Heat transfer and flow structure of a hot annular impinging jet

Infrared thermography and PIV have been used to investigate the flow and heat transfer of quasi-annular jets. The principal parameter studied is the blockage ratio corresponding to the ratio of the inner diameter over the outer Dint/D. The mass flow rate has been taken constant between the different configurations for comparison purpose and a circular jet have also been studied for reference purpose. Results show that the presence of inner diameter create inner shear layer structures that are bring below the jet main flow causing an increase in heat transfer rate. Moreover, higher blockage ratio also increase the ambient air entrainment into the jet before impingement. Finally, taking into account both heat transfer rate and pressure drop, an optimum blockage ratio has been determined.