Experimental investigation of flow and heat transfer characteristics in the bend region of matrix channel

Matrix cooling is gaining attention as an advanced internal cooling strategy for gas turbines, offering both enhanced mechanical integrity and superior heat transfer. However, the aerothermal behavior in bend regions, especially downstream of the matrix, remains insufficiently explored. This study presents a detailed experimental investigation of flow dynamics and heat transfer across the bend section that occurs downstream of the matrix channel. Two matrix configurations, i.e., (i) 3-subchannel (3SC) and (ii) 4-subchannel (4SC), are systematically studied at Reynolds numbers (Re) of 5,000, 7,500, and 10,000. High-resolution particle image velocimetry (PIV) and liquid crystal thermography (LCT) techniques have been used for multi-plane aerothermal measurements to elucidate the correlation of complex flow with thermal fields. Results indicate that the matrix emanates the corotating vortices, leading to spatially non-uniform secondary flows, including the emergence of Dean-type vortices at the downstream bend. In particular, the 4SC matrix promotes stronger vortex-driven mixing, yielding significant local and average heat transfer enhancement in the bend region. At Re = 10,000, the 4SC channel achieves a peak heat transfer augmentation of 133 % relative to a smooth baseline, while incurring only a slight increase in friction factor. Across all conditions, the 3SC and 4SC configurations deliver thermal performance factors (TPF) of up to 2.09 and 2.34, respectively. These findings support the potential of matrix cooling to deliver high thermal effectiveness in next-generation internal cooling applications.