Thermophysical properties of silver oxide dispersed in sodium chloride

THERMOPHYSICAL PROPERTIES OF SILVER
OXIDE DISPERSED IN SODIUM CHLORIDE
MOHAMED ASLAM BIN MOHAMED IQBAL
Supervisor: Dr. Hung Yew Mun
A Thesis
submitted in partial fulfillment of the requirements for the
Degree in Bachelor of Engineering (Mechanical)
Faculty of Engineering
Monash University
June 2013

ii
Certificate of Originality
I hereby declare that this submission is my own work and to the best of my knowledge it
contains no materials previously published or written by another person, nor material which
to a substantial extent has been accepted for the award of any other degree or diploma at
Monash University or any other educational institution, except where due
acknowledgement is made in the thesis. Any contribution made to the research by others,
with whom I have worked at Monash University or elsewhere is explicitly acknowledged in
the thesis.
I also declare that the intellectual content of this thesis is the product of my own work,
except to the extent that assistance from others in the project’s design and conception or in
style, presentation and linguistic expression is acknowledged.
…………………………………………………………..
(MOHAMED ASLAM BIN MOHAMED IQBAL)

iii
Acknowledgements
Firstly, I would like to express my gratitude to my supervisor for this project, Dr.
Hung Yew Mun for giving me an opportunity to do a research on this interesting project.
During the whole process of this research, Dr. Hung has given me guidance and corrected
my wrong in this experiment which has helped me to complete this research under his great
supervision.
Besides that, I would like to thank the mechanical lab assistant, Mr. Nasrun for
showing me how to use KD2Pro, Viscometer and pH meter which is essential in getting
more precise and accurate result and minimizing the error.
In addition, I would also like to thank another lab assistant which is Ms. Farisha for
guiding me in the preparation of my base-fluid (sodium chloride). Finally, I would like to
thanks all others who had provided me support to complete this project. Thank you.

iv
Abstract
Nanoparticles that are dispersed in base fluids are called nanofluids. Nanofluids are
formed by the colloidal suspension of nano sized particles in a base fluid. Common
nanoparticles that are being used are made of metals and oxides whereas the usual base
fluids used are water, organic solution and inorganic solution.
In this research, silver(I) oxide is used as nanoparticles and sodium chloride (NaCl)
solution with concentration of 1 mol is being used as base fluid. Thermophysical properties
that are being investigated in this reseach are thermal conductivity, viscosity and pH of
nanofluids. Nanofluids are synthesis using two-step method. Five data of thermal
conductivity, viscosity and pH are taken ranging from 30 to 80 degree celcius. Research
has been done on five different volume fractions of silver oxide-sodium chloride
nanofluids. The volume fractions that have been researched are 0.05%, 0.1%, 0.2%, 0.3%,
and 0.5%.
The result shows that as the temperature increases, the thermal conductivities of
nanofluids also increase. As for viscosity, it shows that the value drops as the temperature
increases. Finally as for pH, the value increases slightly as the temperature increases.
Besides that, different volume fraction also affects the thermal conductivity and viscosity
of the nanofluids. From the research it can be seen that as volume fraction increases,
thermal conductivities of the nanofluids increases as well. In addition, the viscosity also
increases as volume fraction increase. pH slightly decrease with increase in volume
fraction.
Highest enhancement achieved by this silver oxide and sodium chloride nanofluids
is 192.3%. This happens at volume fraction 0.5% and temperature 61.13 degree celcius.
Lowest viscosity achieved is 0.54 mPa.s which happens at volume fraction 0.05% and
temperature of 60.2 degree celcius. pH shows that nanofluids are in neutral state as they are
in the range of 6.98-7.2 for all volume fractions. This shows that combination of silver
oxide and sodium chloride exhibit an excellent thermoproperties.

v
Table of Contents
Certificate of Originality....................................................................................................... ii
Acknowledgements............................................................................................................... iii
Abstract..................................................................................................................................iv
Table of Contents ...................................................................................................................v
List of Figures ..................................................................................................................... vii
List of Tables ......................................................................................................................... x
Chapter 1 ............................................................................................................................... 1
INTRODUCTION..........................................................................................................................1
1.1 Background.......................................................................................................... 1
1.2 Problem Statement.............................................................................................. 4
1.3 Theory .................................................................................................................. 5
1.4 Project Objective and Hypothesis...................................................................... 6
1.5 Project Outline..................................................................................................... 7
1.6 Importance of Research...................................................................................... 7
Chapter 2 ............................................................................................................................... 9
LITERATURE REVIEW..............................................................................................................9
2.1 Overview .............................................................................................................. 9
2.2 Heat transfer process of Nanofluids .................................................................. 9
2.3 Thermal conductivity of Nanofluids................................................................ 11
2.4 Viscosity of Nanofluid ....................................................................................... 21
2.5 pH of Nanofluids................................................................................................ 24
2.6 Conclusion.......................................................................................................... 25
Chapter 3 ............................................................................................................................. 26
METHODOLOGY.......................................................................................................................26
3.1 Overview ........................................................................................................... 26

vi
3.2 Methodology ..................................................................................................... 26
Chapter 4 ............................................................................................................................. 28
EXPERIMENTAL SET-UP........................................................................................................28
4.1 Overview ............................................................................................................ 28
4.2 Nanofluid............................................................................................................ 28
4.3 Sonication........................................................................................................... 34
4.4 Measuring apparatus ........................................................................................ 38
Chapter 5 ............................................................................................................................. 44
EXPERIMENTAL PROCEDURES...........................................................................................44
5.1 Overview ............................................................................................................ 44
5.2 Sample preparation........................................................................................... 44
5.3 Sonication Process............................................................................................. 46
5.4 Data collection ................................................................................................... 48
5.5 Sonication time .................................................................................................. 52
Chapter 6 ............................................................................................................................. 53
RESULTS AND DISCUSSION...................................................................................................53
6.1 Overview ............................................................................................................ 53
6.2 Results ................................................................................................................ 53
6.3 Discussion........................................................................................................... 68
6.4 Errors ................................................................................................................. 74
Chapter 7 ............................................................................................................................. 75
CONCLUSION.............................................................................................................................75
7.1 Conclusions ........................................................................................................ 75
7.2 Recommendation for future work ................................................................... 76
Chapter 8 ............................................................................................................................. 77
REFERENCES.............................................................................................................................77
APPENDICES .................................................................................................................... 83

vii
List of Figures
Figure 1: Number of `Nanofluids`, `Nanofluids and Heat Transfer`, ‘Nanofluid and
properties` research published in SCOPUS from 1993-2010 [16]. ..................................... 10
Figure 2 : Effect of temperature on thermal conductivity enhancement [31]...................... 16
Figure 3: The percentage of aluminum oxide nanofluids enhancement with different type of
base fluid [35]. ..................................................................................................................... 18
Figure 4 : Best enhancement for 3 different particle sizes at 3 different temperatures [37].19
Figure 5 : Sodium chloride................................................................................................... 29
Figure 6: Distilled water ...................................................................................................... 30
Figure 7: Magnetic Stirrer.................................................................................................... 30
Figure 8 : Parafilm ............................................................................................................... 31
Figure 9 : Aluminium foil.................................................................................................... 32
Figure 10 : Nanofluids covered with aluminium foil before sonication.............................. 32
Figure 11 : Silver(I) oxide nanoparticles in the bottle ......................................................... 33
Figure 12 : Silver(I) oxide nanoparticles in powder form ................................................... 33
Figure 13: Ultrasonic Processor with probe......................................................................... 35
Figure 14: Ultrasonic processor sonication setting.............................................................. 35
Figure 15 : Ultrasonic probe ................................................................................................ 36
Figure 16: Sound Enclosure................................................................................................. 37
Figure 17 : Weighing machine Fx-3000i............................................................................. 38
Figure 18: KD2 Pro device .................................................................................................. 40
Figure 19: KS-1 sensor needle............................................................................................. 40
Figure 20: The SV-10 Vibro Viscometer............................................................................. 41
Figure 21: Sensor plate and temperature sensor .................................................................. 42
Figure 22: PB-10 Standard pH meter................................................................................... 43
Figure 23: Conical-bottom centrifuge tube.......................................................................... 43
Figure 24 : Nanoparticles in base fluids prepared................................................................ 46
Figure 25 : Ultrasonic probe tip at the centre of nanofluid.................................................. 47
Figure 26 : Sonication process............................................................................................. 47
Figure 27 : 5 hours sonication time...................................................................................... 47

