Diffusion-kinetic model of liquid evaporation from a Stefan tube: A solution to the Stefan diffusion problem

Abstract

An analytic model that describes the kinetics of the process of liquid evaporation from a vertical tube with an open end (Stefan tube) into the surrounding gas is presented. This model takes into account the intrinsic kinetics of the liquid evaporation process. The case of liquid evaporation from a Stefan tube without consideration of the Stefan flow was examined. In addition, the case of liquid evaporation from a Stefan tube with consideration of the Stefan flow was examined. In the framework of the presented model, it is shown that there are three regimes of liquid evaporation from a Stefan tube: the kinetic, diffusion, and diffusion-kinetic regimes. In the kinetic regime, the rate of liquid evaporation from the Stefan tube is limited only by the intrinsic kinetics of the liquid evaporation process; in the diffusion regime, the rate of liquid evaporation from the Stefan tube is limited only by the intensity of the mass transfer of vapor molecules from the liquid surface to the top of the Stefan tube; and in the diffusion-kinetic regime, the rate of liquid evaporation from the Stefan tube is affected by both the intrinsic kinetics of the liquid evaporation process and the intensity of the mass transfer of vapor molecules from the liquid surface to the top of the Stefan tube. The calculated data obtained in the framework of the presented model are compared with the available experimental data on the kinetics of evaporation of n-pentane, n-hexane, and water from a Stefan tube into nitrogen. As a result of this comparison, the condensation coefficients of n-pentane and water were determined.