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Feb 22, 2014 (3 years and 3 months ago)

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SEMINAR
(CH
-
510)

On


NANOFLUIDS





BY:


UMESH SHARMA


ID:2011PCH5301


M.Tech (II Sem.)

NANOFLUIDS


Nano

fluids

are

the

new

class

engineered

fluid

with

high

thermal

conductivity

obtained

by

suspending

nanometer

size

(
1
-
100
nm)

particles

in

a

base

fluid

like

water

,ethylene

glycol,

oil

etc
.



NANOPARTICLES AND BASE FLUIDS

Nanoparticles


Aluminum oxide (Al
2
O
3
)



Titanium dioxide (TiO
2
)


Copper oxide (CuO)


Base fluids


Water


Oil


Ethylene glycol

U.S. Choi and J.A. Eastman, “Enhanced heat
transfer using nanofluids” U.S. Patent #6,221,275

Why Use Nanoparticles


Studies

of

thermal

conductivity

of

suspensions

have

been

confined

to


mm
-

or

μ
m
-
sized

particles
.



The

major

challenge

is

the

rapid

settling

of

these

particles

in

fluids
.



Nanoparticles

stay

suspended

much

longer

than

micro
-
particles

and,

if

below

a

threshold

level

and/or

enhanced

with

surfactants/stabilizers,

remain

in

suspension

almost

indefinitely
.


Furthermore,

the

surface

area

per

unit

volume

of

nanoparticles

is

much

larger

(million

times)

than

that

of

microparticles

(the

number

of

surface

atoms

per

unit

of

interior

atoms

of

nanoparticles,

is

very

large)
.



These

properties

can

be

utilized

to

develop

stable

suspensions

with

enhanced

flow,

heat
-
transfer,

and

other

characteristics
.

Methods for Producing Nanoparticles/Nanofluids

Two

nanofluid

production

methods

has

been

developed

in

ANL

to

allow

selection

of

the

most

appropriate

nanoparticle

material

for

a

particular

application
.


In

two
-
step

process

for

oxide

nanoparticles

(“Kool
-
Aid”

method),

nanoparticles

are

produced

by

evaporation

and

inert
-
gas

condensation

processing,

and

then

dispersed

(mixed,

including

mechanical

agitation

and

sonification)

in

base

fluid
.



In

one
-
step

process

simultaneously

makes

and

disperses

nanoparticles

directly

into

base

fluid
;

best

for

metallic

nanofluids
.


-
ZrO
2

in water that produce with two
-

Cu Nanoparticles produced by

Step method direct evaporation into ethyl
ene



glycol

Effect of Particle Clustering

Some

times

nanofluids

are

in

form

of

cluster

when

the

concentration

is

high

or

when

the

time

is

increase
.



It

is

accepted

that

heat

transfer

is

a

surface

phenomenon

and

the

thermal

energy

interaction

take

places

at

the

surface

of

nanoparticles
.



When

the

particles

get

agglomerated,

the

effective

surface

area

to

volume

ratio

decreases,

thus

reducing

the

effective

area

of

thermal

interaction

of

particles

causing

a

decrease

in

the

thermal

conductivity

of

the

fluid
.



Mesh

like

structure

observed,

in

water

based

CuO

nanofluid

of

0
.
1

vol
%
after

sonication

for

(a)

20
min,

(b)

60
min

and

(c)

70

min
.



It

can

be

seen

the

structure

formation

being

only

after

60

min

from

the

sonication
.

Stability of Nanofluid

The

agglomeration

of

nanoparticles

results

in

not

only

the

settlement

and

clogging

of

microchannels

but

also

the

decreasing

of

thermal

conductivity

of

nanofluid
.

So

stability

evaluation

methods

for

nanofluid

are
-
:


Sedimentation

and

Centrifugation


Zeta

potential

analysis


Spectral

absorbency

analysis

Ways to Enhance the Stability of Nanofluid

1
)

Use

of

various

surfactants

in

Nanofluid



Non

ionic

surfactant

without

charge

groups

in

its

head



Anionic

surfactant

with

negatively

charged

groups



Cationic

surfactant

with

positively

charged

groups



Amphoteric

surfactant

with

zwitterionic

head

groups


2
)

Surface

Modification

techniques


3
)

By

dominating

the

repulsive

force

between

the

particles


Stability Mechanism of Nanofluid

Thermal Conductivity

According

to

the

report

of

Argonne

National

Laboratory,

eight

parameters

effect

the

thermal

conductivity

of

nanofluids,

they

got

these

results

from

about

124

researchers

experiments,

these

effects

are
:


1.
Particle

volume

concentration


2.
Particle

materials


3.
Particle

size


4.
Particle

shape


5.
Base

fluid

material


6.
Temperature


7.
Additive


8.
Acidity


Effect of Particle Volume
Concentration:

From the experimental results the
general trend is clear: thermal
conductivity enhancement increases with
increase particle volume concentration.

(Al in water) Al
2
O
3.

Effect

of

Particle

Material
:


The

thermal

conductivity

ratio

is

seen

to

increase

faster

for

metal

than

oxide

particles
.


(Particles

in

ethylene

glycol
)

Effect

of

Particle

Size
:



Most

of

the

researchers

report

that

the

larger

particle

diameters

produce

a

large

enhancement

in

thermal

conductivity

but

in

some

cases

the

experiments

show

the

different

thing
.