viii
Figure 28: KD2 Pro Verification Standard Glycerin ........................................................... 49
Figure 29: KS-1 sensor needle placed at the centre of the base fluid .................................. 49
Figure 30: Correct set up to take viscosity data................................................................... 51
Figure 31: Picture above shows pH Buffer Solution. .......................................................... 52
Figure 32: pH Electrode fully immersed in base fluid......................................................... 52
Figure 33: Effect of temperature on thermal conductivity of 0.05% volume fraction of
Ag2O-NaCl nanofluid .......................................................................................................... 54
Figure 34: Effect of temperature on viscosity of 0.05% volume fraction of Ag2O-NaCl
nanofluid .............................................................................................................................. 55
Figure 35: Effect of temperature on pH of 0.05% volume fraction of Ag2O-NaCl nanofluid
.............................................................................................................................................. 56
Figure 36: Effect of temperature on thermal conductivity of 0.1% volume fraction of Ag2O-
NaCl nanofluid..................................................................................................................... 57
nanofluid .............................................................................................................................. 58
.............................................................................................................................................. 59
NaCl nanofluid..................................................................................................................... 60
nanofluid .............................................................................................................................. 61
.............................................................................................................................................. 62
NaCl nanofluid..................................................................................................................... 63
nanofluid .............................................................................................................................. 64
.............................................................................................................................................. 65
NaCl nanofluid..................................................................................................................... 66

ix
nanofluid .............................................................................................................................. 67
.............................................................................................................................................. 68
Figure 48 : Effect of volume fraction and temperature on thermal conductivity of Ag2O-
NaCl nanofluid..................................................................................................................... 69
Figure 49 : Enhancement of thermal conductivity............................................................... 70
Figure 50 : Viscosity of Ag2O-NaCl nanofluid at different volume fraction and temperature
.............................................................................................................................................. 71
Figure 51 : pH of nanofluids with different volume fraction at different temperature........ 72
Figure 52 : Sedimentation after 4 hours............................................................................... 73

x
List of Tables
Table 1: Summary of literature review on effect of volume fraction on thermal conductivity
.............................................................................................................................................. 13
Table 2: Mass of silver oxide for different volume fraction................................................ 45
Table 3: Calibration using KD2 Pro Verification Standard Glycerin.................................. 48
Table 4: Calibration using distilled water............................................................................ 50
Table 5: Calibration using pH buffer solution of 7.............................................................. 51

1
Chapter 1
INTRODUCTION
1.1 Background
One of the most important processes in either mechanical, electrical, biological or
chemical industry is the heat transfer process. Heat transfer is involved in many operations
in industry such as heating and cooling, materials processing, and machines thermal
management. Therefore, if the performance of heat transfer can be enhanced and improved
further, there can be vast amount of energy saving in the industry, reduction in production
time and increase in machines life span. This will bring a lot of benefit to the manufacturer
as production efficiency will increase. A lot of research has been done to improve the
current process of heat transfer. One of the researches that have been done is on nanofluid.
Nanofluid is a fluid that consists of nanoparticle which is being dispersed in a base
fluid. Common nanoparticles that are being used during research nowadays are
aluminum(III) oxide (Al2O3), copper(II) oxide (CuO), zinc(II) oxide (ZnO), silicone(IV)
oxide (SiO2), and titanium(IV) oxide (TiO2) whereas common base fluid used are the
organic base fluid ethylene glycol, oil and inorganic base fluid, water [1]. From research, it
is known that most nanofluids have superior thermo-physical properties which includes
thermal conductivity and viscosity than the its base fluid such as water [2]. This shows that
nanofluids have high potential to replace the current fluid used in heat transfer industry.
There has been much research done to create different kind of nanofluids in order to
improve the common base fluid heat transfer performance. These experimental studies has
been done by many since the work of Maxwell [3] who presented the theory of effective
thermal conductivity of suspension calculation. There are so many findings on nanofluids
as it is now after years of research and experiments done since his theory is presented.

2
Nanofluids are the colloidal suspensions of nano-sized oxide or metals that have
been dispersed in base fluids. The efficient size of nano-sized oxide or metals is below 100
nanometers where it can be dispersed stably in the base fluid. Nanofluids are proven to
enhance the heat transfer performance of base fluid greatly [4]. The suspended nano-sized
oxide or metal will increase the thermal conductivity of the newly formed fluid hence
giving the fluid higher capability in their heat exchanging process for more efficient heat
transfer processes. The development on nanofluids can help the industries in reducing the
size of thermal equipment which will bring a healthy competition between companies to
develop a high performance fluid.
The level of nanofluids heat transfer enhancement is determined by few
modification. For instance, different volume fraction of nanoparticles dispersed in the
chosen base fluid will give different level of enhancement to the nanofluids thermal
conductivity and so does the nanoparticles size [5]. According to Maxwell`s [3] theory, the
suspension of solid particles in base fluid can improve the thermal conductivity of the fluid
because it is known that solid have a higher magnitude of thermal conductivity than liquid.
Nevertheless, one of the problem he did not account in is theory is the size of coarse
particle. Coarse particles is big hence they have higher chance of encountering
sedimentation which will increase the resistance in the fluid`s flow and can cause erosion.
That is when scientist tries to reduce the size of coarse particles and they have tried to do
experiments using nanoparticles.
During research, most of the scientist and engineer will use volume fraction as
small as 0.01% up until as big as 20% of nanoparticles to investigate the heat transfer
enhancement of nanofluids. The readings of thermo-physical properties such as the
viscosity and thermal conductivity are taken during experiment. These properties
combination play an important role in the enhancement and decrement of fluids heat
transfer capabilities. Besides that, pH of the nanofluids is taken as well to investigate the
behavior and stability of the newly formed fluid. Low pH fluid form will exhibit acidic

3
behavior which can cause corrosion while neutral pH will behave like water and high pH
will have behavior of alkaline fluid.
Basically there are many ways to produce nanoparticles. One of the common ways
is by laser pyrolysis. Laser pyrolysis is a gas phase process which is used to produce nano-
sized metals and oxides. Average size of nanoparticles produced by laser pyrolysis is 10-
200nm. Besides that there are several other ways to produce nanoparticles which can be
grouped as liquid-phase method, inert-gas condensation method, mechanical grinding, sol-
gel process, and hydrothermal method [6]. They are all used to produce different type of
nanoparticles.
As for nanofluids, there are two common ways to produce them which are two-step
technique and one-step technique. In two-step method, there will be two steps in preparing
the nanofluid. First step is the production of nanoparticles in dry form. After dry
nanoparticles are produced, they will be dispersed into the base fluid used in the research
which is the second step. Two-step method works well with oxide nanoparticles and
nanoparticles with high volume concentration but less efficient with metal nanoparticles
[7]. The challenge encounter in this method is aggregation during experiment which is
caused by the high surface energy of nanoparticles. This problem is hard to overcome but
can be reduced by using ultrasound and high shear technique [8]. Besides that,
nanoparticles that have gone through surface treatment also showed some excellent ability
in dispersion and does not aggregate [9].
Single step technique on the other hand is a technique where nanoparticles are
manufacture and nanofluids are prepared simultaneously. This method uses physical vapor
deposition (PVD) technique where dry nanoparticles are condensed directly in a flowing
low vapor-pressure fluid [8]. The nanofluids formed using one-step technique display a
much better characteristic in dispersion of nanoparticles as less agglomeration occurs and
the nanofluid is more stable [4]. Nevertheless, two-step technique is more popular because
one-step technique cannot be used to mass produce which reduces its commercial value
[10].

4
For this research project, the thermo-physical properties which include thermo
conductivity, viscosity and pH of nanofluids will be analyzed. The nanoparticles that is
being used in this experiment is silver(I) oxide (Ag2O) with average size around 60 nm.
Base fluid chosen for this experiment is sodium chloride which is prepared in lab. The
concentration of sodium chloride used is 1 mol. The experiment would look at the effect of
different volume fraction of nanoparticles at different temperature on thermo-physical
properties of nanofluid.
1.2 Problem Statement
Technologies are getting more advance every day. The growth in technology is so
fast and device produced is getting smaller. Therefore one of the biggest challenges that
grow with the growth of technology is heat transfer management. Heat transfer occurs in
many industries electronics, lighting, manufacturing or transportation. Overheat seems to
be a problem for most device. The conventional way to manage heat is by using heat
transfer fluid to exchange heat and provide cooling. As production is getting bigger, the
area of heat exchanging process to manage the heat needs to be increased to sustain the
bigger production of devices which is undesirable. Therefore there is an urge for a better
performance heat transfer fluid and researches on nanofluids is being proposed to overcome
the problem.
Many researches have been done on nanofluids. Most of them are using organic
solutions as base fluids which are water, oil and ethylene glycol. The results are then
tabulated for different volume concentration at different temperature for different particle
size. Although there have been a lot of findings by a lot of research, the data have no
generalize equation to generalize the findings as data will not have the same trend for
different volume faction, different particle size and different method used to produce the
nanofluid. Hence to find the best performance fluid more variety of research needs to be
done. Besides that, most of the research done is by using organic solution as base fluid and
water. Since there is little research done on dispersion of nanoparticles in inorganic

5
mixtures, a trial with sodium chloride as inorganic base fluid is being experimented. The
thermo-physical properties of the nanofluids formed are being analyzed as it gives the best
insight on the nanofluid heat transfer capabilities
1.3 Theory
1.3.1 Volume Fraction
Volume fraction can be defined as volume of a constituent which will be divided by
total volume of a mixture [11]. In this research, volume fractions are being presented in
percentage and can be calculated as follow:
( ) (1.1)
1.3.2 Density
Density can be defined as heaviness of an object at a constant volume. Density can
be calculated by dividing mass to the volume [12]. In this experiment, density is used to
calculate the mass of nanoparticles that will be used to form the nanofluids according to the
volume fraction chosen. The equation of density is as follow:
(1.2)
1.3.3 Enhancement
Enhancement can be defined as improvement value of an object`s properties. In this
experiment, enhancement of thermal conductivity is calculated in percentage by dividing
the difference of thermal conductivity of nanofluids and the base fluids then dividing them
with the thermal conductivity of base fluid at respective temperature before multiplying

