Ionic Winds for Enhanced Cooling in Portable Platforms

While cooling of the microchip continues to receive significant interest in most electronic devices, portable platforms such as notebooks, multi-use cellular phones, and ultra-mobile personal computers (PCs) present unique thermal management challenges as well. Cooling non-processor components such as wireless devices and the skin of the device are becoming the important thermal management drivers, and volume and power constraints are limiting the practicality of including larger or additional conventional fans. Ionic wind engines are devices which generate air flow with no moving parts, and feature low power consumption and a small volumetric footprint. An ionic wind is produced when positive air ions are accelerated in a particular direction by an electric field, and exchange momentum with neutral air molecules, thus generating a body force on the air. In the presence of an existing bulk flow, an ionic wind distorts the boundary layer and increases the local cooling effect at a heated wall. A free-standing ionic wind engine with an electrode gap of approximately 1 mm has been constructed. Experiments show that the ionic wind engine can enhance the local heat transfer coefficient of a low-speed flow by as much as 50%. The impact of the ionic wind is shown to increase with current and decrease as the bulk flow increases.