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Thermal Management Enabling Enhanced


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  • 1. ◆ Thermal Management: Enabling Enhanced Functionality and Reduced Carbon Footprint Domhnaill Hernon, Todd Salamon, Roger Kempers, Shankar Krishnan, Alan Lyons, Marc Hodes, Paul Kolodner, John Mullins, and Liam McGarry Communications equipment providers are increasingly being required to meet two often-conflicting targets in the design of their hardware, namely, enhanced product functionality and reduced carbon footprint. Development of enhanced thermal management technologies has the potential to positively impact both functionality, by enabling higher processing density on circuit boards, and carbon footprint, by reducing the energy needed to maintain component operating temperatures within their prescribed limits. In this paper we present an overview of the thermal management challenges facing the communications industry today. We then highlight several technologies being developed at Bell Labs that address these challenges, including novel heat sink designs for enhancing heat transfer to air; liquid cooling solutions that enable operation of extremely high heat density cabinets and simultaneously reduce or eliminate the need for room-based air conditioning systems; thermal interface materials with reduced thermal resistance that allow components to operate at lower temperatures; vortex generators that enhance local heat transfer; and thermoelectric module assemblies that enable waste-heat recovery. © 2009 Alcatel-Lucent. Introduction Telecommunication equipment providers face information and communications technology (ICT) considerable thermal challenges with the introduc- industry that face thermal challenges [1]. Note that tion of each new generation of equipment. In recent the filled circles correspond to representative Alcatel- years, thermal management has become one of the Lucent products and are in line with trends for high- main limiting factors in the design of a new system. density communication products. High-density This is mainly due to the ever-increasing demand for communications equipment in telecommunications more functionality, which inevitably results in central offices is subject to standards such as the increased packaging density and complexity and ther- Network Equipment Building System (NEBS) in mal (power) densities. Figure 1 illustrates the power North America and European Telecommunication dissipation trends per unit product footprint as a func- Standards Institute (ETSI) that, for example, place tion of time for different market segments in the limits on acoustic noise emissions and require Bell Labs Technical Journal 14(3), 7–20 (2009) © 2009 Alcatel-Lucent. Published by Wiley Periodicals, Inc. Published online in Wiley InterScience ( • DOI: 10.1002/bltj.20385
  • 2. 15 year reliability, which make designing thermal management solutions challenging [10]. Extreme Panel 1. Abbreviations, Acronyms, and Terms density equipment and computer server equipment 3D—Three-dimensional have higher thermal densities as per Figure 1; how- CO—Central office ever, they have less stringent acoustic noise limits [9] CRAC—Computer room air conditioning ETSI—European Telecommunication Standards and reliability specifications (5 to 10 years). Institute Energy costs and the potential for regulations ICT—Information and communications mandating carbon emission reductions are driving technology telecom service providers to seek new approaches for NEBS—Network Equipment-Building System reducing their energy usage. For example, the U.K. R—Resistance Climate Change Act seeks to reduce carbon dioxide TEM—Thermoelectric module TIM—Thermal interface material emissions by at least 26 percent by 2020 and 80 per- VG—Vortex generator cent by 2050 relative to a 1990 baseline [8]. In the context of the telecommunications industry, global energy usage was 552 TWh in 2007 and accounted for 303 MtonsCO2e (equivalent to 63 1 gigawatt power ment components [3]; therefore, innovative thermal plants or €48.5B in electricity costs) and is expected to management solutions can play a substantial role in increase at a 5 percent compounded annual growth achieving energy and carbon emission reductions rate under current business-as-usual conditions [4]. in telecom. However, developing such cost-effective, Up to 50 percent of the total energy budget for a data reliable, and energy-efficient approaches to thermal center or central office can be for thermal manage- management remains a technical challenge. 