Combined field and diffusion charging of aerosol particles in the continuum regime

Abstract

The charging of aerosol particles by unipolar ions in an electric field has been studied theoretically by means of a numerical solution technique. The technique involves calculating the particle charging rate by solving the macroscopic ion diffusion equation in an electric field by relaxation and then integrating the particle charging rate to determine the particle charge as a function of charging time. Results are presented showing the dimensionless particle charge, γ, as a function of dimensionless time, τ, for various dimensionless electric fields, ω. The study provides a rigorous solution to the problem of combined field and diffusion charging of aerosol particles in the continuum regime. Comparison of the theoretical results with the experimental data of Hewitt (1957) and those of Smith et al. (1977) shows that there is good agreement between the theoretical and experimental results. The discrepancy between theory and experiment is of the same order of magnitude as the estimated uncertainties in the experimental data themselves.