Flow structure and heat transfer characteristics in a 90-deg turned pin fined duct with different dimple/protrusion depths

In this study, numerical simulations are performed to investigate the effect of the dimple/protrusion depth on the flow structure and heat transfer characteristics in a 90-deg turned channel with pin fins. The pin fins and dimple/protrusion are arranged on the endwall surface with staggered layout. Five different dimples/protrusions depth-to-diameter ratios are investigated, i.e., [Formula presented]=0,0.1,0.2,0.3,0.4. The Reynolds number ranges from 8500 and 60,000. Results of the flow structure, heat transfer on the endwall surface and friction factor are investigated in this study. Results indicate that the dimple/protrusion depth has a remarkable influence on the flow structure and heat transfer. The horseshoe vortex generated by the pin fin is decreased while the impingement effect within the dimple is increased as the dimple depth increased. In a pin fin channel with protrusion, a new horseshoe vortex which causes a high Nusselt number near the endwall is induced after adoption the protrusion. The higher protrusion depth induces a higher Nusselt number. It is also found that the volume goodness factor is increased after adoption the dimple/protrusion compared to pure pin fin channel.