Simulation of Film Condensation from Moving Vapor of Refrigerant-21 on a Horizontal Tube Bundle Using the VOF Method

Abstract

Considerable progress has been made by now in developing mathematical models, algorithms, and available computational tools for simulating heat and mass transfer processes. Advanced approaches yield detailed information on various characteristics of mass transfer in two-phase fluids, in particular during film condensation of vapors. Models developed by various teams are implemented in CFD-codes (ANSYS Fluent, OpenFOAM, Star-CCM+, etc.). To check existing models and select the best one, cross-verification of models and algorithms implemented in various CFD codes and their verification against available and reliable experimental data are needed. In this paper, cross-verification of the VOF (Volume of Fluid) model and the algorithms implemented in the author’s ANES code was carried out against the problem of vapor condensation on a single tube. The calculations were performed using the ANES and ANSYS Fluent CFD-codes. The predictions by the ANSYS Fluent code have been demonstrated to depend on the settings of the algorithms for solving the conservation equation for the liquid volume fraction. Recommendations are presented for setting this code to obtain better agreement of the predictions with experimental data and theoretical relationships. The ANSYS Fluent code was used for two-dimensional simulation of refrigerant-21 condensation in a small tube bundle. Characteristics of the tube bundle (bank) were equal to those of the tube bundle used in the experimental setup of the Institute of Thermophysics, Siberian Branch, Russian Academy of Sciences (tube diameter = 16 mm, transverse tube bundle pitch \({{S}_{1}}\) = 26 mm, longitudinal tube bundle pitch \({{S}_{2}}\) = 15 mm). Condensation of saturated vapor having a saturation temperature of \({{T}_{{sat}}}\) = 333.15 K and arriving at the tube bundle at a velocity of up to 1.2 m/s was studied. The predictions demonstrate qualitative and quantitative agreement with the experimental data.