Experimental Investigation of the Effect of Copper
Nanowires on Heat Transfer and Pressure Drop
for a Single Phase Microchannel Heat Sink
M.S. Thesis Defense
July 19, 2010
M. Yakut Ali, M.S. Candidate
Dr. Jamil A. Khan, Advisor
July 19, 2010
Thesis Defense, USC
Outline of the presentation

Introduction



Overview of Heat Sinks for Electronics Cooling
Motivation / Problem Statement
Experimental facilities/ Setup




Synthesis of Cu Nanowires on Cu Heat Sink
Characterization of Cu Nanowires using SEM
Flow Loop and Test Section Design & Fabrication
Data acquisition and Post Processing

Results and Discussions

Summary and Future Works
July 19, 2010
Thesis Defense, USC
Overview of Heat sinks for Electronics Cooling
 A heat sink is a term for a component
that efficiently transfers heat generated
within a solid material to a fluid medium,
such as air or a liquid.
Microprocessor heat sink
 For high power electronics cooling,
many alternative cooling schemes have
been examined in recent years to meet
this demand.
Liquid Cooled Microchannel
Heat Sink is on The Rise
Motherboard Heat sink
Image Source : http://en.wikipedia.org/wiki/Heat_sink
Microchannel Heat Sink
Microchannel Heat Sink
 removal of large amount of heat from
a small area
 Dense package
 Small foot-print cooling scheme
Tuckerman and Pease 1981
 Larger surface area per unit volume
 Dimensions from 10 to 1000 µm
 Channels may be rectangular, circular
or trapezoidal
Dixit et al. 2007
July 19, 2010
 Single-phase/two-phase
Enhancing Microchannel Heat Transfer is the Focus!
Thesis Defense, USC
Motivation
Motivation
Moore’s Law
# of Transistors in a given area doubles every 2 years due to reduction
of transistor size
Ref. : Moore GE 1965 Electronics 38 : 114–117 and Intel Website
http://en.wikipedia.org/wiki/Moore's_law
Motivation
Advancement in Nanotechnology
Launay et al. 2006, Microelectronics Journal
Mudawar et al. 2009, IJHMT
Li C. et al. 2008, Small
Chen R. et al. 2009, Nano Letters
July 19, 2010
Diatz et al. 2006
Thesis Defense, USC
Proposed Investigation
Proposed Investigation
Outlet
Inlet
Heat Flux from Bottom
Typical Microchannel
Heat Sink
Heat Flux from Bottom
Cu
nanowires
Nanowires Coated
Microchannel Heat Sink
Approach:






Synthesis of Cu nanowires on Cu heat sink
Characterization of CuNWs
Design and Fabrication of Experimental Thermal and Flow loop
Design Experimental metrics
Assessment and Comparison of the thermal performance and pressure drop results
Investigation of surface Morphology before and after the heat transfer experiments
July 19, 2010
Thesis Defense, USC
Cu Nanowires Growth on Cu Heat Sink
Synthesis and Characterization of Nanowires on Heat Sink
Copper Heat Sink
Synthesis : Electrochemical technique
PAA Template
PAA Template on Cu Substrate
Cu Heat Sink
Growth Conditions
Electrochemical Deposition
Washing away PAA template
Tao Gao et al. 2002
July 19, 2010
Voltage
-0.3 V
Time
3600 s
Electrolyte
CuSO4 .5H2 O+ H2SO4
Thesis Defense, USC
Cu Nanowires Growth on Cu Heat Sink
Experimental Facilities
Top plate/ cover plate
Pre-moistened
filter paper
Cu foil
Rubber Cushion
PAA template
Intermediate plate
Cu heat sink
Cu foil
Flow loop
Base plate
Exploded View of the Reactor Components
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Cu Nanowires Growth on Cu Heat Sink
Experimental Facilities
Assembled Reactor
Digital Photographs of Reactor components
July 19, 2010
Electrochemical Work Station
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Characterization of Cu Nanowires
Characterization : SEM
Bare Cu Heat Sink
Cu Nanowires on Heat Sink
July 19, 2010
Thesis Defense, USC
Experimental Facilities for Convective Heat Transfer Experiments
Flow Loop
Control Valve
Test Section
Degasifier and
Filter
Liquid Reservoir
Gear Pump
Data Acquisition
Computer
Liquid Reservoir
Schematic diagram of the flow loop
July 19, 2010
Thesis Defense, USC
Experimental Facilities for Convective Heat Transfer Experiments
Experimental Facilities
Digital Photographs
July 19, 2010
Thesis Defense, USC
Experimental Facilities for Convective Heat Transfer Experiments
Test Section
Cover plate
Coolant in
Inlet plenum
Pressure ports
Housing
Coolant out
Copper Heat Sink
Cartridge Heater
Insulation Block
Thermocouples Location
Insulation Block
Base plate /
Support plate
Exploded view of Test Section Components
July 19, 2010
Thesis Defense, USC
Experimental Facilities for Convective Heat Transfer Experiment
Cover Plate
O-Ring Seal
Outlet port
Inlet port
Housing
Insulation Block
Support Plate
Cartridge Heater
Insulation Block
Bolts
Assembly of the test section
July 19, 2010
Thesis Defense, USC
Digital Photographs of Test Section Components
Summary
July 19, 2010
Thesis Defense, USC
Experimental Procedure, Postprocessing and Uncertainty Analysis
Postprocessing

