Effects of rib turbulator on heat/mass transfer for impingement/effusion cooling with crossflow

The present study has been conducted to investigate the effect of rib arrangements on an impingement/effusion cooling system with initial crossflow. Two perforated plates are placed in parallel and staggered arrangements with a gap distance of 2d and crossflow passes between the injection and effusion plates. Both the injection and effusion hole diameters (d) are 10 mm and Reynolds number based on the hole diameter and hole-to-hole pitch are fixed to 10,000 and 6d, respectively. Square transverse ribs (3 mm) of various rib arrangements are installed on the effusion plate. With the initial crossflow, locally low transfer regions are formed and level of heat transfer rate get decreased with increasing flow rate of crossflow because wall jets are swept and stagnation regions are affected by crossflow. With rib turbulators, flow and heat transfer patterns are changed because the ribs protect near-wall flows including wall jets and generate secondary flow in a duct. For M≥1.0, overall heat transfer is promoted when ribs are installed on the effusion surface, and higher values are obtained with smaller pitch of ribs. For low blowing ratio of M=0.5, the ribs have adverse effects on heat/mass transfer because the ribs prevent wall jets from spreading and enhancing heat transfer.