Multi-Pass Serpentine Cooling Designs for Negating Coriolis Force Effect on Heat Transfer: Smooth Channels

The combined action of Coriolis and centrifugal buoyancy forces results in nonuniform heat transfer coefficient on pressure and suction side internal walls, hence leading to nonuniform metal temperatures and increased thermal stresses. The present study addresses the problem of nonuniform heat transfer distribution due to rotation effect and proposes novel designs for serpentine cooling passages, which are arranged along the chord of the blade. The two configurations were four-passage and six-passage serpentine smooth channels. Detailed heat transfer coefficients were measured using transient liquid crystal thermography under stationary and rotating conditions. Heat transfer experiments were carried out for Reynolds numbers ranging from 12,294 to 85,000 under stationary conditions. Rotation experiments were carried out for the Rotation numbers of 0.05 and 0.11. Heat transfer enhancement levels of approximately two times the Dittus-Boelter correlation (for developed flow in smooth tubes) were obtained under stationary conditions. Under rotating conditions, we found that the four-passage configuration had slightly lower heat transfer compared with the stationary case, and the six-passage configuration had higher heat transfer on both the leading and trailing sides compared with the stationary case. The leading and trailing side heat transfer characteristics were near-similar to each other for both the configurations, and the rotating heat transfer was near-similar to the stationary condition heat transfer.