Nucleation of Supersaturated Vapors in Nozzles. I. H2O and NH3

Abstract

Measurements have been made of the results of homogeneous nucleation of NH₃ and H₂O vapors expanding in steady flow in a supersonic air nozzle. From the effect of the nucleation and growth of liquid from the vapor phase on the nozzle pressure distribution, the point of incidence of condensation is readily detected. Experimental results have been compared with the predictions of the classical nucleation rate equation and with the quantum‐statistical treatment of Lothe and Pound. While H₂O nucleation rates are in agreement with the classical equation, NH₃ nucleation follows the very much higher rates (12 to 18 orders of magnitude) of the Lothe–Pound equation. A mass accommodation coefficient of 0.01 < ξ < 0.1 for H₂O was inferred from the experimental data.