10,000 eme Density 8,000 Communication - Extr 6,000 Blade And Custom Compute Servers - 1U, Heat Load Per Product Footprint 4,000 n - High Density RNC Communicatio er (watts/equipment sq.ft.) Compute Servers - 2U And Great MMAP 2,000 UNITE Storage Servers 1,000 nsity De 800 reme n - Ext Workstations (Standalone) 600 icatio mun Com 400 rs Serve pute Com ers Serv age Tape Storage 200 Stor ) lone nda s (Sta tion ksta 100 Wor age Tape Stor 60 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 2014 Year Of Product Announcement MMAP—Multimedia Access Platform Reprinted with permission from ASHRAE Datacom Equipment Power Trends and Cooling RNC—Radio Network Controller Applications, Provisioning for Future Loads, 2005. Copyright American Society of Heating, UNITE—Multi service optical switch Refrigerating and Air-Conditioning Engineers, Inc., Figure 1. Plot illustrating the power dissipation trends across a number of different industries. 8 Bell Labs Technical Journal DOI: 10.1002/bltj
  • 3. It is clear that enhanced thermal management extend the limits of air cooling above those currently solutions can have a positive impact on the function- possible using conventional techniques. ality and carbon footprint of a product. The following Structured “3D” Heat Sinks for Enhanced Air Cooling sections describe novel technologies that Bell Labs has Parallel-fin heat sinks are ubiquitous in electron- developed to enable future generations of equipment. ics cooling; however, it is known that standard Although this paper is focused on telecom equipment, extruded aluminum parallel-fin heat sinks are it is noted that the technologies are also applicable to approaching their cooling limit for modern high-density electronics cooling in general. telecom equipment. In order to provide adequate cooling, the thermal designer must now employ sig- Extending the Limits of Air-Cooling nificantly more expensive solutions, e.g., copper heat The limits of standard air-cooling technologies sinks with embedded heat pipes in the base for have been reached in the telecom environment. The enhanced spreading. To extend the limits of air-cooling, current method of reducing junction temperatures by the Thermal Management Research Group at Bell attaching a parallel-fin heat sink to the heat generat- Labs has developed new methods to manufacture ing component with a thermal interface material complex “3D” heat sink designs, where “3D” refers (TIM) and then passing air over the heat sink with to the inherently three-dimensional nature of the fans does not provide adequate cooling for the hottest design. components on a circuit pack in the most extreme Using an investment casting approach enables conditions. It is for these reasons that research into complex heat sink designs to be fabricated as one liquid cooling has gained significant interest in the monolithic structure that would not be possible using last decade. In order to delay the introduction of liq- conventional manufacturing techniques. Examples uid cooling into Alcatel-Lucent products (because of are shown in Figure 2. The level of complexity of the reliability and cost considerations) it was decided to 3D heat sinks can be seen in the metal foam heat sink research a number of novel technologies that would in Figure 2a and in the slotted honeycomb heat sink (a) Foam heat sink cast from silver (b) Honeycomb heat sink with slots cast from copper Figure 2. Monolithic heat sink structures. DOI: 10.1002/bltj Bell Labs Technical Journal 9
  • 4. Flow inlet Flow exit Temperature 354 348 343 337 331 325 319 y 314 308 302 z x Heated base Figure 3. Numerical simulation of the temperature distribution between the fins of a fin-foam heat sink. in Figure 2b. The heat transfer of 3D heat sinks is velocity upstream of the heat sink. The results in enhanced by substantially increasing the heat transfer Figure 4 show that, when compared to the parallel-fin surface area and also by manipulating the airflow to heat sink, significant performance gains are obtained enhance mixing. Numerical and analytical studies by employing the 3D heat sink architectures. have been performed to understand the underlying flow physics and heat transfer mechanisms, and Vortex Generators to Enhance Parallel-Fin Heat Transfer detailed experimental investigations have been under- In the thermal design cycle there is a constant taken that demonstrate the advantages of the new compromise between using a low-cost solution that heat sink designs. may not supply adequate thermal margins and using In Figure 3, a plane cut through a fin-foam heat an expensive solution that will work. Considering the sink illustrates the temperature variation downstream constraints that thermal designers face on perfor- of the fine-scale foam ligaments based on numerical mance and cost, we propose novel and inexpensive