Chapter 15
Thermophysical Characteristics
of Nanofluids: A Review
Chou-Yi Hsu, Gargibala Satpathy, Fatma Issa Al Kamzari, E. Manikandan,
Yathrib Ajaj, and Aithar Salim Al Kindi
Abstract Rapid advancement in nanotechnology over the past 10 years has given
scientists and technologists plenty to consider. One of the amazing results of such
innovation is nanofluid, in which metallic and non-metallic nanoparticles are suspended colloidally in commonly used base fluids. The peculiar thermal behaviour of
nanoscale fluids was only recently discovered by leading researchers, and since
then, nanofluids have been the subject of intense investigation all around the world.
This is because they have the potential to be an improved thermophysical heat transmission fluid and because they are crucial for uses like oil recovery and medicine
delivery. Recent research on nanofluids has revealed that these fluids have superior
heat transmission and wetting properties. In addition, water-based nanofluids are
more environmentally friendly than mineral oil quench medium. Due to these
potential benefits, quench media based on nanofluids have been developed for use
in heat treatment procedures. It was unexpected and outside the realm of thencurrent theories that nanofluids with comparable low particle concentrations would
have a larger thermal capacity (conductivity). According to the experimental findings, the thermal conductivity of nanofluids increases with decreasing particle size.
C.-Y. Hsu
Department of Pharmacy, Chia Nan University of Pharmacy and Science,
Tainan, Taiwan
G. Satpathy
Central Research Laboratory, Sree Balaji Medical College & Hospital (SBMCH),
Bharath Institute for Higher Education & Research (BIHER), Bharath University,
Chennai, Tamil Nadu, India
F. I. Al Kamzari · Y. Ajaj (*) · A. S. Al Kindi
Engineering Department, Faculty of Engineering and Computer Science, German University
of Technology in Oman, Halban, Oman
E. Manikandan
Central Research Laboratory, Sree Balaji Medical College & Hospital (SBMCH), Bharath
Institute for Higher Education & Research (BIHER), Bharath University,
Chennai, Tamil Nadu, India
Solid-State Nanoscale Laboratory, Department of Physics, Thiruvalluvar University,
Vellore, Tamil Nadu, India
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2023
J. A. Malik, M. J. S. Mohamed (eds.), Modern Nanotechnology,
https://doi.org/10.1007/978-3-031-31104-8_15
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Micrometre-sized particle-based fluid suspensions reveal no such significant augmentation. Another critical characteristic that demands the same focus is viscosity,
which has a significant influence on heat transmission. Nanofluid stability is essential to their successful operation in thermal systems.
In addition to this, a number of other thermophysical characteristics, for instance,
thermal conduction, heat flux, density, viscosity, and specific heat, are crucial for
materials to keep their thermophysical characteristics after manufacture for an
extended period of time. But before nanofluids can be used commercially, there are
a few problems that need to be fixed. Stability and functioning performance are the
two key concerns of nanofluids. In light of the fact, the intention of this chapter is to
provide thorough analysis on thermophysical features of nanofluids and some
potential opportunities for upcoming research that could be important as the literature in this field is lengthened across an extensive range of fields, including heat
transfer, physics, chemical engineering, material science, and synthetic chemistry.
Keywords Nanotechnology · Nanofluid · Thermophysical · Heat transmission ·
Wetting properties · Thermal conductivity · Nanofluid stability · Operational
performance · Synthetic chemistry
15.1
Introduction
Nanoparticle-containing base fluids (nanofluids) have evolved as a novel category
of fluids with extraordinary features of improved heat transfer. A new category of
fluids called nanofluids has been developed with increased heat transfer qualities
and were synthesized in 1965 by Choi (1995) by means of dispersing nanoparticles
(nanorods, nanotubes, nanofibers, nanosheet, nanowires, or droplets) in base fluids
(Fig. 15.1). Compared to colloidal solutions, the diluted suspensions of nanofluids
have a higher heat transmission surface between the fluid and the particles. These
benefits make nanofluids useful in various divisions such as electronic applications,
power generation, air conditioning, chemical synthesis, nuclear system cooling,
heating and cooling procedures, space and defence, solar absorption, transportation
and microelectronics energy storage, magnetic sealing, friction reduction, biomedical application, and nano drug delivery (Das et al. 2006; Yu and Xie 2012). It is
therefore possible to construct lighter and more compact heat exchangers as significantly less fluid is needed than the base fluid. Further, nanofluids might be crucial
in the removal of extra energy produced by the burning of fuel in the automotive
sectors. Nanofluids can lose heat through the radiator’s walls when flowing through
the tubes. If there are big and small particles floating in the base fluid, heat transfer
is improved. Larger particles sediment and corrode the channels through which they
flow, causing overall wear and tear of the pipes and channels. Both of these issues
have been resolved by nanofluids for heat transmission. The suspensions are significantly steadier and can produce lesser attritions along with efficient transfer of heat
features than the base fluids (Keblinski et al. 2002; Das 2015).
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Fig. 15.1 Nanoparticles suspended in base fluid
Rapid advancement in nanotechnology over the past 10 years has facilitated the
development of new materials that outperform and possess superior qualities than
prior materials. This development of nanomaterials has led to the creation of versatile nanofluids. Compared to solids, conventional fluids have inferior thermal–physical characteristics. The use of extended-surface materials such as fins and
microchannels, surface vibration, fluid suction/injection, and the use of electrical
and magnetic fields have all been abandoned to boost heat transfer. Consequently,
much research has been done on novel technologies with the aim of improving the
thermophysical characteristics of conventional fluids (Duangthongsuk and
Wongwises 2010; Gupta et al. 2017). In light of the fact that the literature in this
field is expanded across an extensive range of fields, comprising material science,
heat transfer, chemical engineering physics, and synthetic chemistry, the goal of this
article is to exhaustively review and elucidate the thermal conductivity, viscosity,
and specific heat of nanofluids and some potential opportunities for upcoming
research that could be useful.
15.2 Various Types of Nanofluids
Nanoparticles were added to thermofluids in 1995 to augment their thermal
characteristics (Choi and Eastman 1995). Since then, extensive work has been done
on creating nano-based fluids with distinctive thermophysical characteristics, for
example, thermal conductivity, thermal diffusivity, and viscosity (Prasher et al.
2006; Yoo et al. 2007; Chamsa-Ard et al. 2017). Studies have revealed that adding
small quantity of nanoparticles can increase the thermophysical features of a variety
of fluids. Various types of nanoparticles that have been studied comprise metal
oxides (Fe3O4, Al2O3, CuO, SiO2, TiO2, and ZnO), carbides (SiC, TiC), pure metals
(Au, Ag, Cu, Al, and Fe), and a variety of carbon materials (graphite, diamond, and
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single- and multiwall carbon nanotubes). Many of these different kinds of nanoparticles have been used in liquids including water, water/ethylene glycol, ethylene
glycol, and oils. Consequently, they fall into two basic categories: single-material as
well as hybrid nanofluids (Chamsa-Ard et al. 2017; Prasad et al. 2017; Sawant
et al. 2021).
15.2.1
Single-Material Nanofluids
Choi and Eastman (1995) suggested that in single-material nanofluids a specific
kind of nanoparticle is employed to produce the suspension using several procedures (Fig. 15.2). Different studies have claimed that this type of nanofluids performs better because they have base fluids that are much beneficial thermophysically
(Tawfik 2017; Modak et al. 2018; Sawant et al. 2021).
15.2.2
Hybrid Nanofluids
In the most sophisticated subcategory of nanofluids, hybrid nanofluids which are
suspended in a base fluid contain a variety of nanoparticles of different types
(Fig. 15.3). Jana et al. (2007) conducted the first experimental research on this kind
of fluid with the goal of improving the fluid’s thermal conductivity exceeding that
of a typical single-material type nanofluid. They looked at Cu nanoparticles, CNTs
Fig. 15.2 Single type
nanofluid
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(carbon nanotubes), Au nanoparticles, and their subsequent hybrids such as CNT-Cu/
H2O as well as CNT-Au/H2O that are all dispersed in water. In accordance with the
test results, Cu/H2O nanofluids had the highest thermal conductivity of all the samples examined, and this conductivity increased linearly as the particle concentration
increases. Although the CNT-Cu/H2O nanofluid was less stable than other nanofluid
types, it did achieve a longer settling time compared to other varieties of nanofluids.