6
them by hundred to get the percentage. The temperatures have the difference of ± 1 degree
celcius. The equation is as follow:
( )
–
(1.3)
1.4 Project Objective and Hypothesis
1.4.1 Objective
The main objective of this research project is to investigate the thermo-physical
properties which are thermal conductivities and viscosities of nanofluid that is formed by
dispersing silver oxide in sodium chloride solution at different temperatures using five
different volume fractions. The volume fractions that are to be investigated are 0.05%,
0.1%, 0.2%, 0.3% and 0.5%. Besides that, pH of the nanofluid formed also is being
investigated.
Another objective is to compare the thermal conductivity and viscosity of the
nanofluids formed and inorganic base fluid, sodium chloride with no nanoparticles
suspended in the fluid. The thermal conductivity and viscosity are taken five times in the
range of 30 degree celcius to 80 degree celcius.
1.4.2 Hypothesis
After doing some readings on some research projects which are relevant to this
project, hypotheses are made in line with the project objective. The hypotheses made are as
follow:
1. It is expected that thermal conductivity and will increase as the temperature of
nanofluid increases.
2. It is expected that viscosity will decrease as the temperature of nanofluid increases.

7
3. It is expected that thermal conductivity and viscosity will increase when the volume
fraction of nanoparticles in nanofluid increases.
4. It is expected that thermal conductivity and viscosity of nanofluid is much higher
than the thermal conductivity and viscosity of the base fluid as temperature
increases.
5. The pH is expected to have little changes as temperature and volume fraction
increases.
1.5 Project Outline
This project will focus on effect of volume fraction on the thermal conductivity and
viscosity of the nanofluid. As there is no literature on silver oxide being dispersed in
sodium chloride, this research will emphasize more on the trend of the thermal conductivity
and viscosity when temperature rises and when the volume fraction changes. The
experimental data will be presented in the form of graph based on the data acquired during
the experiment. The data will be compared to the existing literature on silver nanofluids
that uses different kind of base fluid.
1.6 Importance of Research
The growth in technologies in the industry has increase the need for more efficient
cooling system than the conventional cooling system. As technologies are getting more
advance and devices are getting smaller and smaller each day hence the needs for better
heat management has been one of the most important aspect to look into. It plays an
important role in ensuring their performance. There are some interests in extended surface
thermal technologies such as fins that are used to improve the efficiency of cooling fluids
but the improvement is limited. Hence, this has called on the research on nanofluids.

8
Nanofluids have shown big potential in heat transfer enhancement and have the
ability to replace the conventional fluid used in heat transfer process which includes water,
oil and ethylene glycol. Nanofluids are made by dispersion of nanoparticles inside a base
fluid. They are known to have higher thermal conductivity than the normal base fluid. High
thermal conductivity of nanofluids will improve the process efficiency of equipment and
increase the life span of equipment as there will be less thermal limitation on them.
Therefore research on nanofluid is important to cope with the growth of industry and the
miniaturization of devices.

9
Chapter 2
LITERATURE REVIEW
2.1 Overview
This part of thesis will cover the researches that have been done by previous
researchers on nanofluids that will help to gain the basic knowledge of nanofluids in order
to complete this research project. Besides that, literature review also is used as guidance to
validate the trend of results obtained in the experiment. The early part of the literature
review is organized by general topics on heat transfer before the topics that are related to
the research objective is being covered. These topics are important to complete the analysis
of the result.
2.2 Heat transfer process of Nanofluids
The growth of technology has called on to the replacement of the traditional
transport fluid like water. One of the potential fluid that has been discovered by scientist
and engineers as its replacement is nanofluid. Nanofluid is one of the challenges in science
world in order to solve thermal management issue that has been encountered in these
technology savvy days. Nanofluids have shown some interesting signs in its ability to
enhance the quality of heat transfer due to their excellent characteristics. Therefore many
researches has been done to get nanofluids as the new transport fluid in medium that are
using fluid as heat transfer medium. There are a few of researches that have shown
promising results of nanofluid heat transfer enhancement.

10
For example, Eastman et al. [13] reported a 15% increment of heat transfer
coefficient when copper oxide is dispersed in pure water compared to the pure water
without nanoparticles. The volume fraction used in the experiment is 0.9%.. There are also
several other research that shows that with low volume fraction of nanoparticles in base
fluid can enhance the heat transfer performance of nanofluid by almost 20% [14]. This
proves that nanofluids hold a great potential as heat transfer medium to replace the
conventional fluids.
Despite the potential that has been shown by nanofluids in the transfer enhancement
ability, they cannot be used as heat transfer medium yet. This is because there are still
problems in sedimentation and shearing flow when preparing nanofluids [15]. Besides that
the research done is still in primary stage and most of the research still lies on basic
knowledge of the nanofluids [14]. There are still little references on nanofluid properties
and heat transfer performance of nanofluids that have been published. Below is the chart
that shows research that has been published from 1993 until 2010 in SCOPUS database:
Figure 1: Number of `Nanofluids`, `Nanofluids and Heat Transfer`, ‘Nanofluid and
properties` research published in SCOPUS from 1993-2010 [16].
0 50 100 150 200 250
1993
1995
1996
1997
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
Nanofluids
Nanofluids
and Heat
Transfer
Nanofluids
and
properties

11
From figure 1 we see that the number of research in nanofluids and heat transfer as
well as nanofluids properties has increased a lot in recent years from 2005. It will keep
growing as more research on nanofluids heat transfer and nanofluids properties should be
done in order to understand the behavior of the nanofluids and be ready to be used in the
industry.
2.3 Thermal conductivity of Nanofluids
Thermal conductivity is one of the important thermo-physical properties to be
researched on in nanofluid. Usually the addition of nanoparticles in base fluid will result in
increment of thermal conductivity. The extent of thermal conductivity increment is affected
by few factors such as volume fractions, particles size, type of base fluids and temperature
[17]. Therefore in this section of literature review, study of these factors will be done to
give more understanding towards how thermal conductivity of nanofluids are affected
which is important for this research project.
2.3.1 Effects of Volume Fraction on Thermal Conductivity of Nanofluids
Many studies have been done to study the effect of volume fraction on the thermal
conductivity of nanofluids. First ever study of thermal conductivity which are done Masuda
et al. [18]. They used Al2O3 as nanoparticles and water as base fluid to prepare the
nanofluids. Nanoparticles are suspended in the base fluid by using two-step nanofluid
preparation method. In this study, they found that by using volume fraction of 4.3% at
31.85 degree celcius, thermal conductivity of nanofluids has been increased as much as
32.4% which is very high. They also found a trend which shows that as volume fraction
increases, the thermal conductivity of nanofluids increases as well. More research has been
done since their findings on this.

12
Li and Peterson [19] also have conducted an experiment to investigate the effect of
volume fraction on nanoparticles. In his experiment, he uses Al2O3 as nanoparticles and
water as base fluid as well. He prepared nanofluids with 2%, 4%, 6%, 8%, and 10%
volume fraction. The results again show that as volume fraction increases, thermal
conductivity of nanofluids increases together with it. Result from the experiment is that at
10% volume fraction of Al2O3 suspended in water at temperature of 34 degree celcius,
enhancement of 30% in thermal conductivity of nanofluid is observed.
Besides that, Hong et al. [20] have conducted an experiment using iron
nanoparticles and dispersing them into ethylene glycol solution. The result again shows that
with increasing number of volume fraction, the higher thermal conductivity of the
nanofluids become. The highest enhancement of iron nanoparticles in this experiment is at
volume fraction of 0.55% which gives 18% enhancement. The iron nanoparticles in this
case are being prepared using chemical vapor condensation process. Then the nanofluids
are prepared using two step methods.
As for silver nanofluids, not many experiments has been conducted to find the
thermal conductivity of them. There is an experiment has been conducted by Lee et al. [21]
with silver as nanoparticles and two base fluids are used as base fluids which are
water/ethylene glycol mixture and water/ammonia mixture. The experiment is done using
two-step method and it is observed that increment in volume fraction results in increment
of thermal conductivity.
There are few others research that has been done by researchers and most of them
found consistent result that as volume fraction increase, thermal conductivity of nanofluids
increase as well. All the research findings can be tabulated and summarize as shown table
below:

13
Table 1: Summary of literature review on effect of volume fraction on thermal conductivity
Source Nanofluids
Volume
fraction (%)
Best
enhancement
(%)
Masuda et al.
[18]
Al2O3 / Water 1.3 - 4.3 32.4
Li and Peterson
[19]
Al2O3 / Water 2.0 – 10.0 30
Hong et al. [20]
Fe / Ethylene
Glycol
0.1 – 0.55 18
Lai et al. [22] Al2O3 / Water 0 – 1.0 8
Jung et al. [23] Al2O3 / Water 0.5 – 1.8 32
Yi-Min and
Xuan [24]
Cu / Water 0.5 – 2.0 39
Ding et al. [25]
MWCNT /
Water
0.1 – 1.0 350
Wen and Ding
[26]
Al2O3 / Water 0.6 – 1.6 42

14
From the table summarize, it the best enhancement all happens at highest volume
fraction from the range except for Ding et al. [25] research as the 350% enhancement of
multi wall carbon nanotubes(MWNCT)/water nanofluid happens at volume fraction of
0.5%. The researchers reckon that the inconsistency of the results happen because of the
interaction between the walls of nanotubes during experiment. Besides that, the study done
by Murshed et al. [27] also gives an inconsistent results. They used hot-wire method to
determine the thermal conductivity of titanium oxide/water nanofluids which are varied
between 0.5% - 5% volume fraction. Result shows inconsistent trend in the thermal
conductivity of the nanofluids especially at low volume fraction. The researchers reckon
that either addition of cetyltrimethyl ammonium bromide (CTAB), long sonication time or
hydrophobic surface force might be the reason behind the inconsistent behavior. Therefore
we can conclude that thermal conductivity increases together with volume fraction for most
cases.
2.3.2 Effects of Temperature on Thermal Conductivity of Nanofluids
Different temperatures will give different thermal conductivity reading.
Temperature changes will change the kinetic energy of particles and atoms of nanofluids
hence giving a different reading of thermal conductivity [28].
An experiment has been conducted by Ravikanth and Debendra [29] on effect of
temperature on thermal conductivity. They used two-step method to prepare the nanofluids.
copper oxide is used as nanoparticle and mixture of ethylene glycol and water is used as
base fluid with 60:40 ratios. From the experiment, they have found that thermal
conductivity increase by 22.4% at temperature of 25 degree celcius and as temperature
increase the thermal conductivity increases as well. The highest temperature used is 90
degree celcius and have the highest enhancement with 47.8% of enhancement. Their
experiment shows that increase in temperature of nanofluids will increase their transfer
conductivity as well.

15
Besides that, Ghosh et al. [30] have done a study on effect of temperature on
copper-aluminum(Cu9Al4) nanofluids on thermal conductivity. In this experiment, they
have used copper-aluminum nanoparticles with the size of 4 nm diameter and water as base
fluid. Nanofluids with 0.48% volume fraction are prepared using two-step method. In the
experiment, they have found that as temperature increases, the thermal conductivity
enhacement increase as well. At temperature of 25 degree celcius, enhancement is about
90% and as it increases to about 43 degree celcius, the enhancement increases to about
105%. The highest temperature where data is taken is at about 55 degree celcius and the
enhancement shows is about as high as about 120%. This shows that as temperature
increase, thermal conductivity increases as well.
Walvekar et al. [31] also has conducted an experiment on effect of temperatures on
thermal conductivity enhancement. In their experiment, they use carbon nanotubes (CNT)
as nanoparticles and water as base fluids. They have also added gum arabic(GA) as
stabilizer in this experiment to form carbon nanotubes nanofluid. The volume fractions of
0.01%, 0.02%, 0.04%, 0.08% and 1% are used in their experiment. The temperatures are
set to be from 25 degree celcius until 60 degree celcius. The results they have found is as
follow:

16
Figure 2 : Effect of temperature on thermal conductivity enhancement [31].
As shown in figure 2, they have found that at every volume fraction, as temperature
increases, the enhancement of thermal conductivity increases as well. The highest
enhancement of 287.5% is observed at temperature of 60 degree celcius for 0.1% volume
fraction. Therefore we can conclude that for most cases in nanofluids research, thermal
conductivity will increase as temperature increase.
2.3.3 Effects of Base Fluids on Thermal Conductivity of Nanofluids
Different base fluids have different thermal conductivity. When preparing
nanofluids, nanoparticles will be dispersed in a base fluid. Therefore, depending on the
base fluids used, the thermal conductivity enhancement will be different. The difference
happens because of viscosity of base fluid will affects the Brownian motion of
nanoparticles and resulting in changes of thermal conductivity [32].
0
50
100
150
200
250
300
350
0.01 0.02 0.04 0.08 0.1
Enhancement(%)
volume fraction (%)
Effect of temperature on thermal
conductivity enhancement
25 º C
30 º C
40 º C
50 º C
60 º C

17
There has been an experiment done by Beck et al. [33] on effects of different base
fluid on alumina nanofluids. In this experiment, they have used water, ethylene glycol and
mixture of ethylene glycol with 50:50 ratios as base fluid. The thermal conductivity are
measured using hot-wire method. In this experiment, the alumina nanoparticles used have
an average size of 12 mm. The result shows that the highest enhancement is when alumina
is dispersed in ethylene glycol followed by ethylene glycol/water mixture and finally water.
This shows that different base fluid does give different type of enhancement.
Besides that, an experiment is done by Wang et al. [34] on alumina and copper
oxides nanoparticles dispersed in four different base fluids which are water, ethylene
glycol, vacuum pump fluid and engine oil. For alumina nanoparticles, the best
enhancement happens when it is dispersed in ethylene glycol followed by engine oil and
water. The lowest enhancement happens in vacuum pump base fluid. As for copper
nanoparticles, the base fluids that they tested with are only ethylene glycol and water. In
this case it has been concluded that both base fluid gives about the same enhancement to
the thermal conductivity. These again show that base fluid does affect thermal conductivity
enhancement but it is not necessarily one base fluid is superior to another. It depends on
nanoparticles reaction towards the base fluid.
Xie et al. [35] also have conducted an experiment to analyze the effect of base
fluids on thermal conductivities of nanofluids. In their experiment, they used hot-wire
method to determine thermal conductivity of nanofluid. Nanoparticles used in the
experiment are aluminum oxide with volume fraction of 5%. The base fluids used in the
experiment are water, glycerol, ethylene glycol, and pump oil. The results can be
summarized as below:

18
Figure 3: The percentage of aluminum oxide nanofluids enhancement with different type of
base fluid [35].
As shown in figure 3, the best enhancement happens when aluminum oxide is
dispersed in pump oil followed by ethylene glycol, glycerol and water respectively. Besides
that, it is also found in this experiment that the thermal conductivity enhancement is lower
for higher base fluid initial thermal conductivity. This experiment is consistent with
Maxwell`s [3] theory.
Liu et al. [36] have conducted an experiment with using multi walled carbon
nanotubes (MWCNT) nanoparticles as nanoparticles with ethylene glycol and synthetic
engine oil as base fluid. In this experiment, hot-wire method are used to measure thermal
conductivity. The experiment shows that the MWCNT/synthetic engine oil nanofluids have
a bigger enhancement than the MWCNT/ethylene glycol nanofluids. MWCNT/synthetic
engine oil nanofluids have thermal enhancement of 30% whereas MWCNT/ethylene glycol
nanofluids have 12.4% of thermal conductivity.
0 5 10 15 20 25 30 35 40
Al2O3 + Water
Al2O3 + Glycerin
Al2O3 + Ethylene Glycol
Al2O3 + Pump Oil
Type of Nanofluids and Enhancement (%)

19
All these research have proven that type of base fluid does affect the thermal
conductivity of nanofluids forms. Hence more combination of nanoparticles and base fluids
can be researched on to find the best combination to be used in industry.
2.3.4 Effects of Particle Size on Thermal Conductivity of Nanofluids
Particles size of nanoparticles play an important role in determining thermal
conductivity of nanofluids. There are ranges of different sizes of nanoparticles used in
preparation of nanofluids but the effective size is below 100nm.
An experiment has been conducted by Teng et al. [37] on effect of aluminum oxide
particle size on thermal conductivities of Al2O3 / Water nanofluids. Two-step method is
used to produce the nanofluids in this experiment and particles sizes used are 30 nm, 50nm
and 100nm. The experiment is done at three different temperatures which 10 degree
celcius, 30 degree celcius and 50 degree celcius. The results can be summarized as follow:
Figure 4 : Best enhancement for 3 different particle sizes at 3 different temperatures [37].
0
2
4
6
8
10
12
14
16
10 30 50
Bestenchancement(%)
Temperature (Celcius)
Best enhancement for different particles size
100 nm
50 nm
30 nm

20
From figure 4, it can be seen that at every temperature, particles size of 30 nm gives
the best enhancement to the thermal conductivity of nanofluids formed. This is because as
the size of particle become smaller, the surface area of solid-liquid interface is bigger.
Hence more collisions happen among particles resulting in higher Brownian motion
creating a higher value of thermal conductivity.
Chopkar et al. [38] studied the effect of particles size on thermal conductivity of
Al2Cu and Ag2Al nanoparticles using two different base fluid which are water and ethylene
glycol. In their research, they used 30nm and 120nm nanoparticles. Nanofluids are
prepared using two-step method and thermal conductivity is determined by hot-wire
method. For both base fluid, Al2Cu and Ag2Al nanoparticles with 30nm shows greater
thermal conductivity enhancement than 120nm nanoparticles. This again shows that
smaller nanoparticles resulted in higher enhancement.
There is also a research done by Mintsa et al. [39] on effect of particle size on
thermal conductivity of nanofluids. In their experiment, aluminium oxide is used as
nanoparticle and water is used as base fluid. Aluminium oxides used have the size of 36 nm
and 47 nm. The nanofluids are prepared using two-step method and thermal conductivities
are taken in the range from 20 degree celcius to 50 degree celcius. In their experiment, they
observed that at room temperature, the thermal conductivity of both particle size has about
the same thermal conductivities. Nevertheless, as temperature increase, the nanofluids
prepared with aluminium oxide with size of 36nm shows higher enhancement than
nanofluids prepared with aluminium oxide with the size of 47 nm. Hence this again shows
that smaller particle size increase thermal conductivity of nanofluids.
Therefore, we can conclude that in most cases of nanofluids research it can be
observed that thermal conductivity of nanofluids increases as particle size decrease. This
happens in most of the experiments done by researchers.

