An investigation into flow and heat transfer for a slot impinging synthetic jet

According to the latest trends in miniature consumer and military electronics, there is a need for compact cooling solutions to meet performance requirements at compact volumes. Successful technology must feature a thin profile and a small footprint area, while still removing a significant amount of heat dissipation. Impinging synthetic jets driven by a piezoelectric membrane are a promising method for cooling small-scale electronics. In this paper, we explore the thermal response of a miniature synthetic jet impinging upon a vertical heater. In addition, we study the local flow field using the particle image velocimetry (PIV) technique to couple heat transfer with fluid dynamics. Heat transfer results show that the maximum cooling performance occurs with a jet-to-surface spacing of 5 ⩽ H/Dh ⩽ 10, which is associated with the flow consisting of coherent vortex structures. There is a degradation of heat transfer for closer jet-to-surface spacings, such as H/Dh = 2. This was due to the incomplete growth of the vortices, along with re-entrainment of warm air from the impinging plate back into the jet flow. There was also some warm air sucked back into the jet during the suction phase of the synthetic jet. For a fixed value of Reynolds number, cooling was improved at high Stokes numbers, but with a reduced coefficient of performance.