Transitional droplet growth and diffusion coefficients

The droplet growth models of Gyarmathy and Young, valid for arbitrary Knuds en numbers, are compared with experimental growth results obtained from exp ansion wave tube experiments. Growth experiments of iz-pentanol in helium w ere performed at approximately 1 bar, resulting in growth curves stretching from the transition regime (Kn approximate to1) to the continuum regime (K n much less than 1). Droplet growth experiments of water in helium and wate r in nitrogen were performed at elevated pressures, when the mean free path is small; hence, these growth curves are situated near the continuum regim e. For Kn > 0.1, the Gyarmathy model appears to describe the experimental g rowth curves better than the Young model. However, for Kn < 0.02, the Young model gives the best results. For the water-helium and water-nitrogen syst ems new experimental diffusion coefficients are obtained, which are in good agreement with literature data. (C) 2000 Elsevier Science Ltd. All rights reserved.