21
2.4 Viscosity of Nanofluid
Viscosity is one of important properties in nanofluids. This determines the behavior
of nanofluids if they are to be applied in real application since viscosity affects the pressure
drop during convection. Similar to thermal conductivity, viscosity are affected by some
parameters which are volume fraction of nanoparticles used to form the nanofluids,
temperature of nanofluids and also particle size of nanoparticles used during the synthesis
of nanofluids. [17].
2.4.1 Effects of Volume Fraction on Viscosity of Nanofluids
Different volume fraction of nanoparticles dispersed in base fluids will form
nanofluids of different volume fractions. This is because addition of nanoparticles will
disrupt the attraction between molecules in the base fluids.
There are limited amount of studies that has been done on effect of volume fraction
on viscosity. There is a study done by Wang et al. [34] to measure the effect of volume
fraction on viscosity. He uses two nanofluids in his study which are aluminum oxide
nanoparticles and water as base fluid and also aluminum oxide as nanoparticles and
ethylene glycol as base fluids. In their study, it shows that as volume fraction of aluminum
oxide increases in base fluids, the viscosity also increases as well. This happens for both
nanofluids that they have prepared.
Besides that, Das et al. [40] also has done an experiment using aluminium oxide as
nanoparticles and water as base fluids. In their experiment, they have found that increase in
volume fraction also increase the viscosity of nanofluids. Besides that, they also have
deduced the possibility of nanofluids having non-Newtonian and viscoelastic behaviour in
some cases. Therefore more study on viscosity of nanofluid need to be done before they
can be used in real application.
Ding et al. [25] has done a research using carbon nanotubes as nanoparticles and
water as base fluids. They found out that viscosity of nanofluids formed increase as volume

22
fraction increase. Besides that, they also found that there are shear thinning behaviour in
nanofluids where shear rate are higher at the wall which indicates its ability to provide a
good fluid flow performance.
Therefore in can be concluded that as volume fraction increases, viscosity of
nanofluids also increase. This trend is almost the same for most cases done by few
researchers.
2.4.2 Effects of Temperature on Viscosity of Nanofluids
As temperature changes, the viscosity of nanofluids also change. There are many
researches that have shown that temperature increase can reduce the viscosity of
nanofluids. This is because as temperature increase, the molecular attraction of nanofluids
atoms are affected hence reducing the viscosity of nanofluids.
Yang et al. [41] have conducted an experiment to observe the effect of temperature
on viscosity. In their experiment, they have used graphite with volume fraction of 2% as
nanoparticles and automatic transmission fluid (ATF) as base fluid. The experiments are
done using four different temperatures which are 35, 43, 50 and 70 degree celcius. They
found that as temperature increase, the viscosity of nanofluids formed decreased. The
highest viscosity is at 35 degree celcius and the lowest viscosity is at 70 degree with the
value of 41.4 mm2
·s−1
and 12.2 mm2
·s−1
respectively.
Besides that, Anoop et al. [42] also has done a study on effect of temperature on
viscosity. In their experiment, three nanofluids are used which are combination of copper
oxide and ethylene glycol, aluminum oxide and ethylene glycol, and aluminum oxide and
water. They uses volume fraction of 0.5%, 1%, 2%, 4%, and 6% and regulate the
temperature from 20 to 50 degree celcius. They have found that all three nanofluids at
every volume fractions have the same trend which is as temperature increases, the viscosity
of nanofluids decreases.

23
Namburu et al. [43] research shows that viscosity decreases exponentially with the
increment of temperature. They use copper oxide ranging from 0 to 6.12% volume fraction
as nanoparticles and mixture of ethylene glycol with water as base fluids. In their
experiment, they have used temperature in the range from 35 to 50 degree celcius. Besides
that, they also found that nanofluids acts like a Newtonian fluids in that range of
temperature.
Therefore it can be concluded that as temperature increases, viscosities of the
nanofluids will decrease. This is consistent in the study done by few researchers on the
effect of temperature on viscosity of nanofluids.
2.4.3 Effects of Particle Size on Viscosity of Nanofluids
Nanoparticles come in many sizes. Therefore studies on effect of particle size on
viscosity of nanofluids are done by some researcher. The results show different kind of
trend.
Nguyen et al. [44] have conducted an experiment on effect of aluminum oxide size
on the viscosity of the nanofluids formed using water as base fluids. In their experiment,
aluminum oxide with 36 nm and 47 nm and volume fraction of 4% are used. They found
that viscosity of nanofluids using 36 nm aluminum oxide nanoparticles is lower by 5% than
one with size of 47 nm. As volume fraction increase, the viscosity difference is greater.
Therefore they have concluded that as particle sizes increase, viscosity of nanofluids also
increases.
He et al. [45] also have conducted an experiment to determine that particle size
have on nanofluids viscosity. In his experiment, titanium oxide with the size of 95 nm, 145
nm and 210 nm are used as nanoparticles and water is used as base fluids. They have found
that as the nanoparticle size increase, the nanofluids viscosities also increase. Their findings
is consistent with the studies done by Nguyen et al. [44].

24
On contrary, Lu and Fan [46] found that viscosity decreases as particle size increase
during their experiment. They use aluminum oxide as nanoparticles in addition to water and
ethylene glycol as the base fluids. Besides that, they also discovered that for nanoparticles
with the size more than 30 nm, the change in shear viscosity is very small.
Anoop et al. [42] also have the same result as Lu and Fan [46] during their
experiment. They use 45 nm as well as 150 nm of aluminum oxide as nanoparticles and
water as base fluid. In the experiment, they observed that the viscosity is lower for the
sample using 150 nm of aluminum oxide than the viscosity using 45 nm of aluminum oxide
at all 2%, 4%, and 6% volume fraction.
Therefore more research needs to be done in order to understand the behavior of the
effect of particle sizes on the viscosities of nanofluids as researchers experimental results
have shown contradiction between them.
2.5 pH of Nanofluids
Currently, there is very little research done on the pH of nanofluids. pH of
nanofluids is an important properties since it affects the stability of nanofluids. There is
very little research done on effect of pH on nanofluids.
Yousefi et al. [47] has done a research using multi walled carbon nanotubes
(MWCNT) as nanoparticles and water as base fluids. In their research, they use Triton X as
additive to regulate pH of nanofluids to 3.5, 6.5 and 9.5. They found that a nanofluid is
most stable at pH 3.5 followed by 6.5 and lastly is 9.5. The author suggest that this
phenomenon happens because as solution become more acidic, there will be higher charges
at nanofluids surface which helps reducing the nanoparticles aggregation hence producing a
more stable nanofluids.

25
There is also a study done by Murshed et al. [48] on effect of pH in nanofluids
stability. In their experiment, they used titanium oxide as nanoparticles and water as base
fluids. The experiment is conducted by using pH 3.4 and pH 9. They found that the thermal
conductivity decrease by 2% at pH 9. Therefore they conclude that pH have very small
effect on nanofluid.
Wang et al. [49] also has conducted an experiment on finding optimum pH for
nanofluids combination of copper as nanoparticles and water as base fluid also aluminum
oxide as nanoparticles and water as base fluids. In their research, they found that the
optimum pH for combination of copper and water nanofluids is 9.5 whereas optimum pH
for combination of aluminum oxide and water nanofluids is 8.
The findings show that different combinations of nanofluids have different optimum
pH. Therefore more studies should be done on effect of pH on nanofluids because there are
so many contradictions in researchers’ findings.
2.6 Conclusion
From literature study, the findings of previous researchers on thermal conductivity,
viscosity and pH of nanofluids are studied and summarize. Besides that, it can be seen that
very little studies are done using silver oxide nanoparticles and almost no study are being
done using sodium chloride solution as base fluid. Therefore in this research, silver oxide is
chosen as nanoparticles and sodium chloride is chosen as the base fluids. In addition, there
are very little research done on viscosity and pH of nanofluids. Therefore study on
viscosity and pH are done on nanofluids as they play an important role in enhancing the
thermal conductivity of nanofluids.

