Direct Contact Heat Transfer to Vaporizing Drop in Immiscible Liquids

摘要

Direct contact heat transfer between single drops of n-pentane vaporizing in a series of 0,30,65 and 98 per cent (by volume) glycerol-distilled water solutions has been studied using cine-photography. The experiments have been carried out varying initial diameter from 1.0 to 3.5 mm and the temperature difference between the two immiscible liquids from 1.0 to 13.9C using a new nucleation technique. The nucleation technique is based on surface properties of teflon and avoids the drop from getting superheated. It has been shown that under conditions of thermal equilibrium a thin film of residual liquid should exist over the entire inside surface of vaporizing drop due to the effect of surface forces and not because of sloshing of the residual liquid, as visualized by Simpson and Co-workers. A semi-analytical expression for instantaneous heat transfer co-efficient as a function of vaporization has been developed. Another semi-analytical expression has been developed for the total vaporization time.