Electronics Protection - November/December 2013 - (Page 14)

Feature Silent Air Cooling: A New Approach to Thermal Management Alexandra Foley, Technical Writer COMSOL, Inc. continuous stream of laminar airflow. It involves the application of For reading books on the train, debates at the dinner table and a voltage between two electrodes, generating a very high electric browsing in bed, thin and light tablets have become an essential field near one of them that creates positively charged nitrogen tool for entertainment, ions. The ions created are clarification and communicapushed towards the second tion. Serious data handling, electrode generating a conhowever, calls for the power stant pressure source (see of a bigger device and when Figure 1). tablet users, accustomed Because the electric to silent running, turn on a field does not change with notebook, or an even thintime there are no pressure ner Ultrabook, the first thing waves, so there is virtually they notice is noise. no sound. In addition to A fundamental requirebeing noise-free, Silent Air ment for optimal perforCooling (SAC) fits in a very mance, removing heat from thin cavity, 4 mm and below, electronic devices is an unsince it doesn't need rotatavoidable necessity and for ing fan blades and doesn't Figure 1. Working principle of Silent Air Cooling. portable computers this has, need an air plenum above up to now, been achieved by or below it. a small mechanical fan. The trend toward 'thin' Ultrabooks means "Simulation has been at the core of our product development that a typical fan unit is now squeezed into a height of less than because the team needed to take in account electrostatics, charge 10 mm. With a couple of millimeters allowance top and bottom generation and transport, fluid dynamics and heat transfer (see for air gaps and casing, the actual fan blade measures only a few Figure 2). We are in a niche field and there was no dedicated simmillimeters and that is pushing the limit of effectiveness. Although ulation software for this when we started, so we looked at several some of the latest fans can operate in cavities of less than 5 mm, offers," said Jewell-Larsen. "We even considered a custom-made performance is markedly diminished because smaller blades software at one point. We then began using COMSOL Multiphysics move less air with each revolution and thus have to turn faster, because of its in-built flexibility." creating even more noise. The truth is that engineers have nearly exhausted the potential for improving fan technology just as the consumer threshold for noise tolerance has fallen even further. As a University of Washington student in 2001, Nels JewellLarsen recognized the need for research in this area and began a development program. Developing a silent replacement for rotary Figure 2. Multiphysics plot of a two stage Silent Air Cooling air mover. fans has been the core of his work since then. For the past five Space charge density as a surface map (red color indicates higher space years he has been Senior Program Manager heading up a specialist charge density) with space charge flux lines shown by white lines. Air velocity displayed as arrows, with arrow length linearly scaled to velocity. development effort within Tessera Technologies, Inc. where Ken Honer is the division lead. "We've put together the best team in the world," said JewellGustavo Joseph, Head Thermal Engineer, expands on this. "Many Larsen. "We called on experts in areas such as material science, software packages can easily simulate the movement of fluid or mechanical and electrical design, thermal management and high electrostatic forcvolume manufacturing. We have been able to turn my original es independently. idea into a real-life product that is leaps and bounds beyond the What is very diffiearly university lab prototypes where it started." cult to simulate is As a result, Tessera Technologies launched a technology based the generation of on this technology called Tessera Silent Air Cooling. ions, their transport in an electric field and the force Rotating Blades Not Required generated on air "Probably the first thing to note is that Silent Air Cooling is molecules resultFigure 3. Silent Air Cooling unit not a fan, since it does not use a rotating blade to move air," said ing in the needed Jewell-Larsen. "It uses an electric field and charged air to create cooling flow. airflow, a totally different concept. Electronics cooling has never COMSOL Multiphysics is the only commercial off-the-shelf (COTS) been done this way before." available software that would allow us to build all our own equaThe technology relies on an electric field that charges and tions and couple them into the already available fluid dynamics pushes nitrogen molecules in ambient air; these collide with other and electrostatics capabilities." molecules in the air, transferring momentum and producing a 14 November/December 2013 www.ElectronicsProtectionMagazine.com http://www.ElectronicsProtectionMagazine.com

Table of Contents for the Digital Edition of Electronics Protection - November/December 2013

New Features Make F-Series TeraFrame Gen 3 One of CPI’s Most Advanced Cabinets
Silicones for High Reliability and Yield in Electronic Applications
Surge and Transient Protection for Telephone, CATV & Satellite Services
Thermal Management of LEDs: Looking Beyond Thermal Conductivity Values
Understanding NEMA Ratings for Electrical Enclosures
Silent Air Cooling: A New Approach to Thermal Management
VadaTech Releases Rugged Conduction-Cooled MicroTCA Ecosystem
Directable Inverted Blowers Deliver High Volume Air Flow
Cima NanoTech Launches Ultra Low Resistance Sante EMI Shielding Film
Littelfuse Introduces Surge-Tolerant Fuses
ProTek Devices’ TVS Array Provides Circuit Protection in Computing Applications
Reell’s PolyTorq Technology Expands Capabilities For Hinge and Torque Insert Applications
Industry News

Electronics Protection - November/December 2013