Effect of upstream vortex generators on a longitudinally-finned heat sink

The effects of vortex generators (VG´s) on fluid flow and heat transfer have been studied extensively in the literature. The majority of these studies have examined the effects of using VG´s in heat exchanger applications. Other investigations have examined the role of placing VG´s in channel flow or on a heated flat plate owing to the fact that these experimental set-ups facilitate easy comparison to theory while at the same time simulating heat exchanger conditions. There is little information available on the hydraulic and thermal effects of placing VG´s upstream of a longitudinally-finned heat sink. In this experimental investigation, a pair of wall mounted delta winglets are used to induce unsteady flow upstream of a longitudinally-finned heat sink in fully ducted developing flow to evaluate the efficacy of using them for enhanced heat transfer in this configuration. Results are presented for the spanwise variation of the streamwise pressure drop downstream of a VG in duct flow. It is also shown how the local pressure drop in the duct changes in the vicinity of the VG. Thermal resistance versus pressure drop data are presented for three different heights of delta winglet with constant angle of attack and spacing. It shown that heat transfer enhancement is possible in this configuration with a reduction in thermal resistance of up to 10% at constant pressure drop for the VG that occupies the total duct height. The variation in thermal resistance with distance of VG from the heat sink is also presented.