Acoustics and heat transfer characteristics of piezoelectric driven central orifice synthetic jet actuators

Abstract

Growth in computational capacity combined with a decrease in the size of digital devices has led to increasing demand for more active and efficient cooling of electronics. In this study, an experimental investigation into two different sizes of central orifice Synthetic Jet Actuators (SJAs) is conducted to evaluate their heat transfer as well as noise generation characteristics. Two SJAs (40 mm and 20 mm) are examined, covering a distinct span of frequencies ranging from low to medium (<5500 Hz) in regards to the effect of SJA size over performance. The SJAs’ disk deflection, structural frequency, and jet exit velocity were measured to fully characterize the jet performance. The maximum Nusselt number for the largest SJA was 3 times more than the smallest SJA, where the evaluation of stroke length suggests no effective synthetic jet formation for the smallest SJA. The noise from the SJAs was measured in an anechoic chamber using three microphones, Fast Fourier Transform (FFT) of the sound pressure levels provide contributions to different tones in the resulting noise. 1/3 Octave Constant Percentage Bandwidth (CPB) analysis was performed to identify the frequency bands making the largest contribution to the noise. The largest SJA showed the highest heat transfer at acceptable noise levels during the operation below resonance frequency.