Experimental investigation of heat transfer characteristics and wall pressure distribution of swirling coaxial confined impinging air jets

In the present study, swirling coaxial confined impinging turbulent air jets issuing from a novel designed nozzle is studied experimentally. Heat transfer characteristics and pressure distribution on the impingement plate are analyzed. Experiments have been conducted at different dimensionless nozzle-to-plate distances (H/D = 0.5, 1.0, 1.5, 2.0 and 2.5) and dimensionless flow rates (Q∗ = 0.25, 0.50 and 0.75) for a constant total flowrate of 1.33 × 10−3 m3 s−1 (80 L/min). The results show that the flowrate ratio improves the uniformity of the heat transfer through the impingement surface and increases the average Nusselt number. Also, the intensity of convective heat transfer is shown to enhance significantly with decreasing nozzle-to-plate distance. With regards to the pressure distribution, subatmospheric regions occur on the impingement plate. Contribution of swirl is also compared against the pure circular impingement jet condition (Q∗ = 0.0).