Because of this, the fluid may maintain its thermal conductivity for a much longer
before it degrades (Otanicar et al. 2010; Ali et al. 2018).
15.3
Methods of Preparation of Nanofluids
It takes more than merely combining nanoparticles with the base fluid to produce
nanofluids. Stabilization and correct mixing are necessary under specific environmental circumstances to produce nanofluids with homogeneously distributed
nanoparticles and may have a substantial influence on the thermophysical features
of the nanofluid. The thermophysical characteristics and tendency to agglomerate
two nanofluids that are comparable to one another but were created using different
techniques (Fig. 15.4) are most likely to differ from one another. This is due to the
Fig. 15.3 Hybrid
nanofluid
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fact that a solid–liquid combination alone cannot form nanofluids; rather, a suspension with a number of qualities including homogeneity, chemical and physical stability, dispersibility, and durability are required. The size range of the nanoparticles
employed in nanofluids is 1–100 nm, and they come in a variety of geometries,
including nanoreefs, nanospheres, nanoboxes nanotubes, and nanoclusters.
According to a few reports (Lee et al. 2016; Harikrishnan et al. 2017; Kaggwa and
Carson 2019), the synthesis process determines the nanoparticles’ morphology;
additionally, there is a great relation between the nanoparticle size and the thermal
conductivity, which is a major factor in improving heat transfer. There are several
ways to prepare nanofluids, and they may be further divided into two categories: the
one-step method, also referred to as the bottom-up technique, and the top-down
strategy, also referred to as the two-step method (Chamsa-ard et al. 2017; Ali
et al. 2018).
15.3.1
Single-Step Method
In this approach, the synthesis as well as distribution of nanoparticles into the base
fluid is combined in single step as presented in Fig. 15.5. One of the most popular
methods for making nanofluids, the single-step direct evaporation approach,
depends on solidifying nanomaterials that were gaseous in the base fluid before.
This technique identified as vacuum evaporation onto a running oil substrate
(VEROS) method was devised by Akoh et al. (1978). The main objective of this
procedure was to create nanoparticles; nonetheless, it ended up being quite challenging to separate the created fluid mixture of nanoparticles into their dry form. In
this situation, condensation and phase change of a material from the vapour stage
Fig. 15.4 Physical and chemical methods of synthesizing nanofluids
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Fig. 15.5 Bottom-up method of nanofluid synthesis
into the heat transfer fluid may be the reason for the development of nanoparticles.
The base liquid, which might be ethylene glycol or oil, is put in a revolving cylindrical drum with a regulating heater-boat-evaporator, as well as heat exchanger cooler
device. The internal surface of the drum develops a thin liquid layer as it rotates. An
adjustable heater-boat-evaporator with a nanomaterial source put within its evaporator is situated close to a section of the spinning thin liquid layer. The evaporant
matter is heated, causing some of it to evaporate and form nanoparticles, which are
afterwards absorbed by the liquid film to produce nanofluid. In their modified
VEROS method, Wagener et al. (1996) synthesized dispersions with Fe and Ag
nanoparticles utilizing high pressure magnetron sputtering. Eastman et al. (1996)
used a customized VEROS approach to efficiently condense Cu vapour with a moving low-vapour-pressure EG to generate the Cu/EG nanofluid containing Fe and Ag.
Cu nanofluid was produced in one step by Zhu et al. (2004) via a chemical process.
Al2O3 nanofluid was created by Tran and Soong (2007) using high-power optical
vaporization in one-step process. Although the single-step approach has the benefit
of creating the least amount of nanoparticle agglomeration, it is expensive and
hence probably not practicable on an industrial scale (Kaufui 2009; Yu and Xie
2012; Sawant et al. 2021).
15.3.2
Two-Step Method
Because the single-step approach is more expensive than the two-step procedure,
the two-step technique is more commonly used. In comparison with the one-step
strategy, the two-step approach is best method for creating nanofluids because it has
small processing charges and a large supply of commercially available nanoparticles from several businesses. A schematic representation of the two-step method
utilized to create nanofluid is shown in Fig. 15.6. The creation of nanoparticles,
nanofibers, nanotubes, and other nanomaterials using this method occurs in a separate step prior to their addition to the base fluid or purchased as dry powder (Ali
et al. 2018; Kaggwa and Carson 2019). Magnetic stirrers, homogenizers, ultrasonic
baths, high-shear mixers, and bead mills are some of the frequently used apparatus
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Fig. 15.6 Top-down method of nanofluid synthesis
for dispersing nanoparticles in base fluid. By using chemical or physical processes,
the nanoparticles employed in this procedure are initially created as dry powders.
Higher magnetic force agitation, ultrasonic agitation, high-shear mixing, homogenizing, and ball milling will next be used to disperse the nanosized powder into a
fluid in the second processing stage. The interfacial forces between the molecules of
the base fluid as well as the nanoparticles can be reduced by adding stabilizing
agents, such as surfactants. Figure 15.7 illustrates the key procedures for creating
nanofluids. The two-step method has a significant amount of particle aggregation as
a disadvantage in comparison with the one-step method. In spite of these drawbacks, this approach remains the well-familiar method for creating nanofluids in
lesser or greater quantities and may be employed to generate almost any variety of
nanofluid (Haddad et al. 2014; Ali et al. 2018; Kaggwa and Carson 2019).
15.4 Thermophysical Characteristics
A broad variety of commercial, industrial, and domestic processes and appliances,
such as those used in the chemical processing, solar energy generation and conversion, air conditioning and refrigeration, the gas and oil industries, and electronics
cooling, require familiarity and thoughtful understanding of heat transfer. The
phrase “heat transfer enhancement” in thermal engineering refers to the augmentation of a system’s thermal performance. Several methods have been suggested as
strategies to improve heat transmission during the past 10 years (Siddique et al.
2010; Léal et al. 2013; Sheikholeslami et al. 2015). The base fluid’s thermophysical
characteristics, for example, specific heat, viscosity, and thermal conductivity, alter
as a consequence of the integration of nanoparticles, which has an impact on convective heat transmission. The degree to which various nanomaterials alter their
parameters varies. Some of the key variables that greatly affect the thermophysical
characteristics include the nanoparticle concentration, purity level, size, and form of
the nanomaterials. Viscosity, density, thermal conductivity, and specific heat are
known to have an impact on conduction and convection. Therefore, correct thermophysical property data are necessary for any heat transport model. To ascertain these
characteristics of the nanofluids under various operating circumstances, several
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Fig. 15.7 Main steps in preparing nanofluids
investigations have been conducted. Some of them claimed that as compared to
normal fluids, nanofluids had improved thermal characteristics (Das 2017; Chen
et al. 2019). The performance of heat transmission is closely correlated with the
hybrid nanofluid’s characteristics (Hamzah et al. 2017; Chen et al. 2019). The flow
of these dual phases of nanofluids in the evaporation and the condensing areas must
thus be analysed in terms of their thermophysical properties. It is crucial to explore
the fundamental thermophysical features of the nanofluids consecutively to maximize the performance of the nanofluids in the systems. The most recent review of
the thermophysical characteristics of several nanofluids is provided in this section.
