July 19, 2010Thesis Defense, USC 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

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, 2010Thesis Defense, USC

Image Source : 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.  For high power electronics cooling, many alternative cooling schemes have been examined in recent years to meet this demand. Microprocessor heat sink Motherboard Heat sink Liquid Cooled Microchannel Heat Sink is on The Rise

Microchannel Heat Sink Tuckerman and Pease 1981  removal of large amount of heat from a small area  Dense package  Small foot-print cooling scheme  Larger surface area per unit volume  Dimensions from 10 to 1000 µm  Channels may be rectangular, circular or trapezoidal  Single-phase/two-phase Dixit et al Microchannel Heat Sink Thesis Defense, USCJuly 19, 2010 Enhancing Microchannel Heat Transfer is the Focus!

Ref. : Moore GE 1965 Electronics 38 : 114–117 and Intel Website Moore’s Law Motivation # of Transistors in a given area doubles every 2 years due to reduction of transistor size

Advancement in Nanotechnology Motivation Li C. et al. 2008, Small Chen R. et al. 2009, Nano Letters Diatz et al July 19, 2010Thesis Defense, USC Mudawar et al. 2009, IJHMT Launay et al. 2006, Microelectronics Journal

Proposed Investigation Thesis Defense, USCJuly 19, 2010 Cu nanowires Heat Flux from Bottom Inlet Outlet Typical Microchannel Heat Sink Nanowires Coated Microchannel Heat Sink  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 Approach:

Cu Nanowires Growth on Cu Heat Sink Synthesis and Characterization of Nanowires on Heat Sink Synthesis : Electrochemical technique Tao Gao et al Copper Heat Sink Cu Heat Sink PAA Template PAA Template on Cu Substrate Electrochemical Deposition Washing away PAA template July 19, 2010Thesis Defense, USC Growth Conditions Voltage-0.3 V Time3600 s ElectrolyteCuSO 4.5H 2 O+ H 2 SO 4

Cu Nanowires Growth on Cu Heat Sink Experimental Facilities Flow loop July 19, 2010Thesis Defense, USC Top plate/ cover plate Base plate Cu foil Intermediate plate Rubber Cushion Cu foil Cu heat sink Pre-moistened filter paper PAA template Exploded View of the Reactor Components

Cu Nanowires Growth on Cu Heat Sink Experimental Facilities Digital Photographs of Reactor components July 19, 2010Thesis Defense, USC Assembled Reactor Electrochemical Work Station

Characterization of Cu Nanowires Characterization : SEM July 19, 2010Thesis Defense, USC Bare Cu Heat Sink Cu Nanowires on Heat Sink

Experimental Facilities for Convective Heat Transfer Experiments Flow Loop July 19, 2010Thesis Defense, USC Test Section Data Acquisition Liquid Reservoir Gear Pump Degasifier and Filter Control Valve Liquid Reservoir Computer Schematic diagram of the flow loop

Experimental Facilities for Convective Heat Transfer Experiments Experimental Facilities Digital Photographs July 19, 2010Thesis Defense, USC

Experimental Facilities for Convective Heat Transfer Experiments July 19, 2010Thesis Defense, USC Cover plate Housing Coolant in Coolant out Pressure ports Cartridge Heater Insulation Block Base plate / Support plate Inlet plenum Copper Heat Sink Test Section Thermocouples Location Exploded view of Test Section Components

Experimental Facilities for Convective Heat Transfer Experiment July 19, 2010Thesis Defense, USC Insulation Block Support Plate Cover Plate Outlet port Housing O-Ring Seal Cartridge Heater Bolts Inlet port Insulation Block Assembly of the test section

Digital Photographs of Test Section Components Summary July 19, 2010Thesis Defense, USC

Experimental Procedure, Postprocessing and Uncertainty Analysis Postprocessing July 19, 2010Thesis Defense, USC  Sensible Heat Gain by Coolant  Power Input to Cartridge Heater  Average Heat Transfer Coefficient  Log Mean Temperature Difference Nomenclature: ρ = Density of water at T m C p = Specific Heat of Water at T m V = Voltage I = Current A ht =Heat Transfer Area T i = Inlet Temperature T o = Outlet Temperature T s = Surface Temperature T m = Mean Temperature Ts,j =Heat Sink Surface Temperature Tc,j=Thermocouple reading k Cu = Thermal Conductivity of Copper s = Distance from thermocouple location to top surface q’’ = Heat flux  Heat Sink Surface Temperature

Experimental Procedure, Postprocessing and Uncertainty Analysis Postprocessing  Average Nusselt Number  Hydraulic Diameter  Friction Factor Nomenclature: Nu= Nusselt Number h = Average convective heat transfer coefficient D h = Hydraulic diameter k f = Thermal conductivity of the fluid at T m A c = Channel cross sectional area P w = Wetted Perimeter µ = Viscosity of water at T i Q = Flow Rate T m = Mean Temperature L = Length of test section Pr = Prandtl number ∆p = Pressure drop  Dimensionless Hydrodynamic Axial Distance  Reynolds Number  Dimensionless Thermal Axial Distance

Experimental Procedure, Postprocessing and Uncertainty Analysis Uncertainty Analysis July 19, 2010Thesis Defense, USC ParameterUncertainty DhDh 3% Re5% q6% P1% ∆T LMTD 9% h11% Nu12% x+x+ 5% x*5% Kline and McClintock : Measured Parameter Uncertainty Pressure0.25% Temperature±0.3 ̊C Voltage±0.01V Current0.4% Flow Rate0.02% Measurement UncertaintyPropagated Uncertainty

Experimental Procedure, Postprocessing and Uncertainty Analysis Test Procedure July 19, 2010Thesis Defense, USC Test # Reynolds Number (Re) Width, w (mm) Height, b (µm) Length, L (mm) Hydraulic Diameter D h ( µm) Aspect ratio, α = w/b (Dimensionless)

Results Results : Surface Wettability Characteristics July 19, 2010Thesis Defense, USC ̊ Bare Cu Heat SinkCuNWS Coated Heat Sink Improvement in Surface Wettability!

Results Results : Bare Microchannel Heat Sink July 19, 2010Thesis Defense, USC Heat Transfer Results Re x+x x*

Results July 19, 2010Thesis Defense, USC Results : Bare Microchannel Heat Sink Heat Transfer Results

Results July 19, 2010Thesis Defense, USC Results : Bare Microchannel Heat Sink Heat Transfer Results

Results July 19, 2010Thesis Defense, USC Results : Bare Microchannel Heat Sink Pressure Drop Results

Results July 19, 2010Thesis Defense, USC Results : Comparison between Bare and CuNWs Coated Microchannel Heat Sink Heat Transfer Results

Results July 19, 2010Thesis Defense, USC Results : Comparison between Bare and CuNWs Coated Microchannel Heat Sink Heat Transfer Results

Results July 19, 2010Thesis Defense, USC Results : Comparison between Bare and CuNWs Coated Microchannel Heat Sink Heat Transfer Results

Results July 19, 2010Thesis Defense, USC Results : Comparison between Bare and CuNWs Coated Microchannel Heat Sink Pressure Drop Results

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, 2010Thesis 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 8 th Thermal Engineering Conference, Mar 13-17, 2011, Honululu, Hawaii, USA (Abstract has been accepted). July 19, 2010Thesis Defense, USC

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, 2010Thesis Defense, USC

Conclusion Thanks! ? July 19, 2010Thesis Defense, USC