Department of Mechanical Engineering, MSRIT Page 1 of 22
3. LITERATURE REVIEW
4. PREPARATION METHODS FOR NANOFLUIDS
5. THERMAL CONDUCTIVITY OF NANO FLUIDS
6. MATERIALS USED FOR NANOPARTICLES AND
7. ADVANTAGES OF NANOFLIDS
9. APPLICATION OF NANOFLUIDS
Department of Mechanical Engineering, MSRIT Page 2 of 22
Nanoﬂuids are engineered colloidal suspensions of nanoparticles in a base ﬂuid.Ingeneral the
size of these nanoparticles vary from 1-100nm.The type of nanoparticleused is directly
dependent on the enhancement of a required property of the baseﬂuid.
All physical mechanisms have a critical length scale, below which the physical properties of
materials are changed. Therefore particles<100 nm exhibit properties that are considerably
deferent from those of conventional solids. The noble properties ofnanophase materials come
from the relatively high surface area to volume ratio that is due to the high proportion of
constituent atoms residing at the grain boundaries. The thermal, mechanical, optical, magnetic,
and electrical properties of nanophasematerials are superior to those of conventional materials
with coarse grain structures.
Department of Mechanical Engineering, MSRIT Page 3 of 22
Suspended nano particles in conventional fluids are called nanofluids. Recent
development of nanotechnology brings out a new heat transfer coolant called ‘nanofluids. these
fluids exhibit larger thermal properties than conventional coolants. Nanofluids can be
considered to be the next-generation heat transfer fluids because they offer exciting new
possibilities to enhance heat transfer performance compared to pure liquids. Micrometer-sized
particle-fluid suspensions exhibit no such dramatic enhancement. Nanofluids are expected to
have superior properties compared to conventional heat transfer fluids, as well as fluids
containing micro-sized metallic particles. The much larger relative surface area of
nanoparticles, compared to those of conventional particles, not only significantly improves heat
transfer capabilities, but also increases the stability of the suspension.
Department of Mechanical Engineering, MSRIT Page 4 of 22
Nanofluids are suspensions of nanoparticles in a base fluid, typically water. The term
nanoparticle comes from the Latin prefix ‘nano’. It prefix is used to denote the 10-9
part of a
unit. In this context, nano-particles can be termed as the particles with a size in the range of a
few nanometers. Traditionally, nanoparticles have a size between 100-2500 nm. Particles
smaller than 100 nm are termed ultrafine. These objects are being extensively explored due to
their possible applications in medical, optical and electronics fields.
The most popular nano-particles that use to produce nanofluids are: aluminum oxide (Al2O3),
copper (II) oxide (CuO), copper (Cu). Water, oil, decene, acetone and ethylene glycol are the
most common base fluids being used in producing nanofluids.
“Nano-particles can be produced from several processes such as gas
condensation, mechanical attrition or chemical precipitation techniques. Gas
condensation processing has an advantage over other techniques.” (“Critical
Review of heat transfer….,” 2007)
Department of Mechanical Engineering, MSRIT Page 5 of 22
PREPARATION METHODS FOR NANOFLUIDS
1. TWO-STEP METHOD
Two-step method is the most widely used method for preparing nanofluids.
Nanoparticles,Nanofibers, nanotubes or other nanomaterials used in this method are first
produced as dryPowders by chemical or physical methods. Then the nanosized powder will be
dispersedInto a fluid in the second processing step with the help of intensive magnetic force
agitation,Ultrasonic agitation, high-shear mixing, homogenizing and ball milling. Two-step
method isThe most economic method to produce nanofluids in large scale, because
nanopowderSynthesis techniques have already been scaled up to industrial production levels.
Due to theHigh surface area and surface activity, nanoparticles have the tendency to aggregate.
TheImportant technique to enhance the stability of nanoparticles in fluids is the use
ofSurfactants. However the functionality of the surfactants under high temperature is also aBig
concern, especially for high temperature applications.
2. SINGLE-STEP METHOD
In the single step method the nanoparticles are produced and dispersed
Simultaneously into the base fluid.