calculations using FLUENT*. In Figure 4, experimen- heat transfer enhancement solutions that can be tal results compare a standard parallel-fin heat sink to placed upstream of heat generating components or three novel heat sink designs. The comparisons are heat sinks anywhere on a circuit pack. made using the thermal resistance (R) of the heat sink, One solution that has proven useful is to place which is defined as the ratio of the temperature differ- vortex generators (VGs) upstream of the heat sink. ence between the maximum temperature on the base VGs produce unsteady flow, which augments mixing of the heat sink and the (inlet) ambient air to the and thins boundary layers, thereby leading to power input into the heat sink. The velocity is the inlet enhanced heat transfer. Figure 5 demonstrates that a 10 Bell Labs Technical Journal DOI: 10.1002/bltj
  • 5. 4.5 4 Parallel plate Slotted hexagon Fin-foam 3.5 Schwartz R ( C/W) 3 2.5 2 1.5 1 0 1 2 3 4 5 Velocity (m/s) 3D—Three dimensional Figure 4. Experimental results for three different 3D heat sink designs. 3 Heat sink 2.5 VG R ( C/W) Duct 2 Inflow 1.5 1 10 100 Pressure drop (Pa) No VG 10.3 W VG#1 AoA 21.5 L 50 mm VG#2 AoA 21.5 L 50 mm VG#3 AoA 21.5 L 50 mm R—Thermal resistance VG—Vortex generator Figure 5. Results showing a 10 percent reduction in the thermal resistance of a parallel-fin heat sink when a vortex generator is placed upstream. DOI: 10.1002/bltj Bell Labs Technical Journal 11
  • 6. 10 percent reduction in the thermal resistance of a surface roughness at a thermal interface between two parallel-fin heat sink can be achieved by placing vor- devices. tex generators upstream of the heat sink in a fully A state-of-the-art test rig for measuring the ther- ducted arrangement. The inset is a schematic of the mal resistance of TIMs-filled interfaces was designed experimental setup. In Figure 5, the difference in VG and built in order to quantify the performance of types is the percentage of the duct height that these novel TIMs. The measurement sensitivity of the they occupy: VG 1 occupies half of the duct height; TIMs test apparatus was evaluated using self-contact VG 2 occupies three quarters of the duct height; and resistance tests and showed the ability to accurately VG 3 occupies the full duct height [5]. measure very low thermal contact resistances (6e-5 m2K/W) with better than 2 percent uncertainty Micro-Textured Metal Thermal Interface Materials and low input power levels of 10 W. These baseline Another significant bottleneck in product design measurements showed a degree of precision and sen- is the need for thermal interface materials that ther- sitivity heretofore not achieved in previous test setups, mally couple the heat load from a package to the heat and clearly demonstrated the ability of the apparatus sink attached to it, which, in turn, dissipates the to test even the thinnest, most conductive TIMs with heat to the air. Commercially available TIMs have low good confidence [6]. effective thermal conductivities, implying that they Figure 6 illustrates the performance comparison have limited ability to transport heat. The goal of the between commercially available graphite pads and current TIMs research effort is to improve upon exist- novel metallic micro-textured TIMs. Initial testing of ing commercially available TIMs by creating micro- hollow cone arrays (shown in the inset) manufac- textured metal structures that provide multiple, tured by electroplating onto printed wax patterns and continuous, thermally conductive metallic paths that subsequently melting the wax away showed effective plastically deform to accommodate imperfections and thermal conductivities in excess of 4.5 W/(m·K), 6 Effective thermal conductivity (W/mK) 5 4 3 2 1 MMT-TIM Conventional graphite pad 0 0 0.5 1 1.5 2 2.5 3 Pressure (MPa) MMT—Metal micro-textured TIM—Thermal interface material Figure 6. Performance comparison between commercially available graphite pads and novel metallic micro-textured TIMs. 12 Bell Labs Technical Journal DOI: 10.1002/bltj
