Numerical Investigation of Turbulent Mass Transfer in a 90° Bend

Document Type : Research Article

Authors

Department of Chemical Engineering, Isfahan University of Technology, Isfahan, I.R. IRAN

Abstract

This paper presents a numerical study of local mass transfer coefficients in a 90° bend using the RNG version of k–e 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.

Keywords

Main Subjects


 
[1] Sprague P.J., "Mass Transfer and Erosion Corrosion in Pipe Bends",Ph.D.Thesis,University of  Exeter, England, (1984).
[2] Sprague P.J., Patrick M.A., Wragg A.A., Coney M.W.E., Mass Transfer and Erosion Corrosion in Pipe Bend, in: "Proceedings of the Eighth Congress of European Federation of Corrosion", 18.1-18.6 (1989).
 
[3] Bergstrom D.J.B., Adamopoulos T., Postlethwaite J., Numerical Prediction of Wall Mass Transfer Rates in Turbulent Flow Through a 900 Two-Dimensional Bend, The Canadian Journal of Chemical Engineering., 76: 728-737 (1998).
 
[4] Wang J., Shirazi S.A., A CFD Based Correlation for Mass Transfer Coefficient in Elbows, Int. J. Heat and Mass transfer, 44: 1817-1822 (2001).
[5] Asadi T., Nasr Esfahany M., Numerical Prediction of Mass Transfer Coefficient in Turbulent Flow Through a 90° Bend, "Proceedings of CHT-08 ICHMT International Symposium on Advances in Computational Heat Transfer , (ICHMT)",Marrakech, Morocco, CHT-08-137 (2008)
[6] Bird R.B., Stewart W.E., Lighfoo E.N.t, "Transport Phenomena", John Wiley & Sons, New York (2001).
[8] Yakhot V., Orszag S.A., Thangam S., Gatski T.B., Speziale C.G., Development of Turbulence Models for Shear Flows by A Double Expansion Technique, Physics of Fluids, 4: 1510-1520 (1992).
[9] Enayet M., Gibson M., Yianneskis M., Laser Doppler Measurements for Laminar and Turbulent Flow in Pipe Bend, Int. J. Heat Fluid Flow, 3: 213-220 (1982).
 [10] Achenbach E., Mass Transfer from Bend of Circular Cross-Section to Air, in: "Future EnergyProduction Systems", Academic Press, New York., 1: 327-337 (1976).
[11] Treybal R.E., "Mass Transfer Operation", McGraw Hill, New York, (1980).
[12] Coney M.W.E., "Erosion Corrosion: The Calculation of Mass Transfer Coefficients", CEGB Report RD/L/N197/80 CERL, (1980).
[3] Bergstrom D.J.B., Adamopoulos T., Postlethwaite J., Numerical Prediction of Wall Mass Transfer Rates in Turbulent Flow Through a 900 Two-Dimensional Bend, The Canadian Journal of Chemical Engineering., 76: 728-737 (1998).