Investigation of the Effect of Vortex Generation on Flow Structure and Heat Transfer Enhancement using Particle Image Velocimetry (PIV) 2017-01-1609

In this experimental work, a flow field test system embedded with different vortex generators was installed to investigate the impact of vortex generation on heat transfer of air flow in a horizontal channel, and the flow structure was evaluated using a particle image velocimetry (PIV) system. Three different configurations of vortex generators were fitted vertically on a flat plate, at attack angles of 15^o, 30^o, and 45^o, and tested at four different incoming air velocities. An axial fan was used to supply the flow of air through the test section. The effects of Reynolds number, attack angle, and the shape of vortex generators were examined in this work. The experimental results showed that, the presence of vortex generators had considerable effect on temperature distribution, pressure drop, and heat transfer augmentation in the channel flow. Compared with the smooth channel, the heat transfer rate was enhanced by (6.7% - 30.1%), (9% - 36.8%), and (8.7% - 31%) while the pressure drop increased by (2.1% - 26.3%), (7.6% - 52.7%), and (14.5% - 48.3%) with a small single delta winglet pair, a large single delta winglet pair, and two small VG pairs deployed in a V-formation array, respectively. The PIV experimental results showed that the flow field produced from a winglet pair of vortex generators is a counter-rotating pair of vortices that formed at the location immediately following the trailing edge of VGs, and the vortices pair disperses while moving downstream. These vortices are much larger with a large single winglet pair type compared to the other two VG types.