Transitional droplet growth and diffusion coefficients

The droplet growth models of Gyarmathy and Young, valid for arbitrary Knudsen numbers, are compared with experimental growth results obtained from expansion wave tube experiments. Growth experiments of n-pentanol in helium were performed at approximately 1 bar, resulting in growth curves stretching from the transition regime (Kn≈1) to the continuum regime (Kn≪1). Droplet growth experiments of water in helium and water in nitrogen were performed at elevated pressures, when the mean free path is small; hence, these growth curves are situated near the continuum regime. For Kn > 0.1, the Gyarmathy model appears to describe the experimental growth 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 systems new experimental diffusion coefficients are obtained, which are in good agreement with literature data.