Figure: Schematic diagram of nanofluid production Evaporation of materials into low-
vapour-pressure liquids system designed for direct.
Department of Mechanical Engineering, MSRIT Page 6 of 22
THERMAL CONDUCTIVITY OF NANO FLUIDS
The fluids that have been traditionally used for heat transfer applications have a rather
low thermal conductivity. Taking into account the rising demands of modern technology, it has
been recently proposed that dispersion of small amounts of nanometres-sized solids in the fluid
called nanofluids can enhance the thermal conductivity of the fluids.
• This increase in the thermal conductivity is predicted to be because of the
1. Brownian motion
2. Interfacial layer (nanolayer)
3. Volume fraction of particles
Department of Mechanical Engineering, MSRIT Page 7 of 22
It has been found that the Brownian motion of nanoparticles at the molecular and
nanoscale level is a key mechanism governing the thermal behaviour of nanoparticle–fluid
suspensions ("nanofluids"). The enhancement in the effective thermal conductivity of
nanofluids is due mainly to the localized convection caused by the Brownian movement of the
• It is postulated that the enhanced thermal conductivity of a nanofluids, when
Compared to conventional predictions, is mainly due to
• Brownian motion which produces micro-mixing.
• This effect is additive to the thermal conductivity of a static dilute suspension.
• Keff = kstatic + kbrownian
• Since the speed of thermal wave propagation is much faster than the particle
Brownian motion, the static part cannot be neglected
Department of Mechanical Engineering, MSRIT Page 8 of 22
Fig: Brownian motion of nanoparticles
Interfacial layer (nanolayer)
Although liquid molecules close to a solid surface are known to form Layered
structures, little is known about the connection between this Nanolayer and the thermal
properties of solid/liquid suspensions. It is assumed that the solid-like nanolayer acts as a
thermal bridge between a solid nanoparticle and a bulk liquid and so is key to Enhancing
thermal conductivity. From this thermally bridging nanolayer idea, a structural model of
nanofluids that consists of solid was suggested. Nanoparticles, bulk liquid and solid-like
nanolayers. Conventional pictures of solid/liquid suspensions do not have this nanolayer.The
thermal conductivity of the nanolayer on the surface of the nanoparticle is not known.
However, because the layered molecules are in an intermediate
Department of Mechanical Engineering, MSRIT Page 9 of 22
Physical state between a bulk liquid and a solid the solid-like nanolayer of liquid molecules
would be expected to lead to a higher thermal Conductivity than that of the bulk liquid.
Fig: Schematic cross section of nanofluids structure consisting of nanoparticles, bulk
liquid, and nanolayers at solid/liquid interface.
Fig: Single spherical particle with interfacial layer in a fluid medium.
Department of Mechanical Engineering, MSRIT Page 10 of 22
Highly conductive nanoparticles of very low volume fractions distributed in a quiescent liquid
(called ‘nanofluids’) may measurably increase the effective thermal conductivity of the
suspension when compared to the pure liquid.
Graph: thermal conductivity vs volume fraction
Department of Mechanical Engineering, MSRIT Page 11 of 22
MATERIALS USED FOR NANOPARTICLES
AND BASE FLUIDS
NANOPARTICLE MATERIALS INCLUDE
Oxide ceramics – Al2O3, CuO
Metal carbides – Sic
Nitrides – AlN, SiN
Metals – Al, Cu
Non-metals – Graphite, carbon nanotubes
Layered – Al + Al2O3, Cu + C
BASE FLUIDS INCLUDE
Ethylene- or tri-ethylene-glycols and other coolants
Oil and other lubricants
Department of Mechanical Engineering, MSRIT Page 12 of 22
ADVANTAGES OF NANOFLUIDS
High specific surface area and therefore more heat transfer sur- face between particles
High dispersion stability with predominant Brownian motion of particles.
Reduced pumping power as compared to pure liquid to achieve equivalent heat transfer
Reduced particle clogging as compared to conventional slurries, thus promoting system
Adjustable properties, including thermal conductivity and surface wet ability, by
varying particle concentrations to suit different applications.
