Heat transfer enhancement and turbulent flow in a high aspect ratio channel (4:1) with ribs of various truncation types and arrangements

- Ribbed channels with various truncation types and arrangements are studied.
- Liquid Crystal Thermography (LCT) is successfully applied.
- Truncated ribs reduce pressure loss penalty but keep heat transfer enhancement.
- The staggered arrangement results in complex flow paths.

Ribs are often employed in internal cooling passages of turbine blades to augment heat transfer with cooling air flowing through the internal ribbed passages. The present work concentrates on truncated ribs to improve thermal performances with continuous ribs in a high aspect ratio channel. With various truncation types and arrangements of truncated ribs, the optimized thermal performance of ribbed channels is attempted for by taking both heat transfer and pressure drop into consideration. Eight different ribbed channels with various truncation types and arrangements are investigated. Liquid Crystal Thermography (LCT) is employed to measure surface temperature and derive heat transfer coefficients over the ribbed surfaces in the tested channels. The turbulent flow details are presented by numerical calculations with an established turbulence model, i.e. the k-ω SST. From the obtained results, it is found that truncated ribs can reduce the pressure loss penalty without reducing the heat transfer enhancement in the tested channels. By changing the configurations to staggered arrangements, the heat transfer can be further enhanced associated with a moderate pressure drop. The truncated ribs generate transverse vortices at the truncation gaps and reduce the recirculating flow behind the ribs. Enhanced flow mixing contributes to the increased heat transfer. By the staggered arrangement, the flow path becomes more complex and the flow mixing is further enhanced. Truncated ribs are promising for applications in the high aspect ratio channel of the turbine blades and the enhancement factor is about 10%.