Study on Effective Thermal Conduction of the Nanoparticle Suspension Calvin Hong Li Department of Mechanical, Aerospace & Nuclear Engineering Rensselaer Polytechnic Institute Troy, NY December 31, 2003

Presentation Outline IntroductionBackground Effective Thermal Conduction Adsorption Layer Brownian Motion Conclusions

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

Research on Effective Thermal Conductivity Theoretic Study Theoretic Study Hamilton and Cross （ 1962 ） Hamilton and Cross （ 1962 ） Maxwell (1881) Maxwell (1881) Experimental Study Experimental Study Transient Wire Method Transient Wire Method (Nagasaka & Nagashima) (Nagasaka & Nagashima) Thermal Probe Method Thermal Probe Method Other methods Other methods

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

Experimental Setup

Current 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 Applications Study on Other thermal Properties and Applications

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

Preparation of Nanoparticle Suspension Methods ： One-step Method Methods ： One-step Method Two-step Method Two-step Method Stability ：（ 1 ） PH Value ； Stability ：（ 1 ） PH Value ； （ 2 ） Chemical Method ； （ 2 ） Chemical Method ； （ 3 ） Physical Method 。 （ 3 ） Physical Method 。

Material: SiO2 nanoparticle, Mean diameter 25nm ， Purity （ >99.9% ）， non crystal. Pure water and ethanol Pure water and ethanol Preparation of the suspension: dispersed with microwave.

Setups Error Evaluation Thermal ProbeTransient wire

Experimental Results Thermal Probe Method Thermal Probe Method The higher of the suspension’s temperature, the higher the effective thermal conductivity The higher the ratio of nanoparticle in the suspension, the higher the effective thermal conductivity

Experimental Results Transient Wire Method 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 。

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. 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.

Action between surface atoms and fluid atoms or

Agglomeration of Nanoparticles SiO2nanoparticles Hitachi 200CX TEM 1:120,000

Distribution of particles and the agglomeration Four particle agglomerati- on Two particle agglomerati- on Single particle huge agglomerati- on Multiparticl-e agglomerati- on

Distribution of particles and the agglomeration Agglomerations

The calculation of the thickness of adsorption layer

Particle, adsorbed layer and free basefluid : Two dimension surface work when ， there is here So then

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 。 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 Analysis force acted on nanoparticles Simulation of the Brownian motion effect of nanoparticles having on basefluid Simulation of the Brownian motion effect of nanoparticles having on basefluid

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

diameter Water （ 26 centigrade ） air （ 26 centigrade ） （ um ） Brownian motion The displacement of particles with Brownian motion per second （ um ）

With heat flux and the T gradient ， ， is fluid molecule’s means the movement is in the slipping or temp. jumping area. The Knudsen number with the particle’s diameter: mean free moving distance,

CFD Simulation Micro convecti on zone Particle Layer of fluid molecules

Single particle moving model Distribution of particles in suspension Velocity of Brownian motion

One, two and ten particles cases Mesh for ten particles case Mesh for single particle case

Temp. field around one particlePressure field around one particle Velocity field around one particle Moving situation

Comparing and contrasting of one and two particles cases Temperature field comparing and contrasting horizon plate Temperature field comparing and contrasting upright plate

Ten particles case Temperature field Velocity field

Conclusion Observation on the particles and their agglomeration Observation on the particles and their agglomeration Getting the effective thermal conductivity data through two kind of methods. Getting the effective thermal conductivity data 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 Suspension Study on the viscosity Study on the viscosity Study on the capillary performance and chemical behavior Study on the capillary performance and chemical behavior Study on the application as the refrigerant in MEMS Study on the application as the refrigerant in MEMS

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. 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.

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 ： 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 ：

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. 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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