Optimization of heat transfer and pressure drop in a solar air heater with ribbed surface

Document Type : Research Article

Authors

Department of Mechanical Engineering K. N. Toosi University of Technology, Tehran, Iran

Abstract

Repeated ribs are used to enhance heat transfer in turbine blades and solar air heaters. The ribs have significant effect on the characteristics of heat transfer and fluid flow. Application of ribs enhances the heat transfer significantly, however simultaneously the pressure drop increases. As a result a balance must be made between the improvement in heat transfer and additional power to overcome the elevated pressure drop. In this study, the effect of ribs on the thermal performance of a flat plate solar air heater is investigated to find the optimum set of parameters in a flat plate solar air heater with ribbed surfaces. Genetic algorithm used to perform the optimization. The optimization carried out to meet two objectives, to attain higher thermal efficiency and to guarantee a practical temperature difference in the inlet and outlet of air flow. In a relatively large range of Reynolds numbers from 2300 to 25000, the fluid flow and heat transfer were evaluated. In order to validate the results, comparison has been made with available data in literature. It was found that the application of ribs improve the thermal efficiency about 10% in low air mass flows, however at higher air flow the additional power due to the pressure drop diminish the effect and even might decrease the efficiency.

Keywords

Main Subjects


[1] Kays, W. M., A. L. London, “Compact heat exchangers”,third Ed., New York: McGraw-Hill, 1984.
[2] Bergles, A. E., “Handbook of Heat Transfer”, third edition, New York: McGraw-Hill, 1998.
[3] Bergles, E. and R. M. Manglik, “Current progress and new developments in enhanced heat and mass transfer”, Journal of Enhanced Heat Transfer, 20.1 (2013): 1-15.
[4] Dipprey, D. F., “An experimental investigation of heat and momentum transfer in smooth and rough tubes at various prandtl numbers”, PhD thesis, California institute of technology, 1961.
[5] Webb, R. L. , E. R. G. Eckert and R. J. Goldstein, “Heat transfer and friction in tubes with repeated-rib roughness”, Int J. Heat Mass Transfer, 14 (1971): 601–617.
[6] Han, J.C., L.R. Glicksman and W.M. Rohsenow, “An investigation of heat transfer and friction for ribroughened surfaces”, Int. Journal of Heat and Mass Transfer, 21.8 (1978): 1143–1156.
[7] Han, J. C., “Heat transfer and friction characteristics in rectangular channels with rib turbulators”, ASME J. Heat Transfer, 110 (1988): 321–328.
[8] Han, J. C., Y. M. Zhang and C. P. Lee, “Augmented heat transfer in square channels with parallel, crossed and V shaped angled ribs”, ASME J. Heat Transfer, 113 (1991):590–596.
[9] Parson, J. A., J. C. Han, Y. M. Zhang, “Effects of model orientation and wall heating condition on local heat transfer in a rotating two-pass square channel with rib turbulators”, Int. J. Heat Mass Transfer, 38.7 (1995): 1151-1159.
[10] Bejan, A. and A. D. Kraus, “Heat transfer handbook”, John Wiley & Sons, 2003.
[11] Elyyan, M. A., A. Rozati and D. K. Tafti, “Investigation of dimpled fins for heat transfer enhancement in compact heat exchangers”, Int. J. Heat Mass Transfer, 51 (2008): 2950-2966.
[12] Patankar, S.V., C. H. Liu and E.M. Sparrow, “Fully developed flow and heat transfer in ducts having streamwise periodic ariations of cross sectional area”,J. Heat Transfer, 99 (1977): 180-186.
[13] Yongsiri, K., P. Eiamsa-ard, K. Wongcharee and S.Eiamsa-ard, “Augmented heat transfer in a turbulent channel flow with inclined detached-ribs”, Case Studies in Thermal Engineering, 3, 2014.
[14] Xie, G., S. Zheng, W. Zhang and B. Sunden, “A numerical study of flow structure and heat transfer in a square channel with ribs combined downstream half-size or same-size ribs”, Applied Thermal Engineering, 61.2 (2013): 289–300.
[15] Xie, G., J. Liu, P. M. Ligrani and B. Sunden, “Flow structure and heat transfer in a square passage with offset mid-truncated ribs”, International Journal of Heat and Mass Transfer, 71 (2014): 44–56.
[16] Moon, M., M. Park and K. Kim, “Evaluation of heat transfer performances of various rib shapes”, Int. J. of Heat and Mass Transfer, 71 (2014): 275–284.
[17] Kahrom, M., B. Zafarmand and A .Exier, “Heat Transfer Enhancement from a Flat Plate by Vortex Shedding Behind a Triangular Obstacle”, Amirkabir journal of Science & Research, 41.2 (2010): 37-46.(In Persian)
[18] Ansari, M. and M. Bazargan, “Modeling of flat plate solar air heater with ribbed surface”, 23rd Annual International Conference on Mechanical Engineering-ISME, 2015.
[19] Bhagoria, J. L., J. S. Saini and S. C. Solanki, “Heat transfer coefficient and friction factor correlations for rectangular solar air heater duct having transverse wedge shaped rib roughness on the absorber plate”, Renew. Energy, 25.3 (2002): 341–369.
[20] Aghaie, A. Z., A. B. Rahimi and A. Akbarzadeh, “A general optimized geometry of angled ribs for enhancing the thermo-hydraulic behavior of a solar air heater channel - A Taguchi approach”, Renewable Energy, 83 (2015): 47-54.
[21] Taslim M. E., “Rib fin effects on the overall equivalent heat transfer coefficient in a rib-roughened cooling channel”, International Journal of Heat Exchangers,4(2005).
[22] Duffie, J. and W. Beckman, “Solar engineering of thermal processes”, Wiley, 2013.
[23] Incropera, F. P. and DeWitt, “Fundamentals of heat and mass transfer”, 5th Edition, New York: John Wiley, 2002.
[24] Han, J.C., “Heat transfer and friction in channels with two opposite rib-roughnened walls,” Trans. ASME Journal of Heat Transfer, 106 (1984).
[25] American Society of Heating, ASHREA Handbook fundamentals, Refrigerating and Air-Conditioning Engineers, 1997.
[26] web site of iran ministry of energy, 2015. <http://www.moe.gov.ir>.
[27] Streed, E. R., J. E. Hill, W. C. Thomas, A. G. Dawson, and B. D. Wood, ‘‘Results and Analysis of a Round Robin Test Program for Liquid-Heating Flat-Plate Solar Collectors”, Solar Energy, 22 (1979): 235.