Experimental investigation of the effect of geometric modifications on the delta winglet type vortex generator on heat transfer

In this study, the effects of geometric modifications as well as the vortex generator blockage ratio on winglet type vortex generator, delta winglet, DW, which has a capability of producing longitudinal vortices and frequently encountered in literature, were investigated experimentally in terms of heat transfer. In order to analyze the thermal performance of smooth channel and the channel in which a vortex generators were positioned; fluid velocity, inlet and outlet fluid temperatures, copper plate surface temperatures as well as the pressure drop along the test region were measured and the necessary dimensional and dimensionless numbers were calculated and the results were presented in graphics. Initially; delta winglet pairs with a flat surfaces were placed in DWP common-flow-up, CFU and common-flow-down, CFD configurations and the thermal performance of the CFU configuration was determined to be higher based on the results of the experiments. In the next step; one small, two small and one large DWs were formed on DWP surfaces. As a result of these modifications, smaller friction factor, f values were obtained compared to the DWP with a flat surface. However, in terms of Nusselt number, higher Nusselt numbers could not be attained compared to flat surfaced DWP. Finally, experiments were carried out for flat surfaced DWP, positioned under CFU configuration, in four different blockage ratios, BR= 0.833, 0.667, 0.50 and 0.333. According to the experimental results, as the blockage ratio is increased, higher Nu numbers were obtained as a consequence of the formation of stronger vortices. An increase in f values was attained due to the increase in resistance against the flow as a result of the increas in frontal area of DWP. In terms of thermal enhancement, the highest TEF value was achieved for BR= 0.667. In this study, pair of DW with BR= 0.50 as well as trapezoidal vortex generator were obtained by dividing the flat surfaced DW with the highest blockage ratio, into two parts. As a result of the experiments, the highest TEF= 1.19 was obtained in lowest Reynolds number.