Coupled Acoustic and Heat Transfer Modeling of a Synthetic Jet

Abstract

Synthetic jets based on acoustic resonators have recently been applied to the active cooling of small, heat generating components such as microelectronics. The synthetic jets considered in this study are constructed using two piezoelectric bimorph disks separated by a donut shaped elastomeric wall with a small orifice in the wall. The piezo disks are energized to actuate out of phase at high frequency to alternately entrain and expel surrounding air. The resulting pulsating jet of air enhances local heat transfer by a factor of at least 3X, and exceeds 8x for small surfaces, compared to natural convection. These synthetic jets also create substantial noise at certain operating conditions that may be objectionable for some applications. This paper develops an analytical model that captures the coupled structural dynamic, acoustic and heat transfer physics, but is also simple enough to investigate the underlying physical behavior of the parameters that govern the jet’s performance and run many trade-o studies. Detailed comparison with experimental results is also discussed. Despite issues with the comparison of some parameters impacting jet performance, such as disk velocity and exit velocity, the predicted sound intensity and heat transfer coecient agree well with experimental test data.