. Lower specific heat
From the literatures, it is found that specific heat of nanofluids is lower than basefluid.
Namburu et al.  reported that CuO/ethylene glycol nanofluids, SiO2/ethylene glycol
nanofluids and Al2O3/ethylene glycol nanofluids exhibit lower specific heat compared to
basefluids. An ideal coolant should possess higher value of specific heat which enable the
coolant to remove more heat.
Department of Mechanical Engineering, MSRIT Page 13 of 22
High cost of nanofluids
Higher production cost of nanofluids is among the Reasons that may hinder the application of
nanofluids in industry. Nanofluids can be produced by either one step or two steps methods.
However both methods require advanced and sophisticated equipments. Lee and Mudawar 
and Pantzali etal. stressed that high cost of nanofluids is among the drawback of nanofluids
Difficulties in production process
Previous efforts to manufacture nanofluids have often employed either a single step that
simultaneously makes and disperses the nanoparticles into base fluids, or a two-step approach
that involves generating nanoparticles and subsequently dispersing them into a base fluid.
Using either of these two approaches, nanoparticles are inherently produced from processes
that involve reduction reactions or ion exchange. Furthermore, the base fluids contain other
ions and reaction products that are difficult or impossible to separate from the fluids. Another
difficulty encountered in nanofluid manufacture is nanoparticles’ tendency to agglomerate into
larger particles, which limits the benefits of the high surface area nanoparticles. To counter this
tendency, particle dispersion additives are often added to the base fluid with the nanoparticles.
Unfortunately, this practice can change the surface properties of the particles, and nanofluids
prepared in this way may contain unacceptable levels of impurities. Most studies to date have
been limited to sample sizes less than a few hundred milliliters of nanofluids. This is
problematic since larger samples are needed to test many properties of nanofluids and, in
particular, to assess their potential for use in new applications
Department of Mechanical Engineering, MSRIT Page 14 of 22
APPLICATION OF NANOFLUID
This section explains applications of nanofluids in industrial, commercial, residential
and transportation sectors based on avail- able literatures.
HEAT TRANSFER INTENSIFICATION
Since the origination of the nanofluids concept about a decade ago, the potentials of
nanofluids in heat transfer applications have attracted more and more attention. Up to now,
there are some review papers, which present overviews of various aspects of nanofluids
including preparation and characterization, techniques for the measurements of thermal
conductivity, theory and model, thermo physical properties, convective heat transfer. In this
part, we will summarize the applications of nanofluids in heat transferEnhancement.
Due to higher density of chips, design of electronic components with more compact
makes heat dissipation more difficult. Advanced electronic devices face thermal management
challenges from the high level of heat generation and the reduction of available surface area for
heat removal. So, the reliable thermal management system is vital for the smooth operation of
the advanced electronic devices. In general, there are two approaches to improve the heat
removal for electronic equipment. One is to find an optimum geometry of Cooling devices;
another is to increase the heat transfer capacity. Recent researches illustrated that nanofluids
could increase the heat transfer coefficient by increasing the thermal conductivity of a coolant.
Jang et al. designed a new cooler, combined micro channel Heat sink with nanofluids. Higher
cooling performance was obtained when compared to the device using pure water as working
medium. Nanofluids reduced both the thermal resistance and the temperature difference
between the heated micro channel wall and the coolant. A combined micro channel heat sink
with nanofluids had the potential as the next generation cooling devices for removing ultra-
high heat flux. Nguyen et al. designed a closed liquid-circuit to investigate the heat transfer
enhancement of a liquid cooling system, By replacing the base fluid (distilled water) with a
nanofluid composed of distilled water and Al2O3 nanoparticles at various concentrations.
