Study on Effective Thermal Study on Effective Thermal Conduction of the Conduction of the

Nanoparticle SuspensionNanoparticle SuspensionCalvin Hong LiCalvin Hong Li

Department of Mechanical, Aerospace & Department of Mechanical, Aerospace & Nuclear Engineering Nuclear Engineering

Rensselaer Polytechnic InstituteRensselaer Polytechnic InstituteTroy, NY 12180 Troy, NY 12180

December 31, 2003

Presentation OutlinePresentation Outline

IntroductionIntroductionBackgroundBackgroundEffective Thermal Effective Thermal ConductionConductionAdsorption LayerAdsorption LayerBrownian MotionBrownian MotionConclusionsConclusions

BackgroundBackground

Nano tech is a very promising field and the Nano tech is a very promising field and the current focus of the world.current focus of the world.

Nanoparticle suspension is a kind of new heat Nanoparticle suspension is a kind of new heat transfer material which has very novel thermal transfer material which has very novel thermal properties. The study on it has covered chemical properties. The study on it has covered chemical physics, interfacial phenomena, heat and mass physics, interfacial phenomena, heat and mass transfer and some even grand fundamental transfer and some even grand fundamental fields. This new material will accompany the fields. This new material will accompany the advancing of future engineering and science advancing of future engineering and science development. development.

Research on Effective Thermal Research on Effective Thermal ConductivityConductivity

Theoretic StudyTheoretic Study Hamilton and CrossHamilton and Cross （（ 19621962 ））

Maxwell (1881)Maxwell (1881)

Experimental StudyExperimental Study Transient Wire Method Transient Wire Method (Nagasaka & Nagashima) (Nagasaka & Nagashima) Thermal Probe MethodThermal Probe Method Other methodsOther methods

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Working TheoryWorking Theory

Thermal Probe MethodThermal Probe MethodTransient Wire MethodTransient Wire Method

Calculating the effective thermal Calculating the effective thermal conductivity by measuring the change of conductivity by measuring the change of voltage of the probe and wirevoltage of the probe and wire

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Experimental SetupExperimental Setup

Current StudyCurrent Study

Preparation of Nanoparticle Suspension Preparation of Nanoparticle Suspension

Study of Effective Thermal Conductivity Study of Effective Thermal Conductivity

Study on Other thermal Properties and Study on Other thermal Properties and Applications Applications

ObjectiveObjective

Measure the effective thermal conductivityMeasure the effective thermal conductivity

Reveal the interaction between particle and fluid

Study the effect of Brownian motion on effective thermal conductivity

Preparation of Nanoparticle Preparation of Nanoparticle SuspensionSuspension

MethodsMethods ：： One-step MethodOne-step Method

Two-step MethodTwo-step Method

StabilityStability ：（：（ 11 ）） PH ValuePH Value ；； （（ 22 ）） Chemical MethodChemical Method ；； （（ 33 ）） Physical MethodPhysical Method 。 。

Material: SiO2 nanoparticle, Mean diameter Material: SiO2 nanoparticle, Mean diameter 25nm 25nm ，， PurityPurity （（ >99.9%>99.9% ），）， non non crystal.crystal.

Pure water and ethanolPure water and ethanol

Preparation of the suspension: dispersed Preparation of the suspension: dispersed with microwave.with microwave.

Setups Error EvaluationSetups Error Evaluation

纯水测量值

0. 45596

0. 45598

0. 456

0. 45602

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1.1

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Thermal Probe Transient wire

Experimental ResultsExperimental Results Thermal Probe MethodThermal Probe MethodThe higher of the suspension’s temperature, the higher the The higher of the suspension’s temperature, the higher the

effective thermal conductivityeffective thermal conductivityThe higher the ratio of nanoparticle in the suspension, the The higher the ratio of nanoparticle in the suspension, the

higher the effective thermal conductivity higher the effective thermal conductivity

Si O2 nanopart i cl e suspensi on

0. 599

0. 649

0. 699

0. 749

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0 20 40 60

temperature C

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理论纯水

测量用水

质量浓度0. 1 %为

质量浓度0. 5 %为

Experimental ResultsExperimental ResultsTransient Wire MethodTransient Wire MethodWt ratio of 0.1%Wt ratio of 0.1% ，， effective thermal conductivity is 9.452% effective thermal conductivity is 9.452%

higher than pure waterhigher than pure water ；；Wt ratio of 0.2%Wt ratio of 0.2% ， ， effective thermal conductivity is 10.6% effective thermal conductivity is 10.6%

higherhigher ；；Wt ratio of 0.5%Wt ratio of 0.5% ，， 17.4% higher17.4% higher 。 。

Si O2 nanoparti cl e suspensi on

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Results AnalysisResults Analysis With the high surface/volume ratio of With the high surface/volume ratio of

nanoparticles, basefluid is adsorbed on the nanoparticles, basefluid is adsorbed on the surface of nanoparticles. This lay of adsorbed surface of nanoparticles. This lay of adsorbed basefluid can help nanoparticles from basefluid can help nanoparticles from agglomerating. Meanwhile, the particles do the agglomerating. Meanwhile, the particles do the Brownian motion in the basefluid, which will help Brownian motion in the basefluid, which will help to form a micro convection around them. the to form a micro convection around them. the adsorption and Brownian motion help the adsorption and Brownian motion help the nanoparticle suspension to have very novel nanoparticle suspension to have very novel effective thermal conduction. effective thermal conduction.

