On using axisymmetric turbulent impinging jets swirling as Burger's vortex for heat transfer applications. Single and multi-objective vortex parameters optimization

The effect on heat transfer from a heated flat plate to an impinging jet swirling according to the Burger's vortex is addressed in this work. Both the nozzle-to-plate distance and the Reynolds number (based on the jet diameter) have been considered constants during the study and equal to 4 jet radii and 23,000, respectively, while the input (or design) parameters are defined by the vortex structure, i.e. the dimensionless swirl intensity S and vortex core δ. They have been varied between 0.1 and 1.25 and between 0.05 and 0.8, respectively. On the other hand, the output parameters have been the area-weighted average and stagnation Nusselt numbers and the heat transfer uniformity. Thanks to several CFD numerical simulations, different response surfaces of the output parameters have been obtained which have allowed us to use them in the optimization algorithms avoiding hundreds of simulations. Regarding the single/multi-objective optimization, we find that swirling jets always perform better than axial ones when analyzing the area-weighted average Nusselt number, even becoming the improvement of the heat transfer around 10% higher; at the stagnation point, the swirling jet performs better only in a small region for low values of S and δ, even becoming the heat transfer around 3% higher; and regarding the uniformity of the heat transfer, when using swirling jets it is more uniform in a small region for high values of δ and medium ones of S, even becoming the uniformity around 20% higher. Additionally, three multi-objectives have been also considered and the corresponding Pareto Front with the set of optimal solutions obtained from the optimization process. Some of them have been finally simulated and analyzed.