Effect of Upwind and Downwind Directions of Right-Trapezoidal Winglet-Vortex-Generators in a Solar-Air-Heater

Abstract

Two directions of right-trapezoidal winglet vortex generators, namely, upwind and downwind directions, were numerically investigated to understand how they affect the thermo-hydraulic performance of the heat exchanger in a solar air heater. The results showed that the Nusselt number, friction factor, and thermal enhancement factor were higher when the vortex generator was installed in an upwind direction. This was because of the magnitude and the position of the airflows’ velocity. That is, faster airflows were induced in the region adjacent to the absorber plate when the vortex generator was installed in the upwind direction. As a result, high convection rates occurred and then increased the overall convective heat transfer rates of the solar air heater. Therefore, Nusselt number and thermal enhancement factor were higher. Nevertheless, the faster airflows also caused increased form drags due to vortex generator blockage, resulting in higher friction factor.

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No potential conflict of interest was reported by the author(s).

Additional information

Notes on contributors

Roytor Charoensin-O-larn

Roytor Charoensin-O-larn is a Lecturer in the Department of Mechanical Engineering, Chulalongkorn University, Bangkok, Thailand. He earned his Ph.D. in Mechanical Engineering from the University of Washington, USA in 2022. His research interests include computational fluid dynamics and combustion.

Boonchai Lertnuwat

Boonchai Lertnuwat is an Associate Professor in the Department of Mechanical Engineering, Chulalongkorn University, Bangkok, Thailand. He earned his Ph.D. in Mechanical Engineering from the University of Tokyo, Japan in 2003. He has been studying the shape of the Taylor bubble under different conditions and recently he has been studying the thermo-hydraulic performance of winglet vortex generators in solar air heaters.