THERMAL SCIENCE

International Scientific Journal

NUMERICAL STUDY OF MIXED CONVECTION AND ENTROPY GENERATION IN THE POISEULLE-BENARD CHANNEL IN DIFFERENT ANGLES

ABSTRACT
The issue of entropy generation and Nusselt number in Poiseuille-Benard channel flow are analyzed by solving numerically Navier-Stokes and energy equations with the use of the classic Boussinesq incompressible approximation. The Nusselt number is studied as a function of q. In addition variations of entropy generation and the Bejan number as a function of q and j are studied. The channel angle (q) and irreversibility (j) were changed from -25 to 30 and from 10-5 to 1, respectively, whereas Reynolds, Peclet, and Rayleigh numbers were fixed at Re = 10, Pe = 20/3, and Ra = 104. More over the positive and negative effect of buoyancy force on flow field, Nusselt number and entropy generation are discussed. Optimum angle for dif- ferent irreversibilities are specified by definition h as the rate of the Nusselt number to the entropy generation, the optimum angle was distinguished for different irreversibility. Results show that the Nusselt number changes very slightly and is almost constant when q changes from -10 to 10 and the Nusselt number decreases sharply when q increases from 20 to 30 or decreases from -15 to -25. Moreover it has been found that the entropy generation due to heat transfer is localized at areas where heat exchanged between the walls and the flow is maximum, while the entropy generation due to fluid friction is maximum at areas where the velocity gradients are maximum such as vortex centers. Consequently when q is decreased from -15 to -25 or is increased from 20 to 30 entropy generation for small irreversibilities decreases and increases sharply for large irreversibilities.
KEYWORDS
PAPER SUBMITTED: 2008-07-30
PAPER REVISED: 2009-05-24
PAPER ACCEPTED: 2009-07-27
DOI REFERENCE: https://doi.org/10.2298/TSCI1002329N
CITATION EXPORT: view in browser or download as text file
THERMAL SCIENCE YEAR 2010, VOLUME 14, ISSUE 2, PAGES [329 - 340]
REFERENCES
  1. Bejan, A., A Study of Entropy Generation in Fundamental Convective Heat Transfer, ASME, J. Heat Transfer, 101 (1979), 4, pp. 718-725
  2. Bejan, A., Second-Law Analysis in Heat Transfer, Energy, 5 (1980), 8-9, pp. 721-32
  3. Bejan, A., Second-Law Analysis in Heat Transfer and Thermal Design, Adv. Heat Transfer, 15 (1982), 1, pp. 1-58
  4. Bejan A., Fundamentals of Exergy Analysis, Entropy-Generation Minimization, and the Generation of Flow Architecture, International Journal of Energy Research, 26 (2002), 7, pp. 545-565
  5. Perez-Blanco, H., Irreversibility in Heat-Transfer Enhancement, in: Second Law Aspects of Thermal Design, ASME, Heat Transfer Division, 33 (1984), pp. 19-26
  6. Ouellette, W. R., Bejan, A., Conservation of Available Work (Exergy) by Using Promoters of Swirl Flow in Forced Convection Heat-Transfer, Energy, 5 (1980), 7, pp. 587- 596
  7. Bejan, A., Entropy Generation Minimization, CRC Press, Boca Raton, Fla., USA, 1996
  8. Bejan, A., Entropy Generation through Heat and Fluid Flow, John Wiley and Sons, New York, USA, 1982
  9. Nag, P. K., Kumar, N., Second Law Optimization of Convection Heat Transfer through a Duct with Constant Heat Flux, International Journal of Energy Research, 13 (1989), 5, pp. 537-543
  10. Sahin, A. Z., Irreversibilities in Various Duct Geometries with Constant Wall Heat Flux and Laminar Flow, Energy, 23 (1998), 6, pp. 465-473
  11. Sahin, A. Z., Thermodynamics of Laminar Viscous Flow through a Duct Subjected to Constant Heat Flux, Energy, 21 (1996), 12, pp. 1179-1187
