An investigation into momentum and temperature fields of a meso-scale synthetic jet

Abstract

Thermal management has become a critical part of advanced micro and nano electronics systems due to high heat transfer rates. More constraints such as compactness, small footprint area, lightweight, high reliability, easy-access and low cost are exposed to thermal engineers. Advanced electronic systems such as laptops, tablets, smart phones and slim TV systems carry those challenging thermal needs. For these devices, smaller thermal real estates with higher heat fluxes than ever have created issues that current thermal technologies cannot meet those needs easily. Therefore, innovative cooling techniques are necessary to fulfill these aggressive thermal demands. Synthetic jets have been studied as a promising technology to satisfy the thermal needs of such tight electronics devices. The effect of nozzle-to-surface distance for a synthetic jet on its cooling performance has neither been studied extensively nor been well-understood. In a few available experimental studies, it was reported that synthetic jet performance is very sensitive to this distance and when the jet gets closer to the hot surface its performance degrades. Therefore, a computational study has been performed to understand the flow physics of a small-scale synthetic jet for a jet-to-surface spacing of H/Dh=5. Spatial discretization is implemented via a second order upwind scheme and a second order implicit scheme is used for temporal discretization to ensure stability. It is found that pulsating flow at the nozzle exit generates vortices and these vortices seem to have minimal effect on the target surface profiles. Local surface pressure, velocity, turbulence profiles and heat transfer coefficient distributions are determined, then the effects of jet frequency as well as near-wall vortices are discussed.