Comparison study on the calculation formula of evaporation mass flux through the plane vapour-liquid interface

Abstract

In order to understand the influence of various factors on the evaporation rate on the vapor-liquid interface, the evaporation process of water in pure steam environment was calculated based on the statistical rate theory (SRT), and the results were compared with those from the traditional Hertz-Knudsen equation. It is found that the evaporation rate on the vapor-liquid interface increases with the increase of evaporation temperature and evaporation temperature difference and the decrease of vapor pressure. When the steam is in a superheated state, even if the temperature of the liquid phase is lower than that of the vapor phase, the evaporation may also occur on the vapor-liquid interface; at this time, the absolute value of the critical temperature difference for occurring evaporation decreases with the increase of vapor pressure. When the evaporation temperature difference is smaller, the theoretical calculation results based on the SRT are basically the same as the predicated results from the Hertz-Knudsen equation; but the deviation between them increases with the increase of temperature difference.