Heat transfer of a sweeping jet impinging at narrow spacings

Sweeping jet, featuring with temporally continuous and spatially oscillating flow, has attracted a large amount of attention. In the present study, the heat transfer and flow characteristics of a sweeping jet impinging at narrow spacings were investigated. Effects of Reynolds number (i.e., Re = 5000, 10,000, 15,000) and jet-to-wall spacing (i.e., H/D = 0.5, 1.0, 2.0, 3.0) on heat transfer were quantified extensively by using the TSP technique. A high resolution Particle Image Velocimetry (PW) system was applied to correlate the heat transfer results with the flow fields pertinent to jet impingements. The heat transfer of sweeping jet was found to increase as the Reynolds number increased and as the jet-to-wall spacings decreased. At Re = 5000 and 10,000, compared to the circular jet, the sweeping jet demonstrated a lower heat transfer in the near-nozzle regions (i.e., x/D < 4) but slightly higher performance in the far regions. At Re = 15,000, however, it exhibited an improved performance across the domain at H/D = 0.5 and 1.0, with a maximum of 40% enhancement around the stagnation region. In general, the sweeping jet could provide superior performance to the circular jet at high Reynolds number and narrow spacing.