Enhancement of Heat Transfer Using Delta-Winglet Type Vortex Generators with a Common-Flow-up Arrangement

Simulations of a coolant air flowing in a heat exchanger with delta-winglet type vortex generators in common-flow-up configuration have been performed to unveil the salient heat transfer characteristics. The heat exchanger is approximated as a periodic rectangular channel with heated walls and a pair of built-in tubes near the inlet and outlet. The heat transfer characteristics of the heat exchangers with vortex generators near the inlet, outlet, and both inlet and outlet have been compared. The Navier-Stokes equations together with the energy equation are solved employing unstructured finite volume method. The simulations reveal a significant enhancement in heat transfer because of the strong swirling motion originating from the streamwise longitudinal vortices behind the pair of delta winglets. The spiraling flow entrains air into the core and causes intermixing of the fluid layers to disrupt the growth of the thermal boundary layer. A parametric study on the angles of attack identifies the conditions under which enhancement in heat transfer can lead to significant miniaturization of the heat exchangers. The analysis also reveals interesting flow structures behind the winglets and correlates them to the mechanism of heat transfer.

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