Measured data have clearly shown that the inclusion of nanoparticles within the distilled water
has produced a considerable enhancement in convective heat transfer coefficient of the cooling
Department of Mechanical Engineering, MSRIT Page 15 of 22
block. With particle loading 4.5 vol%, the enhancement is up to 23% with respect to that of the
base fluid. It has also been observed that an augmentation of particle concentration has
produced a clear decrease of the junction temperature between the heated component and the
cooling block. Silicon micro channel heat sink performance using nanofluids containing Cu
nanoparticles was analyzed. It was found nanofluids could enhance the performance as
compared with that using pure water as the coolant. The enhancement was due to the increase
in thermal conductivity of coolant and the nanoparticle thermal dispersion effect. The other
Advantage was that there was no extra pressure drop since the nanoparticle was small and
particle volume fraction was low. The thermal requirements on the personal computer become
much stricter with the increase in thermal dissipation of CPU. One of the solutions is the use of
heat pipes. Nanofluids, employed as working medium for conventional heat pipe, have shown
The suspended nanoparticles tend to bombard the vapour bubble during The bubble formation.
Therefore, it is expected that the nucleation size of vapour bubble is much smaller for fluid
with suspended nanoparticles than that without them. This may be the major reason for
reducing the thermal resistance of heat pipe.. For example, at the input power of 80.0 W,
diamond nanofluid could reduce the temperature difference between the evaporator and the
condenser from 40.9 to 24.3°C. This study would accelerate the development of a highly
efficient cooling device for ultrahigh-heat-flux electronic systems. The thermal performance
investigation of heat pipe indicated that nanofluids containing silver or titanium nanoparticles
could be used as an efficient cooling fluid for devices with high energy density. For a silver
nanofluid, the Temperature difference decreased 0.56-0.65℃ compared to water at an input
power of 30-50 W. For the heat pipe with titanium nanoparticles at a volume concentration of
0.10%, the thermal efficiency is 10.60% higher than that with the based working fluid. These
positive results are promoting the continued research and development of nanofluids for such
Nanofluids have great potentials to improve automotive and heavy-duty engine cooling
rates by increasing the efficiency, lowering the weight and reducing the complexity of thermal
management systems. The improved cooling rates for automotive and truck engines can be
used to remove more heat from higher horsepower engines with the same size of cooling
system. Alternatively, it is beneficial to design more compact cooling system with smaller and
Department of Mechanical Engineering, MSRIT Page 16 of 22
lighter radiators. It is in turn benefit the high performance and high fuel economy of car and
truck. Ethylene glycol based nanofluids have attracted much attention in the application as
engine coolant due to the low-pressure operation compared with a 50/50 mixture of ethylene
glycol and water, which is the nearly universally used automotive coolant. The nanofluids has a
high boiling point, and it can be used to increase the normal coolant operating temperature and
then reject more heat through the existing coolant system . The experimental platform was the
transmission of a four-wheel drive vehicle. The used nanofluids were prepared by dispersing
Cut and Al2O3 nanoparticles into engine transmission oil. The results showed that
CuOnanofluids produced the lower transmission temperatures both at high and low rotating
speeds. From the thermal performance viewpoint, the use of nanofluid in the transmission has a
clear advantage. The researchers of Argonne National Laboratory have assessed the
applications of nanofluids for transportation. The use of high-thermal conductive nanofluids in
radiators can lead to a reduction in the frontal area of the radiator up to 10%. The fuel saving is
up to 5% due to the reduction in aerodynamic drag. It opens the door for new aerodynamic
automotive designs that reduce emissions by lowering drag. The application of nanofluids also
contributed to a reduction of friction and wear, reducing parasitic losses, operation of
components such as pumps and compressors, and subsequently leading to more than 6% fuel
savings. In fact, nanofluids not only enhance the efficiency and economic performance of car
engine, but also will greatly influence the structure design of automotives. For example, the
engine radiator cooled by a nanofluid will be smaller and lighter. It can be placed elsewhere in
the vehicle, allowing for the redesign of a far more aerodynamic chassis. By reducing the size
and changing the location of the radiator, a reduction in weight and wind resistance could
enable greater fuel efficiency and subsequently lower exhaust emissions. Computer simulations
from the US department of energy’s office of vehicle technology showed that nanofluid
coolants could reduce the size of truck radiators by 5%. This would result in a 2.5% fuel saving
at highway speeds.
