Two new techniques promise significantly greater cooling capacity for electronic equipment while taking up less space and using a lot less power. The Georgia Institute of Technology, School of Mechanical Engineering, developed the technologies and licensed them to Innovative Fluidics of Atlanta.
Synthetic jet ejector arrays (SynJets) cool two to three times as much as fans and use two-thirds less energy, according to professor Ari Glezer and research engineer Raghav Mahalingam at the Atlanta-based school.
A SynJet employs a diaphragm mounted in a cavity with one or more orifices (see the figure). Electromagnetic or piezoelectric drivers vibrate the diaphragm at 100 to 200 times a second, sucking air into the cavity and expelling it. The rapid cycling of air into and out of the module creates pulsating cooling jets that can be directed to precise locations.
Although the jets move 70% less air than comparably sized fans, the air flow's tiny vortices make the flow turbulent, encouraging efficient mixing with ambient air and breaking up thermal boundary layers. These layers, which form on the fins of heatsinks, hurt the performance of fan-based systems. Other advantages include more precise direction of the air flow and the lack of friction parts to wear out. "You get a much higher heat transfer coefficient with synthetic jets," said Mahalingam.
The second cooling technique, vibration-induced droplet atomization (VIDA), targets systems needing higher cooling levels. VIDA uses atomized liquids, like water, to carry heat away from components. High-frequency vibrations produced by piezoelectric actuators create sprays of tiny droplets inside a closed cell attached to the component to be cooled. The droplets form a thin film on the heated surface, letting evaporation remove thermal energy.
The heated vapor then condenses, either on the exterior walls of the cooling cell or on tubes carrying the liquid coolant through the cell. The liquid is then pumped back to the vibrating diaphragm for reuse.
Fluidics has produced several prototype SynJets and expects commercial products to be available within 15 months. The VIDA technology will take longer to commercialize.
The Defense Advanced Research Projects Agency, the U.S. Navy, and the National Science Foundation supported research leading to these technologies, assisted by companies like Intel. The Georgia Research Alliance and Georgia Tech's VentureLab program are supporting commercialization.
Georgia Institute Of Technologywww.gatech.edu
