Novel Formulae for Deposition Efficiency of Electrically Neutral, Submicron Aerosol Particles in Bipolarly Charged Fibrous Filters Derived Using Brownian Dynamics Approach

Abstract

Brownian dynamics (BD) method was employed to calculate the single fiber deposition efficiencies of electrically neutral, submicron aerosol particles in bipolarly charged and non-charged fibrous filters. It was found that a considerable increase in the deposition efficiency can be achieved by increasing the fiber charge density and that it is accompanied by a noticeable shift of the most penetrating particles size towards smaller particles. The results of the BD simulations obtained for various fiber charge densities and various particle diameters allowed us to derive new formulae relating a gain in the deposition efficiency due to action of the electrostatic force to the dimensionless polarization parameter, N _{σ 0} . These equations are applicable in much wider range of N _{σ 0} than other correlations available in the literature. A simple approximate rule for recalculating the form of the proposed formulae for another filter packing density was also presented. Theoretically predicted values of the deposition efficiency in bipolar electret filters were compared with our own experimental data as well as with the data available in the literature and a satisfactory agreement, better than in the case of other existing correlations, was obtained.

Acknowledgments

The work was financed from the budget means for science in 2006–2009 as a research project.