Unsteady state evaporation in weightlessness

Abstract

The problem of phase transition is one of the key problems in modern science and technology. Evaporation of liquids and condensed gases in a multi-component atmosphere usually takes place under non-equilibrium conditions in the presence of heat fluxes. Phase equilibrium and transitions in the absence of heat fluxes are investigated thoroughly nowadays. The existing Hertz-Knudsen and Clausius-Clapeyron models describe phase coexisting curve and non-equilibrium states (deviations from this curve) in the absence of heat fluxes. The present paper deals with investigations of non-equilibrium phase transitions in the presence of heat, mass and momentum fluxes through the phase interface. The model is based on mass, momentum and energy fluxes conservation equations on phase interface. The problem of unsteady state evaporation of condensed gas in multicomponent atmosphere is solved under the assumption that parameters of the interface are located within phase coexisting hyperspace in the phase space of parameters. A selfsimilar solution of the unsteady problem is obtained providing the possibility to follow temperature and concentration of species profiles' evolution in time. The mass rate of evaporation as a function of time is determined. For validation of the mathematical model, experiments on unsteady evaporation of liquefied oxygen were carried out. The dynamics of temperature, density and concentration profiles near the phase interface were investigated experimentally. Comparisons show good qualitative and quantitative agreement of theoretical and experimental results. A unique approach is worked out to solve problems of non-equilibrium phase transitions in the presence of heat fluxes.