Detailed heat transfer measurements on rectangular channels with partial length 3D round-edged rib turbulators

Rib turbulators are essential for cooling turbine blade internal channels efficiently exposed to the high heat flux of gas turbine engines. While the ideal sharp-edged rib turbulators offer excellent heat transfer benefits, they are associated with high wall friction, which impacts the power required to pump cooling air. Here, we demonstrate that a partial-length 3D round-edged geometry, which changes the local flow compared to a sharp-edged rib, improves aspects of the thermal performance characteristics of internal cooling channels significantly. Experiments are implemented to reveal heat transfer and flow within a ribbed rectangular internal passage with 45°-staggered partial-length 3D round-edged rib arrangements on two opposing walls. Local heat transfers of the smooth walls and round-edged rib itself have been measured using transient liquid crystals and novel rib analysis methods. Augmented local heat transfer mechanisms in the inter-rib regions, which are hardly predicted by numerical simulations, are identified as being driven by two dominant flow structures: vortex and turning flow. Our experimental measurements highlight the significant contribution to heat transfer of the rib itself. Compared to sharp-edged ribs, 3D round-edged ribs have a high thermal performance factor. These findings provide insight into the design of internal cooling channels with realistic rib geometries. • Investigation into heat transfer and flow in rectangular channels with partial-length 3D round-edged rib turbulators. • Experimental measurement of local heat transfer coefficients on smooth walls and round-edged ribs. • Identify two different mechanisms of augmented heat transfer differentiated by rib height. • Assessment of contributions to heat transfer of each surface in ribbed internal cooling channels. • Provides new insight into the design of internal cooling channels with realistic ribs.