26
Chapter 3
METHODOLOGY
3.1 Overview
In this project, proper methodology is required to complete this project in order.
Therefore the first phase of this research project is the planning phase to make sure this
research moves in orderly manner. Secondly it will move to the experiment phase where
the experiment is conducted after a proper plan has been done. After experiment has been
done, the research moves to the analysis phase where results are sorted and analyzed
properly.
3.2 Methodology
3.2.1 Planning Phase
Planning phase is the most important phase of in this research project because
without a proper planning, this research will not be able to be completed within the time
given. First step in this phase is to determine the objectives of this research. The objective
of the research is stated in the Chapter 1 of the report. After determining the objective,
basic knowledge to conduct the research and analyzing the results are obtained by doing
some literature reading which are documented in Chapter 2. After knowing the objectives
and knowledge on how to conduct the research, the experiment will moves to the
experiment before finally going to the analysis phase which will be explained in the next
phase.

27
3.2.2 Experiment Phase
In experiment phase, there will be three steps to be done. First is the set-up phase
where all the instruments needed to be used in the experiment are tested and calibrated to
get as little error as possible. This will be explained in Chapter 4 of the report. After going
through set-up phase, the experiment will move to the sample preparation phase where
nanoparticles and base fluids are prepared before experiment is conducted. This will be
explained in Chapter 5 of the report. Finally after experiment is conducted, all the data are
collected using the instrument that has been calibrated which are explained in Chapter 4 of
the report.
3.2.3 Data Analysis
In this phase of methodology, all the data obtained from experiment is recorded and
tabulated in excel. The data of thermal conductivity of nanofluids, viscosity of nanofluids,
and also pH of nanofluids using 0.05% volume fraction, 0.1% volume fraction, 0.2%
volume fraction, 0.3% volume fraction and 0.5% volume fraction at temperature in the
range of 30 to 80 degree celcius are analyzed and graphs of them are generated. The graph
that compares the effect of temperature and volume fraction on thermal conductivity,
viscosity and pH are presented and discussed as well. These will all be placed in Chapter 6
of the research. Besides that, the suggestion for further improvement and summary of this
research will be explained in Chapter 7.

28
Chapter 4
EXPERIMENTAL SET-UP
4.1 Overview
In this chapter, the setup of experiment will be explained. There are three type of
setup needs to be done which are used to conduct this experiment which are nanofluids
setup, sonication setup and measuring equipment setup.
4.2 Nanofluid
In this experiment, base fluid used is sodium chloride with molarity of 1 mol.
Therefore to form sodium chloride solution, an amount of sodium chloride are used and
dispersed in a volume of distilled water. As for nanoparticles, silver(I) oxide is used.
4.2.1 Base fluid
SODIUM CHLORIDE
Sodium chloride is obtained from Monash University Sunway Campus Chemical
Laboratory in powder form. This sodium chloride is produced by R & M Chemicals Ltd.
and has an ionic formula of NaCl. It has molar mass of M = 58.44 g/mol. Sodium chloride
is inorganic compound and widely used in food preservation. It is also very soluble in water
with solubility of 359 g/L. Figure 5 shows the sodium chloride used in the experiment.

29
Figure 5 : Sodium chloride
DISTILLED WATER
Distilled water is obtained from Monash University Sunway Campus Chemical
Laboratory. Distilled water is water that is produced by distillation. Distillation is done to
remove impurities in the water and the process of distillation includes boiling of water and
condensing the steam in a clean container. Figure 6 shows the distilled water used in the
experiment

30
Figure 6: Distilled water
MAGNETIC STIRRER
Magnetic stirrer used in this experiment is bought by Monash University Sunway
Campus Chemical Laboratory. It is made by Heidolph Instrument. The model of the stirrer
used is MR Hei Standard. The purpose of using magnetic stirrer is to make sure the sodium
chloride is totally dispersed in distilled water and homogeneous. Besides that, it is also used
to heat up the base fluid for enhancement calculation as it has heater function as well.
Figure 7 shows the magnetic stirrer used in the experiment.
Figure 7: Magnetic Stirrer

31
PARAFILM
Parafilm used in this experiment is obtained from the Monash University Sunway
Campus Chemical Laboratory. It is made by Pechiney Plastic Packaging Company.
Parafilm is a plastic paraffin film and known for its ductility, malleability, odourless and
cohesive behaviour. In this experiment, parafilm is used to cover beaker of the base fluid
prepare in order to avoid any dust from entering the fluid not used. Figure 8 shows the
parafilm used in this experiment.
Figure 8 : Parafilm
ALUMINUM FOIL
Aluminum foil is obtained from Monash University Sunway Campus Mechanical
Laboratory. The aluminum foild used is made by Diamond. Aluminum foil is a thin
aluminum metal that is prepared with thickness as small as 0.2 mm. Aluminum foil is used
to cover the nanofluids during sonication to prevent the evaporation of base fluids to the
surrounding. Aluminum foil instead of parafilm because parafilm tends to deform at high

32
temperature while aluminum foil does not. Figure 9 shows the aluminum foil used in the
experiment and figure 10 shows the nanofluids covered with aluminum foil.
Figure 9 : Aluminium foil
Figure 10 : Nanofluids covered with aluminium foil before sonication

33
4.2.2 Nanoparticle
Nanoparticles used in this experiment is silver(I) oxide. Silver(I) oxide has the
molecular formula of Ag2O. It is obtained from Sigma-Aldrich with product number of
85260 in powder form. It has the particle size of about 60 nm. The density of silver oxide
used is 7.143 g/cm3
and the molecular mass is 231.735 g/mol. Nanoparticles used are
shown in figure 11 and figure 12.
Figure 11 : Silver(I) oxide nanoparticles in the bottle
Figure 12 : Silver(I) oxide nanoparticles in powder form

34
4.3 Sonication
Sonication is the process where nanofluids are synthesis. This is the part where
nanoparticles will be dispersed in the base fluid using sonication process. Therefore before
experiment is conducted, there are few setups need to be done. First is the setting of
ultrasonic processor, followed by sound enclosure setting and ultrasonic probe.
4.3.1 Ultrasonic Processor
Ultrasonic processor is used in the preparation of nanofluid in two-step method.
Sonication has the role of dispersing silver(I) oxide in sodium chloride solution to form
silver nanofluids. The ultrasonic processor used in this experiment is made by Qsonica with
the model of Q 700. This sonicator specification for power is 700 watts and frequency is 20
kHz and voltage of 110V at 60 kHz. The amplitude in this experiment is set at 20 because
according to the instruments manual, it is safe amplitude in sonication of liquid less than
250mL. In this experiment, the amount of liquid used is 120 ml. The sonication process is
set to be 5 hours and shutdown temperature is set to be 90 degree celcius. The pulse on
time is 3 seconds and pulse off time is 1 seconds.
Based on operator`s manual, the ultrasonic electric generator will converts the
alternative current power to a 20kHz signal. The transducer then will be the signal to a
mechanical vibration which then are amplified and transmitted to the nanoparticles and
base fluid mixture by the longitudinal expansion and contraction of ultrasonic probe. The
constant vibration will create a pressure waves in the sample. As the amount of vibration
increase, microscopic bubbles are formed in the sample. These microscopic bubbles will
implode creating shock waves and increase the sample`s temperature. This is known as
cavitation. Although the effect is minimal, as thousands of cavitation happens, high energy
is released in the cavitation field. Figure 13 shows the ultrasonic processor used in the
experiment and figure 14 show the settings done for the sonication process.

35
Figure 13: Ultrasonic Processor with probe
Figure 14: Ultrasonic processor sonication setting.

36
4.3.2 Ultrasonic Probe
In this experiment, the ultrasonic probe used has the model number of CL-334.
Probe has diameter of 0.5 inch which provide high intensity sonication. According to the
manufacturer, probe with diameter 0.5 inch are recommended for small samples ranging
from 10 to 250 mL samples. Larger samples will requires larger probe diameter because the
small diameter may not be able to disperse the large sample completely. In this experiment
0.5 inch as probe diameter is enough as the sample used has the volume of only 120 mL.
There are two methods to use ultrasonic probe which are direct sonication and indirect
sonication.
Direct sonication is done by inserting the probe directly into the sample and let
sonication process starts. This is used in this experiment. Probes can are made from
titanium. Indirect sonication on the other hand is done by inserting the probe in a tube and
the tube will transmit the ultrasonic energy to the water. This method is used if the sample
size is very small as this eliminates the probability of sample loss by evaporation. Figure 15
shows the probe used in the experiment.
Figure 15 : Ultrasonic probe

37
4.3.3 Sound Enclosure
Sonication is a very noisy process. Therefore sonication process is done in a sound
enclosure where probes are inserted there. The inside of sound enclosure is covered with
polystyrene. According to manufacturer’s manual, sound enclosure can reduce the noise by
almost 20 dBa.
Besides that, the enclosure also contains an internal support rod as well as converter
mounting system which will hold the probe tightly inside the enclosure. There is a window
in front of the enclosure to monitor the sonication process. In addition, sonication process
produces waves which will attract dust from surrounding. Therefore this enclosure can
reduce the probability of dust entering the sample during sonication process. Figure 16
shows the sound enclosure used in the experiment.
Figure 16: Sound Enclosure
Sound Enclosure

