A comparative study of fluid flow and heat transfer in the tube with multi-V-winglets vortex generators

In this paper, a new multi-V-winglets vortex generator was proposed and its influence on fluid flow and thermal transfer was studied. It was found that the thermal transfer was enhanced with the increasing number of winglets, while the friction resistance was growing. Therefore, punching holes on the surface of vortex generators were used to enhance overall performance by reducing friction resistance. The simulation results showed that jet flow appeared when fluid passed through hole, which impacted the recirculation zone and removed the stagnant fluid. Thus, local heat transfer was enhanced and friction loss was decreased. Meanwhile, the pitch of multi-Vwinglets vortex generator had an important role in heat transfer and friction loss, which could increased the Nusselt number of the smooth tube by 130.57-156.42%. Furthermore, the results were proved using the principle of entropy generation. The maximum performance evaluation factor was 2.83 when the number of winglets was 8, the holes were on the outer surface of winglets and the pitch was 25 mm.