Flow and heat transfer characteristics of transverse perforated ribs under impingement jets

An experimental study was conducted to investigate heat transfer and flow characteristics under impingement of a multiple circular jet array with perforated rib surfaces (PRS) and solid rib surfaces (SRS). Heat transfer results were obtained using an infrared thermal imaging technique. Velocity measurements were made with a Laser-Doppler Anemometry (LDA) system. The heat transfer results of the rib surfaces are compared with those of a smooth plate. Best heat transfer performance was obtained with the PRS arrangements. The presence of rib perforation produces higher heat transfer coefficients than the smooth plate and SRS surfaces. Correlations have been developed for the average Nusselt number for the perforated rib surfaces based on projected and total area. The velocity measurements were obtained for the case where the jet-to-plate distances at H/d equal to 2, 4, 8 and at a Reynolds number of 10,000. Positions of maximum radial and axial velocities and Reynolds stress distributions have been determined for PRS, SRS and smooth plates. For some locations, the production of turbulence kinetic energy and radial velocities are higher for the PRS surfaces as compared to SRS and smooth surfaces.