38
4.4 Measuring apparatus
Measuring apparatus used in this experiment are weighing machine which is used to
prepare nanoparticles and base fluids, thermal conductivity analyzer which is used to
measure thermal conductivity, vibro viscometer which is used to measure viscosity and
finally pH meter which is to measure the pH of the nanofluids. Conical-bottom centrifuge
tubes on the other hand are used to store the fluid to take the thermal conductivity reading.
4.4.1 Weighing Machine
Weighing machine used is obtained from Monash University Sunway Campus
Mechanical lab. The weighing machine used is made by A & D Instruments Ltd. and the
model of the weighing machine used is FX- 3000i series. This machine has the accuracy of
± 0.002g. This weighing machine is used to measure the weight of nanoparticles and
sodium chloride. Parafilm is place on the weighing machine and re-zero before
nanoparticles and sodium chloride is placed on them to make sure the correct weight are
used in the experiment. Figure 17 shows the weighing machine used in the experiment to
measure the weight of nanoparticles and sodium chloride.
Figure 17 : Weighing machine Fx-3000i

39
4.4.2 Thermal Conductivity Analyzer
Thermal conductivity analyzer used in this experiment is obtained from Monash
University Sunway Campus Mechanical Laboratory. It is made by Decagon devices, Inc.
and the model is called KD2 Pro. A small needle with KS-1 sensor is used to measure the
thermal conductivity of the nanofluids for 60 seconds and the value will be displayed at
KD2 Pro displaying device. KD2 Pro has the accuracy of ± 5%.
KD2 Pro is constructed with the working principle of hot wire method. According
to manual given by operator, there are two temperature response equations to explain how
KD2 Pro works. First is the when 0 < t ≤ t1
( ) (4.1)
After the heating is off, for t > t1 , the temperature change equation is defined as:
̇
( ) ( ( )
) (4.2)
where,
̇ = rate of heat dissipation
k = thermal conductivity of the medium
Ei = exponential integral
r = radial distance from heating source
t = time
t1 = heating time
α = thermal diffusivity

40
The thermal properties of material and thermal diffusivity are determined by fitting
the time series for heating in equation 1 and for cooling in equation by using non-linear
square method which is explained in the literature given by the operator. KD2 Pro also will
display the error during measurement and according to the manual error of 0.01 or less will
give the accurate reading of thermal conductivity. Figure 18 shows the KD2 Pro used in the
experiment and figure 19 show the KS-1 sensor needle.
Figure 18: KD2 Pro device
Figure 19: KS-1 sensor needle

41
4.4.3 Vibro Viscometer
Vibro viscometer used is provided by Monash University Sunway Campus
Mechanical Laboratory. It is made by A & D Instrument Ltd. and the model of the
viscometer is SV-10. This viscometer has the accuracy of ± 1%. SV-10 viscometer
measures the viscosity of the fluid by controlling the amplitude of the sensor plate which is
place inside the sample. Electric current will drive the sensor plate to determine the
viscosity. This viscometer can determine the dynamic viscosity of the sample ranging from
0.3 mPa.s to 10 000 mPa.s according to the manual. SV-10 also can determine the
temperature of the samples by having one temperature sensor place in between the two
sensor plates. Changes in temperature and viscosity can be observed clearly from the
viscometer display. Figure 20 shows the vibro viscometer used in the experiment and figure
21 shows the sensor plate and temperature sensor in viscometer.
Figure 20: The SV-10 Vibro Viscometer

42
Figure 21: Sensor plate and temperature sensor
4.4.4 pH meter
pH meter used is provided by Monash University Sunway Campus Mechanical
Laboratory. It is made by Sartorius Company with model number of PB-10. This pH meter
has measuring accuracy of ± 1% in pH reading and ± 0.2 degree celcius in temperature
reading. pH meter has an electrode which is integrated with temperature sensor to measure
the pH and temperature of sensor. The electrode are placed inside the sample and pH of the
sample will be displayed on pH meter. PB-10 pH meter can measure a range of pH from 0
to 14 and temperature in the range of -5 to 105 degree celcius according to operator`s
manual. Figure 22 shows the pH meter used in the experiment.
Sensor
plate
Temperature
sensor

43
Figure 22: PB-10 Standard pH meter.
4.7 Conical-bottom centrifuge tubes
Conical-bottom centrifuge tubes are supplied by Monash University Sunway
Campus Mechanical Laboratory. It has 50mL capacity and used to store nanofluids in order
to take thermal conductivity data. The tubes can withstand temperature in the range of -40
to 80 degree celcius. Figure 23 shows the conical centrifuge tube used in the experiment.
Figure 23: Conical-bottom centrifuge tube

44
Chapter 5
EXPERIMENTAL PROCEDURES
5.1 Overview
In this experiment, there are three major processes in completing this experiment.
Firstly is the sample preparation process. Then after sample are prepared, it will go through
sonication process and finally the data collecting process.
5.2 Sample preparation
There are two samples needs to be prepared which are the sodium chloride base
fluids and silver oxide with volume fraction of 0.05%, 0.1%, 0.2%, 0.3% and 0.5%.
5.2.1 Base fluids preparation procedure
1. One litres of one mol sodium chloride (NaCl) solution are prepared;
i) Molar mass of NaCl = 58.44 g/mol
ii) Molarity of NaCl = 1 mol
( ) (5.1)
Weight of NaCl = 58.44 g/mol x 1 mol
= 58.44 g
2. Weight 58.44 g of NaCl powder on FX-3000i weighing machine
3. Place the NaCl powder in a 1 litres beaker
4. Add distilled water until it reaches 1 litres
5. Place the 1 litres beaker on a magnetic stirrer for 2 minutes to make the solution
homogenous
6. Pour 120 ml of sodium chloride in a 150 ml beaker

45
5.2.2 Nanoparticles preparation procedure
1. Amount of nanoparticles needed are calculated for volume fraction.
a. Volume concentration (φ = Vnanoparticles / Vbase fluids x 100)
b. φ = 0.05%
c. V basefluid = 120 mL
d. Density of Al2O, = 7.143 g/mL
Mass nanoparticles is calculated using,
2. Weight 0.428 g of silver oxide on Fx-3000i weighing machine
3. Place the nanoparticles inside the 120mL sodium chloride
4. Step 1 until 3 is repeated for sample preparation of 0.1%, 0.2%, 0.3% and 0.5%
volume fraction. Calculations of mass of others are in Appendices.
Table 2: Mass of silver oxide for different volume fraction
Volume Fraction (%) Mass of Nanoparticles (g)
0.05 0.428
0.1 0.856
0.2 1.712
0.3 2.568
0.5 4.280

46
Figure 24 : Nanoparticles in base fluids prepared
5.3 Sonication Process
After nanoparticles are placed in base fluids, the beaker is covered with aluminum
foil. This is to prevent dust from entering the nanofluids during sonication process and also
to prevent the evaporation of nanofluids. The beaker is then placed in the sound enclosure
and ultrasonic probe are placed in the middle of total volume of the beaker. This is to
prevent the probe from touching the wall of beaker incase the beaker moves during
sonication process. Besides that, placing the probe in the middle of the total volume also
makes the efficiency of sonication higher as all nanoparticles are being covered during the
process. After that sonication process will start. Sonication process is chosen as it can
reduce the aggregation during nanofluids synthesis. The sonicator is set to run for 5 hours
with 3 seconds pulse on and 1 second pulse off. This is to prevent the sonicator from
overheating and breakdown. After sonication process is done, nanofluids are formed and
data are ready to be collected. Data are collected 5 times in the range of 30 degree celcius
to 80 degree celcius. As for base fluid, it is heated until 80 degrees using Heidolph MR Hei
Standard and thermal conductivity and viscosity are taken so at temperature difference of ±
1 degree celcius of the data taken for nanofluids for enhancement calculation.

47
Figure 25 : Ultrasonic probe tip at the centre of nanofluid
Figure 26 : Sonication process
Figure 27 : 5 hours sonication time

48
5.4 Data collection
In this experiment, three thermo-properties of nanoparticles are taken. Firstly
thermal conductivity of nanofluids is taken using KD2Pro. Five data are taken in the range
of 30 to 80 degree celcius. Then viscosity of nanofluids is taken using SV-10 Vibro
Viscometer. Five data are taken as well in the range of 30 to 60 degree celcius. Finally PB-
10 pH meter is used to measure the pH of nanofluids. Five data again are taken in the range
of 30 to 70 degree celcius.
5.4.1 KD2 Pro
KD2 Pro is used to measure the thermal conductivity in this experiment. Before
thermal conductivity of the nanofluids is taken, calibration of KD2 Pro and KS-1 sensor are
conducted using KD2 Pro Verification Standard Glycerin. KD2 Pro Verification Standard
Glycerin has thermal conductivity of 0.285 W/m.K. Five measurement are taken during
calibration and the results is as follow.
Table 3: Calibration using KD2 Pro Verification Standard Glycerin
Temperature (⁰C) Thermal Conductivity (W/ m.K) Error
24.59 0.282 0.0083
24.78 0.285 0.0038
25.03 0.283 0.0074
24.97 0.282 0.0086
24.69 0.283 0.0077
The results shows error which is less than 0.01 hence the measurement is almost accurate.
In this experiment, nanofluids formed are placed in conical-bottom centrifuge tube
for data collection. The KS-1 sensor needle is place in the middle of the tube and hold for
60 seconds to get accurate data. Movement of needle can affect the accuracy of data
acquired. Besides that of KS-1 sensor needle also needs to be straight as bended sensor will
affect accuracy of data acquired as well.