15.4.1
Thermal Conductivity
From the available literature, the most researched aspect of nanofluids is their
improved thermal conductivity, which is generally accepted to be the primary cause
for the considerable improvements in heat transfer rates that have been reported. To
look at how nanofluids’ thermal conductivity changes, several theoretical and
experimental studies have been undertaken on diverse base fluids (propylene glycol,
ethylene glycol, methanol, glycerol, paraffin, gear oil, engine oil, etc.) using a variety of nanoparticles. Figure 15.8 shows the thermal conductivities of different solids
as well as liquids. Addition of NPs to the base fluids increases their thermal conductance. Brownian motion and the interfacial nanolayer are the key phenomena that
govern the thermodynamic activity of nanomaterial solutions that are adjacent to a
solid particle surface generate layered structures that are crucial for regulating the
thermal characteristics of nanoparticles–fluid dispersions. Choi and Eastman (1995)
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claimed that adding a minute amount of nanoparticles might improve the thermal
conductivity of the base fluid. Hemmat-Esfe et al. (2014) looked into ferromagnetic
nanoparticle suspensions in ethylene glycol. These researchers focused on the
effects of temperature, concentration as well as particle size on the viscosity as well
as thermal conductivity of the nanofluids having a concentration up to 3% in the
temperature gradient of 26–55 °C. According to their findings, as temperature and
the volume proportion of solids rose, so did the efficiency of nanofluids. Based on
multi-level homogenization and particle size distribution, Deepak and Dhinakaran
(2016) gave a concept to forecast the thermophysical properties of nanofluids especially the thermal conductivity. They mostly concentrated on the consequences of
Brownian motion, the creation of interfacial layers, and particle clustering. Similar
to this, Lee et al. (2016) showed that raising the temperature as well as particle size
increased the efficiency of nanofluids. Thermal conductivity and viscosity studies,
however, showed that particle size fluctuation was more pronounced than temperature variation. An investigation on the thermophysical characteristics of a nanofluid
made of carbon-based material was done by Ueki et al. (2017). They came to the
conclusion that thermal conductivity was impacted by temperature and nanoparticle
shape. They also discovered that carbon nanopowder increased the conductance of
heat by 7% while carbon black by 19%.
According to Lenin and Joy (2017), different surfactants have different threshold
concentrations for improving thermal conductivity. This variation may be caused by
changes in the degree of nanoparticle accumulation and surfactant molecule conformation on the surface of the nanoparticles. According to them, base fluids with
inferior thermal conductivities as well as dielectric constants exhibited greater rises
in thermal conductivity when compared with the base fluids with higher thermal
conductivities. According to Yang et al. (2017), environmental elements (temperature, pH value, base fluid, and the standing duration) and particle parameters (particle type, shape, loading, and size) have an impact on thermal conductivity. The
Fig. 15.8 Thermal conductivities of different solids and liquids
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variance in thermal conductivity improvement reported in the literature may be significantly attributed to the aforementioned parameters as well as preparation
techniques.
15.4.1.1
Factors Controlling the Thermal Conductivity of Nanofluids
The thorough analysis leads to the conclusion that base fluid material, temperature,
particle dimensions, form, and composition, among other variables, impact the thermal conductivity of nanofluids (Ranakoti et al. 2012; Pastoriza-Gallego et al. 2014).
The various elements controlling the thermal conductivity of nanofluids are depicted
in Fig. 15.9.
Size of Particles
The development of nanofluids’ thermal conductivity is significantly influenced by
particle size. While the thermal conduction of nanofluids rises with particle size, the
consistency of the suspension declines. The size range of the produced nanoparticles is between 5 and 100 nm. The impact of nanoparticle dimension on the base
fluid was explored by Paul et al. (2010). The impact of particle dimension on the
thermal conduction quotient of alumina (Al2O3)/water nanofluids was investigated
by Teng et al. (2010). The findings of the experiment demonstrated that decreasing
particle size enhances the thermal conductivity of nanofluids.
Shape of Particles
In nanofluid research, cylindrical and spherical particles are typically utilized as
particle types. Nanoparticles’ cylinder forms feature a significant length to diameter
ratio. The impacts of the form of the nanoparticles, such as cylindrical or spherical,
on the improvement of thermal conductivity of SiC nanofluids were initially examined by Xie et al. (2002a, b). Murshed et al. (2008a, b) also evaluated at how cylindrical and spherical nanoparticles affected the thermal properties included
conductivity of nanofluids.
Composition of Particle and Base Fluid
The several types of particle materials utilized for the formation of nanofluids
include metal carbides, oxide ceramics, metals, nitrides, and nonmetals. Both single
and multiwalled carbon nanotubes are having high thermal conductance and are
thus employed as particle material. Base fluids including water, ethylene/propyleneglycols, biofluids, and motor oil are used to create nanofluids for thermal energy
transfer processes.
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Fig. 15.9 Factor affecting the thermal conductivity of nanofluids
Temperature
Both the temperature of the base fluid and the thermal conductivity of the particles
affect the thermal conductivity of the nanofluids. The clustering of nanoparticles
and Brownian motion are impacted by temperature variations, which also reveal
deviations in the thermophysical properties and the heat transfer of nanofluids. Yu
et al. (2009b) noted the temperature-dependent increase in thermal conductance for
nanofluids encasing ZnO nanoparticles. With rising temperatures, nanofluids’ thermal conductivity increased. The thermal conductivity of nanofluids was experimentally investigated by Duangthongsuk and Wongwises (2010). TiO2 nanoparticles
dispersed in water at a volume concentration of 0.2 to 2 vol% were employed in this
investigation. The findings demonstrated that when the temperature of the nanofluids improved, so did their measured thermal conductivity. Kole and Dey (2011)
inspected the thermal effects on the improvement of heat transfer characteristics for
CuO-gear oil nanofluids. The results specified that at ambient temperature, the
greatest boost of 10.4% was acquired with 0.025 volumes present of CuO nanoparticles, and it rises up to 11.9% at 80 °C temperature. According to research by
Suganthi et al. (2014a, b), the maximum thermal conductivity improvement was
attained at the lowest temperature, and it declined as temperature increased
(10–30 °C). According to the logic, the ethylene glycol molecular layer’s thickness
rose as temperature decreased and its well-ordered organization of liquid molecules,
in comparison with the bulk liquid, had a greater thermal conductivity while as from
30 °C up to 60 °C, no improvement was seen. This was explained owing to the drop
in thermal conductivity caused by the thinner liquid layers counteracting the upsurge
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in thermal conductance caused by Brownian movements of particles at maximum
temperatures. Manikandan et al. (2014) also showed that sand in propylene glycol
had a higher thermal conductivity of 46.2% for 2 vol% nanofluids around 10 °C.
Additives
The introduction of additives keeps the nanoparticles in suspension and stops them
from clumping together. As a result, it is anticipated that they will increase the thermal conductivity of nanofluids. Both with and without additions, Eastman et al.
(2001) conducted various experiments on Cu in ethylene glycol. According to the
findings, additives can significantly boost the thermal conductivity of nanofluids.
Cu-gear oil nanofluids with 0.1–2% volume concentration of Cu nanoparticles were
created by Kole and Dey (2013) using oleic acid surfactant. 2 vol% of the Cu
nanoparticles increased thermal conductivity by 24% at room temperature. Li et al.
(2008) examined the impact of adding sodium dodecyl benzene sulfonate as a surfactant on the thermal conductivity of Cu-H2O nanofluids. The findings showed that
the SDBS surfactant concentration of nano-suspensions had a substantial control on
the improvements of Cu-H2O nanofluids with regard to their thermal characteristics
and conductivity.
Acidity (pH)
There are not many studies looking at how base fluid pH affects the thermal
conductivity of nanofluids. After doing various studies on Al2O3/water nano-based
fluids, Xie et al. (2002a, b) were the pioneers to study how a rise in pH resulted in a
fall in thermal conductivity ratio. The findings revealed that the thermal conductance
increase of Al2O3/water nano-based fluids varied from 23% up to 19% when the pH
rises to 11.5, from 2. Additionally, Li et al. (2008) demonstrated how pH affects the
thermal conductivity of Cu-H2O nanofluids. The impact of pH levels on the thermal
conductivity of the nanofluids was also investigated by Zhu et al. (2009). In this
work, Al2O3-H2O nanofluids were created, and water’s thermal conductivity was
examined at various pH levels. The combined use of a chemical dispersant and pH
treatment is suggested to improve thermal conductivity while maintaining the practical use of nanofluids.
Clustering
Another factor that may impact a nanofluid’s thermal conductivity is clustering. The
clustering of nanofluids at high concentrations and for longer periods of time
reduces the effective area of thermal contact between particles, lowering the fluid’s
thermal conductivity. Researchers Keblinski et al. (2002) and Hong et al. (2006)
explored how clustering affected the thermal conductivity of nanofluids. Testing
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Fe3O4/water nanofluids, Zhu et al. (2006) witnessed that the raise in thermal conductance was mostly caused by clustering and nanoparticle alignment. Several theoretical models were created by researchers to forecast the rise in thermal conductivity,
and numerous tests were performed to relate the results with the models’
predictions.
