Study on flow control and heat transfer performance based on secondary dimple/protrusion

Dimple and protrusion are effective on heat transfer enhancement process. These structures have broad application prospects on heat transfer devices such as heat exchangers, cooling channels in gas turbine blades and so on. Numerical simulation was adopted to investigate the heat transfer and flow friction performance of rectangular channel with secondary dimple/protrusion structure. Viscous Navier-Stokes equations were solved using shear-stress transport (SST) turbulence model. The section diameter of secondary protrusion was taken into account to discuss their relationship with heat transfer and flow friction performance. The results indicate that: the import of secondary protrusion can bring obvious flow control effect on the flow performance near the main dimple cavity and the wake area downstream the dimple while changing the Nu number distribution in these areas. The heat transfer process in regions of dimple cavity and downstream wake area are strengthened considerably compared with that in single dimple channel. The enhancement of heat transfer is more obvious with larger protrusion section diameter (D). From the pressure loss coefficient analysis, we concluded that the extra pressure loss brought by secondary protrusion is very tiny. Secondary protrusion is one kind of effective heat transfer enhancing method with little flow resistance.