An empirical study on vortex-generator insert fitted in tubular heat exchangers with dilute Cu-water nanofluid flow

doi:10.1016/j.cjche.2016.01.014

Abstract

Abstract: The heat transfer enhancement (HTE) in tubular heat exchangers fitted with vortex-generator (VG) inserts is experimentally investigated. The studied four parameters and ranges are:winglets-pitch ratio (1.33, 2.67, and 4), winglets-length ratio (0.33, 0.67, and 1), winglets-width ratio (0.2, 0.4, and 0.6), and Reynolds number (5200 to 12200). The testing fluids are the water and Cu-water nanofluid at the volumetric fraction of 0.2%. The results obtained on HTE, pressure drop, and performance evaluation criterion (PEC) are compared with those for water in a smooth tube. It is found that the VG inserts with lower winglets-pitch ratio and higher winglets-length/width ratios present higher values of HTE and pressure drop. Over the range studied, the maximum PEC of 1.83 is detected with the Cu-water nanofluid inside the tube equipped with a VG insert at the winglets-width ratio of 0.6 for the maximum Reynolds number, when the heat transfer rate and pressure drop are 1.24 times and 2.03 times of those in the smooth tube. Generalized regression equations of the Nusselt number, friction factor, and PEC are presented for the tubular heat exchangers with the VG inserts for both water and Cu-water nanofluid. It is concluded that the main advantage of the VG inserts is their simple fabrication and considerable performance, particularly at higher Reynolds number.

Key words: Heat transfer enhancement, Vortex-generator insert, Nanofluid, Turbulent flow, Correlation

摘要： The heat transfer enhancement (HTE) in tubular heat exchangers fitted with vortex-generator (VG) inserts is experimentally investigated. The studied four parameters and ranges are:winglets-pitch ratio (1.33, 2.67, and 4), winglets-length ratio (0.33, 0.67, and 1), winglets-width ratio (0.2, 0.4, and 0.6), and Reynolds number (5200 to 12200). The testing fluids are the water and Cu-water nanofluid at the volumetric fraction of 0.2%. The results obtained on HTE, pressure drop, and performance evaluation criterion (PEC) are compared with those for water in a smooth tube. It is found that the VG inserts with lower winglets-pitch ratio and higher winglets-length/width ratios present higher values of HTE and pressure drop. Over the range studied, the maximum PEC of 1.83 is detected with the Cu-water nanofluid inside the tube equipped with a VG insert at the winglets-width ratio of 0.6 for the maximum Reynolds number, when the heat transfer rate and pressure drop are 1.24 times and 2.03 times of those in the smooth tube. Generalized regression equations of the Nusselt number, friction factor, and PEC are presented for the tubular heat exchangers with the VG inserts for both water and Cu-water nanofluid. It is concluded that the main advantage of the VG inserts is their simple fabrication and considerable performance, particularly at higher Reynolds number.

关键词: Heat transfer enhancement, Vortex-generator insert, Nanofluid, Turbulent flow, Correlation

M. Khoshvaght-Aliabadi, M. H. Akbari, F. Hormozi. An empirical study on vortex-generator insert fitted in tubular heat exchangers with dilute Cu-water nanofluid flow[J]. Chin.J.Chem.Eng., 2016, 24(6): 728-736.

References

[1] S. Chokphoemphun, M. Pimsarn, C. Thianpong, P. Promvonge, Heat transfer augmentation in a circular tube with winglet vortex generators, Chin. J. Chem. Eng. 23(4) (2015) 605-614.

[2] L.S. Sundar, M.K. Singh, Convective heat transfer and friction factor correlations of nanofluid in a tube and with inserts:a review, Renew. Sust. Energ. Rev. 20(2013) 23-35.

[3] D. Kim, Y. Kwon, Y. Cho, C. Li, S. Cheong, Y. Hwang, J. Lee, D. Hong, S. Moon, Convective heat transfer characteristics of nanofluids under laminar and turbulent flow conditions, Curr. Appl. Phys. 9(2009) 119-123.

[4] W. Duangthongsuk, S. Wongwises, An experimental study on the heat transfer performance and pressure drop of TiO₂-water nanofluids flowing under a turbulent flow regime, Int. J. Heat Mass Transf. 53(2010) 334-344.

[5] M. Chandrasekar, S. Suresh, A. Chandra Bose, Experimental studies on heat transfer and friction factor characteristics of Al₂O₃/water nanofluid in a circular pipe under laminar flow with wire coil inserts, Exp. Thermal Fluid Sci. 34(2) (2010) 122-130.

[6] L.S. Sundar, K.V. Sharma, Turbulent heat transfer and friction factor of Al₂O₃ Nanofluid in circular tube with twisted tape inserts, Int. J. Heat Mass Transf. 53(7-8) (2010) 1409-1416.