INDUSTRIAL COOLING APPLICATIONS
The application of nanofluids in industrial cooling will result in great energy savings
and emissions reductions. For US industry, the replacement of cooling and heating water with
nanofluids has the potential to conserve 1 trillion Btu of energy. For the US electric power
industry, using nanofluids in closed loop cooling cycles could save about 10-30 trillion Btu per
Department of Mechanical Engineering, MSRIT Page 17 of 22
year (equivalent to the annual energy consumption of about 50,000–150,000 households). The
associated emissions reductions would be approximately 5.6 millionMetric tons of carbon
dioxide, 8,600 metric tons of nitrogen oxides, and 21,000 metric tons of sulphur dioxide.
Experiments were performed using a flow-loop apparatus to explore the performance of
polyalphaolefinnanofluids containing exfoliated graphite nanoparticle fibres in cooling. It was
observed that the specific heat of nanofluids was found to be 50% higher for nanofluids
compared with polyalphaolefin and it increased with temperature. The thermalDiffusivity was
found to be 4 times higher for nanofluids. The convective heat transfer was enhanced by ~10%
using nanofluids compared with using polyalphaolefin. Ma et al proposed the concept of nano
liquid-metal fluid, aiming to establish an engineering route to make the highest conductive
coolant with about several dozen times larger thermal conductivity than that of water. The
liquid metal with low melting point is expected to be an idealistic base fluid for making super
conductive solution which may lead to the ultimate coolant in a wide variety of heat transfer
enhancement area. The thermal conductivity of the liquid-metal fluid can be enhanced through
the addition of more Conductive nanoparticles.
HEATING BUILDINGS AND REDUCING POLLUTION
Nanofluids can be applied in the building heating systems. Kulkarni et al. evaluated
how they perform heating buildings in cold regions. In cold regions, it is a common practice to
use ethylene or propylene glycol mixed with water in different proportions as a heat transfer
fluid. So 60:40 ethylene glycol/water (by weight) was selected as the base fluid. The results
showed that using nanofluids in heat exchangers could reduce volumetric and mass flow rates,
resulting in an overall pumping power savings. Nanofluids necessitate smaller heating systems,
which are capable of delivering the same amount of thermal energy as larger heating systems,
but are less expensive this lowers the initial equipment cost excluding nanofluids cost. This
will also reduce environmental pollutants because smaller heating units use less power, and the
heat transfer unit has less liquid and material waste to discard at the end of its life cycle.
Department of Mechanical Engineering, MSRIT Page 18 of 22
NUCLEAR SYSTEMS COOLING
The Massachusetts Institute of Technology has established an interdisciplinary centre for
nanofluids technology for the nuclear energy industry. The researchers are exploring the
nuclear applications of nanofluids, specifically the following three: 1) main reactor coolant for
pressurized water reactors (PWRs). It could enable significant power up rates in current and
future PWRs, thus enhancing their economic performance. Specifically, the use of nanofluids
with at least 32% higher critical heat flux (CHF) could enable a 20% power density up rate in
current plants without changing the fuel assembly design and without reducing the margin to
CHF; 2) coolant for the emergency core cooling systems (ECCSs) of Both PWRs and boiling
water reactors. The use of a nanofluids in the ECCS accumulators and safety injection can
increase the peak-cladding-temperature margins (in the nominal-power core) or maintain them
in up rated cores if the nanofluids has a higher post-CHF heat transfer rate; 3) coolant for in-
vessel retention of the molten core during severe accidents in high-power- density light water
reactors. It can increase the margin to vessel breach by 40% during severe accidents in high-
power density systems such as Westinghouse APR1000 and the Korean APR1400. While there
exist several significant gaps, including the nanofluids thermal-hydraulic performance at
prototypical reactor conditions and the compatibility of the nanofluids chemistry with the
reactor materials. Much work should be done to overcome these gaps before any applications
can be implemented in a nuclear power plant.