  • 7. 3.00E-04 2.50E-04 Supplier A - ALU test data 2.00E-04 Supplier B - ALU test data RA (m2K/W) Supplier A - Claimed performance 1.50E-04 1.00E-04 5.00E-05 0.00E+00 0 0.5 1 1.5 2 2.5 3 Pressure (MPa) ALU—Alcatel-Lucent TIM—Thermal interface material Figure 7. Discrepancy between suppliers’ claimed TIM performance and measured performance. which is comparable to best-in-class, commercially This property is beneficial for protecting underlying available TIMs, with greater than 60 percent com- electronic components as it results in additional compli- pression and over 1.5 mm compliance. Microscale ver- ance without increased force. The simulations have also sions of such millimeter-scale structures are in shown that thermal contact between micro-textured progress. The test apparatus has also been used to TIM features, including thermal self contact, can be an evaluate a number of commercially available TIMs important mechanism for increasing the number of and to compare them to manufacturer specifications heat conduction paths through the TIM structure and for thermal performance. Preliminary results, shown thereby substantially reducing its overall thermal in Figure 7, indicate that, depending upon the manu- impedance. facturer, there can be substantial discrepancies (up to 40 percent difference) between the manufacturer- Extreme Thermal Density and Energy-Efficient specified thermal performance and that measured by Cooling Architectures the test apparatus. This capability is immensely valu- Efficient and reliable cooling of central offices and able as it allows an independent evaluation of TIM data centers is one of the key focus areas within the thermal properties. field of thermal management. This is due to the fact Modeling and simulation studies are providing that a significant portion of the energy budget is valuable insight into how feature shape affects expended on cooling equipment. The considerable mechanical and thermal performance. For example, increase in global energy prices since the turn of the certain structures exhibit the property that above a millennium has compounded this problem and ele- critical compression level the force required to fur- vated the importance of novel and scalable thermal ther compress the structure decreases substantially. management solutions. DOI: 10.1002/bltj Bell Labs Technical Journal 13
  • 8. Ceiling Ceiling Liquid cooled electronics Pump Liquid Liquid Liquid-to-liquid supply supply heat exchanger Rack Rack Rack Rack CRAC CRAC Floor tiles Floor tiles Floor tiles Chilled water supply and return Floor slab Floor slab Floor slab From: Dispersing waste heat into To: Transferring waste heat into a liquid central office air coolant and piping outside the CO (a) Current central office and data center (b) Bell Labs novel central office air-cooled architecture liquid-cooling architecture CRAC—Computer room air conditioner CO—Central office Figure 8. Typical telecom central office architecture and Bell Labs novel central office liquid-cooling architecture. Discussed in the following two sections are novel low heat-carrying capacity of air compared to thermal architectures that Bell Labs has developed liquid. to reduce the impact on the environment and also 4. In some cabinet configurations, heated air out- reduce the operating costs for our customers. put from a lower shelf is fed directly into the adja- cent upper shelf, making cooling of shelves Central Office Cooling Architectures farther downstream of the cool air input progres- Figure 8 provides schematics of both a conven- sively more challenging. tional central office (CO) architecture and Bell Labs’ Bell Labs is developing a liquid-cooled architec- novel CO liquid cooling architecture. The typical archi- ture, as illustrated in Figure 8b, wherein the need for tecture of a CO is shown in Figure 8a. In this system, hot and cold aisles and raised floors is removed. The cold air from a computer room air conditioning basic principle behind this architecture is to place (CRAC) unit is ejected into cold aisles situated between finned heat pipes between each shelf within a cabinet, rows of equipment sitting on a raised floor. The cold air as shown in Figure 9. The finned heat pipes are con- is passed through the cabinet, picking up heat from nected to building chilled water on the outside of the the hot components, and is then expelled to a hot cabinet, which provides cooling. The heat pipes have aisle. This architecture has several shortcomings: very high effective thermal conductivities and they 1. Cooling density is limited by the amount of air can therefore efficiently transport heat from the hot that can be circulated within acoustic limits. air inside the cabinet to the building chilled water 2. Due to complex flow patterns, hot air can become supply on the outside. An illustration of this is shown entrained into the cold aisle, thereby reducing in Figure 9a. Advantages of this architecture are cooling capacity. accommodation of extreme thermal densities via 3. Moving large quantities of air within the CO liquid cooling and improved energy efficiency by and CRAC unit is very expensive due to the bringing coolant directly to the cabinet and eliminating 14 Bell Labs Technical Journal DOI: 10.1002/bltj
