Axisymmetric numerical investigation of the heat transfer enhancement from a heated plate to an impinging turbulent axial jet via small vortex generators

The consequences of installing one or two vortex generators on a flat plate under axisymmetric conditions are presented in this work in order to analyse if heat transfer from the plate can be enhanced. Two different configurations have been considered to optimise the radial location of the vortex generators which can improve the heat transfer in comparison with a flat plate without them. To that end, we have conducted several numerical simulations of a turbulent jet impinging against a plate with one or two small tabs and the heat transfer from the plate quantified in terms of the Nusselt number. A jet Reynolds number of 23,000 and a nozzle-to-plate distance of 2 nozzle diameters were used throughout the study. Thanks to a parametric study, with the tab positions as parameters, we obtain different response surfaces which will help us to identify the optimal tab configurations. After that optimization process, we shall show that, for certain radial locations of the tabs, the averaged heat transfer on the tabbed plate can be improved up to around 4.5% with just a 2% of more pumping power due to pressure losses on the tabs. Furthermore, it is even more remarkable the fact that the averaged heat transfer can even be enhanced with around 25% of less pumping power requirements than when the plate is completely flat. We shall show that this effect is due to the fact that the tabs reduce the friction losses on the tabbed plate and, consequently, the pumping power needs. On the contrary, the heat transfer at the stagnation point cannot be ever increased.