15.4.2
Thermal Diffusivity
The term “thermal diffusivity” refers to a substance’s thermal conductivity divided
by the product of that substance’s density and specific heat capacity. The effective
thermal diffusivity of nanofluids has only been briefly discussed in a very small
number of published works (Eggers and Kabelac 2016). Murshed et al. (2006) documented the augment in effective thermal diffusivity of nanofluids through experimentation and discovered that it was more than what Maxwell (1891) had predicted.
The increase in effective thermal diffusivity of nanofluids was seen experimentally
by Murshed et al. (2006), and they discovered that it was more than what Maxwell
(1891) had predicted. It is important to note that they used observed data to determine the effective thermal diffusivity. The laser flash method (Agresti et al. 2013),
the temperature-regulated photoacoustic device created by Agresti et al. (2015), the
thermal wave cavity technique, the hot-wire method, as well as the temperature
oscillation method (Rodriguez et al. 2016) are all experimental methods that can be
employed to measure the actual thermal diffusivity. The absolute thermal diffusivity
value of liquids is measured using the thermal lens method, which is a sensitive
approach. This approach is advantageous because of its extremely high sensitivity,
minimal sample volume required, and reliance on the thermo-optical characteristics
of the solvent (Joseph et al. 2010).
15.4.3 Viscosity
Viscosity is yet another critical component in heat transfer applications owing to its
reliance on the pressure loss and the pumping power. The tendency of the solution
to oppose the flow is called as viscosity of nanofluid. It can also be described as the
relationship between shear stress and shear rate. Viscosity is the thinness or thickness of a fluid in non-scientific terminology. It is determined by dividing the tangential tension on a liquid in streamlined flow by the velocity gradient. The increase in
effective viscosity brought on by the more nanoparticles in the base fluid negates the
advantage of nanofluids’ enhanced heat transfer. The demands for pumping power
rise as a result of the increase in viscosity, which causes greater pressure losses. The
viscosity of base fluid, nanoparticle concentration, shape of particles, diameter,
type, temperature, pressure, pH value, and shear rate are the primary factors that
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affect the effective viscosity (Eggers and Kabelac 2016). Other important factors
are temperature, pressure, and pH value.
The seminal study by Choi and Eastman (1995) made the important assumption
that the viscosity of the nanofluids would not be considerably affected by the addition of nanoparticles, yet this is not always the case. For instance, Namburu et al.
(2007) tested the viscosity of copper oxide nanoparticles distributed in a solution of
water and ethylene glycol and discovered that it was four times as thick as the base
fluid at a volume concentration of 6.12%. They also came to the conclusion that as
the concentration of nanoparticles grows so does the viscosity of nanofluids. CuoH2O nanofluids’ apparent viscosity was studied by Li et al. (2002), and the findings
revealed that viscosity declines with inclining temperature and rises with increasing
concentration. Al2O3-H2O nanofluids produced comparable findings for Wu et al.
(2009). Hemmat-Esfe and Saedodin (2014) made a similar discovery with zinc
oxide/ethylene viscosity. Glycol nanofluids rose dramatically with particle volume
concentration, as did Mariano et al. (2015) and Yu et al. (2009a), who also highlighted the point that the impacts of the nanofluid’s augmentation of heat transmission were counterbalanced by the need for more power to pump the fluid.
15.4.3.1
Effects of Various Factors on the Viscosity of Nanofluids
The viscosity of nanofluids is influenced by a variety of variables, including
temperature (Jiang et al. 2017), volume concentration, particle dimension, form,
and shear rate (Fig. 15.10).
Volume Concentration
The most significant component of cooling medium is the volume concentration of
nanofluids, which has a direct impact on the viscosity of nanofluids. Numerous
studies have demonstrated that the viscosity of nanofluids is influenced by the
weight percentage of nanoparticles (Das et al. 2003; Pastoriza—Gallego et al. 2011)
and that it rises as particle concentrations rise. The increase in viscosity, according
to Sundar et al. (2013) and Abareshi et al. (2011), is brought on by the particle volume concentration. Hung and Chou (2012) examined the MWCNTs nanofluid’s
viscosity and examined at how the additive amounts of the MWCNTs and the chitosan in the water affected the suspension performance. Rashin and Hemalatha
(2013) investigated the viscosity of a new, two-step-prepared, copper oxide-coconut
oil nanofluid of varied concentrations. According to Namburu et al. (2007), raising
the volume concentration of nanofluids causes it to become more viscous. Saeedinia
et al. (2012) examined the viscosity of stable CuO-base oil nanofluids with various
particle weight fractions of 0.2–2% at various temperatures. The viscosity of nanofluids with various nanoparticle volume fractions was tested by Murshed et al.
(2008a, b) and discovered to be much greater than base fluids while Manikandan
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Fig. 15.10 The viscosity of nanofluids is affected by a number of factors
et al. (2014) and Suganthi et al. (2014a, b) demonstrated a decrease in viscosity with
the inclusion of nanoparticles.
Morphology
The viscosity as well as pumping capacity of the cooling system can be influenced
by the particle size and shape. In their study of the two distinct Al2O3 particle sizes,
36 and 47 nm, Nguyen et al. (2008) demonstrated that the latter had greater viscosity. According to Chevalier et al. (2007), the size of nanoparticles decreased as shear
viscosity increased. SiO2/water and SiO2/EG nanoparticles with diameters of 35,
94, and 190 nm were measured in various volume fractions.
Shear Rate
Another factor that can affect the viscosity of non-Newtonian nanofluids is shear
rate. Experimental research on the viscosity of water-based nanofluids containing
carbon nanotubes was conducted by Halelfadl et al. (2013). The outcomes demonstrated that at large particle loadings, the nanofluids functioned as shear-thinning
15 Thermophysical Characteristics of Nanofluids: A Review
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materials. The nanofluids behaved like Newtonian fluids at lower particle concentrations. The relative viscosity of nanofluids at high-shear rates was also shown not
to vary with temperature. The impact of shear rate on the viscosity of EG-based
nanofluids containing ZnO nanoparticles was investigated by Yu et al. (2009b). The
findings showed that ZnO-EG nanofluids behave in a Newtonian manner at low
volume concentrations (0.02). ZnO-EG nanofluids exhibit non-Newtonian characteristics at greater volume concentrations (0.03).
Temperature
One of the most significant factors determining viscosity is temperature. The
influence of temperature on the viscosity of the water-Al2O3 nanofluid with 36 and
47 nm particle dimensions was investigated by Nguyen et al. (2008). The findings
showed that while temperature rises obviously lower nanofluids’ dynamic viscosity,
it does so considerably with particle volume fraction. Al2O3-water nanofluid
viscosity was determined by Mena et al. (2013) in the temperature range of 5–20 °C
with nanoparticle volume fractions <1 vol%. The findings showed that within this
range of low temperature and volume percentage, the viscosity of Al2O3-water
nanofluid presented a good agreement. Suganthi and Rajan (2012) conducted an
experimental study on ZnO nanoparticle-water nanofluids. This study looked at
how temperature affected the zeta potential and hydrodynamic size distribution
during a heating as well as cooling cycle. The findings demonstrated that when
temperature (35–55 °C) increased, the relative viscosity decreased. The findings of
a study by Turgut et al. (2009) on the thermal conductance as well as viscosity of
TiO2-deionized water at temperatures from 13 to 55 °C revealed that viscosity
declined with temperature.
15.4.4
Density
An essential thermophysical characteristic is density, which is crucial for assessing
the heat transmission capabilities of nanofluids. The Nusselt number, pressure loss,
friction factor, as well as Reynolds number are all directly impacted. This characteristic of nanofluids has not been extensively examined by researchers. Experimental
research on the densities of zinc oxide (ZnO), antimony-tin oxide, and alumina
(Al2O3) was conducted by Vajjha et al. (2009). The densities of nanofluids at various
temperatures were calculated by Sundar et al. (2007). With rising temperatures, it
was discovered that density decreased. In a similar manner, Harkirat (2010) determined the density of Al2O3 nanoparticles distributed in water utilizing specific gravity bottles at various temperature ranges (30–90 °C) and nanofluid concentrations
(1–4%). He noted that the density of nanofluids is greater than that of base fluids
and rises as the volume percentage of nanoparticles rise from 1% to 4%. Up to
roughly 80 °C, increase in temperature caused a drop in the density of nanofluids.