  • 9. Water Fins Heat pipe Outside Inside cabinet cabinet Hot air from upstream electronics components (a) Schematic of the internal structure of (b) New large-scale heated wind tunnel the finned heat pipe assembly used to validate the efficacy of the finned heat pipe design Figure 9. Finned heat pipe architecture. room-level CRAC units. Another advantage is that shown a 30ºC heat-sink temperature drop at 20 W the heat pipes ensure almost constant inlet air tem- power input and velocity of 2 m/s [7]. This corre- perature at each shelf, thereby ensuring greater relia- sponds to a 56 percent decrease in the thermal resis- bility of downstream components. In order to tance of the fluid-cooled heat sink assembly when accurately validate the performance of this new cool- compared to the same heat sink cooled using ing architecture, a large-scale heated wind tunnel only air [7]. facility (see Figure 9b) was manufactured. Energy Harvesting Using Thermoelectric Module Enhanced Air-Cooling Using Mist and Vapor Chamber Solutions Air is limited in its heat-carrying capacity. It is Immense quantities of heat are generated in cen- well known that liquids have a much higher heat- tral offices and data centers, with typical magnitudes carrying capacity when compared to gases owing to of the order of hundreds of kW. However, energy the fact that liquids have significantly larger specific from this waste heat is not used. One solution to this heat (two to three orders of magnitude larger on a problem is to harvest or scavenge waste heat from the volumetric basis) and have the ability to undergo equipment via thermoelectric modules (TEMs) that a phase change, e.g., evaporate. However, introducing convert heat directly to electricity via the thermo- liquid near electronics poses serious reliability issues. electric effect. Our solution is to introduce dielectric liquid This research program will improve the perfor- droplets into the airflow within our cabinets (shown mance of standard TEMs by the following two methods: schematically in Figure 10 and detailed in [2]). Using 1) by using non-silicon-based power amplifiers (such this approach, we have calculated an enhancement as gallium nitride) that operate at much higher tem- of 7X more heat dissipation with a possible reduction peratures and that significantly increase the thermo- in energy consumption. Initial experiments have dynamic efficiency of a TEM operating in generation DOI: 10.1002/bltj Bell Labs Technical Journal 15
  • 10. Mist from collectors Pumped to atomizer Mist condenses on heat pipes and falls by gravity into collector Pump Hot components Atomizer Large droplets of mist from atomizer directed into circuit packs Figure 10. Schematic illustrating the mist cooling solution. mode and 2) by coupling the TEMs to very effective and at low cost thus pose severe challenges to the ther- heat-spreading devices such as vapor chambers that mal engineer. Bell Labs’ Thermal Management spread the heat over large surface area arrays of TEMs Research Group has developed a suite of novel thermal to further increase efficiency. It is the goal of this management technologies that impact Alcatel-Lucent research project to use this approach to recover upward of 10 percent of the energy used to power our equipment in certain applications. Figure 11 illus- Die Die trates a simplified schematic of the technology. Electricity Hot Vapor chamber generated V Conclusions by TEM It is now clear that thermal management of next- Thermoelectric module generation telecommunications hardware is one of the key limiting factors in realizing increased product functionality. At the same time, environmental con- siderations and associated regulation will likely place Heat sink constraints on carbon emissions, which will have a Cold direct impact on equipment power consumption, owing to the fact that up to 50 percent of the total TEM—Thermoelectric module energy budget for a data center or central office can be for the thermal management component. The goals of Figure 11. achieving significant power reductions while also pro- Illustration of TEM and vapor chamber waste heat viding greater functionality, reduced form factor, recovery system. 16 Bell Labs Technical Journal DOI: 10.1002/bltj