Action between surface atoms and Action between surface atoms and fluid atomsfluid atoms

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or 2

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24 2/OSi

Agglomeration of NanoparticlesAgglomeration of Nanoparticles

SiO2nanoparticles Hitachi 200CX TEM 1:120,000

Distribution of particles and the Distribution of particles and the agglomerationagglomeration

Four particle agglomerati-on

Two particle agglomerati-on

Single particle

huge agglomerati-on

Multiparticl-e agglomerati-on

Distribution of particles and the Distribution of particles and the agglomerationagglomeration

Agglomerations

The calculation of the thickness of The calculation of the thickness of adsorption layeradsorption layer

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Particle, adsorbed layer and free basefluid

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Study on the interaction between Study on the interaction between particles and basefluidparticles and basefluid

There are two ways how the heat is conducted in There are two ways how the heat is conducted in fluid. One is that molecules move in a area which is like fluid. One is that molecules move in a area which is like a cell, the other is that some molecules can get high a cell, the other is that some molecules can get high energy and move out the original cell to other adjacent energy and move out the original cell to other adjacent cells. So it seems that the Brownian motion of cells. So it seems that the Brownian motion of nanoparticles will change this process greatly by nanoparticles will change this process greatly by breaking the cell or helping molecules move to other cell breaking the cell or helping molecules move to other cell with rather low energy. And therefore the suspension with rather low energy. And therefore the suspension shows greater effective thermal conductivityshows greater effective thermal conductivity 。。

Analysis force acted on nanoparticlesAnalysis force acted on nanoparticles

Simulation of the Brownian motion effect of nanoparticles Simulation of the Brownian motion effect of nanoparticles having on basefluidhaving on basefluid

Force AnalysisForce Analysis

（（ 11 ）） Thermal Swimming ForceThermal Swimming Force ： ：

（（ 22 ）） Short range agglomerating forceShort range agglomerating force ： ：

（（ 33 ）） Electrostatic ForceElectrostatic Force ： ：

（（ 44 ）） Surface tensionSurface tension ： ：

diameterdiameter WaterWater （（ 26 26 centigradecentigrade ））

airair （（ 26 26 centigradecentigrade ））

（（ umum ）） Brownian motionBrownian motion Brownian motionBrownian motion

0.10.1 2.362.36 29.429.4

0.250.25 1.491.49 14.214.2

0.50.5 1.051.05 8.98.9

1.01.0 0.750.75 5.95.9

The displacement of particles with Brownian motion per second （ um ）

With heat flux q

and the T gradient ，

Rkn 2/

，

is fluid molecule’s

110－Kn means the movement is in the slipping or temp. jumping area.

The Knudsen number with the particle’s diameter:

mean free moving distance,

CFD SimulationCFD Simulation

Micro convection zone

Particle

Layer of fluid molecules

tkT

x

22

Single particle moving model

Distribution of particles in suspension

The vel oci t y of nano- par t i cl e' s Br owni an mot i on

0

0. 001

0. 002

0. 003

0. 004

0. 005

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Velocity of Brownian motion

One, two and ten particles One, two and ten particles casescases

Mesh for ten particles caseMesh for single particle case

Temp. field around one particle Pressure field around one particle

Velocity field around one particleMoving situation

Comparing and contrasting of one Comparing and contrasting of one and two particles casesand two particles cases

Temperature field comparing and contrasting horizon plate Temperature field comparing and contrasting

upright plate

Ten particles caseTen particles case

Temperature field Velocity field

ConclusionConclusion Observation on the particles and their Observation on the particles and their

agglomerationagglomeration

Getting the effective thermal conductivity data Getting the effective thermal conductivity data through two kind of methods. through two kind of methods.

Calculating the thickness of adsorbing layer Calculating the thickness of adsorbing layer

Simulating the Brownian motion and its effect.Simulating the Brownian motion and its effect.

Other Study on Nanoparticle Other Study on Nanoparticle SuspensionSuspension

Study on the viscosityStudy on the viscosity

Study on the capillary performance and Study on the capillary performance and

chemical behavior chemical behavior

Study on the application as the refrigerant Study on the application as the refrigerant in MEMSin MEMS

MD SimulationMD Simulation In case that there is not a good way to In case that there is not a good way to

observe the adsorbed layer basefluid observe the adsorbed layer basefluid moleculesmolecules ，， the MD method should be the MD method should be used to study the adsorption process and used to study the adsorption process and its effect on the energy. Through the MD its effect on the energy. Through the MD simulation, hoping to get the information of simulation, hoping to get the information of kinetic energy, potential energy and other kinetic energy, potential energy and other changes in the process. changes in the process.

Effects between fluid moleculesEffects between fluid molecules Since the fluid molecules have polarity, based on the Since the fluid molecules have polarity, based on the

L-J modelL-J model ，， the model for the effect between fluid the model for the effect between fluid

molecules can be Stockmayer potential modelmolecules can be Stockmayer potential model ：：

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Brownian MotionBrownian Motion

Get experimental data of difference Get experimental data of difference viscosity basefluid, Find out the viscosity basefluid, Find out the relationship between viscosity and relationship between viscosity and effective thermal conductivity. Hence effective thermal conductivity. Hence reveal deeper the contribution of Brownian reveal deeper the contribution of Brownian motion.motion.

Thank you!Thank you!

And Happy NewAnd Happy New Year! Year!