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Beyond this point, densities of 1–4% nanofluids were essentially constant but were
still higher than those of water. In an experiment, Pastoriza-Gallego et al. (2009)
evaluated three distinct nanofluids containing dispersions of Al2O3 nanoparticles at
varying concentrations (0.5–7% in weight fraction) (water). For three different temperatures (283.15, 298.15, and 313.15) as well as pressure range (atmospheric to
25 MPa), density was measured. According to observations, smaller particles have
a more pronounced impact on volumetric behaviour. Despite this, it was discovered
that size had a minimal overall impact. As the number of nanoparticles grows, so
does the density. When compared to the other two samples with lower size nanoparticles, the departure from the equation rises with particle loading. The density of an
alumina (Al2O3)/water nanofluid was estimated experimentally by Teng and Hung
(2014). The findings demonstrate that the variation of the density with equation falls
between 1.50% and 0.06% and between 0.25% and 2.53%, respectively. Furthermore,
when the particle loading of the nanofluid increased, the computed findings of density showed a higher divergence. The analysis of the literature reveals that there has
been very little experimental research on the density of nanofluids. In order to
achieve the precise values of density, more study is thus necessary to define the correction factor and correlations dependent on the fluctuation of nanofluids, particle
size, temperature, and particle loading, among other factors.
15.4.5
Specific Heat
One of the fundamental characteristics of nanofluids is specific heat, which plays a
crucial part in determining how quickly they transport heat. Specific heat is the total
amount of heat requisite to raise the temperature of a unit gram of nanofluids by one
degree centigrade. In comparison with research on thermal conductivity and viscosity, there is less on the specific heat of nanofluids. The purpose of a nanofluid’s
specific heat capacity is to control the temperature variance that affects the efficiency of heat transmission and flow (Wang et al. 2010). The specific heat capacity
values of nanofluids can be considerably changed by a small addition of nanoparticles (Shin and Banerjee 2014). The literature reveals that the specific heat of nanobased fluid declines with an upsurge in the volume concentration as well as rises
with temperature. It relies on the specific heat of the base fluid and nanoparticle, the
volume concentration of nanoparticles, and the temperature of the fluids (Nelson
et al. 2009; Zhou et al. 2010). The specific heat capacity of nanoparticles was studied by Wang et al. (2006) in relation to size and temperature. Yang et al. (2008)
investigated the specific heat of super carbon nanotubes (ST) using the molecular
structure, mechanics technique. The outcome demonstrated that the specific heat of
the ST was almost independent of the size, chirality, and length of the ST at a given
temperature. Tiznobaik and Shin (2013) assessed the specific heat capacity of nanofluids based on high temperature molten salts. To generate high temperature operating fluids, a molten salt eutectic was mixed with four different sized silicon-dioxide
nanoparticles (5, 10, 30, and 60 nm in diameter). The specific heat capacity of
15 Thermophysical Characteristics of Nanofluids: A Review
355
nanofluids was measured using a differential scanning calorimeter. Regardless of
the size of the incorporated nanoparticles, the findings showed that the specific heat
capacity of nanomaterials was increased by 25%.
The specific heat capacity of exfoliated graphite nanoparticle fibres dispersed in
polyalphaolefin at mass concentrations of 0.6% and 0.3% was measured by Nelson
et al. (2009) using a differential scanning calorimeter. They discovered that as the
temperature rose, the nanofluid’s specific heat augmented as well. The nanofluid
was shown to have a 50% higher specific heat capacity than PAO at a concentration
of 0.6% by weight. According to Zhou et al. (2010), the base fluids, nanoparticle
size, and volume concentration significantly affect the specific heat capacity of
nanofluids. The specific heat of composites, including aligned multiwall carbon
nanotubes, graphite powder, and oriented single-wall and multiwall carbon nanotubes contained in a porous aluminium matrix, was investigated by Pradhan et al.
(2009) between 300 and 400 K. According to the findings, MWCNTs and SWCNTs
behave similarly in terms of specific heat when compared to bulk graphite powder.
Above room temperature, the aligned MWCNTs’ specific heat was less intense and
less temperature-dependent than the bulk. The specific heat of three nanofluids
including Al2O3, SiO2, and ZnO nanoparticles was studied by Vajjha and Das
(2012). The base fluid for the first two was a 60:40 mass ratio of ethylene glycol to
water, while the base fluid for the third was deionized water. Different particle volume concentrations and temperatures were used in the experiments. Experimental
research on the specific heat capacity of CuO-base oil nanofluids with particle
weight fractions of 0.2–2% at various temperatures was done by Saeedinia et al.
(2012). In this experiment, nanofluids demonstrated a lower specific heat capacity
than the base fluid, and this specific heat capacity falls as the concentration of nanofluids rises. The outcome showed that at 40 °C, the specific heat of nanofluids containing a 2 wt% fraction was approximately 23% lower than that of the basic fluid.
15.4.6
Surface Tension
Very little study has been done on surface tension. There are no specific studies on
the surface tension of nanofluids in the literature. It can be defined as the force acting over the surface of the liquid per unit length of the surface perpendicular to the
force. Since bubble departure and interfacial equilibrium depend on surface tension,
it has a substantial impact on the boiling process (Das et al. 2008). Surface tension
of nanofluids created without the addition of any surfactant was observed to alter
just little, in contrast to the major effects of surfactant addition during nanofluid
synthesis (Das et al. 2003; Pantzali et al. 2009). The surfactant affects the surface
tension of nanofluids by acting as an interfacial shell between the nanoparticles and
base fluids (Kathiravan et al. 2009; Ramesh and Prabhu 2011). As temperature and
nanoparticle concentration rise, surface tension drops (Murshed et al. 2008a, b;
Jeong et al. 2008; Peng et al. 2010). Thus, it is evident from the aforementioned
study that the addition of nanoparticles to the base fluids will modify their
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thermophysical characteristics. According to an investigation of the standard
cooling curve by Gestwa and Przyecka (2010), adding 1% of Al2O3 nanoparticles to
a 10% polymer water solution cause cooling rates to rise from 98 to 111 °C/s. When
quenching a stainless-steel probe, Babu and Kumar (2011) also noticed variable
cooling speeds when adding varying concentrations of CNT to the water. By
adjusting the particle volume concentration, particle volume, particle material,
particle size, particle shape, and base fluid, it is possible to generate fluids with
variable cooling capabilities by altering the thermophysical properties of the base
fluids with the addition of nanoparticles. The heat treatment industry would benefit
enormously from the synthesis of quenching media with different cooling intensities.
15.4.7
Pressure Drop Characteristics
Pressure drop characteristics have received very little research attention. The
literature does not contain any particular studies on pressure drop of nanofluids.
This characteristic is also anticipated to play a crucial role in regulating how well
the nanofluids function in systems with high heat conductivity and viscosity.
However, it is believed that the quantity of studies on this feature in the literature is
insufficient to draw a general conclusion regarding its influence on the properties of
nanofluid heat transfer. The viscosity of nanofluids will get more viscous after being
added nanoparticles, and they will also lose pressure as they flow (Alawi et al. 2015;
Feroskhan et al. 2022). Identical research on nanofluids containing water as a based
fluid was conducted by Madhesh et al. (2014), and it was discovered that the friction
factor and consequent pressure drop of the nanofluid were significantly influenced
by the concentration of hybrid Cu-TiO2 nanoparticles. They said that because
hybrid nanoparticles have a large volume fraction (let’s say, 2 vol%) and a density
gradient that increases friction, the pressure drop of nanofluid during its flow is
caused by increasing the friction factor.