  • 11. equipment from the component to the central office Thermal Interface Material Tester,” Proc. 11th level, and use different cooling solutions, such as 3D Intersociety Conf. on Thermal and heat sinks, vortex generators, microtextured metal Thermomechanical Phenomena in Electronic Syst. (ITherm '08) (Orlando, FL, 2008), thermal interface materials, novel liquid-based cooling pp. 221–226. architectures, and energy harvesting solutions that [7] N. Kumari, P. Kolodner, A. M. Lyons, T. R. S. recover waste heat. Enhanced thermal management Salamon, M. S. Hodes, V. Bahadur, and S. V. will enable increased functionality and reduced car- Garimella, “Numerical Analysis of Mist-Cooled bon footprint, and thereby become one of the key High Power Components in Cabinets,” Proc. market differentiators for telecom equipment ASME/Pacific Rim Tech. Conf. and Exhibition on Packaging and Integration of Electronic and providers. Photonic Syst., MEMS, and NEMS (InterPACK Acknowledgements '09) (San Francisco, CA, 2009). The authors would like to acknowledge the con- [8] United Kingdom, Department for Environment, Food and Rural Affairs (DEFRA), “Climate tinued financial support from the Irish Development Change Act 2008,” Chap. 27, 2008, Agency (IDA). The authors also acknowledge the con- tributions from Vaibhav Bahadur and Niru Kumari. echange/uk/legislation . [9] United States Department of Labor, *Trademark Occupational Safety and Health Administration FLUENT is a registered trademark of Ansys, Inc. (OSHA), “Occupational Noise Exposure,” References 1910.95, Standards 29 CFR, 1981. [1] American Society of Heating, Refrigerating and [10] Verizon Laboratories, “Guidelines for Physical Air-Conditioning Engineers, ASHRAE Design: Next Generation Network Equipment,” Handbook—Fundamentals, ASHRAE, Atlanta, SIT.NEBS.TM.NPI.2004.018, Aug. 26, 2004. GA, 2005. [2] V. Bahadur, M. Hodes, A. Lyons, S. Krishnan, and S. V. Garimella, “Enhanced Cooling in a (Manuscript approved May 2009) Sealed Cabinet Using an Evaporating- Condensing Dielectric Mist,” Proc. 11th Inter- DOMHNAILL HERNON is a member of technical staff in society Conf. on Thermal and Thermomechani- the Thermal Management Research Group cal Phenomena in Electronic Syst. (ITherm ‘08) at Alcatel-Lucent Bell Labs in (Orlando, FL, 2008), pp. 1191–1198. Blanchardstown, Ireland. He earned a B.Eng. [3] R. Brown, E. Masanet, B. Nordman, B. Tschudi, in aeronautical engineering and received his A. Shehabi, J. Stanley, J. Koomey, D. Sartor, Ph.D.titled “Experimental Investigation into P. Chan, J. Loper, S. Capana, B. Hedman, the Routes to Bypass Transition,” from the University of R. Duff, E. Haines, D. Sass, and A. Fanara, Limerick. He joined the thermal management research Report to Congress on Server and Data Center group at Bell Labs Ireland in 2006. His current research Energy Efficiency—Public Law 109-431, focus is on projects that extend the current limits of air- Lawrence Berkeley National Laboratory, LBNL- cooling, and additional research interests include high- 363E, Aug. 2007. fidelity measurements in the complex flow field [4] Climate Group, Smart2020: Enabling the Low downstream of vortex generators, and intelligent Carbon Economy in the Information Age, airflow system design. He has authored 12 technical Global eSustainability Initiative (GeSI), 2008, papers and has eight patents pending. . [5] D. Hernon, “Effect of Upstream Vortex TODD SALAMON is a member of technical staff in the Generators on a Longitudinally-Finned Heat Physical Technologies Research Domain at Sink,” Proc. 11th Intersociety Conf. on Thermal Alcatel-Lucent Bell Labs in Murray Hill, New and Thermomechanical Phenomena in Jersey. He holds B.S. degrees in chemistry Electronic Syst. (ITherm ‘08) (Orlando, FL, and chemical engineering from the 2008), pp. 480–488. University of Connecticut, Storrs, and a [6] R. Kempers, P. Kolodner, A. Lyons, and A. J. Ph.D. in chemical engineering from the Massachusetts Robinson, “Development of a High-Accuracy Institute of Technology. Since coming to Bell Labs, DOI: 10.1002/bltj Bell Labs Technical Journal 17
  • 12. he has worked on applying modeling and simulation to the program is to transfer heat more efficiently, gain a more fundamental understanding of enabling higher computing densities while reducing the microfluidics, electronics cooling, transport phenomena amount of energy required. He forged collaborative in optical fiber manufacturing, design of photonic research projects with Irish universities and Bell Labs in crystal fibers, and Raman and erbium amplifier Murray Hill while building relationships with business dynamics and control in optically transparent networks. units across Europe. He is currently a professor at the He has authored over 30 publications and conference College of Staten Island and the Graduate Center at the presentations and holds four U.S. patents. City University of New York (CUNY). He was awarded a NYSTAR Faculty Development Program award, and is ROGER KEMPERS is a member of technical staff at also the co-director of the Center for Engineered Alcatel-Lucent Bell Labs in Blanchardstown, Polymer Materials, a NYSTAR-funded CART program. Ireland. He earned a B.Eng. and an M.A.Sc. Dr. Lyons has published over 30 refereed articles in in mechanical engineering