Electrostatic precipitation of aerosols under zero net flow conditions

The efficiency of aerosol removal by electrostatic precipitation has been studied in an enclosure formed between the electrodes of a cylindrical condenser. The key feature of this arrangement is that, unlike most other electrostatic precipitator systems, the aerosol source is fully contained within the enclosure and there is no net air throughput. In the experiments, the central electrode was charged to direct current potentials of up to 30 kV and supported small carbon fiber brushes, the resultant corona discharge from which produced copious gaseous ions. Measurements were made of the relationship between the ion current and applied electrode voltage and of the decay of preestablished aerosol clouds derived from the abrasion of flax twine. These latter measurements were carried out using a size-selective optical particle counter which gave simultaneous results for particles in two different size ranges. Theoretical models based on appropriate assumptions regarding the effect of the ion space charge distribution on the electric field—and hence on the charging and migration of particles—within the enclosure were developed for the cases of completely still air and air undergoing mixing owing to recirculatory flows between the electrodes (induced by the electric wind of the corona discharge). Predictions from these models are compared with the experimental results. Possible applications of this mode of electrostatic precipitation to localised dust control in workplaces are discussed.