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Delta-winglet vortex generators (VGs) are known to enhance the heat transfer between the energy-carrying fluid and the heat transfer surfaces in plate-fin-and-tube banks. In this study optimal angles of attack of the delta-winglets are investigated based on the Pareto optimal strategy. The optimization process combines a CFD analysis, genetic algorithms and the response surface methodology. The angle of attack of a pair a delta-winglet-type VGs mounted behind each tube is varied between β = −90° and +90°. Three circular tube rows with inline and staggered tube arrangements are investigated for Reynolds numbers from 200 to 1200 (based on the inlet height and inlet velocity). The flow structure and heat transfer behavior is analyzed in detail for certain cases and the staggered and the inline tube arrangements are compared. Finally, for each of these arrangements the optimal sets of angles of attack for different Reynolds numbers are presented.
For circular finned tubes often used in heat exchangers, the wake regions behind the tubes are regions with low heat transfer coefficient. Delta-winglet vortex generators on the fin surfaces reduce the width of the wake regions and improve the overall heat transfer rate. The present work studies numerically the effect of enhancing the performance of the finned-tubes using delta-winglets. Simulations were carried out on a model of three circular tube rows with circular fins for Reynolds numbers of 500, 700, and 900 (based on the inlet velocity and the hydraulic diameter of unit cell). Eighteen basic configurations with different number and positions of delta-winglets were investigated. The flow and heat transfer behaviors are analyzed for certain configurations. Finally, the optimal configurations are presented based on the Pareto optimality strategy.