Nano Fluids-project Report.docx

HEAT TRANSFER IN A VERTICAL TEST SECTION BY USING DI/AG+ NANO-FLUID Page | 1

A project submitted In partial fulfillment of the requirement for the award of the degree of

BACHELOR OF TECHNOLOGY (B. Tech) IN MECHANICAL ENGINEERING By

CHOKKAPU SYAM KIRAN (Regd. No-315132920059)

Under the Guidance of Mr. P.N.E.NAVEEN M.Tech, Assistant Professor Department of Mechanical engineering S.V.P. ENGG. COLLEGE

DEPARTMENT OF MECHANICAL ENGINEERING

SANKETIKA VIDYA PARISHAD ENGINEERING COLLEGE (Approved by A.I.C.T.E., New Delhi and Govt. of A.P. & Affiliated to Andhra University) P.M.PALEM, VISAKHAPATNAM-530041

2016-2019

TABLE OF CONTENT 1. 2. 3. Page | 2 4. 5. 6.

LITERATURE DECLARATION AKNOWLEDGEMENT ABSTRACT LIST OF FIGURES LIST OF TABLES

 INTRODUCTION:  HEAT TRANSFER  TYPES OF HEAT TRANSFER  TYPES OF FLOWS  TYPES OF HEAT EXCHANGERS  WORKING PRINCIPLE OF SHELL AND TUBE  TYPES OF Fluid  HEAT TRANSFER BY HEAT EXCHANGER

 REVIEW OF LITERATURE  TYPES OF NANO FLUIDS  SOLUBLE NANO FLUIDS  WORKING OF DI/AG+ NANO FLUID  WORKING OF DI/ALUM NANO FLUID  THERMAL ANALYSIS OF HEAT TRANSFER USING HEAT EXCHANGER

 EXPERIMENT SETUP 1. AL 7075 T6 ALLOY CYLINDER PIPE WITH ANGULAR PASSAGES 2. SHELL AND TUBE TYPE HEAT CYLINDER 3. ELECTRONIC SKETCH 4. ELECTRICAL WIRING (LAYOUT)

 RESULTS AND CALUCLATION  REFERENCES

SANKETIKA VIDYA PARISHAD ENGINEERING COLLEGE (Approved by A.I.C.T.E., New Delhi and Govt. of A.P. & Affiliated to Andhra University)

P.M.PALEM, VISAKHAPATNAM-530041 Page | 3

CERTIFICATE This is to certify that the project work entitled “HEAT

TRANSFER IN VERTICAL TEST SECTION BY USING DI/AG+ NANO FLUIDS” is a bonafide record of work done and submitted by CHOKKAPU SYAM KIRAN with Regd.No:315132920059, under my supervision in partial fulfillment of the requirements for the award of the degree of BACHELOR OF TECHNOLOGY IN MECHANICAL ENGINEERING from Andhra University, Visakhapatnam during the academic year 2018-2019.

INTERNAL GUIDE:

HEAD OF THE DEPARTMENT

Mr. P.N.E NAVEEN M.Tech, (Ph.D.)

Ms. M. CHAITANYA MAYEE M.Tech, (Ph.D)

Assistant Professor, Dept. of Mechanical engineering, S.V.P. Engineering College, Visakhapatnam.

Head of the Department Dept. of Mechanical engineering, S.V.P. Engineering College, Visakhapatnam.

EVALUATION SHEET

Page | 4 1. Name of the Student 2. Title of the Project

: CH.SYAM KIRAN : HEAT TRANSFER IN VERTICAL TEST SECTION BY USING DI/AG+ NANO-FLUIDS

3. Specialization of B.TECH.

: MECHANICAL ENGINEERING

4. Date of Examination/ Viva voce

:

This Dissertation is approved by the Board of Examiners

External Examiners

:

Internal Examiner

: (D. RAVI VIKRANTH)

