A Model for Determining the Rate of Interfacial Heat and Mass Transfer Using the VOF Method for Numerically Solving Evaporation and Condensation Problems

Abstract

The volume-of-fluid (VOF) method, supplemented by models of interfacial heat and mass transfer, is a universal and very effective tool for simulation and detailed analysis of intricate processes occurring in systems with phase transitions. The key feature of this method is that it can quite accurately and in detail describe the physical pattern of running processes in the presence of a sharp phase boundary and provide quantitative data on the distribution of local heat-transfer characteristics and the dynamics of the interphase boundary and associated phenomena, thereby making the VOF method advantageous in researches and engineering practice. Development and improvement of heat and mass transfer models and efficient numerical VOF algorithms, as well as preparation of recommendations for the application of these approaches, are an urgent problem. This paper proposes an approach to the prediction of interfacial heat and mass transfer rate, which is based on the analysis of phase transitions in single-component systems using the linear theory of nonequilibrium processes. The results are presented of verification calculations performed for several standard problems. The classical problems of one-dimensional boiling and condensation (the Stefan problem) are examined as are such problems as vapor condensation in tubes of different orientations, condensation from stagnant or moving vapor on the surface of smooth horizontal tubes, and film boiling on the surface of horizontal cylinders. The predictions are verified against classical solutions and available experimental data. Calculations were carried out for fluids with different thermophysical properties, including water, pentane, propane, R-113, R-21, and R-142b. The maximum ratio of the densities of liquid and vapor phases was as high as 1600 (water at atmospheric pressure). The simulation results demonstrate the versatility of the proposed approach, which allows us to recommend it for solving a variety of engineering problems.