Thermal and hydraulic characteristics of trapezoidal winglet across fin-and-tube heat exchanger (FTHE)

Abstract

Heat transfer augmentation by using vortex generator (VG) as an enhancement method in plain fin-and-tube heat exchanger (FTHE) has recently captured high attention of many researchers. In the present study, the flow characteristics and thermal performance across the FTHE with and without trapezoidal winglet vortex generator (TWVG) are investigated using dye injection technique by experimental approach and numerical simulation using finite volume method. Two types of TWVG are used, namely flat trapezoidal winglet (FTW) and curved trapezoidal winglet (CTW), either arranged in common flow up (CFU) or in common flow down (CFD) arrangements. In this study, Reynolds number (Re), angle of attack (β) and aspect ratio (Ʌ) in the range of 500–2500, 10–90° and 2–3 were used respectively. From the experimental study, the results show that the heat transfer can be enhanced by using certain TWVG geometry, arrangement, Ʌ and β to reduce the wake region size at the rear portion of the tubes. Meanwhile, from the numerical simulation, augmentation towards the heat transfer rate is normally accompanied with higher pressure drop penalty. It is inferred that FTW in CFU arrangement at Λ = 3 and β = 10° was found to give the best thermal and hydraulic performance across the FTHE channel when both heat transfer enhancement and pressure drop penalty are considered.