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    Thermal-hydraulic performance of the circular-slice-shaped-winglet for tube bank heat exchanger
    (Elsevier France-Editions Scientifiques Medicales Elsevier, 2022) Tepe, Ahmet Umit; Yilmaz, Harun
    In this study, heat transfer performance of circular-slice-shaped-winglet (CSSW) for tube bank heat exchanger (TBHE) was numerically investigated. Circular-slice angle (alpha = 5 degrees, 10 degrees and 20 degrees), layer gap (h/d = 0.08, 0.14, and 0.20) and winglet diameter (D/d = 1.60, 1.76 and 1.92) were analyzed as geometric parameters to obtain optimal design. Comprehensive numerical simulations were conducted under both laminar and turbulent flow (1100 <= Re <= 8500) conditions. Navier Stokes Equations were solved by using RNG k-epsilon turbulence model (with enhanced wall treatment). Colburn-j factor (j), friction factor (f), modified London area goodness factor (j/f(1/3)) and performance evaluation criterion (PEC) were investigated quantitatively. Flow characteristics were also analyzed to elucidate the underlying physics of the effects of CSSW on thermal-hydraulic performance for TBHE. Results were compared with the data related to bare tube heat exchanger, and showed that the highest modified London area goodness factor is 26.34% with alpha = 10 degrees, h/d = 0.20 and D/d = 1.92 CSSW winglet design. Additionally, numerical calculations revealed that PEC increased to 1.356 with these CSSW design parameters, which corresponds to reduction of the required total heat transfer area by 36.60% compared to the bare tube heat exchanger for the same heat duty at a fixed pumping power.