[7] M.T. Naik, G.R. Janardana, L.S. Sundar, Experimental investigation of heat transfer and friction factor with water-propylene glycol based CuO nanofluid in a tube with twisted tape inserts, Int. Commun. Heat Mass Transfer 46(2013) 13-21.

[8] M.C.S. Reddy, V.V. Rao, Experimental investigation of heat transfer coefficient and friction factor of ethylene glycol water based TiO₂ nanofluid in double pipe heat exchanger with and without helical coil inserts, Int. Commun. Heat Mass Transfer 50(2014) 68-76.

[9] S. Suresh, K.P. Venkitaraj, P. Selvakumar, M. Chandrasekar, A comparison of thermal characteristics of Al₂O₃/water and CuO/water nanofluids in transition flow through a straight circular duct fitted with helical screw tape inserts, Exp. Thermal Fluid Sci. 39(2012) 37-44.

[10] M. Saeedinia, M.A. Akhavan-Behabadi,M. Nasr, Experimental study on heat transfer and pressure drop of nanofluid flow in a horizontal coiled wire inserted tube under constant heat flux, Exp. Thermal Fluid Sci. 36(2012) 158-168.

[11] M.T. Naik, S.S. Fahad, L.S. Sundar, M.K. Singh, Comparative study on thermal performance of twisted tape and wire coil inserts in turbulent flow using CuO/water nanofluid, Exp. Thermal Fluid Sci. 57(2014) 65-76.

[12] H.A. Mohammed, H.A. Hasan, M.A.Wahid, Heat transfer enhancement of nanofluids in a double pipe heat exchanger with louvered strip inserts, Int. Commun. HeatMass Transfer 40(2013) 36-46.

[13] H.A. Mohammed, A.A. Al-aswadi, N.H. Shuaib, R. Saidur, Convective heat transfer and fluid flow study over a step using nanofluids:a review, Renew. Sust. Energ. Rev. 15(2011) 2921-2939.

[14] Payamavaran Nanotechnology Fardanegar (PNF) Nano Engineering & Manufacturing Co. www.pnf-co.com

[15] W. Yu, D.M. France, J.L. Routbort, S.U.S. Choi, Review and comparison of nanofluid thermal conductivity and heat transfer enhancements, Heat Transfer Eng. 29(5) (2008) 432-460.

[16] A. Ghadimi, R. Saidur, H.S.C.Metselaar, A review of nanofluid stability properties and characterization in stationary conditions, Int. J. Heat Mass Transf. 54(2011) 4051-4068.

[17] H.E. Ahmed, H.A. Mohammed, M.Z. Yusoff, An overview on heat transfer augmentation using vortex generators and nanofluids:approaches and applications, Renew. Sust. Energ. Rev. 16(2012) 5951-5993.

[18] J.M. Wu, Q.W. Tao, Numerical study on laminar convection heat transfer in a rectangular channel with longitudinal vortex generator, part A:verification of field synergy principle, Int. J. Heat Mass Transf. 51(5-6) (2008) 1179-1191.

[19] S. Eiamsa-ard, P. Promvonge, Influence of double-sided delta-wing tape insert with alternate-axes on flow and heat transfer characteristics in a heat exchanger tube, Chin. J. Chem. Eng. 19(3) (2011) 410-423.

[20] W.M. Kays, A.L. London, Compact Heat Exchangers, third ed. Kreiger Publishing, Melbourne, 1984.

[21] S. Eiamsa-ard, C. Thianpong, P. Eiamsa-ard, Turbulent heat transfer enhancement by counter/co-swirling flow in a tube fitted with twin twisted tapes, Exp. Thermal Fluid Sci. 34(2010) 53-62.

[22] S.J. Kline, F.A. McClintock, Describing uncertainties in single-sample experiments, Mech. Eng. 75(1953) 3-8.

[23] V. Gnielinski, New equations for heat and mass transfer in turbulent pipe and channel flow, Int. Chem. Eng. 16(1976) 359-368.

[24] R.H. Notter, M.W. Rouse, A solution to the Graetz problem-III. Fully developed region heat transfer rates, Chem. Eng. Sci. 27(1972) 2073-2093.

[25] B.S. Petukhov, Heat transfer and friction in turbulent pipe flow with variable physical properties, in:J.P. Harnett, T.F. Irvine (Eds.), Advances in Heat Transfer, Academic Press, New York 1970, pp. 504-564.

[26] M. Khoshvaght-Aliabadi, F. Hormozi, A. Zamzamian, Effects of geometrical parameters on performance of plate-fin heat exchanger:vortex-generator as core surface and nanofluid as working media, Appl. Therm. Eng. 70(2014) 565-579.