ME381R Lecture 1
Overview of Microscale Thermal Fluid Sciences and Applications
Dr. Li Shi
Department of Mechanical Engineering
The University of Texas at Austin
Austin, TX 78712
www.me.utexas.edu/~lishi
lishi@mail.utexas.edu
Microprocessor Evolution
2
Localized Heating in VLSI Chips
DT=20C
80C
90C
108C
Mean-time-to-failure due to
electromigration increase x5
Dependence of mean time
between failure on temperature
110C
1 cm
On chip temperature contour
Steve Kang et al. Electrothermal analysis of
VLSI Systems, Kluwer 2000
3
Telecommunication Data Rate Evolution
Data Rate (bits/sec)
12
10
DWDM
WDM
1.00 GB Hard Drive
9
10
Fiber
Doubles
every 16
months
Coaxial circuits
1.44MB Floppy Disk
6
10
Transcontinental cable
Telephone
3
10
Telegraph
1
1800
1850
Doubles every
4.7 years
1900
1950
2000
2050
Year
4
Howard Banks, "Life at 100 billion bits per second", Forbes Magazine, Oct. 6, 1997
Thermal Issues in Optoelectronic Integrated Circuits
Affolter, WDM Solutions (supplement to Laser Focus
World), P.65 June 2001, www.wdm-solutions.com
Electroabsorption
modulator
Waveguide
Ridge
20um
A. Shakouri, J. Christofferson, Z. Bian, and P. Kozodoy, “High Spatial Resolution Thermal5Imaging of
Multiple Section Semiconductor Lasers,” Proceeding of Photonic Devices and System Packaging
Symposium (PhoPack 2002), pp22-25, July 2002, Stanford CA.
IC Thermal Management Challenge
Courtesy: Prof. Ken Goodson, DARAPA Thermal Management Workshop
6
Electroosmotic Microchannel Cooling System
7
Cooligy 150 W PC Prototype
8
Thermoelectric Refrigeration
• Marlow Single-Stage
Thermoelectric cooler
• Consumer
• Electronics
• Optoelectronics
• Automobile
• No moving parts: quiet
• No CFC: clean
• Low efficiency
9
Efficient Thin Film Thermoelectric Coolers
Venkatasubramanian et al, Nature 413, P. 597 (2001)
10
Thin film superlattice
How far exponential growth in electronics and fiber optics can continue?
Airplane Speed- Past, Present, Future
McMasters & Cummings, Journal of Aircraft, Jan-Feb 2002
The brick wall due to heating, fabrication cost,
quantum mechanics …
Future challenges & opportunities: transportation,
communication, energy, health care …
11
Direct Thermal to Electric Energy
Conversion
• Electric power generator with no
moving part
• Power sources for NASA space probe
• NAVY Electric Ships (Seapower 21)
• Waste heat recovery (cars, power
plants, …)
• Microscale power sources
Spacecraft Power Source
Efficient
Nanostructured
Thermoelectric
Power Generator
12
Microfluidic Chip for Continuous Glucose Monitoring
(J. Zahn et al.)
13
1 km
Length Scale
Aircraft
Automobile
1m
Human
Computer
Butterfly
1 mm
Microprocessor Module
Fourier’s law,
Novier-Stokes
MEMS
Blood Cells
Wavelength of Visible Light
1 mm
Microprocessor, NEMS
100 nm l
Nanotubes, Nanowires
Width of DNA
1 nm
14
Fourier’s Law for Heat Conduction
Q (heat flow)
Hot
Th
Cold
Tc
L
Th  Tc
dT
Q  kA
 kA
L
dx
Thermal conductivity
15
Microscopic Origins of Thermal Fluid Transport
--The Particle Nature
Materials
Dominant energy carriers
L
Gases:
Molecules
Hot
Metals:
Electrons
Insulators:
Phonons
(crystal vibration)
Cold
In micro-nano scale thermal fluid systems, often L < mean free path of collision
of energy carriers & Fourier’s law breaks down
 Particle transport theories or molecular dynamics methods
16