The influence of particle concentration, temperature, as well as surfactants on the
surface tension of nanofluids might be comprehensively represented by
Khaleduzzaman et al. (2013). They proved that raising the concentration of nanoparticles raised the surface tension of nanofluids, but increasing the temperature of the
nanofluids and the amount of surfactants caused the surface tension of the nanofluids to decrease. Further, understanding how surface tension of nanofluids affects
their thermal performance, more research on this topic has to be done. Similar studies (Mahbubul et al. 2013, 2015) concerning the pressure decline, density, and specific heat of nanorefrigerants that are existing in the literature have demonstrated
that the properties of nanorefrigerants are altered by the nanoparticles that are
seeded within them. However, it is urgently important to conduct more tests for the
identical combination of base fluids and nanoparticles in order to clarify the order
of physical mechanisms responsible for the improved thermal performance of
nanofluids.
15 Thermophysical Characteristics of Nanofluids: A Review
15.5
357
Conclusion
The majority of the literature on thermophysical properties is included in this
current study. The thermophysical features of the basal fluids are anomalously
changed when nanoparticles are added. This review reveals that there are still
discrepancies, necessitating a thorough experimental investigation of the
thermophysical characteristics of nanofluids. Before being employed for commercial
purposes, several things must be addressed. The key findings from this review study
are as follows:
• Data on enhanced heat transfer reported by several reports vary considerably.
• While preparing nanofluids and enhancing their qualities, there are a few
obstacles that must be addressed.
• Since nanofluids are expensive and challenging to manufacture, efforts should be
made to develop nanofluids that are efficient and affordable.
• New varieties of nano-based fluids with increasing thermal conductivity and
decreasing viscosity must be developed to full fill the demands of heat transfer
applications.
• There is little study utilizing solid, liquid, and hybrid nanofluids; nonetheless,
this subject might be further investigated for developing nanotechnology in the
next decades.
• These are some prospective research directions for nanofluids that might be
pursued in order to expand their expenditure in diverse fields.
• Finally, in order to expound the sequence of physical principles for the improved
thermal performance of nanofluids, more experiments for the identical combination of base fluids and nanoparticles must be conducted immediately.
References
Abareshi M, Sajjadi SH, Zebarjad SM, Goharshadi EK (2011) Fabrication, characterization, and
measurement of viscosity of α-Fe2O3-glycerol nanofluids. J Mol Liq 163(1):27–32
Agresti F, Barison S, Battiston S et al (2013) Influence of molecular weight of PVP on aggregation
and thermal diffusivity of silver based nanofluids. In: Nanotechnology, TechConnect,
Washington, DC, pp 366–369
Agresti F, Ferrario A, Boldrini S, Miozzo A, Montagner F, Barison S, Pagura C, Fabrizio M,
Fabrizio M (2015) Temperature controlled photoacoustic device for thermal diffusivity
measurements of liquids and nanofluids. Thermochim Acta 619:48–52
Akoh H, Tsukasaki Y, Yatsuya S, Tasaki A (1978) Magnetic properties of ferromagnetic ultrafine
particles prepared by vacuum evaporation on running oil substrate. J Cryst Growth 45:495–500
Alawi OA, Sidik NAC, Kherbeet AS (2015) Measurements and correlations of frictional pressure
drop of TiO2/R123 flow boiling inside a horizontal smooth tube. Int Commun Heat Mass
Transf 61:42–48
Ali N, Teixeira JA, Addali A (2018) A review on nanofluids: fabrication, stability, and
thermophysical properties. J Nanomater 2018:1–33
358
C.-Y. Hsu et al.
Babu K, Prasanna Kumar TS (2011) Effect of CNT concentration and agitation on surface heat flux
during quenching in CNT nanofluids. Int J Heat Mass Transf 54(1–3):106–117
Chamsa-Ard W, Brundavanam S, Fung CC, Fawcett D, Poinern G (2017) Nanofluid types,
their synthesis, properties and incorporation in direct solar thermal collectors: a review.
Nanomaterials (Basel) 7(6):131
Chen JLT, Oumer AN, Azizuddin AA (2019) A review on thermo-physical properties of bio, nonbio and hybrid nanofluids. J Mech Eng Sci 13(4):5875–5904
Chevalier J, Tillement O, Ayela F (2007) Rheological properties of nanofluids flowing through
microchannels. Appl Phys Lett 91(23):233103
Choi SUS (1995) Enhancing thermal conductivity of fluids with nanofluids, developments and
applications of non-Newtonian flows. ASME, Argonne, United States, p 99
Choi SUS, Eastman JA (1995) Enhancing thermal conductivity of fluids with nanoparticles. ASME
Int Mech Eng Congress Expo 66:99–105
Das S (2015) Nanofluids for heat transfer: an analysis of thermophysical properties. IOSR J Appl
Phys 7(5):34–40
Das PK (2017) A review based on the effect and mechanism of thermal conductivity of normal
nanofluids and hybrid nanofluids. J Mol Liq 240:420–446
Das SK, Putra N, Roetzel W (2003) Pool boiling characteristics of nano-fluids. Int J Heat Mass
Transf 46(5):851–862
Das SK, Choi SUS, Patel HE (2006) Heat transfer in nanofluids—a review. Heat Transf Eng
27(10):3–19
Das SK, Prakash Narayan GP, Baby AK (2008) Survey on nucleate pool boiling of nanofluids: the
effect of particle size relative to roughness. J Nanopart Res 10(7):1099–1108
Deepak SR, Dhinakaran S (2016) A multi-level homogenization model for thermal conductivity
of nanofluids based on particle size distribution (PSD) analysis. Powder Technol 30:310–317
Duangthongsuk W, Wongwises S (2010) An experimental study on the heat transfer performance
and pressure drop of TiO2-water nanofluids flowing under a turbulent flow regime. Int J Heat
Mass Transf 53(1–3):334–344
Eastman JA, Choi US, Li S, Thompson LJ, Lee S (1996) Enhanced thermal conductivity through
the development of nanofluids. MRS Online Proc Libr 457:3–11
Eastman JA, Choi SUS, Li S, Yu W, Thompson LJ (2001) Anomalously increased effective thermal
conductivities of ethylene glycol-based nanofluids containing copper nanoparticles. Appl Phys
Lett 78(6):718–720
Eggers JR, Kabelac S (2016) Nanofluids revisited. Appl Therm Eng 106:1114–1126
Feroskhan M, Venugopal T, Almakayeel NM, Khan TMY, Alghamdi S, Almuflih AS, Gobinath
N (2022) Fundamentals, thermophysical properties, and heat transfer characteristics of
nanorefrigerants: a review. J Nanomater 2022:1–18
Gallego MJ, Casanova C, Legido JL, Piñeiro MM (2011) CuO in water nanofluid: influence of
particle size and poly dispersity on volumetric behaviour and viscosity. Pastoriza Fluid Phase
Equilib 300(1):188–196
Gestwa W, Przylecka M (2010) The modification of sodium polyacrylate water solution cooling
properties by Al2O3. Adv Mater Sci Eng 2010:1–5
Gupta M, Singh V, Kumar R, Said Z (2017) A review on thermophysical properties of nanofluids
and heat transfer applications. Renew Sust Energ Rev 74:638–670
Haddad Z, Abid C, Oztop HF, Mataoui A (2014) A review on how the researchers prepare their
nanofluids. Int J Therm Sci 76:168–189
Halelfadl S, Estellé P, Aladag B, Doner N, Maré T (2013) Viscosity of carbon nanotubes waterbased nanofluids: influence of concentration and temperature. Int J Therm Sci 71:111–117
Hamzah MH, Sidik NAC, Ken TL, Mamat R, Najafi G (2017) Factors affecting the performance of
hybrid nanofluids: a comprehensive review. Int J Heat Mass Transf 115:630–646
Harikrishnan AR, Das SK, Agnihotri PK, Dhar P (2017) Particle and surfactant interactions
effected polar and dispersive components of interfacial energy in nanocolloids. J Appl Phys
122(5):054301
15 Thermophysical Characteristics of Nanofluids: A Review
359
Harkirat (2010) Preparation and characterization of nanofluids and some investigation in
biological applications. Master of technology in chemical engineering [thesis] report, Thapar
University Patiala
Hemmat Esfe M, Saedodin S (2014) An experimental investigation and new correlation of
viscosity of ZnO–EG nanofluid at various temperatures and different solid volume fractions.