ACKNOWLEDGEMENT I express a deep sense of gratitude to my guide and Head of the department Mrs. M. CHAITANYAMAYEE, for his able guidance and cooperation throughout my project work. I Page | 5

am highly grateful to him for providing all the facilities for the completion of the project work. I am very much thankful to the principal Prof. (Dr.) RAMJEE, S.V.P. Engineering College for his encouragement and cooperation to carry out this work. I am very much thankful to Associate Prof. P.N.E NAVEEN & Associate Prof. D.RAVI VIKRANTH, Department of Mechanical, S.V.P Engineering College for his encouragement and cooperation to carry out this work. I express sincere thanks to all the teaching staff and non-teaching staff of Department of Mechanical for providing a great assistance in accomplishment of my project. I am very much thankful to the management of S.V.P. Engineering College for their encouragement and cooperation to carry out this work. I would like to thank my parents, friends, and classmates for their encouragement throughout my project period directly or indirectly in completing this project successfully.

(Regd. No: 315132920059) (HEAT TRANSFER BY USING DI/AG+ NANO FLUID)

SELF DECLARATION I hereby declare that the project work entitled “HEAT TRANSFER IN

Page | 6

VERTICAL TEST SECTION BY USING DI/AG+ NANO FLUID” is a record of an original work done by me for the award of the degree, Master of Technology with specialization in Machine Design submitted to the Department of Mechanical Engineering, Andhra University, during the academic year 2015-2019. This work is not submitted to any other institutions for award of other degree as it is my own contributed work.

CHOKKAPU SYAM KIRAN (Regd. No: 315132920059)

ABSTRACT

Page | 7

Forced convective heat transfer from a vertical circular tube conveying deionized (DI) water or very dilute Ag-DI water Nano-fluids (less than 0.02% volume fraction) in a cross flow of air has been investigated experimentally. Some experiments have been performed in a wind tunnel and heat transfer characteristics such as thermal conductance, effectiveness, and external Nusselt number has been measured at different air speeds, liquid flow rates, and nanoparticle concentrations. The cross flow of air over the tube and the liquid flow in the tube were turbulent in all cases. The experimental results have been compared and it has been found that suspending Ag nanoparticles in the base fluid increases thermal conductance, external Nusselt number, and effectiveness. Furthermore, by increasing the external Reynolds number, the external Nusselt number, effectiveness, and thermal conductance increase. Also, by increasing internal Reynolds number, the thermal conductance and external Nusselt number enhance while the effectiveness decreases. The procedure consists of measuring the temperature of a certain heating material in horizontal and vertical orientation. Experimental studies of forced convection heat transfer from horizontal and vertical heat sources in carried out. It is conducted to determine the effects of Reynolds number and nusselt number on heat transfer. The air stream velocity was varied from (28 to 72) m/s to obtain the large range of the Reynolds numbers .The experiment results for horizontal tubes are obtained for range of Reynolds number (2.6 × 104 to 6.4 × 104), Nusselt number (37.75 – 226.98) and for vertical tubes are obtained for the range of Reynolds number (4 × 104 to 6.9 × 104), Nusselt number (41.45 – 245.56). A correlation for the convective heat transfer coefficients is obtained. The present experimental correlation is compared with available correlation equations and experimental data. The comparisons show very good agreement. A correlation for convective heat transfer coefficient of Nano-fluids, based on transport property and D/x for 8 mm tube has been evolved. The correlation predicts variation in the local Nusselt number along the flow direction of the Nano-fluid. A good agreement (±10%) is seen between the experimental and predicted results.

