Electronics Cooling Designs: EFA

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Thermal Management keeps the heat off

Fluid ExceloratorFor the two previous blogs we have been looking at devices of thermal management and electronics cooling systems.  The first discussion in the series was on Heat Pipes, a fairly common cooling source for many electronics, followed by Heat Sinks, an equally common device. Last week we looked at a more unique cooling device known as the Peltier Cooling Plate. With the size of microelectronic parts decreasing and their thermal output increasing, the need for a greater thermal exchange surface has arisen.  This week examines another unique device known as Electrostatic Fluid Accelerator (EFA), a device that works without any moving parts whatsoever.

How an Electronic Fluid Accelerator Works

Instead of using fan blades to move air or another fluid, an EFA pumps fluids using an electric field to propel electrically charged air molecules.  There are three basic steps in an EFA; the first is ionizing the air molecules. Because air is normally neutrally charged, the EFA must first make them ions in order to manipulate them. Second, the EFA uses the ions like a wall to push neutral molecules in a desired direction. Lastly it recaptures and neutralizes the ions to create a net charge of zero. This process is repeated over and over to create a cooling air flow. One of the general flaws in an EFA is that energy is wasted due to the slight raise in temperature of the air and electrodes as they move and battle the molecules traveling in unwanted directions. The large advantage however to EFAs are that they produce no vibration and have no parts to wear out and their power consumption and airflow are controlled electronically allowing them to be run in an optimal fashion to maximize cooling and efficiency.

Small Variety of Uses for an Electronic Fluid Accelerator

While the full range of uses for the EFA are still being discovered due to its relatively new technology, they are currently used in a small variety of systems. Due to the size of the EFA device, it limits the amount of airflow that can be generated, so the uses for this type of cooling are still limited. The most common use for this technology is to be placed directly on top of a microprocessor where it would produce downward air flow onto the heated upper surface of the unit.  A potential implementation of EFA is to integrate it with a microprocessor to make one unit that will cool as it operates.

Engineering Thermal Management for tomorrow

Licensed engineers in many of the different disciplines are looking for ways to make this integration a reality. By utilizing Computer aided design (CAD), as well as Computational fluid dynamics (CFD), engineers can test and analyze different methods and designs for using this technology. The next step that many electrical engineers are working to implement in Electronic Fluid Accelerators would be to fabricate electrodes and airflow surfaces down to the micron scale, thus lowering manufacturing costs and increasing efficiency.  Another would be to generate higher velocity airflow by generating more ions and a higher density of ions, however the maximum voltage which can be applied to the electrodes is limited to the breakdown strength of air, thus resulting in a spark.  Lastly the goal, as with any process, is to maximize the efficiency of the fluid flow. As noted above, CAD and CFD can be used to tune the fluid flow and create additional accelerating electrodes which would then increase the charged fluid and in turn increase efficiency. However this concept requires much more testing and development.  Another prototype idea in the works is to create a device for widespread commercial use, but first the operating life would need to be determined before that step can be taken.

So as you can see, there is more going on inside that electronic device than you would think. As devices get smaller as well as faster, the heat generated is also increasing. We have discussed a few of the thermal management methods for electronics cooling that are being used today as well as being developed for tomorrow.



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