Exp Thermal Fluid Sci 55:1–5
Hemmat Esfe M, Saedodin S, Mahian O, Wongwises S (2014) Efficiency of ferromagnetic
nanoparticles suspended in ethylene glycol for applications in energy devices: effects of
particle size, temperature, and concentration. Int Commun Heat Mass Transf 58:138–146
Hong KS, Hong TK, Yang HS (2006) Thermal conductivity of Fe nanofluids depending on the
cluster size of nanoparticles. Appl Phys Lett 88(3):031901
Hung YH, Chou WC (2012) Chitosan for suspension performance and viscosity of MWCNTs. Int
J Chem Eng Appl 3(5):347–353
Jana S, Salehi-Khojin A, Zhong W (2007) Enhancement of fluid thermal conductivity by the
addition of single and hybrid nano-additives. Thermochim Acta 462(1–2):45–55
Jeong YH, Chang WJ, Chang SH (2008) Wettability of heated surfaces underpool boiling using
surfactant solutions and nano-fluids. Int J Heat Mass Transf 51(11–12):3025–3031
Jiang W, Du K, Li Y, Yang L (2017) Experimental investigation on influence of high temperature
on viscosity, thermal conductivity and absorbance of ammonia-water nanofluids. Int J Refrig
82:189–198
Joseph SA, Hari M, Mathew S, Sharma G, Soumya H, Hadiya VM, Radhakrishnan P, Nampoori
VPN, Nampoori VPN (2010) Thermal diffusivity of rhodamine 6G incorporated in silver
nanofluid measured using mode-matched thermal lens technique. Opt Commun 283(2):313–317
Kaggwa A, Carson JK (2019) Developments and future insights of using nanofluids for heat transfer
enhancements in thermal systems: a review of recent literature. Int Nano Lett 9(4):277–288
Kathiravan R, Kumar R, Gupta A (2009) Characterization and pool boiling heat transfer studies of
nanofluids. J Heat Transf 131:1–8
Kaufui V (2009) Wong, Omar De Leon. Appl Nanofluids Curr Future 2:5
Keblinski P, Phillpot SR, Choi SUS, Eastman JA (2002) Mechanisms of heat flow in suspensions
of nanosized particles (nanofluids). Int J Heat Mass Transf 45(4):855–863
Khaleduzzaman SS, Mahbubul IM, Shahrul IM, Saidur R (2013) Effect of particle concentration,
temperature and surfactant on surface tension of nanofluids. Int Commun Heat Mass Transf
49:110–114
Kole M, Dey TK (2011) Role of interfacial layer and clustering on the effective thermal conductivity
of CuO–gear oil nanofluids. Exp Thermal Fluid Sci 35(7):1490–1495
Kole M, Dey TK (2013) Enhanced thermophysical properties of copper nanoparticles dispersed in
gear oil. Appl Therm Eng 56(1–2):45–53
Léal L, Miscevic M, Lavieille P, Amokrane M, Pigache F, Topin F, Nogarède B, Tadrist L (2013)
An overview of heat transfer enhancement methods and new perspectives: focus on active
methods using electroactive materials. Int J Heat Mass Transf 61:505–524
Lee SL, Saidur R, Sabri MFM, Min TK (2016) Effects of the particle size and temperature on the
efficiency of nanofluids using molecular dynamic simulation. Numer Heat Transfer Part A
69(9):996–1013
Lenin R, Joy PA (2017) Studies on the role of unsaturation in the fatty acid surfactant molecule on
the thermal conductivity of magnetite nanofluids. J Colloid Interface Sci 506:162–168
Li J, Li Z, Wang B (2002) Experimental viscosity measurements for copper oxide nanoparticle
suspensions. Tsinghua Sci Technol 7(2):198–201
Li XF, Zhu DS, Wang XJ, Wang N, Gao JW, Li H (2008) Thermal conductivity enhancement
dependent pH and chemical surfactant for Cu−H2O nanofluids. Thermochim Acta
469(1–2):98–103
Madhesh D, Parameshwaran R, Kalaiselvam S (2014) Experimental investigation on convective
heat transfer and rheological characteristics of Cu−TiO2 hybrid nanofluids. Exp Thermal Fluid
Sci 52:104–115
360
C.-Y. Hsu et al.
Mahbubul IM, Saidur R, Amalina MA (2013) Heat transfer and pressure drop characteristics of
Al2O3-R141b nanorefrigerant in horizontal smooth circular tube. Procedia Eng 56:323–329
Mahbubul IM, Saadah A, Saidur R, Khairul MA, Kamyar A (2015) Thermal performance analysis
of Al2O3/R-134a nanorefrigerant. Int J Heat Mass Transf 85:1034–1040
Manikandan S, Shylaja A, Rajan KS (2014) Thermo-physical properties of engineered dispersions
of nano-sand in propylene glycol. Colloids Surf A Physicochem Eng Asp 449:8–18
Mariano A, Pastoriza-Gallego MJ, Lugo L, Mussari L, Piñeiro MM (2015) Co3O4 ethylene
glycol-based nanofluids: thermal conductivity, viscosity and high pressure density. Int J Heat
Mass Transf 85:54–60
Maxwell JC (1891) A treatise on electricity and magnetism. Clarendon Press, Oxford
Mena JB, Ubices de Moraes AA, Benito YR, Ribatski G, Parise JAR (2013) Extrapolation of
Al2O3-water nanofluid viscosity for temperatures and volume concentrations beyond the range
of validity of existing correlations. Appl Therm Eng 51(1–2):1092–1097
Modak M, Chougule SS, Sahu SK (2018) An experimental investigation on heat transfer
characteristics of hot surface by using CuO-water nanofluids in circular jet impingement
cooling. J Heat Transf 140(1):1–10
Murshed SMS, Leong KC, Yang C (2006) Determination of the effective thermal diffusivity of
nanofluids by the double hot-wire technique. J Phys D Appl Phys 39(24):5316–5322
Murshed SM, Tan SH, Nguyen NT (2008a) Temperature dependence of interfacial properties and
viscosity of nanofluids for droplet-based microfluidics. J Phys D 41:1–5
Murshed SMS, Leong KC, Yang C (2008b) Investigations of thermal conductivity and viscosity of
nanofluids. Int J Therm Sci 47(5):560–568
Nabeel Rashin M, Hemalatha J (2013) Viscosity studies on novel copper oxide–coconut oil
nanofluid. Exp Thermal Fluid Sci 48:67–72
Namburu PK, Kulkarni DP, Misra D, Das DK (2007) Viscosity of copper oxide nanoparticles
dispersed in ethylene glycol and water mixture. Exp Thermal Fluid Sci 32(2):397–402
Nelson IC, Banerjee D, Ponnappan R (2009) Flow loop experiments using polyalphaolefin
nanofluids. J Thermophys Heat Transf 23(4):752–761
Nguyen CT, Desgranges F, Galanis N, Roy G, Maré T, Boucher S, Angue Mintsa H (2008)
Viscosity data for Al2O3–water nanofluid—hysteresis: is heat transfer enhancement using
nanofluids reliable? Int J Therm Sci 47(2):103–111
Otanicar TP, Phelan PE, Prasher RS, Rosengarten G, Taylor RA (2010) Nanofluid-based direct
absorption solar collector. J Renew Sustain Energy 2(3):13
Pantzali MN, Kanaris AG, Antoniadis KD, Mouza AA, Paras SV (2009) Effect of nanofluids on
the performance of a miniature plate heat exchanger with modulated surface. Int J Heat Fluid
Flow 30(4):691–699
Pastoriza-Gallego MJ, Casanova C, Páramo R, Barbés B, Legido JL, Piñeiro MM (2009) A study
on stability and thermophysical properties (density and viscosity) of Al2O3 in water nanofluid.
J Appl Phys 106(6):064301
Pastoriza-Gallego MJ, Lugo L, Cabaleiro D, Legido JL, Piñeiro MM (2014) Thermophysical
profile of ethylene glycol-based ZnO nanofluids. J Chem Thermodyn 73:23–30
Paul G, Pal T, Manna I (2010) Thermo-physical property measurement of nano-gold dispersed
water based nanofluids prepared by chemical precipitation technique. J Colloid Interface Sci
349(1):434–437
Peng H, Ding G, Hu H, Jiang W (2010) Influence of carbon nanotubes on nucleate pool boiling
heat transfer characteristics of refrigerant-oil mixture. Int J Therm Sci 49(12):2428–2438
Pradhan NR, Duan H, Liang J, Iannacchione GS (2009) The specific heat and effective thermal
conductivity of composites containing single-wall and multi-wall carbon nanotubes.
