Numerical simulation of air-steam mixture condensation flows in a vertical tube

In this study, a fully compressible three-phase numerical model for steam condensation flow in the presence of air is presented. The model solves the Reynolds-averaged Navier-Stokes equation coupled with two interface advection equations. The Lee condensation model was applied to simulate the mass and energy transfer processes via interfaces. Several test cases were simulated for the air-steam mixture condensation flow in a vertical tube with different air mass fractions to verify the numerical model. The validity was demonstrated through comparisons of the centerline temperatures along the tube and experimental data; the results were in good agreement with experimental data. A detailed radial profile of the temperature, species mass fraction, and velocity was analyzed. A developing thin condensate water film along the tube and the thickest film layer at the outlet tube wall of approximately 4.0 mm were observed. Air accumulation at the steam-water interface was also represented. In addition, the effects of air mass fraction on the characteristics of the condensation rate were investigated.