Flow structure and heat transfer characteristics of a dimpled wedge channel with a bleed hole in dimple at different orientations and locations

In this study, the heat transfer and friction factor characteristics of a dimpled surface with a bleed hole in the converge channel is studied using a numerical method. The converge angle of the channel is approximately 12.7°. The installation angle of the bleed hole ranges from −30° to 30°. The diameter of the bleed hole is 0.5 mm. The Reynolds number of the main flow is between 8500 and 60,000. The mass flow rate of each bleed hole is 0.5% of the total mass flow rate at the inlet. A dimple without a bleed hole is used as the Baseline. It is found that the bleed hole significantly destroys the low-speed-recirculation. The area of reverse region decreases and the strength of secondary vortex increases as the installation angle increases. The spiral point and reattachment line are also changed as the installation angle changes. This is more distinct for a bleed hole at α = 30°. The primary vortex and spiral point are almost invisible. Two regions with a high turbulent kinetic energy and a high Nusselt number are found. The area-averaged Nu number ratios increase as the installation angle increases. The thermal performance is also improved by the bleed hole.