Simulation of Condensation of Stagnant or Moving Saturated Vapor on a Horizontal Tube Using the Volume-of-Fluid (VOF) Method

The processes of film condensation of stagnant and moving vapor on a single tube and various tube bundles were examined in many studies. Nevertheless, the local characteristics of heat transfer and the details of the interaction of the flowing down condensate with a moving vapor flow, which can have a significant effect on the characteristics of the condensation process in tube bundles, are not well understood. The paper presents the results of simulation of the condensation of practically stagnant and of moving saturated vapor on a horizontal cylinder. The mathematical model of a two-phase flow is based on the Volume of Fluid (VOF) method, which is implemented in the in-house CFD-code ANES. The main advantage of the proposed simulation method is that it can capture the interface without any assumptions. The modified Lee model was used to model interfacial mass transfer. An algorithm is proposed for the automatic selection of a constant in this model on the basis of the specified properties of the coolant and parameters of the computational grid. The model was validated against the classical Nusselt solutions for a vertical plate and a horizontal cylinder, known calculating correlations, and predictions obtained using a simplified condensation model proposed by the authors of this paper in previous studies. Information is presented on the drip-off diameters of droplets, the dynamics of heating of subcooled condensate droplets after their drip-off from the tube surface, and the effect of external tube spraying on the condensation rate. The obtained data are compared with the available experimental results.