Influence of jet temperature and nozzle shape on the heat transfer distribution between a smooth plate and impinging air jets

Experiments are performed to study the effects of nozzle shape, jet temperature and nozzle to distance (z/de) on heat transfer distribution due to impingement of air jet on a smooth flat plate. Thin metal foil technique is employed in this study for measuring local wall temperature. Influence of jet temperature (70-175 °C) on local heat transfer and effectiveness is studied for different Reynolds numbers (5000-23,000) and jet to plate distances (1-10) for circular jets. Influence of nozzle shape (circular, square and triangular) on local heat transfer distribution and effectiveness is studied for Reynolds number of 10,000 and 23,000 at different jet to plate distances. Reynolds number is calculated on the basis of equivalent diameter (10 mm). Nusselt number measured based on equivalent diameter is the highest for a circular nozzle in comparison with square and triangular nozzles. The effect of jet temperature on heat transfer is found marginal and axis switching is observed for non-circular jets. The axis switching for triangular and square nozzles mechanism is governed by ωx dynamics.