Homogeneous and heterogeneous nucleation in a laminar flow aerosol generator

Abstract

The formation of aerosol particles by homogeneous and heterogeneous nucleation has been studied experimentally using a laminar flow aerosol generator. Dry gas (N₂ or air) saturated with dibutylphthalate (DBP), either particle-free or containing an ultrafine monodisperse aerosol, was cooled well below the saturation temperature causing the highly supersaturated vapor to nucleate. The resulting particle number concentrations were observed under various conditions of the gas stream and properties of the introduced foreign condensation nuclei. The dependence of the nucleation rate on the vapor concentration, cooling rate, and seed aerosol concentration was studied. Comparisons of the measured number concentrations with predictions based on the model of A. J. Pesthy, R. C. Flagan, and J. H. Seinfeld (J. Colloid Interface Sci. 91, 525 (1981)) showed good qualitative agreement when the classical homogeneous nucleation rates were enhanced by a factor of 10⁵–10⁷. The laminar flow aerosol generator is found to be an effective system for the study of the influence of foreign particles on the rate of homogeneous nucleation of a vapor.

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