49
Figure 28: KD2 Pro Verification Standard Glycerin
Figure 29: KS-1 sensor needle placed at the centre of the base fluid

50
5.4.2 SV-10 Vibro Viscometer
SV-10 Vibro Viscometer is used to measure the viscosity of nanofluid. Before
viscosity of nanofluids are taken, viscosity of distilled water at are tested using vibro
viscometer observe the accuracy of the viscometer. According to operator`s manual,
distilled water can be used to test the accuracy of the viscometer. Therefore five data are
taken using distilled water. It is known that distilled water has a viscosity of 1.05 mPa.s at
25 degree celcius. The result of testing is as follow:
Table 4: Calibration using distilled water
Temperature (⁰C) Viscosity (mPa.s)
24.9 1.05
25.0 1.04
24.9 1.05
25.1 1.04
25.0 1.05
The data taken only have differences of 0.01 mPa.s between them which show that the
device is working properly.
When taking readings, sample is poured until 35 mL or 45 mL mark. Besides that,
for accurate reading, half of the thin bended side of the sensor is immersed into the
samples. Avoid vibration when taking reading as it can reduce the accuracy of the result
taken. If possible, use a vibration free table when taking reading.

51
Figure 30: Correct set up to take viscosity data
5.2.3 PB-10 pH meter
PB-10 pH meter is used to measure the pH of nanofluids. Before measurements are
taken, the pH meter is calibrated using pH buffer solution. Five data are taken using pH 7
buffer solutions.
Table 5: Calibration using pH buffer solution of 7
Temperature (⁰C) pH level
25.1 7.00
24.9 7.01
25.0 7.00
24.9 7.00
25.1 6.99
The data obtain from calibration of pH meter shows difference of only 0.01 in pH reading
and 0.01 for temperature reading. This shows that pH meter is working properly.
In this experiment, electrode of pH meter must be fully immersed in the liquid
sample in order to obtain accurate results. Besides that, the data must be taken on a
vibration free table as vibration will reduce the accuracy of data collected.

52
Figure 31: Picture above shows pH Buffer Solution.
Figure 32: pH Electrode fully immersed in base fluid.
5.5 Sonication time
In this experiment, sonication time is chosen to be 5 hours. This is because
experiment when using 3 hours and 4 hours sonication time gives very fluctuating data on
thermal conductivity and also pH. Besides that, the viscosity difference also is huge. This is
because of agglomeration of samples and stability of nanoparticles affected the results. At 5
hours sonication time, the data of thermal conductivity, viscosity and pH is more stable.
The graph that compares the differences of data obtained for thermal conductivity
sonication time of 3, 4 and 5 hours for 0.05% volume fraction is presented in Appendices.

53
Chapter 6
RESULTS AND DISCUSSION
6.1 Overview
In this chapter, the results obtained from the experiments done will be presented in
graphs. Every finding on thermal conductivity, viscosity and pH of Ag2O-NaCl nanofluids
in every volume fraction of 0.05%, 0.1%, 0.2%, 0.3%, and 0.5% will be analyzed and
comparison of the difference between volume fraction and temperature will be discussed
thoroughly.
6.2 Results
In this part, the findings of thermal conductivity, viscosity and pH of Ag2O-NaCl
nanofluids with volume fraction 0.05%, 0.1%, 0.2%, 0.3% and 0.5% are presented in
graph.
6.2.1 Volume fraction of 0.05% Ag2O-NaCl nanofluid
This section will be divided into three parts which are thermal conductivity,
viscosity and pH of nanofluids. As mentioned in section 5.2.2, amount of silver(I) oxide
used in this section is 0.428 g and 120 mL of sodium chloride solution forming 0.05%
Ag2O-NaCl nanofluid.

54
THERMAL CONDUCTIVITY
Thermal conductivity is the ability of an object or substance in conducting heat. It is
measured in watts per meter kelvin ( W/m.K ). The graph of thermal conductivity against
temperature for 0.05% volume fraction of Ag2O-NaCl nanofluid is presented in figure 33;
Figure 33: Effect of temperature on thermal conductivity of 0.05% volume fraction of
Ag2O-NaCl nanofluid
From figure 33, it can be see that the as temperature of Ag2O-NaCl nanofluid
increase, thermal conductivity also increases. This is consistent with the study done in
literature review in section 2.3.2. The highest thermal conductivity achieved for volume
fraction of 0.05% is at temperature 74.4 degree celcius with the value of 0.713 W/m.K.
0.65
0.66
0.67
0.68
0.69
0.7
0.71
0.72
30 40 50 60 70 80
ThermalConductivity(W/m.K)
Thermal Conductivity vs Temperature of
0.05% volume fraction of Ag2O-NaCl nanofluid
0.05% volume fraction
Linear (0.05% volume
fraction)

55
VISCOSITY
Viscosity is a measurement of fluids resistivity from undergoing deformation under
shear stress or tensile stress. Viscosity also can be defined as molecular attraction between
molecules inside fluids. Viscosity has the unit of mPa.s. The graph of viscosity against
nanofluid
increase, viscosity decreases. This is consistent with the study done in literature review in
section 2.4.2. The lowest thermal viscosity achieved for volume fraction of 0.05% is at
temperature 60.2 degree celcius with the value of 0.54 mPa.s.
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
30 40 50 60 70
Viscosity(mPa.s)
Viscosity vs Temperature of 0.05% volume
fraction of Ag2O-NaCl nanofluid
fraction)

56
PH
In nanofluids, pH is used to determine the state of nanofluids. pH are measured in
the range of 1 until 14. The graph of pH against temperature for 0.05% volume fraction of
Ag2O-NaCl nanofluid is presented in figure 35;
From the graph, the highest pH is at temperature 60.3 degree celcius with pH of
7.19 and the lowest pH is at temperature 32.9 with pH of 7.11. Nanofluid is neutral.
7.1
7.11
7.12
7.13
7.14
7.15
7.16
7.17
7.18
7.19
7.2
30 40 50 60 70
pH
pH vs vs Temperature of 0.05% volume
fraction of silver nanofluids
fraction)

57
NaCl nanofluid
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
30 40 50 60 70 80
Thermal Conductivity vs Temperature of 0.1%
volume fraction of Ag2O-NaCl nanofluid
Linear (0.1% volume fraction)

58
VISCOSITY
nanofluid
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
30 40 50 60 70
Viscosity(mPa.s)

59
PH
7.06
7.08
7.1
7.12
7.14
7.16
7.18
7.2
30 40 50 60 70
pH
pH vs vs Temperature of 0.1% volume
Linear (0.1% volume
fraction)

60
NaCl nanofluid
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
30 40 50 60 70 80
Temperature(Celcius)
Linear (0.2% volume
fraction)

61
VISCOSITY
nanofluid
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
30 40 50 60 70
Viscosity(mPa.s)

62
PH
7
7.02
7.04
7.06
7.08
7.1
7.12
7.14
7.16
30 40 50 60 70
pH
pH vs Temperature of 0.2% volume fraction
of Ag2O-NaCl nanofluid
Linear (0.2% volume
fraction)

63
NaCl nanofluid
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
30 40 50 60 70 80
volume fraction ofAg2O-NaCl nanofluid

64
VISCOSITY
nanofluid
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
30 35 40 45 50 55 60
Viscosity(mPa.s)

65
PH
7
7.02
7.04
7.06
7.08
7.1
7.12
7.14
30 40 50 60 70
pH
Linear (0.3% volume
fraction)

66
NaCl nanofluid
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
30 40 50 60 70 80

67
VISCOSITY
nanofluid
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
30 35 40 45 50 55 60
Viscosity(mPa.s)

68
PH
6.3 Discussion
In discussion part, the effect of volume fractions and temperatures on thermal
conductivity, viscosity and pH are discussed. Enhancement of thermal conductivity and
comparison of viscosity and pH between base fluids with nanofluids are discussed as well.
6.98
7
7.02
7.04
7.06
7.08
7.1
30 35 40 45 50 55 60
pH
Linear (0.5% volume
fraction)

Thermophysical properties of silver oxide dispersed in sodium chloride

Thermophysical properties of silver oxide dispersed in sodium chloride

Recommended

Recommended

More Related Content

What's hot

What's hot (16)

Viewers also liked

Viewers also liked (7)

Similar to Thermophysical properties of silver oxide dispersed in sodium chloride

Similar to Thermophysical properties of silver oxide dispersed in sodium chloride (20)

Recently uploaded

Recently uploaded (20)

Thermophysical properties of silver oxide dispersed in sodium chloride