Augmented Performance and Wake Management in Finned Tube Arrays Through Hierarchical Deployment of Toe-Out Winglets

Downsizing the heat exchanger without compromising its heat exchange capacity is highly desirable for containing the box volume of a thermal management system. This investigation seeks to substantially boost the thermal compactness of a widely used gas-to-liquid heat exchanger, called finned tube arrays. For that purpose, winglet-type vortex generators are adopted. The novelty of the present study lies in the fact that it uses regression analysis to develop thermo-hydraulic functional correlations corresponding to three diverse design parameters of winglet-type vortex generators: the attack angle, the location and the geometric aspect ratio. In addition, enhancement in the wake-affected heat transfer is specifically examined, followed by a proof-of-concept study by making the best design(s) of vortex generators perform under widely varying operating conditions. Based on a thermo-hydraulic assessment of the generators' attack angle, 45-degrees is the limiting value of optimal attack angle. Although multiple winglet locations are found to deliver the desired thermal augmentation, a few locations incur disproportionate flow loss whereas majority locations facilitate linearized thermal augmentation. It is encouraging to find that the relative Colburn j-factor of the modified heat exchanger increases with the Reynolds number, despite the absolute values bearing an inverse correlation. While the highest augmentation in the average Colburn j-factor equals 44.1%, it is 150.1% over the wake-affected fin surface.