Enhanced heat transfer in a heat exchanger square-duct with discrete V-finned tape inserts

doi:10.1016/j.cjche.2014.05.018

Abstract

Abstract: The article presents an experimental and numerical study on thermal performance enhancement in a constant heatfluxed square-duct inserted diagonallywith 45°discrete V-finned tapes (DFT). The experimentswere carried out by varying the airflow rate through the tested square duct with DFT inserts for Reynolds number from 4000 to 25000. The effect of the DFT with V-tip pointing upstream at various relative fin heights and pitches on heat transfer and pressure drop characteristics was experimentally investigated. Both the heat transfer and pressure drop were presented in terms of Nusselt number and friction factor respectively. Several V-finned tape characteristics were introduced such as fin-to duct-height ratio or blockage ratio (R_B=e/H=0.075, 0.1, 0.15 and 0.2), fin pitch to duct height ratio (R_P=P/H=0.5, 1.0, 1.5 and 2.0) and fin attack angle, α=45°. The experimental results reveal that the heat transfer and friction factor values with DFT inserts increase with the increment of R_B but the decrease of RP. The inserted square-duct at R_B=0.2 and R_P=0.5 provides the highest heat transfer and friction factor while the one with R_B=0.1 and R_P=1.5 yields the highest thermal performance. Also, a numerical simulation was conducted to investigate the flow structure and heat transfer mechanism inside the tested duct with DFT inserts.

Key words: Heat exchanger, Square duct, Discrete V-fins, Thermal enhancement, Friction factor

摘要： The article presents an experimental and numerical study on thermal performance enhancement in a constant heatfluxed square-duct inserted diagonallywith 45°discrete V-finned tapes (DFT). The experimentswere carried out by varying the airflow rate through the tested square duct with DFT inserts for Reynolds number from 4000 to 25000. The effect of the DFT with V-tip pointing upstream at various relative fin heights and pitches on heat transfer and pressure drop characteristics was experimentally investigated. Both the heat transfer and pressure drop were presented in terms of Nusselt number and friction factor respectively. Several V-finned tape characteristics were introduced such as fin-to duct-height ratio or blockage ratio (R_B=e/H=0.075, 0.1, 0.15 and 0.2), fin pitch to duct height ratio (R_P=P/H=0.5, 1.0, 1.5 and 2.0) and fin attack angle, α=45°. The experimental results reveal that the heat transfer and friction factor values with DFT inserts increase with the increment of R_B but the decrease of RP. The inserted square-duct at R_B=0.2 and R_P=0.5 provides the highest heat transfer and friction factor while the one with R_B=0.1 and R_P=1.5 yields the highest thermal performance. Also, a numerical simulation was conducted to investigate the flow structure and heat transfer mechanism inside the tested duct with DFT inserts.

关键词: Heat exchanger, Square duct, Discrete V-fins, Thermal enhancement, Friction factor

Watcharin Noothong, Supattarachai Suwannapan, Chinaruk Thianpong, Pongjet Promvonge. Enhanced heat transfer in a heat exchanger square-duct with discrete V-finned tape inserts[J]. , 2015, 23(3): 490-498.

