Proper cavity shape can mitigate confinement effect in synthetic jet impingement cooling

Abstract

Experimental study was conducted to investigate the effect of orifice cavity shape on resonance frequency and heat transfer characteristics of synthetic jets. The main purpose of the study is to characterise the effect of orifice cavity shapes at small jet-to-surface spacings. The velocity measurement results show that the resonance frequency is a weak function of cavity volume as the resonance frequency remains same for all the cavity shapes considered in the present study. It is noticed that approximately the same pressure is generated inside different orifice cavities at a given radial location of the orifice cavity. The results of heat transfer experiments reveal that the orifice cavity confinement plays a major role at smaller jet-to-surface spacings. The heat transfer enhancement at lower jet-to-surface spacings for orifice cavity with least confinement is three times higher as compared with that of orifice cavity with maximum confinement. At higher jet-to-surface spacings, the confinement effect is negligible and maximum heat transfer enhancement is obtained for all the orifice cavities irrespective of their shape. The application of optimum orifice cavity shape can overcome the limitation of degradation of performance of synthetic jet at lower jet-to-surface spacings.