Acoustic and heat transfer aspects of an inclined impinging synthetic jet

• We show that high heat transfer and low noise level can simultaneously be achieved.
• Noise level is acceptable with synthetic jet.
• A local maxima in heat transfer coefficient may occur at 60° inclination.
• The flow is direct impingement (cross flow) at large (small) impingement angle.
• A region is identified where synthetic jet can be placed with <10% compromise in Nu.

Acoustic and heat transfer study was undertaken to study the effect of orifice dimensions and operating parameters on the noise level generated and heat transfer capabilities of synthetic jets. The objective is to choose the orifice diameter and operating frequency such that high velocity and low noise level can simultaneously be achieved. The study was extended to determine the effect of inclination of impinging synthetic jet on the heat transfer from a uniformly heated flat plate. The average heat transfer coefficient was determined as a function of inclination angle of synthetic jet relative to the plate, for jet to surface spacing (z/d) between 3 and 15 with Reynolds number (Re = 5865) and Stokes number (S = 75.45). The maximum heat transfer coefficient occurs for normal impingement (θ = 90°) for all spacings. A non-monotonic reduction in the average heat transfer coefficient is observed as the angle of jet impingent is decreased. It is found that the flow is predominantly direct impingement at large impingement angles (θ > 40°) which changes to cross flow for θ < 40°. The synthetic jets can be used at the optimum angle of impingement and spacing without serious reduction in average heat transfer coefficient. These results are significant for design of cooling solution in space-constrained applications.