JECTC  Vol.2 No.4 , December 2012
Effects of Baffle on Entropy Generation in Separated Convection Flow Adjacent to Inclined Backward-Facing Step
Abstract: Numerical simulations of a two-dimensional laminar forced convection flow adjacent to inclined backward-facing step in a rectangular duct are presented to examine effects of baffle on flow, heat transfer and entropy generation distributions. The main aim of using baffles is to enhance the value of convection coefficient on the bottom wall. But the useful energy can be destroyed due to intrinsic irreversibilities in the flow by the baffle. In the present work, the amount of energy loss is estimated by the computation of entropy generation. The values of velocity and temperature which are the inputs of the entropy generation equation are obtained by the numerical solution of momentum and energy equations with blocked-off method using computational fluid dynamic technique. Discretized forms of the governing equations in the (x, y) plane are obtained by the control volume method and solved using the SIMPLE algorithm. Numerical expressions, in terms of Nusselt number, entropy generation number, Bejan number and coefficient of friction are derived in dimensionless form. Results show that although a baffle mounted onto the upper wall increases the magnitude of Nusselts number on the bottom wall, but a considerable increase in the amount of entropy generation number takes place because of this technique. For validation, the numerical results for the Nusselt number and entropy generation number are compared with theoretical findings by other investigators and reasonable agreement is found.
Cite this paper: Bahrami, A. , Nassab, S. and Hashemipour, M. (2012) Effects of Baffle on Entropy Generation in Separated Convection Flow Adjacent to Inclined Backward-Facing Step. Journal of Electronics Cooling and Thermal Control, 2, 53-61. doi: 10.4236/jectc.2012.24006.

[1]   B. F. Armaly, F. Durst, J. C. F. Pereira and B. Schonung, “Experimental and Theoretical Investigation of Backward-Facing Step Flow,” Journal of Fluid Mechanics, Vol. 127, 1983, pp. 473-496. Hdoi:10.1017/S0022112083002839

[2]   G. C. Vradis, V. Outgen and J. Sanchez, “Heat Transfer over a Backward-Facing Step: Solutions to a Benchmark,” Benchmark Problems for Heat Transfer Codes, ASME HTD, Anaheim, 1992, pp. 27-34.

[3]   D. W. Pepper, K. L. Burton and F. P. Bruenckner, “Numerical Simulation of Laminar Flow with Heat Transfer over a Backward-Facing Step,” Benchmark Problems for Heat Transfer Code, ASME HTD, Anaheim, 1992, pp. 66-80.

[4]   G. Vradis and L. Van Nostrand, “Laminar Coupled Flow Downstream an Asymmetric Sudden Expansion,” Journal of Thermophysics Heat transfer, Vol. 6, No. 2, 1992, pp. 288-295. Hdoi:10.2514/3.357

[5]   L. Kaiktsis, G. E. Karniadakis and S. A. Orszag, “Onset of Three-Dimensionality Equilibria, and Early Transition in Flow over a Backward-Facing Step,” Journal of Fluid Mechanics, Vol. 231, 1991, pp. 501-528. Hdoi:10.1017/S0022112091003488

[6]   N. Tylli, L. Kaiktsis and B. Ineichen, “Side Wall Effects in Flow over Backward-Facing Step: Experiments and Numerical Solutions,” Physics of Fluids, Vol. 14, No. 11, 2002, pp. 3835-3845. Hdoi:10.1063/1.1506163

[7]   D. Brakely, M .Gabriela, M. Gomes and R. D. Henderson, “Three-Dimensional Instability in Flow over a Backward-Facing Step,” Journal of Fluid Mechanics, Vol. 473, 2002, pp. 167-190.

[8]   H. I. A. Mulaweh, “A Review of Research on Laminar Mixed Convection Flow over Backward and Forward-Facing Steps,” International Journal of Thermal Sciences, Vol. 42, No. 9, 2003, pp. 897-909. Hdoi:10.1016/S1290-0729(03)00062-0

[9]   J. H. Nie, Y. T. Chen and H. T. Hsieh, “Effects of a Baffle on Separated Convection Flow Adjacent to Backward-Facing Step,” International Journal of Thermal Sciences, Vol. 48, No. 3, 2009, pp. 618-625. Hdoi:10.1016/j.ijthermalsci.2008.05.015

[10]   E. Abu Nada, “Numerical Prediction of Entropy Generation in Separated Flows,” Entropy, Vol. 7, No. 4, 2005, pp. 234-252. Hdoi:10.3390/e7040234

[11]   E. Abu Nada, “Entropy Generation Due to Heat and Fluid Flow in Backward-Facing Step Flow with Various Expansion Ratios,” International Journal of Exergy, Vol. 3, No. 4, 2006, pp. 419-435. Hdoi:10.1504/IJEX.2006.010234

[12]   E. Abu Nada, “Investigation of Entropy Generation over a Backward-Facing Step under Bleeding Conditions,” Energy Conversion and Management, Vol. 49, No. 11, 2009, pp. 3237-3242. Hdoi:10.1016/j.enconman.2007.10.031

[13]   S. V. Patankar, “Numerical Heat and Mass Transfer and Fluid Flow,” Hemisphere Publishing Corporation, Washington DC, 1980.

[14]   A. Bejan, “Entropy Generation through Heat and Fluid Flow,” Wiley, New York, 1982.

[15]   S. V. Patankar and B. D. Spalding, “A Calculation Procedure for Heat, Mass and Momentum Transfer in Three-Dimensional Parabolic Flow,” International Journal of Heat Mass Transfer, Vol. 15, No. 10, 1972, pp. 1787-1806. doi:10.1016/0017-9310(72)90054-3