COAGULATION OF SYMMETRICAL AND ASYMMETRIC BIPOLAR AEROSOLS

Coagulation of charged aerosols is investigated by developing a sectio nal numerical model for both particle size and charge distributions an d accounting for electrostatic dispersion. Symmetric bipolar charging increases the coagulation rate when particles are highly charged. Asym metric bipolar charging results in a faster decrease in the particle n umber concentration, but does not actually result in larger particles as the decrease in number concentration is dominated by the electrosta tic dispersion and not by the coagulation of particles. The performanc e of a simpler model in the literature is evaluated by comparing its p redictions against those of the above sectional model. The simple mode l is most accurate for initially mildly asymmetric bipolar aerosols at short residence times. (C) 1997 Elsevier Science Ltd.