Simulation of the Condensation Processes of R113 in a Horizontal Pipe by the VOF Method

Abstract The results of a numerical analysis of the condensation of R113 freon vapor in a horizontal round pipe with a standard size of 38 × 3 mm in the range of mass velocities from 50 to 150 kg/(m2 s) were presented. Studies of the features of hydrodynamics and heat transfer in the stratified and stratified wave regimes of condensate flow are still relevant due to their insufficient knowledge. Thus, according to recent data, the heat-transfer intensities in the zone occupied by a stream and in the sections of the inner surface of a horizontal pipe wetted with a thin condensate film are comparable. Therefore, for an adequate assessment of the real contribution of the stream region to the average heat transfer coefficient along the pipe perimeter, the existing methods should be refined. The VOF (Volume of Fluid) method realized in in-house CFD-code ANES was used to simulate a two-phase flow. The intensity of mass transfer was calculated using a modified Lee model in which the relaxation coefficient was determined automatically based on the algorithm proposed by the authors of this work in previous publications. To describe the turbulent transport, a version of Menter’s SST turbulence model was used. Models of mass transfer, turbulent flows of a liquid film and vapor phase, VOF algorithms, and software tools that implement them were verified on experimental data on R113 freon condensation in a downward flow in a vertical pipe. Numerical modeling of condensation processes has been performed and the obtained data have been compared with the results of calculations using various methods recommended in the literature. Information is presented on the distribution of local characteristics along the length and perimeter of the pipe. It is noted that at low values of mass velocity 50 kg/(m2 s) at some distance from the pipe inlet, a hydraulic jump occurs, leading to a significant change in the distribution of the vapor void fraction along the length of the channel.