Numerical study on flow and heat transfer characteristics in an impingement/effusion cooling system with high blockage ribs

Abstract

In this paper a numerical study is conducted to investigate the flow structure and heat transfer performance of jet impingement inside a narrow target channel with high blockage ratio transverse rib turbulators of different arrangements relative to effusion holes on the target wall, which represents a simplified system from mid-chord region of a turbine blade. The rib turbulators are transversely mounted between the locations of the impingement jet and effusion holes. The jet Reynolds number based on the injection hole diameter is 4,000, 8000 and 12,000, respectively. The effect of blockage ratio (e/DH =0.12 0.18 and 0.29) and rib arrangement (in front of or behind the effusion hole) on the flow structure, local and global average heat transfer characteristics in the impingement/effusion cooling systems are numerically investigated with Reynolds Averaged Navier–Stokes (RANS) method in detail. Furthermore, the calculated data on the rib roughened wall are also compared with those on the smooth wall for the impingement/effusion cooling system. Results show that the placement of ribs on the target wall produces a much greater heat transfer enhancement by up to 18%. The local heat transfer distributions and their uniformity are significantly affected by the position of rib turbulators. Moreover, the increase of rib blockage ratio is beneficial to increase the overall heat transfer level and thermal-hydraulic performance of impingement/effusion systems with ribs.