Liquid-Vapour Phase Change Rates and Interfacial Entropy Production

Abstract

Measurements have recently been made of the thermodynamic conditions at the interface during steady state, liquid-vapour phase transitions. In these stationary, nonequilibrium states discontinuities were recorded in the temperature and other intensive properties. Independently of whether evaporation or condensation was taking place, it was found that the interfacial temperature was higher in the vapour phase than that in the liquid. The expression for the interfacial entropy production during these phase change processes is formulated using statistical rate theory. The interfacial entropy production rate is not a minimum when there is a phase change process taking place, but if the system is required to be closed (no net phase change), the interfacial entropy production rate is a minimum. States of minimum entropy production rate can exist arbitrarily far from equilibrium, provided a certain relation exists between the properties of the substance undergoing the phase change. For water, it is found that states of minimum entropy production rate are only slightly displaced from the stationary, nonequilibrium states existing when a net phase change rate is present.