Flow structure and heat transfer characteristics of a pin-finned channel with upright/curved/inclined pin fins under stationary and rotating conditions

This study aims to evaluate the heat transfer performance of different pin fins under stationary and rotating conditions. Three kinds of pin fins (upright, curved and inclined) and two included angles (45° and 60°) between the pin fins and endwalls are studied for Ro varying from 0 to 0.5. Under stationary condition, curved pin fins and inclined pin fins are characterized with much lower friction factors. Among all the pin fins studied, the thermal performance factors of 45° curved pin fins and 45° inclined pin fins show significant improvement by 12.9% and 13.9% compared to upright pin fins, respectively. Jet-like flow, generated behind the curved pin fins and inclined pin fins, can enhance local heat transfer dramatically after impinging on the endwall. Under rotating condition, heat transfer enhancement of curved pin fins show much lower sensitivity to rotation speed compared to other two pin fins. A strong pressure gradient is established close to pin fin trailing edge due to rotation, and longitudinal secondary flow behind the pin fins is induced consequently. The moving direction and strength balance between the jet-like flow and longitudinal secondary flow play crucial roles on the heat transfer.