Determination of the Mean Mobility and Estimation of the Mobility Distribution of Aerosols with a Concentric-Cylindrical Electrostatic Precipitator

Abstract

Concentric-cylindrical electrical condensers, commonly employed in laboratory research work to precipitate charged aerosol particles (electrostatic precipitator, ESP), can also be used to measure the mean electric mobility of the aerosol and to estimate its mobility distribution. A theoretical research has been carried out to describe the performance of an ESP and its application to the determination of aerosol mobility distribution. Two main equations have been derived: the transfer function, i.e. the probability that a particle of a given mobility is transmitted through the ESP; and, from it, the basic equation describing the performance of the precipitator, the penetration–voltage equation. These equations are valid for whatever shape of the flow velocity profile. MonteCarlo simulations have been carried out to compute the penetration–voltage curve and found to be in excellent agreement with the analytical equations. The parameters (geometric mean and standard deviation) of aerosols with lognormal mobility distributions can be estimated with certain accuracy as long as the distribution width is not too large. Finally, the effect of Brownian diffusion (not taken into account in the theoretical model) has been considered in the MonteCarlo simulations and found to be negligible provided that proper ESP geometric dimensions and aerosol flow rate are used.