  12. Shuja, S. Z., Optimal Fin Geometry Based on Exergoeconomic Analysis for a Pin-Fin Array with Application to Electronics Cooling, Exergy, 2 (2002), 4, pp. 248 58
  13. Sara, O. N, et al., Secondary Law Analysis of Rectangular Channels with Square Pin-Fins, Int. Comm. Heat Mass Transfer, 28 (2001), 5, pp. 617-630
  14. Ko, T. H., Ting, K., Entropy Generation and Thermodynamic Optimization of Fully Developed Laminar Convection in a Helical Coil, Int. Comm. Heat Mass Transfer, 32 (2005), 1-2, pp. 214-223
  15. Ko, T. H., Analysis of Optimal Reynolds Number for Developing Laminar Forced Convection in Double-Sine Ducts Based on Entropy Generation Minimization Principle, Energy Conversion and Management, 47 (2006), 6, pp. 655-670
  16. Ko, T. H., Ting, K., Entropy Generation and Optimal Analysis for Laminar Forced Convection in Curved Rectangular Ducts: A Numerical Study, International Journal of Thermal Sciences, 45 (2006), 2, pp. 138-150
  17. Ko, T. H., Numerical Investigation on Laminar Forced Convection and Entropy Generation in a Curved Rectangular Duct with Longitudinal Ribs Mounted on Heated Wall, International Journal of Thermal Sciences, 45 (2006), 4, pp. 390-404
  18. Ko, T. H., Ting, K., Optimal Reynolds Number for the Fully Developed Laminar Forced Convection in a Helical Coiled Tube, Energy, 31 (2006), 12, pp. 2142-2152
  19. Ko, T. H., Thermodynamic Analysis of Optimal Curvature Ratio for Fully Developed Laminar Forced Convection in a Helical Coiled Tube with Uniform Heat Flux, International Journal of Thermal Sciences, 45 (2006 ), 7, pp. 729-737
  20. Ko, T. H., Numerical Investigation on Laminar Forced Convection and Entropy Generation in a Helical Coil with Constant Wall Heat Flux, Numerical Heat Transfer, Part A, 49 (2006), 3, pp. 257-278
  21. Ko, T. H., Numerical Analysis of Entropy Generation and Optimal Reynolds Number for Developing Laminar Forced Convection in Double-Sine Ducts with Various Aspect Ratios, International Journal of Mass and Heat Transfer,49 (2006), 3-4, pp. 718-726
  22. Narusawa, U., The Second-Law Analysis of Mixed Convection in Rectangular Ducts, Heat Mass Transfer, 37 (2001), 2-3, pp. 197-203
  23. Abbassi, H, Magherbi, M., Brahim , A. B., Entropy Generation in Poiseuille-Benard Channel Flow, International Journal of Thermal Sciences, 42 (2003), 12, pp. 1081-1088
  24. Nourollahi, M., Generation of CFD Code for Solving the Fluid Governing Equations in Non-Orthogonal co-ordinate Systems, M. Sc. thesis, Faculty of Mechanical Engineering, Babol Noshirvani University of Technology, Babol, Iran, 2007
  25. Ferziger, J., H., Peric, M., Computational Methods for Fluid Dynamics, Springer-Verlag, Berlin, Heidelberg, New York, USA, 2002
  26. Comini, G., Manzan, M., Cortella, G., Open Boundary Conditions for the Stream Function of Unsteady Laminar Convection, Numerical Heat Transfer, Part B, 31 (1997), 2, pp. 217-234
  27. Evans, G., Paolucci, S., The Thermoconvective Instability of Plane Poiseuille Flow Heated from below: A Benchmark Solution for Open Boundary Flow, International Journal Numerical Method in Fluids, 11 (1990), 7, pp. 1001-1013
  28. Abbassi, H., Turki, S., Nasrallah, S., B., Numerical Investigation of Forced Convection in a Plane Channel with a Built-in Triangular Prism, International Journal of Thermal Sciences, 40 (2001), 7, pp. 649-658

© 2019 Society of Thermal Engineers of Serbia. Published by the Vinča Institute of Nuclear Sciences, Belgrade, Serbia. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International licence