Simulation of R-21 Saturated Vapor Condensation in a Fragment of a Tube Bundle Using the 3D VOF Method

Abstract

The Volume of Fluid (VOF) method supplemented with heat and mass transfer models at the interphase boundary is actively employed in the investigation of film condensation and film boiling, in the calculation of evaporators, for predicting the dynamics of vapor bubble collapse in a pool of subcooled liquid, or for other purposes. The original VOF algorithm proposed by Hirt is intended for the simulation of a single-phase incompressible liquid with a free boundary at which a constant pressure is specified. The extension of the VOF-algorithm to a two-phase fluid, especially with mass transfer, is not a common problem from the standpoint of the rigor of mathematical formulation. In our previous studies, approaches have been developed to the 2D and 3D simulation of heat and mass transfer processes during vapor condensation on the surface of horizontal smooth tubes, and condensation on a smooth tube bundle was simulated in 2D formulation. This paper presents the results of 3D simulation of R-21 refrigerant condensation in a small-sized tube bundle. Characteristics of the tube bundle are the same as those of the tube bundle tested at the Institute of Thermophysics of the Siberian Branch of the Russian Academy of Sciences (SB RAS) (tube diameter is 16 mm, transverse pitch is 26 mm, longitudinal pitch is 15 mm). The condensation was examined in saturated vapor flow at a temperature of \({{T}_{{sat}}}\) = 333.15 K incoming onto the tube bundle at a velocity of up to 0.9 m/s. The 3D predictions agree qualitatively and quantitatively with the 2D predictions and the experimental data. The distribution of condensate in the tube bundle is presented. The spectrums of fluctuations in the average heat transfer for tubes are analyzed. It is pointed out that the thermal boundary layer development region induced by the condensate falling from the upper to lower tubes should be considered.