and Coulombic force in electret filtration is studied by solving convective diffusion equation including Coulombic force, and the numerical results are compared with the experimental data. As a result, the dominant region of either Brownian diffusion or Coulombic force is obtained as a function of Peclet number, Pe, and Coulombic force parameter, K_C. It is shown that there is a negative interaction between Brownian diffusion and Coulombic force, i.e., Coulombic capture efficiency is reduced with decreasing Pe. These results suggest that Brownian diffusion and Coulombic capture efficiency is not a simple sum of Brownian diffusion efficiency and Coulombic capture efficiency.