Flow structure and cooling behavior of air impingement on a target plate

Abstract An experimental data of flow field, pressure coefficient and heat transfer of a jet impinging normally on a flat target plate are presented. The measurements of temperatures and static pressures were carried out for flow from three orifices of 5, 10 and 20 mm diameter for orifice-to-target plate distances of 5, 10, 25, 50, 70, 100 and 120 mm from the orifice exit. The axial development of flow structure of the jet from the orifice was investigated by measuring the radial jet velocity distributions at the same axial distances used to measure heat transfer and static pressure. The results show that pressure coefficients distributions on the target plate are similar to the velocity distributions in the impinging jet which indicates the strong relationship between the two parameters. The pressure coefficients from large orifice diameter are higher than the values from the small orifice diameter for same orifice-to-target plate distance. The results also show a nonlinear increase of heat transfer rate with orifice size and the ratio of axial distance to orifice diameter (X/d). The nonlinear behaviour may be attributed to the complex nature of flow structure at the stagnation region. The high velocity gradients at the stagnation zone leads to higher turbulence and comparatively higher values of heat transfer rates for large orifice diameter.