Jet impingement characteristics from a pulsed radial jet reattachment nozzle

Jets of fluid have been used to cool, heat or dry a surface in many industries including high temperature gas turbines, paper and glass manufacturing plants and electronic components. A Pulsed Radial Jet Reattachment (PRJR) nozzle using a sinusoidal mechanical pulsation of the nozzle to vary the exit velocity has been investigated to determine the flow field, especially near the impingement surface, as a function of nozzle geometry and flow conditions. The present study shows the effects of fluid and geometric parameters on PRJR nozzles. Numerical simulations of air exiting both PRJR and RJR nozzles are presented as a function of the pulsation rate (0, 5, 10, and 20 Hz), nondimensional nozzle-to-plate spacing (H/Rb between 0.571 and 0.875), amplitude ratio, exit angle (θ = 0, 10, 20°), and Reynolds number (2000, 4000, and 6000). The two-dimensional Navier-Stokes equations and a standard k-∈ turbulence model was used to simulate the time varying turbulent flow field of air exiting both nozzles and impinging on a flat plate. The flow field dependence upon the nozzle parameters can then be used to choose parameters that may optimize the heat transferred to the fluid.