Nanotechnology 20(24):245705
Prasad AR, Singh S, Nagar H (2017) A review on nanofluids: properties and applications. Int J Adv
Res Innov Ideas Educ 3(3):70–76
Prasher R, Song D, Wang J, Phelan P (2006) Measurements of nanofluid viscosity and its
implications for thermal applications. Appl Phys Lett 89(13):133108–133110
15 Thermophysical Characteristics of Nanofluids: A Review
361
Ramesh G, Prabhu NK (2011) Review of thermo-physical properties, wetting and heat transfer
characteristics of nanofluids and their applicability in industrial quench heat treatment.
Nanoscale Res Lett 6(1):334
Ranakoti G, Irtisha SD, Kosti S, Nemade R (2012) Heat transfer enhancement by nanofluids.
ME642-convective heat and mass transfer
Rodriguez LG, Iza P, Paz JL (2016) Study of dependence between thermal diffusivity and sample
concentration measured by means of frequency-resolved thermal lens experiment. J Nonlinear
Opt Phys Mater 25(2):1650022
Saeedinia M, Akhavan-Behabadi MA, Razi P (2012) Thermal and rheological characteristics
of CuO–base oil nanofluid flow inside a circular tube. Int Commun Heat Mass Transf
39(1):152–159
Sawant Y, Pathare K, Patel R, Choughule P (2021) Nanofluids with recent application and future
trends. Int J Innov Eng Res Technol 8(6):2394–3696
Sheikholeslami M, Gorji-Bandpy M, Ganji DD (2015) Review of heat transfer enhancement
methods: focus on passive methods using swirl flow devices. Renew Sust Energ Rev 49:444–469
Shin D, Banerjee D (2014) Specific heat of nanofluids synthesized by dispersing alumina
nanoparticles in alkali salt eutectic. Int J Heat Mass Transf 74:210–214
Siddique M, Khaled A-RA, Abdulhafiz NI, Boukhary AY (2010) Recent advances in heat transfer
enhancements: a review report. Int J Chem Eng 2010:1–28
Suganthi KS, Rajan KS (2012) Temperature induced changes in ZnO – water nanofluid: zeta
potential, size distribution and viscosity profiles. Int J Heat Mass Transf 55(25–26):7969–7980
Suganthi KS, Leela Vinodhan VL, Rajan KS (2014a) Heat transfer performance and transport
properties of ZnO–ethylene glycol and ZnO–ethylene glycol–water nanofluid coolants. Appl
Energy 135:548–559
Suganthi KS, Radhakrishnan AK, Anusha N, Rajan KS (2014b) Influence of nanoparticle
concentration on thermo-physical properties of CuO-propylene glycol nanofluids. J Nanosci
Nanotechnol 14(6):4602–4607
Sundar LS, Ramanathan S, Sharma KV, Babu PS (2007) Temperature dependent flow characteristics
of Al2O3 nanofluid. Int J Nanotechnol Appl 1:35–44
Syam Sundar L, Singh MK, Sousa ACM (2013) Investigation of thermal conductivity and viscosity
of Fe3O4 nanofluid for heat transfer applications. Int Commun Heat Mass Transf 44:7–14
Tawfik MM (2017) Experimental studies of nanofluid thermal conductivity enhancement and
applications: a review. Renew Sust Energ Rev 75:1239–1253
Teng TP, Hung YH (2014) Estimation and experimental study of the density and specific heat for
alumina nanofluid. J Exp Nanosci 9(7):707–718
Teng TP, Hung YH, Teng TC, Mo HE, Hsu HG (2010) The effect of alumina/water nanofluid
particle size on thermal conductivity. Appl Therm Eng 30(14–15):2213–2218
Tiznobaik H, Shin D (2013) Enhanced specific heat capacity of high-temperature molten saltbased nanofluids. Int J Heat Mass Transf 57(2):542–548
Tran PX, Soong Y (2007) Preparation of nanofluids using laser ablation in liquid technique (No.
DOE/NETL-IR-2007-161). National Energy Technology Laboratory (NETL), Pittsburgh,
Morgantown, Albany
Turgut A, Tavman I, Chirtoc M, Schuchmann HP, Sauter C, Tavman S (2009) Thermal
conductivity and viscosity measurements of water-based TiO2 nanofluids. Int J Thermophys
30(4):1213–1226
Ueki Y, Aoki T, Ueda K, Shibahara M (2017) Thermophysical properties of carbon-based material
nanofluid. Int J Heat Mass Transf 113:1130–1134
Vajjha RS, Das DK (2012) A review and analysis on influence of temperature and concentration
of nanofluids on thermophysical properties, heat transfer and pumping power. Int J Heat Mass
Transf 55(15):4063–4078
Vajjha RS, Das DK, Mahagaonkar BM (2009) Density measurement of different nanofluids and
their comparison with theory. Pet Sci Technol 27(6):612–624
362
C.-Y. Hsu et al.
Wagener M, Murty BS, Günther B (1996) Preparation of metal nanosuspensions by high-pressure
DC-sputtering on running liquids. MRS Proc 457:149–154
Wang BX, Zhou LP, Peng XF (2006) Surface and size effects on the specific heat capacity of
nanoparticles. Int J Thermophys 27(1):139–151
Wang BX, Zhou LP, Peng XF, Du XZ, Yang YP (2010) On the specific heat capacity of CuO
nanofluid. Adv Mech Eng, SAGE Journals 2:172085
Wu X, Wu H, Cheng P (2009) Pressure drop and heat transfer of Al2O3 -H2O nanofluids through
silicon microchannels. J Micromech Microeng 19(10):11
Xie H, Wang J, Xi T, Liu Y, Ai F, Wu Q (2002a) Thermal conductivity enhancement of suspensions
containing nanosized alumina particles. J Appl Phys 91(7):4568–4572
Xie HQ, Wang JC, Xi TG, Liu Y (2002b) Thermal conductivity of suspensions containing
nanosized SiC particles. Int J Thermophys 23(2):571–580
Yang F, Qiu X, Li Y, Yin Y, Fan Q (2008) Specific heat of super carbon nanotube and its chirality
independence. Phys Lett A 372(46):6960–6964
Yang L, Xu J, Du K, Zhang X (2017) Recent developments on viscosity and thermal conductivity
of nanofluids. Powder Technol 317:348–369
Yoo D, Hong KS, Yang H (2007) Study of thermal conductivity of nanofluids for the application
of heat transfer fluids. Thermochim Acta 455(1–2):66–69
Yu W, Xie H (2012) A review on nanofluids: preparation, stability mechanisms, and applications.
J Nanomater 2012:1–17
Yu W, France DM, Smith DS, Singh D, Timofeeva EV, Routbort JL (2009a) Heat transfer to a
silicon carbide/water nanofluid. Int J Heat Mass Transf 52(15–16):3606–3612
Yu W, Xie H, Chen L, Li Y (2009b) Investigation of thermal conductivity and viscosity of ethylene
glycol based ZnO nanofluid. Thermochim Acta 491(1–2):92–96
Zhou LP, Wang BX, Peng XF, Du XZ, Yang YP (2010) On the specific heat capacity of CuO
nanofluid. Adv Mech Eng 2010:1–4
Zhu HT, Lin YS, Yin YS (2004) A novel one-step chemical method for preparation of copper
nanofluids. J Colloid Interface Sci 277(1):100–103
Zhu H, Zhang C, Liu S, Tang Y, Yin Y (2006) Effects of nanoparticle clustering and alignment on
thermal conductivities of Fe3O4 aqueous nanofluids. Appl Phys Lett 89(2):23123
Zhu D, Li X, Wang N, Wang X, Gao J, Li H (2009) Dispersion behaviour and thermal conductivity
characteristics of Al2O3−H2O nanofluids. Curr Appl Phys 9(1):131–139