SPACE AND DEFENCE
Due to the restriction of space, energy and weight in space station and aircraft, there is a
strong demand for high efficient cooling system with smaller size. You et al. And Vassalo et al.
have reported order of magnitude increases in the critical heat flux in pool
Boiling with nanofluids compared to the base fluid alone. Further research of nanofluids will
lead to the development of next generation of cooling devices that incorporate nanofluids for
ultrahigh-heat-flux electronic systems, presenting the possibility of raising chip power in
electronic components or simplifying cooling requirements for space applications. A number of
military devices and systems require high-heat flux cooling to the level of tens of MW/m2. At
this level, the cooling of military devices and system is vital for the reliable operation.
Department of Mechanical Engineering, MSRIT Page 19 of 22
Nanofluids with high critical heat fluxes have the potential to provide the required cooling in
such applications as well as in other military systems, including military vehicles, submarines,
and high-power laser diodes. Therefore, nanofluids have wide application in space and defence
fields where power density is very high and the components should be smaller and weight less
There is a new initiative which takes advantage of several properties of certain nanofluids to
use in cancer imaging and drug delivery. This initiative involves the use of iron-based
nanoparticles as delivery vehicles for drugs or radiation in cancer patients. Magnetic nanofluids
are to be used to guide the particles up the bloodstream to a tumor with magnets. It will allow
doctors to deliver high local doses of drugs or radiation without damaging nearby healthy
tissue, which is a significant side effect of traditional cancer treatment methods. In addition,
magnetic nanoparticles are more adhesive to tumor cells than non-malignant cells and they
absorb much more power than microparticles in alternating current magnetic fields tolerable in
humans; they make excellent candidates for cancer therapy.
Magnetic nanoparticles are used because as compared to other metal-type nanoparticles, these
provide a characteristic for handling and manipulation of the nanofluid by magnetic force .
This combination of targeted delivery and controlled release will also decrease the likelihood
of systemic toxicity since the drug is encapsulated and biologically unavailable during transit in
systemic circulation. The nanofluid containing magnetic nanoparticles also acts as a super-
paramagnetic fluid which in an alternating electromagnetic field absorbs energy producing a
controllable hyperthermia. By enhancing the chemotherapeutic efficacy, the hyperthermia is
able to produce a preferential radiation effect on malignant cells .
There are numerous biomedical applications that involve nanofluids such as magnetic cell
separation, drug delivery, hyperthermia, and contrast enhancement in magnetic resonance
imaging. Depending on the specific application, there are different chemical syntheses
developed for various types of magnetic nanofluids that allow for the careful tailoring of their
properties for different requirements in applications. Surface coating of nanoparticles and the
colloidal stability of biocompatible water-based magnetic fluids are the two particularly
important factors that affect successful application [43, 44].
For most biomedical uses the magnetic nanoparticles should be below 15 nm in size and stably
dispersed in water. A potential magnetic nanofluid that could be used for biomedical
applications is one composed of FePt nanoparticles. This FePtnanofluid possesses an intrinsic
chemical stability and a higher saturation magnetization making it ideal for biomedical
applications. However, before magnetic nanofluids can be used as drug delivery systems, more
Department of Mechanical Engineering, MSRIT Page 20 of 22
research must be conducted on the nanoparticles containing the actual drugs and the release
Cooling of Microchips
A principal limitation on developing smaller microchips is the rapid heat dissipation. However,
nanofluids can be used for liquid cooling of computer processors due to their high thermal
conductivity. It is predicted that the next generation of computer chips will produce localized
heat flux over 10 MW/, with the total power exceeding 300 W. In combination with thin film
evaporation, the nanofluid oscillating heat pipe (OHP) cooling system will be able to remove
heat fluxes over 10 MW/and serve as the next generation cooling device that will be able to
handle the heat dissipation coming from new technology
So as to obtain experimental data while maintaining the integrity of the OHP system, Arif
employed neutron imaging to study the liquid flow in a 12-turn nanofluid OHP. As a
consequence of the high intensity neutron beam from an amorphous silicon imaging system,
they were able to capture dynamic images at 1/30th of a second. The nanofluid used was
composed of diamond nanoparticles suspended in water.
