Dynamics of Aerosols

This chapter presents dynamics of aerosols. Aerosols, or atmospheric particles, can vary in size from collections of a few molecules to cloud droplets. The evolution of these particles occurs as a result of particle-particle collisions and individual particle growth because of accretion of vapor molecules. The process of individual particle growth can involve chemical reactions occurring in the particles. The chapter also presents the basic conservation equations for the aerosol number concentration as a function of particle size. It discusses the kinetic coefficients that appear in the basic equations and describes dimensionless groups that characterize the aerosol. It also illustrates the results of certain interesting cases of aerosol evolution during pure growth. The dynamic behavior of an aerosol is described by a population balance equation, which can be termed as the general dynamic equation. The evolving size spectra, in the three cases of diffusion-, surface reaction-, and volume reaction-controlled growth, exhibits certain distinct features characteristic of the growth mechanism.