Tab-induced counter-rotating vortex pairs for mixing and heat transfer applications

One of the common passive methods to enhance heat transfer with low pressure drop is the use of vortex generators (VGs). In the present study, an experimental investigation was carried out to explore the effects of single vortex generators on flow dynamics and heat transfer when using air as heat transfer fluid. Mean velocities and surface temperature distributions have been characterized by using particle image velocimetry (PIV) and infrared camera thermography at a fixed Reynolds number of air (Re = 4800). Physical parameters of vortex generators, such as inclination angle and taper angle, were varied to understand the role of VG geometry on flow and heat transfer characteristics. Results to date show that taper angle and inclination angle have distinct effects on local heat transfer behavior. Specifically, the induced counter-rotating vortex pair (CVP) leads to heat transfer enhancement both along the streamwise and spanwise directions. Better cooling effects are found in the down-flow regions due to the acceleration of streamwise velocity in those regions. In general, the effects by the CVP structures on convective heat transfer are evident in the range of x/h < 1.5 - 2 approximately. Results also show that heat transfer enhancement can be correlated directly to the local shear rate at the wall. The results also suggest that the heat transfer rates on the surface depend mainly on flow resistance near the heated wall.