A

consistent

trend

appears

where

in

the

larger

particle

diameters

produce

a

large

enhancement

in

thermal

conductivity
.


(Al

in

water)

Al
2
O
3

Effect

of

Particle

Shape
:


All

of

the

results

indicate

that

elongated

particles

are

superior

to

spherical

for

thermal

conductivity

enhancement
.


(SiC

in

water)
.

Effect

of

Base

Fluid

Material

:

The

results

show

increased

thermal

conductivity

enhancement

for

poorer

(lower

thermal

conductivity)

heat

transfer

fluid
.

The

results

show

the

least

enhancement

for

water,

which

is

the

best

heat

transfer

fluid

with

the

highest

thermal

conductivity

of

the

fluids

compared
.


(Al

in

fluids)

Al
2
O
3

Effect of Temperature:

The

trend

of

all

experimental

shows

increased

thermal

conductivity

enhancement

with

increased

temperature
.


(Al

in

water)

Al
2
O
3

Effect of Additives:


Experiments

have

used

fluid

additives

in

an

attempt

to

keep

nanoparticles

in

suspension

and

to

prevent

them

from

agglomerating
.


The

thermal

conductivity

enhancement

improved

by

using

the

additive
.


(Cu

in

ethylene

glycol)

Effect

of

Acidity

(PH)
:


Limited

studies

have

been

published

on

the

effect

of

fluid

acidity

on

the

thermal

conductivity

enhancement

of

nanofluids
.


But

the

general

trend

is

that

acidity

increases

the

thermal

conductivity

enhancement
.


(Al

in

water)

Al
2
O
3

CONDUCTIVITY OF METALLIC NANOFLUIDS

Three samples of CuO
-
ethylene
glycol were taken

first two stabilizer not added

1)
Labeled old
-

kept for 2 months

2)
Labeled new
-

2 days old

3)
1% Thioglycol acid added


40%increase in conductivity of


acidic nanofluid for 3%


Concentration.


Thioglycol acid improves


dispersion


Metallic nanofluids greater


conductivity compared to
oxide


nanofluids



Effective conductivity of CuO
-
ethylene glycol nanofluid, Eastman et al. (2001)

THERMAL CONDUCTIVITY OF OXIDE NANOFLUIDS


Measurement method

1)Linear relation between thermal
conductivity and volume
fraction.

2) Enhancement in water
-
Cuo
nearly equals ethylene glycol
-
Al
2
O
3

system

3) Ethylene glycol Cuo (24nm)
system indicates maximum
enhancement

4) Water
-
glycol Al
2
O
3
(38nm)
system least increment




Enhanced

thermal

conductivity

of

oxide

nanofluids

(Lee

et

al
.
,

1999
)

Experimental Studies on Thermal Conductivity of Nanofluids


Investigator


Particles


Size

(nm)


Fluids


Observations

Eastman

et

al

(
1997
)


Al
2
O
3
/CuO/Cu

33
/
36
/

water,oil

60% improvement
for 5 vol%

CuO

particles

in

water
.

Lee et al (1999)

Al
2
O
3
/CuO

24
.
4
,
38
.
4
/
18
.
6
,
23
.
6

water,EG

20
%

improvement for 4
vol%

Cuo/EG

mixture
.

Das et al (2003)

Al
2
O
3
/CuO

38
.
4
/
28
.
6

water

2
-
4 fold increase
over range of

21
oC

to

52
oC
.

Hong et al (2005)


Fe

10

EG

18% increase for
0.55 vol% Fe/EG

nanofluids
.

Li and Peterson
(2006)

Al
2
O
3
/CuO

36
/
29

water

enhancement with
volume fraction

and

temperature

Liu et al (2005)

CNTs

Ø
20
-
30

μm

EG,EO

12.4% for EG at 1
vol%, 30% for

EO

at

2

vol
%
.

ADVANTAGES OF NANOFLUIDS



Reduced

Pumping

Power


Minimal

Clogging


Miniaturized

Systems


Compared

with

suspended

particles

of

millimeter
-
or
-
micrometer

dimensions

which

were

used

in

base

fluids

to

enhance

heat

transfer

of

such

fluids,

nanofluids

exhibit

higher

thermal

conductivities
.




Many

types

of

particles

such

as

metallic

and

non
-
metallic,

can

be

added

into

fluids

to

form

nanofluids
.




Suspended

particles

of

the

order

of

millimeters

or

even

micrometers

may

cause

some

severe

problems

such

abrasive

action

of

the

particles

causes

erosion

of

pipelines

which

are

not

that

severe

in

case

of

nanofluids
.







DISADVANTAGES



High

Processing

cost


Agglomeration

at

higher

pH

value

and

also

at

high

temperatures

because

of

the

ability

of

the

particle

to

overcome

thermal

energy

barrier

leading

to

an

increase

in

van

der

waals

forces

and

hence

resulting

in

decrease

of

conductivity
.


Use

of

surfactants

for

stability

which

results

in

lowering

of

conductivity

due

to

the

formation

of

a

thermal

boundary

layer

around

the

particles
.


Application of Nanofluid


Heat

transfer

Intensification


Electronic

Application


Transportation


Industrial

Cooling

Application


Heating

Building

and

Reducing

Pollution


Nuclear

System

Cooling


Space

and

Defense


Solar

Absorption


Mechenical

Application


Magnetic

Sealing


Biomedical

Application