Study on Effective Thermal Conduction of the Nanoparticle Suspension

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Study on Effective Thermal Conduction of the
Nanoparticle Suspension
December 31, 2003

• Calvin Hong Li
• Department of Mechanical, Aerospace Nuclear
  Engineering
• Rensselaer Polytechnic Institute
• Troy, NY 12180

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Presentation Outline

• Introduction
• Background
• Effective Thermal Conduction
• Adsorption Layer
• Brownian Motion
• Conclusions

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Background

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

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Research on Effective Thermal Conductivity

• Theoretic Study
• Hamilton and Cross(1962)
• Maxwell (1881)
• Experimental Study
• Transient Wire Method
• (Nagasaka
  Nagashima)
• Thermal Probe Method
• Other methods

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Working Theory

• Thermal Probe Method
• Transient Wire Method
• Calculating the effective thermal
  conductivity by measuring the change of voltage
  of the probe and wire

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Experimental Setup
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Current Study

• Preparation of Nanoparticle Suspension
• Study of Effective Thermal Conductivity
• Study on Other thermal Properties and
  Applications

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Objective

• Measure the effective thermal conductivity
• Reveal the interaction between particle and
  fluid
• Study the effect of Brownian motion on effective
  thermal conductivity

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Preparation of Nanoparticle Suspension

• MethodsOne-step Method
• Two-step Method
• Stability(1)PH Value
• (2)Chemical Method
• (3)Physical Method?

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• Material SiO2 nanoparticle, Mean diameter 25nm
  ,Purity(gt99.9),non crystal.
• Pure water and ethanol
• Preparation of the suspension dispersed with
  microwave.

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Setups Error Evaluation
Thermal Probe
Transient wire
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Experimental Results

• Thermal Probe Method
• The higher of the suspensions temperature, the
  higher the effective thermal conductivity
• The higher the ratio of nanoparticle in the
  suspension, the higher the effective thermal
  conductivity

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Experimental Results

• Transient Wire Method
• Wt ratio of 0.1,effective thermal conductivity
  is 9.452 higher than pure water
• Wt ratio of 0.2, effective thermal conductivity
  is 10.6 higher
• Wt ratio of 0.5,17.4 higher?

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Results Analysis

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

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Action between surface atoms and fluid atoms


or
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Agglomeration of Nanoparticles
SiO2nanoparticles Hitachi 200CX TEM 1120,000
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Distribution of particles and the agglomeration

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Distribution of particles and the agglomeration
Agglomerations
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The calculation of the thickness of adsorption
layer
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Particle, adsorbed layer and free basefluid
Two dimension surface work
when
,there is
here
So
then
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Study on the interaction between particles and
basefluid

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

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Force Analysis

• (1)Thermal Swimming Force
• (2)Short range agglomerating force
• (3)Electrostatic Force
• (4)Surface tension

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The displacement of particles with Brownian
motion per second(um)
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The Knudsen number with the particles diameter
is fluid molecules
mean free moving distance,
,
means the movement is in the slipping or temp.
jumping area.
With heat flux
and the T gradient,
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CFD Simulation
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Velocity of Brownian motion
Single particle moving model
v
A
B
C
Distribution of particles in suspension
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One, two and ten particles cases
Mesh for ten particles case
Mesh for single particle case
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Temp. field around one particle
Pressure field around one particle
Moving situation
Velocity field around one particle
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Comparing and contrasting of one and two
particles cases
Temperature field comparing and contrasting
horizon plate
Temperature field comparing and contrasting
upright plate
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Ten particles case
Velocity field
Temperature field
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Conclusion

• Observation on the particles and their
  agglomeration
• Getting the effective thermal conductivity data
  through two kind of methods.
• Calculating the thickness of adsorbing layer
• Simulating the Brownian motion and its effect.

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Other Study on Nanoparticle Suspension

• Study on the viscosity
• Study on the capillary performance and chemical
  behavior
• Study on the application as the refrigerant in
  MEMS

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MD Simulation

• In case that there is not a good way to observe
  the adsorbed layer basefluid molecules,the MD
  method should be used to study the adsorption
  process and its effect on the energy. Through
  the MD simulation, hoping to get the information
  of kinetic energy, potential energy and other
  changes in the process.

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Effects between fluid molecules

• Since the fluid molecules have polarity, based
  on the L-J model,the model for the effect
  between fluid molecules can be Stockmayer
  potential model

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Brownian Motion

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

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Thank you!And Happy New Year!