Hydrodynamics and heat transfer characteristics of a novel heat exchanger with delta-winglet vortex generators

The effects of vortex generators on heat transfer and pressure drop of a novel heat exchanger are investigated using computational fluid dynamics (CFD) method. The Reynolds numbers based on fin collar outside diameter varied from 600 to 2600, the attack angle from 10 degrees to 50 degrees, and the aspect ratio from 1 to 4. The numerical results are also analyzed from the view point of field synergy principle, according to which the reduction of the intersection between velocity and temperature gradient is the basic mechanism for augmentation of heat transfer. The results indicate that the enhanced configurations produce the longitudinal vortices and accelerate the flow, which result in significant augmentations of heat transfer with modest pressure drop penalties. It was found that the delta-winglet vortex generator with an attack angle of 20 degrees and an aspect ratio of 2 provides the best integrated performance over the range of Reynolds number computed. The Colburn j-factor of the optimal configuration is shown to increase by 35.1-45.2% with a corresponding increase of 19.3-34.5% in the friction factor. (C) 2009 Elsevier Ltd. All rights reserved.