References

[1] P. Promvonge, S. Skullong, S. Kwankaomeng, C. Thiangpong, Heat transfer in square duct fitted diagonally with angle-finned tape-Part 1: Experimental study, Int. Commun. Heat Mass Transfer 39 (2012) 617-624.
[2] P. Promvonge, S. Skullong, S. Kwankaomeng, C. Thiangpong, Heat transfer in square duct fitted diagonallywith angle-finned tape-Part 2: Numerical study, Int. Commun. Heat Mass Transfer 39 (2012) 625-633.
[3] P. Promvonge, W. Changcharoen, S. Kwankaomeng, C. Thianpong, Numerical heat transfer study of turbulent square-duct flow through inline V-shaped discrete ribs, Int. Commun. Heat Mass Transfer 38 (2011) 1392-1399.
[4] P. Promvonge, S. Sripattanapipat, S. Tamna, S. Kwankaomeng, C. Thianpong, Numerical investigation of laminar heat transfer in a square channel with 45°inclined baffles, Int. Commun. Heat Mass Transfer 37 (2010) 170-177.
[5] P. Promvonge,W. Jedsadaratanachai, S. Kwankaomeng, Numerical study of laminar flow and heat transfer in square channel with 30°inline angled baffle turbulators, Appl. Therm. Eng. 30 (11-12) (2010) 1292-1303.
[6] P. Promvonge, S. Sripattanapipat, S. Kwankaomeng, Laminar periodic flow and heat transfer in square channel with 45°inline baffles on two oppositewalls, Int. J. Therm. Sci. 49 (2010) 963-975.
[7] S. Kwankaomeng, P. Promvonge, Numerical prediction on laminar heat transfer in square duct with 30°angled baffle on one wall, Int. Commun. Heat Mass Transfer 37 (2010) 857-866.
[8] S. Eiamsa-ard, N. Koolnapadol, P. Promvonge, Heat transfer behavior in a square duct with tandem wire coil element insert, Chin. J. Chem. Eng. 20 (5) (2012) 863-869.
[9] S. Eiamsa-ard, V. Kongkaitpaiboon, K. Nanan, Thermohydraulics of turbulent flow through heat exchanger tubes fitted with circular-rings and twisted tapes, Chin. J. Chem. Eng. 21 (6) (2013) 585-593.
[10] S. Eiamsa-ard, C. Thianpong, P. Eiamsa-ard, P. Promvonge, Convective heat transfer in a circular tube with short-length twisted tape insert, Int. Commun. Heat Mass Transfer 36 (2009) 365-371.
[11] S. Eiamsa-ard, P. Promvonge, Heat transfer characteristics in a tube fitted with helical screw-tape with/without core-rod inserts, Int. Commun. Heat Mass Transfer 34 (2) (2007) 176-185.
[12] 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.
[13] P. Promvonge, T. Chompookham, S. Kwankaomeng, C. Thianpong, Enhanced heat transfer in a triangular ribbed channel with longitudinal vortex generators, Energy Convers. Manag. 51 (6) (2010) 1242-1249.
[14] T. Chompookham, C. Thianpong, S. Kwankaomeng, P. Promvonge, Heat transfer augmentation in a wedge-ribbed channel using winglet vortex generators, Int. Commun. Heat Mass Transfer 37 (2010) 163-169.
[15] C. Thianpong, T. Chompookham, S. Skullong, P. Promvonge, Thermal characterization of turbulent flow in a channel with isosceles triangular ribs, Int. Commun. Heat Mass Transfer 36 (2009) 712-717.
[16] S. Skullong, P. Promvonge, Experimental investigation on turbulent convection in solar air heater channel fitted with delta winglet wortex generator, Chin. J. Chem. Eng. 22 (1) (2014) 1-10.
[17] V. Sri Harsha, S.V. Prabhu, R.P. Vedula, Influence of rib height on the local heat transfer distribution and pressure drop in a square channel with 90°continuous and 60°Vbroken ribs, Appl. Therm. Eng. 29 (11-12) (2009) 2444-2459.
[18] A. Gupta, V. Sri Harsha, S.V. Prabhu, R.P. Vedula, Local heat transfer distribution in a square channel with 90°continuous, 90°saw tooth profiled and 60°broken ribs, Exp. Thermal Fluid Sci. 32 (2008) 997-1010.
[19] G. Tanda, Heat transfer in rectangular channelswith transverse and V-shaped broken ribs, Int. J. Heat Mass Transfer 47 (2004) 229-243.
[20] P.R. Chandra, C.R. Alexander, J.C.Han, Heat transfer and friction behaviors in rectangular channels with varying number of ribbed walls, Int. J. Heat Mass Transfer 46 (2003) 481-495.
[21] A. Murata, S. Mochizuki, Comparison between laminar and turbulent heat transfer in a stationary square duct with transverse or angled rib turbulators, Int. J. Heat Mass Transfer 44 (2001) 1127-1141.
[22] J.C. Han, Y.M. Zhang, C.P. Lee, Influence of surface heat flux ratio on heat transfer augmentation in square channels with parallel, crossed, and V-shaped angled ribs, ASME J. Turbomach. 114 (1992) 872-880.
[23] J.C. Han, Y.M. Zhang, C.P. Lee, Augmented heat transfer in square channels with parallel, crossed and V-shaped angled ribs, ASME Heat Transfer 113 (1991) 590-596.
[24] S.C. Lau, R.T. Kukreja, R.D. McMillin, Effects of V-shaped rib arrays on turbulent heat transfer and friction of fully developed flow in a square channel, Int. J. Heat Mass Transfer 34 (7) (1991) 1605-1616.
[25] ANSI/ASME, Measurement uncertainty, PTC 19, Part I, 1-19851986.
[26] R.L. Webb, Performance evaluation criteria for use of enhanced heat transfer surfaces in heat exchanger design, Int. J. Heat Mass Transfer 24 (1981) 715-726.
[27] F.P. Incropera, P.D. Witt, T.L. Bergman, A.S. Lavine, Fundamentals of Heat and Mass Transfer, John-Wiley & Sons, 2006.