from McMaster journals, books, and encyclopedias and has been University in Hamilton, Ontario, Canada. awarded 17 patents with over 24 patent applications Prior to joining Alcatel-Lucent, he was pending. He was co-leader of the photonics strand employed at McMaster’s Thermal Management and thermal management sub-strand of the Center for Research Laboratory, where his work was focused Telecommunications Value Chain Research (CTVR) a primarily on performance modeling and testing of multi-disciplinary group of Irish university researchers wicked heat pipes and nucleate boiling in capillary from 2005 to 2008, and a member of International structures. He is currently pursuing a Ph.D. in Electronics Manufacturing Initiative (iNEMI), Thermal mechanical engineering at Trinity College Dublin. Management Roadmap Committee. Recent research activities include the development, modeling and characterization of advanced thermal MARC HODES is currently a member of the faculty at interface materials. He has authored 11 peer-reviewed the Tufts University Mechanical Engineering publications and has three patents pending. Department in Boston, Massachusetts. He held a succession of appointments over a SHANKAR KRISHNAN is a staff engineer at Battelle/ 10-year period at Bell Labs in Murray Hill, Pacific Northwest National Laboratory New Jersey, prior to his appointment at (PNNL). He received his Ph.D. and M.S.M.E. Tufts. He holds a Ph.D. in mechanical engineering with from Purdue University, West Lafayette, a chemical engineering minor from the Massachusetts Indiana, and B.E. from the PSG College of Institute of Technology. Current research interests Technology, India. His current research work include reduced power consumption precision is on thermal energy conversion and heat exchange temperature using thermoelectric module-variable technologies. Prior to joining PNNL, he was a conductance heat pipe assemblies, energy scavenging postdoctoral member of technical staff at Alcatel- from waste heat using thermoelectric power Lucent Bell Labs Ireland, where he worked on thermal generators, and the theory and applications of management technologies. He has co-authored over superhydrophobic nanostructured surfaces. 25 technical papers, two book chapters, and seven pending patents. PAUL KOLODNER is a distinguished member of technical staff in the Alcatel-Lucent Bell ALAN LYONS was a distinguished member of technical Labs Microsystems and Nanotechnology staff at Alcatel-Lucent Bell Labs when this Research Department in Murray Hill, New paper was written. Over his 28-year career Jersey. He received the A.B. degree in as a Bell Labs researcher, he developed new physics from Princeton University, and the materials and novel manufacturing A.M. and Ph.D. degrees in physics from Harvard technologies for electronic systems. He University. His Ph.D. work was on suprathermal conducted research into polymer composite materials electron emission produced by laser-induced including precursors to carbon, conductive adhesives, breakdown of fast shockfronts. He has worked at Bell metal-polymer nanocomposites, and materials for high Labs since 1980 on a variety of experimental problems frequency signal transmission. Dr. Lyons was a founding including the use of rare-earth-chelate films for high- member of Bell Labs Ireland, where he initiated the resolution fluorescent thermal imaging, convective thermal management research program. The goal of pattern formation, protein photobiology, precision 18 Bell Labs Technical Journal DOI: 10.1002/bltj
  • 13. microlens array characterization, and applications of superhydrophobic surfaces in drag reduction and thermal management. Dr. Kolodner has written or co-authored approximately 80 published papers and has 27 issued or pending patents. JOHN MULLINS is a support engineer in the Alcatel- Lucent Bell Labs Thermal Management Group in Blanchardstown, Ireland. He holds a B.Mech.Eng. from the National University of Ireland, Galway. Mr. Mullins’s current projects include computer-aided design and computer-aided manufacturing (CAD/CAM) support for 3D heat sinks, wind tunnel testing, and microwave antenna design. LIAM McGARRY is a support engineer in the Alcatel- Lucent Bell Labs Thermal Management Group in Blanchardstown, Ireland. He holds a B.Eng. in electronic and electrical engineering from the Dublin Institute of Technology (DIT), and began his career with a succession of appointments within Lucent Technologies before joining its Bell Labs Research group. Mr. McGarry’s current projects include central office cooling at cabinet level, wind tunnel design and testing, and flow visualization using water tunnels. ◆ DOI: 10.1002/bltj Bell Labs Technical Journal 19