Even though nanofluids and OHPs are not new discoveries, combining their unique features
allows for the nanoparticles to be completely suspended in the base liquid increasing their heat
transport capability. Since nanofluids have a strong temperature-dependent thermal
conductivity and they show a nonlinear relationship between thermal conductivity and
concentration, they are high performance conductors with an increased CHF. The OHP takes
intense heat from a high-power device and converts it into kinetic energy of fluids while not
allowing the liquid and vapor phases to interfere with each other since they flow in the same
However, as the heat input increases, the oscillating motion increases and the resultant
temperature difference between the evaporator and condenser does not continue to increase
after a certain power input. This phenonmenon inhibits the effective thermal conductivity of
the nanofluid from continuously increasing. However, at its maximum power level of 336 W,
the temperature difference for the nanofluid OHP was still less than that for the OHP with pure
water, Figure 2. Hence, it has been shown that the nanofluid can significantly increase the heat
transport capability of the OHP.
Department of Mechanical Engineering, MSRIT Page 21 of 22
Lin et al. investigated nanofluids in pulsating heat pipes by using silver nanoparticles, and
discovered encouraging results. The silver nanofluid improved heat transfer characteristics of
the heat pipes.
Nguyen et al. investigated the heat transfer enhancement and behavior of -water nanofluid with
the intention of using it in a closed cooling system designed for microprocessors or other
electronic devices. The experimental data supports that the inclusion of nanoparticles into
distilled water produces a significant increase of the cooling convective heat transfer
coefficient. At a given particle concentration of 6.8%, the heat transfer coefficient increased as
much as 40% compared to the base fluid of water. Smaller nanoparticles also showed higher
convective heat transfer coefficients than the larger ones.
Further research of nanofluids in electronic cooling applications will lead to the development
of the next generation of cooling devices that incorporate nanofluids for ultrahigh-heat-flux
Department of Mechanical Engineering, MSRIT Page 22 of 22
Intensify micro reactors
Nanofluids as vehicular brake fluids
Nanofluids based microbial fuel cell
Department of Mechanical Engineering, MSRIT Page 23 of 22
Downscaling, or miniaturization, has been the major trend in modern science and
technology. Stable suspensions of carbon nanotubes, oxide and metallic nanoparticles in
conventional heat transfer fluids can be achieved by maintaining the particle size below a
threshold level. Studies of nanofluids reveals high thermal conductivities and heat transfer
coefficients compared to those of conventional fluids.
Nanofluids are important because they can be used in numerous applications involving heat
transfer, and other applications such as in detergency. Colloids which are also nanofluids
have been used in the biomedical field for a long time, and their use will continue to grow.
Nanofluids have also been demonstrated for use as smart fluids. Problems of nanoparticle
agglomeration, settling, and erosion potential all need to be examined in detail in the
applications. Nanofluids employed in experimental research have to be well characterized with
respect to particle size, size distribution, shape and clustering so as to render the results most
widely applicable. Once the science and engineering of nanofluids are fully understood and
their full potential researched, they can be reproduced on a large scale and used in many
applications. Colloids which are also nanofluids will see an increase in use in biomedical
engineering and the biosciences.
Further research still has to be done on the synthesis and applications of nanofluids so that they
may be applied as predicted. Nevertheless, there have been many discoveries and
improvements identified about the characteristics of nanofluids in the surveyed applications
and we are a step closer to developing systems that are more efficient and smaller, thus
rendering the environment cleaner and healthier.
Department of Mechanical Engineering, MSRIT Page 24 of 22
 V. Trisaksri, S. Wongwises, Renew. Sust.Energ.Rev. 11, 512 (2007).
 S. Özerinç, S. Kakaç, A.G. Yazıcıoğlu, MicrofluidNanofluid 8, 145 (2009).
 X. Wang, A.S. Mujumdar, Int. J. Therm. Sci. 46, 1 (2007).
 X. Wang, A.S. Mujumdar, Brazilian J. Chem. Eng. 25, 613 (2008).
 Y. Li, J. Zhou, S. Tung, E. Schneider, S. Xi, Powder Technol. 196, 89 (2009).