Sensible Heat Gain by Coolant

Power Input to Cartridge Heater

Average Heat Transfer Coefficient

Log Mean Temperature Difference

Heat Sink Surface Temperature
July 19, 2010
Nomenclature:
ρ = Density of water at Tm
Cp = Specific Heat of Water at Tm
V = Voltage
I = Current
Aht =Heat Transfer Area
Ti = Inlet Temperature
To = Outlet Temperature
Ts = Surface Temperature
Tm = Mean Temperature
Ts,j =Heat Sink Surface Temperature
Tc,j=Thermocouple reading
kCu = Thermal Conductivity of
Copper
s = Distance from thermocouple
location to top surface
q’’ = Heat flux
Thesis Defense, USC
Experimental Procedure, Postprocessing and Uncertainty Analysis
Postprocessing

Average Nusselt Number

Hydraulic Diameter

Reynolds Number

Dimensionless Hydrodynamic Axial Distance


Dimensionless Thermal Axial Distance
Friction Factor
Nomenclature:
Nu= Nusselt Number
h = Average convective heat transfer
coefficient
Dh = Hydraulic diameter
kf = Thermal conductivity of the fluid
at Tm
Ac = Channel cross sectional area
Pw = Wetted Perimeter
µ = Viscosity of water at Ti
Q = Flow Rate
Tm = Mean Temperature
L = Length of test section
Pr = Prandtl number
∆p = Pressure drop
Experimental Procedure, Postprocessing and Uncertainty Analysis
Uncertainty Analysis
Measurement Uncertainty
Propagated Uncertainty
Kline and McClintock :
Measured
Parameter
Uncertainty
Pressure
0.25%
Temperature
±0.3 ̊C
Voltage
±0.01V
Current
0.4%
Flow Rate
July 19, 2010
Parameter
Uncertainty
Dh
3%
Re
5%
q
6%
P
1%
∆TLMTD
9%
h
11%
Nu
12%
x+
5%
x*
5%
0.02%
Thesis Defense, USC
Experimental Procedure, Postprocessing and Uncertainty Analysis
Test Procedure
Test
Reynolds
Width, w Height,
Length,
Hydraulic
Aspect ratio,
#
Number
(mm)
L (mm)
Diameter
α = w/b
Dh ( µm)
(Dimensionless)
b (µm)
(Re)
1
106
5
360
26
672
13.89
2
208
5
360
26
672
13.89
3
316
5
360
26
672
13.89
4
428
5
360
26
672
13.89
5
529
5
360
26
672
13.89
6
636
5
360
26
672
13.89
July 19, 2010
Thesis Defense, USC
Results
Results : Surface Wettability Characteristics
70.5 ̊
Bare Cu Heat Sink
58.0
CuNWS Coated Heat Sink
Improvement in Surface Wettability!
July 19, 2010
Thesis Defense, USC
Results
Results : Bare Microchannel Heat Sink
Heat Transfer Results
8
7
6
Nu
Re
5
4
x+
106
208
316
428
529
636
0.363
0.186
0.123
0.09
0.073
0.060
0.067
0.032
0.021
0.015
0.012
0.010
3
x*
2
1
0
0
200
400
600
800
Re
Experimental results
July 19, 2010
Hausen [39]
Qu [40]
Harms [41]
Thesis Defense, USC
Results
Results : Bare Microchannel Heat Sink
7000
7000
6000
6000
5000
5000
h (W/m2k)
h (W/m2k)
Heat Transfer Results
4000
3000
2000
Heat transfer coefficient
4000
3000
2000
1000
Heat transfer coefficient
1000
0
0
200
July 19, 2010
400
Re
600
800
0
0
0.02
0.04
0.06
0.08
x*
Thesis Defense, USC
Results
Results : Bare Microchannel Heat Sink
Heat Transfer Results
60
Heat Sink Temperature
(̊C)
55
Re=106
Re=208
50
Re=316
Re=428
45
Re=529
Re=636
40
35
30
0
July 19, 2010
1
2
3
4
5
Thermocouple number along heat sink
6
7
Thesis Defense, USC
Results
Results : Bare Microchannel Heat Sink
