A one-dimensional unsteady wall film evaporation model

Abstract

A new analytical solution for the wall film heating up and evaporation with consideration of the unsteady one-dimensional characteristics of the wall film thickness and temperature was developed. A simplified model for predicting the evaporation rate of wall film was suggested. In order to evaluate the heating up and evaporation characteristics of wall film, the influences of the initial wall film thickness, ambient temperature and pressure, convective heat transfer coefficient, and initial film temperature were investigated. The results show that the evolution behavior of the wall film evaporation can be divided into three distinct stages, i.e., initial rapid heating stage, slow heating stage, and final rapid heating stage. Thinner initial wall film evaporates much earlier and quicker than that of the thicker one. The final film surface temperature increases with increasing ambient pressure and temperature as well as the initial film temperature and convective rate. At the end of the evaporation process, the evaporation rate increases with increased ambient pressure when the ambient temperature is high enough, but decreases with increased pressure at low temperatures.