Electronics Cooling

Electronics Cooling December 2012

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Featured Evaluation & Opportunities For Use of Thin Form Factor Synthetic Jets to Low Profile Electronics Cooling Applications Peter de Bock, Andrew Mann, Bryan Whalen, GE Global Research M INTRODUCTION ODERN PORTABLE consumer electronics devices such as ultrabooks, tablets and smartphones are easily recognized for the incredible functionality they offer in very compact packages. Due to advances in semiconductor miniaturization and the development of dual and quad-core architectures, current and next-generation portable devices boost computational and graphics performance capabilities that can outpace former generations desktop computers. Besides logic chips, these platforms can also host an array of other technologies such as storage systems, advanced batteries, touch-screen input and backlight systems. As this rapidly changing landscape of portable devices evolves, a common challenge becomes apparent: How to manage the heat rejection from thin consumer electronics with increasingly higher power dissipation requirements in thin profi le devices. Where ultrabooks are commonly vented, tablets and smartphones predominantly rely on passive heat dissipation mechanisms. Recent evaluation of next generation tablets found that when devices are in full-use, their case temperature can become quite hot, Peter de Bock is a lead thermal systems engineer at GE Global Research in Niskayuna, N.Y. He has more than 10 years experience in developing innovative thermal management solutions for electrical machines and electronics. He holds an MSME degree from Twente Technical University. His past experience includes CFD tool development, electrical machine cooling, thermoelectric system design and heat pipe/vapor chamber design and validation. His current work is focused on developing and characterization of next generation Dual Cool Jet air movers for electronics cooling. de Bock is a member of K-16 committee on Heat Transfer in Electronic Equipment and an active ASME and IEEE reviewer. Andrew Mann is an intern at GE GRC and will be returning to Stony Brook University to complete his M.S. in mechanical engineering. His work in GRC's Electronic Cooling lab includes convection and conduction heat transfer analysis and experimentation. At Stony Brook, Mann will work on laser heat transfer and material removal. Bryan Whalen received his AAS in Industrial Engineering Technology from HVCC in Troy, N.Y. in 1989. He has worked in various mechanical and electrical design and test engineering positions for the past 20 years with such companies as Lockheed Martin, General Dynamics, Plug Power, and with GE Global Research since 2008. He has been cited in several technical publications for his work on piezo synthetic jets and is also a co-inventor on numerous US Patents. Currently he is involved in research and commercialization activities of GE's Dual Cool Jet devices for novel electronics cooling solutions. 28 Electronics COOLING | December 2012 reaching operator handling limits [1]. As next generation tablets with more powerful processors are under evaluation for advanced operating systems [2], thermal management is likely to become critical enough for even air cooling vents to find their introduction into select high power tablets [3]. Significant manufacturing and aerodynamic challenges exist in reducing the dimensions of rotating air mover system components such as bearings or bushings to the sub 4 mm dimension required for modern device implementation[4]. This reflects the disparate trends in the two technology areas, whereby the electrical components have proven far more conducive to miniaturization than their mechanical counterparts. This drives a need for novel miniaturized air mover technologies that can provide air movement using different mechanisms to break this barrier. Technologies such as Ionic Wind [5,6] and Synthetic Jets [7,8] are therefore of interest to solve some of these challenges, each providing their own opportunities and challenges. This article will focus on the evaluation of Synthetic Jets. SYNTHETIC JETS Gutmark et al. [9] pioneered the use of micro fluidic devices for heat transfer for both natural and forced convection. These micro-fluidic devices were found to significantly perturb the thin boundary layer that naturally envelops a heated surface, hence significantly improving heat transfer. Gutmark found heat transfer coefficient enhancement over natural convection of up to

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