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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