Numerical Investigation of Turbulent Mass Transfer in a 90° Bend

This paper presents a numerical study of local mass transfer coefficients in a 90° bend using the RNG version of k– model to include the influence of curvature on the turbulent transport. Simulations were performed for flow through a 90°, 3-D bend for Reynolds numbers of 13500, 90000, and 390000, Schmidt numbers of 2.53 and 700 and curvature ratios of 1.5, 2, and 2.5. The differences between the maximum axial velocity to average velocity (Umax/Uave) predicted by the model and the experimental results reported in the literature was generally less than two percent. Simulation results showed that the ratio of the maximum Sherwood number obtained in the elbow to that obtained in fully developed pipe flow (Sh/Shp) decreased by Reynolds number (Re), Schmidt number (Sc) and curvature ratio (r/D). Maximum local mass transfer coefficient was observed at a distance of about one diameter downstream of the 90° elbow. Numerical predictions were in good agreement with experimental results reported in the literature.