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., www.ashrae.org.
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- http://www.defra.gov.uk/environment/climat
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.
http://www.smart2020.org .
[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