2500
100
2000
90
1500
80
fRe
Pressure drop (Pa)
Pressure Drop Results
1000
70
Calculated from experiments
Morini [43]
Shah and London [44]
Pressure Drop
500
60
0
50
0
100
200
300
400
Re
July 19, 2010
500
600
700
0
200
400
Re
600
800
Thesis Defense, USC
Results
Results : Comparison between Bare and CuNWs Coated
Microchannel Heat Sink
Heat Transfer Results
8
7
6
Nu
5
4
3
Bare Microchannel
2
CuNWs coated heat sink
1
0
0
100
200
300
400
500
600
700
Re
July 19, 2010
Thesis Defense, USC
Results
Results : Comparison between Bare and CuNWs Coated
Microchannel Heat Sink
Heat Transfer Results
7000
6000
6000
5000
5000
4000
4000
h
h
7000
3000
3000
Bare Microchannel Heat sink
CuNWs coated heat Sink
2000
1000
1000
0
0
0
200
July 19, 2010
400
Re
600
Bare Microchannel heat sink
CuNWs coated heat sink
2000
800
0
0.02
0.04
x*
0.06
0.08
Thesis Defense, USC
Results
Results : Comparison between Bare and CuNWs Coated
Microchannel Heat Sink
Heat Transfer Results
60
Temperature (̊C)
59
58
Bare microchannel heat sink
57
CuNWs coated heat sink
56
55
54
53
52
51
Re=106
50
0
July 19, 2010
1
2
3
4
5
Thermocouple number along heat sink
6
7
Thesis Defense, USC
Results
Results : Comparison between Bare and CuNWs Coated
Microchannel Heat Sink
Pressure Drop Results
3000
Pressure drop (Pa)
2500
2000
1500
1000
Bare Microchannel
CuNWs coated microchannel
500
0
0
100
200
300
400
500
600
700
Re
July 19, 2010
Thesis Defense, USC
Results
Results : Assessment of Surface Morphology
SEM Images After Heat Transfer Experiments
Summary and Future Works
Summary




Cu Nanowires have been successfully grown on heat sink
Experimental flow loop and test section has been designed and fabricated
Heat transfer and pressure drop characteristics have been measured
Enhancement in single phase microchannel heat transfer has been
demonstrated
Future Works
 Experimental investigation of effect of CuNWs on two phase heat sink
 Fabrication of CuNWs on lower aspect ratio microchannels
July 19, 2010
Thesis Defense, USC
Publications
Journal Publications
 Ali, M. Y.; Yang, F.; Fang, R.; Li, C.; Khan, J. “Investigation on the Effect of Cu
Nanowires on Heat transfer and Pressure drop Characteristics of Single Phase
Microchannel Heat Sink” , To be Submitted
Conference Proceedings
 Ali, M. Y.; Yang, F.; Fang, R.; Li, C.; Khan, J. “Effect of 1D Cu Nanostructures on
Single Phase Convective Heat transfer of Rectangular Microchannel”
ASME/JSME 8th Thermal Engineering Conference, Mar 13-17, 2011, Honululu,
Hawaii, USA (Abstract has been accepted).
July 19, 2010
Thesis Defense, USC
Acknowledgement
Acknowledgement
 Special thanks to Dr. Guiren Wang and Dr. Chen Li, Mechanical Engineering,
USC and Dr. Qian Wang, Department of Chemistry & Biochemistry, USC.
 Thanks to research group members, specially
Fanghao Yang
Ruixian Fang
 Thanks goes to ONR for financial support under ESRDC Consortium.
 Acknowledge the facilities of EM Centre, USC.
July 19, 2010
Thesis Defense, USC
Conclusion
Thanks!
?
July 19, 2010
Thesis Defense, USC