A numerical study of local heat transfer and velocity distributions between blockages with holes in a rectangular channel

Abstract

A numerical study has been conducted to understand the distributions of the local heat transfer coefficient and the local velocity for turbulent air flow past two or three blockages in a rectangular channel. The blockages had the same cross section as the channel and there was an array of staggered holes in the blockages. The channel with blockages modeled the trailing edge internal cooling passage in gas turbine airfoils. Numerical results were obtained for nine cases with different hole configurations, two or three blockages, two different hole sizes, and two Reynolds numbers of 10,000 and 30,000. The computations were conducted with two turbulent models, standard [k] - [E] model and Reynolds stress model (RSM), and two near wall treatments, non-equilibrium and two-layer zonal near wall treatment, respectively. Based on the experimental results, the results from the Reynolds stress model (RSM) are superior to the results from the standard [k] - [E] model. The hole configurations of this study significantly influence the velocity profiles, therefore, the heat transfer performance. Location of the hole of the upstream blockage significantly changes the velocity profiles; therefore, heat transfer results. The jets through the holes of the upstream blockage significantly affect the heated bottom wall. The smaller hole cases have larger heat transfer than the larger hole cases, but larger pressure drop than the larger hole cases. The smaller hole cases without reattachments of the jet have higher average heat transfer than the larger hole cases with reattachments of the jet because of the decrease of average velocity in the larger hole cases. Adding a third upstream blockage significantly changes heat transfer distribution on the heated bottom wall, although the local velocity distribution between the second and third blockages is not significantly changed.