Interphase heat exchange and kinetics of condensation relaxation in the case of small and moderate Knudsen numbers

Abstract

259 In this paper, we obtained a numerical solution to the problem of heat exchange between a growing droplet and the vapor-gas phase in the cases of small and moderate Knudsen numbers of the droplet. Based on the results obtained, we studied the effect of inter� phase heat exchange on both the dynamics of macro� scopic parameters and the distribution functions inherent in the condensationrelaxation process upon the instantaneous formation of the supersaturated state in the vapor-gas mixture. We compared these results with those obtained in the case of the general setting of the problem, which are based on simplified assumptions concerning the temperature of droplets. The heat release on the droplet surface in the process of bulk condensation plays the role of negative feed� back: elevation of the droplet temperature results in slowing down of the condensation growth, whereas an increase in vapor temperature lowers the degree of supersaturation and, as a consequence, the nucleation rate. The relation between two damping factors is deter� mined by the temperature difference between droplets and vapor. The larger this difference, the stronger the effect of the first factor (i.e., the slowing down of the droplet growth). Otherwise, the effect of the second factor (a decrease in the nucleation rate) predomi� nates. In turn, the temperature difference for droplets and vapor is determined by the intensity of the inter� phase heat exchange. Hence, in the general case, the description of the bulkcondensation kinetics should include the description of three parallel procedures: the formation of novel droplets (nucleation), the con� densation growth of droplets, and the interphase heat exchange. In the literature, two simplifying assump