Effect of internal effusion on aerothermal performance of a three-pass channel roughened by angled ribs and pin-fins with lateral flow exit

The effect of internal effusion on the aerothermal performance of a three-pass channel with smooth walls, the in-lined 45 degrees ribs, and the attached-detached pin-fins along the first, second, and third passes, respec-tively, is experimentally studied by comparing the full-field endwall Nusselt numbers, friction factors, and aerothermal performance indexes between the test channels with and without effusion. The coolant stream that serpentines through the three-pass channel with the inlet Reynolds numbers between 10,0 0 0 and 30,0 0 0 is discharged from the sidewall of the third pin-fin pass. In the internal effusion channel, there are nine pairs of horizontal square slots adjacent to the two channel endwalls for bypassing the near-wall flows behind the angled ribs from the second pass into the third pin-fin pass. The weak heat convection underneath the sealed channel tip of the third pin-fin pass in the non-effusion channel is considerably enhanced by the near-wall flows through the effusion slots, leading to the modified Nusselt number map with regional heat transfer elevations. Along with the significant reduction of streamwise pressure gradients along the second and third passes, the aerothermal performance of the channel with the internal effusion is substantially improved from that without effusion. The endwall-average Nusselt numbers and friction factors of the pin-fin pass in the effusion channel are, respectively, upraised to 1.68- 1.44 and reduced to 0.25-0.33 times the non-effusion channel levels. Under the combined heat-transfer and pressure-drop effects of the internal effusion for the pin-fin pass, the aerothermal performances in-dexes are substantially increased to 3.04-4.24 from the non-effusion channel in the range of 1.46-1.59. To aid the cooling applications to gas turbine static blades, the empirical correlations are developed to determine the regional average Nusselt number and Fanning friction factor of the three-pass channels with and without internal effusion.(c) 2022 Elsevier Ltd. All rights reserved.

Automated summary

The effect of internal effusion on the aerothermal performance of a three-pass channel has been experimentally studied, showing significant improvement in the performance with internal effusion.