Experimental studies on synthetic jet cooling enhancement for portable platforms

As portable platforms including laptops, handheld PCs, and similar handheld electronics become more powerful and more popular, they present unique thermal management challenges. In the past, most thermal management solutions have dealt with directly cooling the microprocessor by way of a heat spreader, heat sink, and fan. However, the microprocessor thermal solution does not cool all areas of the entire platform, and prominent thermal issues arise and must be addressed. For example, maintaining a comfortable skin temperature in portable electronics is a major issue as devices operate at higher powers and with more capabilities. Additionally, the small form factors and limited volume of portable devices make the cooling of the overall platform a significant challenge. Synthetic jets are diaphragm-induced flow devices that can be used to enhance heat transfer in locations otherwise cooled by natural convection or very low-speed forced convection. In this work, the performance of synthetic jets operating perpendicular (i.e., in cross-flow) to a low speed duct flow is investigated. The nature of the jet and bulk flow interaction is studied using particle image velocimetry (PIV) and thermal measurements are taken on a heated duct wall. Synthetic jets are shown to slow down the bulk flow by entraining mass into the flow and creating "dead zones" where the bulk flow is blocked. The heat transfer studies indicate that cooling can be increased in the main body of the synthetic jet stream by as much as 25% but that the jet creates an impediment to the bulk flow which results in other areas of localized heating.