Characteristics of Pressure, Flow, and Heat Transfer in Rotating Internal Cooling Passages With Attached-Detached Ribs

Measurements of flow field, heat transfer coefficient, and wall static pressure distribution were made in a rotating two-pass square duct with detachment of 90° ribs from the first-pass leading wall and second-pass trailing wall as well as attachment of 90° ribs onto the other two opposite walls. Laser-Doppler velocimetry was used to measure the local flow velocity. The ribs were square in cross-section and their detached-distance/height ratio was 0.38. The rib-height/duct-height ratio and the pitch/rib-height ratio were 0.136 and 10, respectively. Duct Reynolds number was fixed at 1×10⁴ and rotating number ranged from 0 to 0.2. Results are documented in terms of the main flow development, cross-stream secondary flow structure, the distributions of the pressure coefficient, the variation of friction factor with Ro, and passage averaged Nusselt number ratios under a constant flow rate and a constant pumping power condition. For CFD reference, the periodic fully developed rotating flow condition is attained after the 6^th rib pair in the first pass. In addition, the relationships between the regional averaged Nusselt number, transverse and convective mean velocity component, and turbulent kinetic energy are addressed. Using these relationships the general superiority of heat transfer enhancement of the attached-detached 90° ribs arrangement over the attached-attached one and detached-detached one can be reasonably illustrated. Simple expressions are obtained to correlate the friction factor with Ro, which are lacking in the published literature. The respective contributions of the ribs and passage rotation on the passage friction loss are identified.