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Contact 1 Contact SWCNT T T 1 T 2 x CISCO Research Symposium August 29-30, 2006 Thermal Engineering Research Motivated by Cooling of Electronic Systems: A National Science Foundation Perspective Alfonso Ortega al.ortega@villanova.edu Former Program Director

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slide1

Contact 1

Contact

SWCNT

T

T1

T2

x

CISCO Research Symposium August 29-30, 2006

Thermal Engineering Research Motivated by Cooling of Electronic Systems:A National Science Foundation Perspective

Alfonso Ortega

al.ortega@villanova.edu

Former Program Director

Thermal Transport and Thermal Processing Program

Coordinator—Active Nanostructures and Nanosystems

The National Science Foundation

technology drivers for research in thermal transport
Technology Drivers for Research in Thermal Transport

Nuclear and conventional steam power generation has driven research in multi-phase flow and transport for 50 years

Terrestrial and aerospace propulsion has provided the technology driver for convective transport research for 60 years

Electronics thermal management is the single most important contemporary technology driver for thermal transport research

power w and heat flux w cm 2 challenges cannot be overstated
Power (W) and heat flux (W/cm2) challenges cannot be overstated

Box, Rack, and Room Level Thermal Management Issues may be just as dominant but are not driving fundamental thermal sciences research

thermal transport research the big picture at nsf
Thermal Transport Research: The Big Picture at NSF
  • Transformative ideas may come from engineered nano-materials and structures (active and passive)
  • High heat flux naturally leads to use of single and two-phase liquids in close proximity to heat source
  • Innovation in materials and manufacturing may transform advanced thermal management strategies
thermal transport opportunities in small scale thermal systems

High efficiency highly compact heat exchangers: liquid to gas or liquid to liquid

Small scale low power pumping

Mini / micro-channel heat exchanger; single phase or multiphase

Nanofluid heat exchange

Non-continuum electron/phonon transport in thin films and solid-state devices

Interfacial phenomena transport

Thermoelectric heat pumping

Thermal Transport Opportunities in Small Scale Thermal Systems
slide6

Solid state

Thermoelectric energy conversion

Joule

Heating

Seebeck Coeff.

Electron Cooling

Reverse Heat Leakage Through Heat Conduction

NSF Award 0506830 NIRTIntegrated Study of Thermoelectric Transport and Energy Conversion in Bismuth-Based NanowiresGang Chen et al. (MIT)

The use of thermoelectric energy conversion has been hampered by low efficiencies

The efficiency scales with the following figure of merit:

Rejected Heat

Thigh

Electrical Power Input

Tlow

Device Dissipated Power

The use of nanocomposites shows great promise for greatly improving efficiencies

state of the art in thermoelectrics

PbSeTe/PbTe

Quantum-dot

Superlattices

(Lincoln Lab)

PbTe/PbSeTe

Nano

Bulk

AgPbmSbTe2+m

(Kanatzidis)

S2s (mW/cmK2) 32 28

k (W/mK) 0.6 2.5

ZT (T=300K) 1.6 0.3

Harman et al., Science (2003)

Bi2Te3/Sb2Te3

Superlattices

(RTI)

Bi2Te3/Sb2Te3

Nano

Bulk

S2s (mW/cmK2) 40 50.9

k (W/mK) 0.6 1.45

ZT (T=300K) 2.4 1.0

Skutterudites

(JPL)

Bi2Te3 alloy

Venkatasubramanian et al., Nature, 2002.

PbTe alloy

Si0.8Ge0.2 alloy

Dresselhaus

State-of-the-Art in Thermoelectrics
slide8

NSF NIRT Award Number: 0238888Nanotube based structures for high resolution control of thermal transportCecilia Richards et al., Washington State

Images of patterned vertically aligned carbon nanotube turf

slide9
NSF Award Number: CTS-0245642 The Critical Heat Flux Condition in Micro-ChannelsJensen, M and T. Borca-Tasciuc, RPI; Kandlikar, S. RIT
  • The primary project objective is to develop a better quantitative and qualitative understanding of and prediction capabilities for the CHF condition in single and multiple parallel micro-channels
  • The CHF condition with water and R123 in single metal tubes and single microfabricated channels is being investigated at RPI
  • The local boiling phenomenon in multiple parallel channels with R123 in large monolithic metal blocks is being investigated at RIT

Test-chip designed to investigate two-phase flow and boiling phenomena in microchannels

slide10

NSF Award Number: CTS-0336757Coupling the High Resolution of Laser Measurements and Finite-Element Simulations to Understand Transport Phenomena during Microdroplet Deposition Daniel Attinger *,Jon Longtin **Columbia University*, State University of New York at Stony Brook**

The temperature under a single impinging droplet was measured using a new thermoreflectance technique

The agreement with the finite element simulations was excellent

slide11
NSF Award Number: CTS-0245642 Atomic Detail of an Evaporating MeniscusJon Freund, Univ Illinois Urbana Champagne
  • Micro-fluidic actuation, nucleate boiling, heat pipes, etc.
  • Coupled evaporation kinetics, viscous flow, surface tension, heat conduction, non-local influence of the wall
    • effect of atomic granularity?
    • proposed continuum models [e.g. Ajaev & Homsy, 2001]
  • Studied with MD using simple fluids (for now)
  • Findings
    • Kapitza resistance important at wall-liquid boundary
    • weakly wetting: good agreement with asymptotic model
    • strongly wetting: failure of Newtonian constitutive model
  • Freund, Phys. Fluids (2005)

Shape

Flux

nanofluids in single phase convection p phelan asu
Nanofluids in Single Phase ConvectionP. Phelan, ASU

Enhanced thermal conductivity is greater than what is predicted by conventional theory

k = nanofluid thermal conductivity

kf= thermal conductivity of base fluid

Conventional theory

metal based micro heat exchangers manufactured using liga w meng s ekkad lsu
Metal Based Micro Heat Exchangers Manufactured using LIGAW. Meng, S. Ekkad, LSU

Nickel micro-post fabrication

where are the frontiers 1 tttp looking forward
Where are the frontiers?1TTTP Looking Forward
  • Micro and Nano-scale Engineering will continue to be the dominant driver of modern Thermal Science
    • High heat flux, small scales, convective and nanoscale interfacial phenomena driven by emerging integrated electronics, future nanoelectronics, and bio-interfaces
    • Synthesis, characterization and modeling of nanomaterials and nanostructures and integration into nanosystems; motivates research in nano-manufacturing
  • Rapid transition of ideas, measurements, and modeling to two emerging, transcendant areas:
    • Sustainable energy (Hydrogen, Nano-photovoltaics)
    • Cellular and Molecular engineering

1”Frontiers in Transport Phenomena Research and Education: Energy Systems, Biological Systems, Security, Information Technology, and Nanotechnology” a NSF/ TTTP Funded Workshop, scheduled for March 2007