Impingement Cooling by Multiple Asymmetric Orifice Jets

This study presents impingement cooling from a flat plate by multiple asymmetric jets. Such jets are discharged through blunt-edge inline orifice holes with a thickness-to-diameter ratio of t/D-j = 0.5 and a jet-to-jet spacing of T/D-j = 4.0, at the Reynolds number of 20,000. First, fluidic features are established both in free exit and with impingement, at varying short target spacing (e.g., H/D-j <= 4.0). Second, thermal characteristics of the jet impingement are elucidated. Results demonstrate that, due to a skewed incidence of the coolant stream upstream of concave orifice holes, the resulting multiple orifice jets are asymmetric and skewed relative to the orifice axis. These results mimic multiple fluidically inclined jets. However, asymmetric entrainment that takes place causes faster mixing with the surrounding fluid at rest as well as faster decay of momentum. This shows more effective cooling from a flat plate for the relatively short H/D-j range than conventional symmetric orifice and nozzle jets.