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INTRODUCTION •

Surfaces, fins, mini-channels and micro-channels appears to be inadequate for the next generation of electronic and optical devices. The other important areas that have also experienced similar problems in thermal management are the areas of power generation, chemical processing, air-conditioning, transportation, microelectronics and optical devices which include lasers, high-power x-rays, optical fibers and communication devices. Further enhancement in heat transfer is always in demand, as the operational speed of these devices often depends on the cooling rate. Improving the thermal conductivity is the key idea to improve the heat transfer characteristics in many heat transfer applications conventional fluids, such as water, engine oil and ethylene glycol are normally used as heat transfer fluids. Although various techniques are applied to enhance the configuration of the heat transfer device, the low heat transfer performance of conventional fluids affects the enhancement of performance, and in turn the compactness of heat exchangers, Thus the usage of extended cs of conventional fluids. It is well known fact that metals in solid form have higher thermal conductivities than those of fluids. It has been shown in many references that, fluids containing suspended metal particles are expected to manifest significantly enhanced thermal conductivities relative to pure fluids. The use of Nano size solid particles as an additive suspended into the base fluid (nanofluids) is a technique for the enhancement of heat transfer. Besides enhanced heat transfer, it is also found that the nanofluids eliminate most of the problems arising with micro size slurries like sedimentation, clogging of small channels, erosion, excessive pressure drop, etc. Thus, nanofluids have greater potential for heat transfer enhancement and are highly suited to application, in practical heat transfer processes. Investigation in convective heat transfer characteristics of nanofluids is being carried out worldwide. One early study by Ahuja showed the capability of micron sized polystyrene suspensions to enhance the convective heat transfer under laminar flow conditions. The results showed significant enhancements of Nusselt number and heat exchanger effectiveness when polystyrene spheres were added to a single phase liquid. However, the use of micron sized particle colloids generally causes particle settling, tube erosion and channel clogging. This issue has been eliminated with the use of stable Nano sized particulate colloids, and this has paved way for researchers to further investigate the enhancement of convective heat transfer with the addition of nano sized particles. Pak and Cho experimentally investigated the hydrodynamic and convective heat transfer characteristics of γ-Al2O3 particles suspended in water at 1-3% volume concentrations. It was found that the Nusselt number for the dispersed fluids increased with

increasing volume concentration and Reynolds number. Eastman et al. conducted heat transfer tests to assess the thermal performance of copper oxide and metallic nanofluids under turbulent flow conditions. Results showed that the heat transfer coefficient of water containing 0.9 vol. % of CuO nanoparticles was improved by more than 15% when compared with pure water. Xuan and Li studied experimentally the single phase flow and heat transfer performance of a nanofluid in tubes for the turbulent flow regime and proposed a heat transfer correlation for the experimental data.

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•

Nanofluids in the entrance region under laminar flow conditions and proposed particle migration to be a reason for the heat transfer enhancement. The nanofluids have higher heat transfer coefficients than that of the base-fluids for the same Reynolds number. Such improvements become more important with increases in the volume concentration of the particle loading. A summary of published experimental investigations on convective heat transfer performance of various nanofluids is presented in Table1 .

TABLE 1: Summary of experimental investigations on convective heat transfer performance of various nanofluids

HEAT TRANSFER: Heat transfer is a discipline of thermal engineering that concerns the generation, use, conversion, and exchange of thermal energy (heat) between physical systems. Heat transfer is classified into various mechanisms, such as thermal conduction, thermal convection, thermal radiation, and transfer of energy by phase changes. Engineers also consider the transfer of mass of differing chemical species, either cold or hot, to achieve heat transfer. While these mechanisms have distinct characteristics, they often occur simultaneously in the same system.

 Types of Heat Transfers  Heat Transfer by Conduction: Page | 10

When particles of matter are in direct contact, heat transfers by means of conduction. The adjacent atoms of higher energy vibrate against one another, which transfers the higher energy to the lower energy, or higher temperature to lower temperature. Fluids and gases are less conductive than solids (metals are the best conductors) due to the fact that they are less dense, meaning that there is a larger distance between atoms.

 Convection Heat Transfer: Convection describes heat transfer between a surface and a liquid or gas in motion. As the fluid or gas travels faster, the convective heat transfer increases. Two types of convection are natural convection and forced convection. In natural convection, fluid motion results from the hot atoms in the fluid, where the hot atoms move upwards toward the cooler atoms in the air--the fluid moves under the influence of gravity.

 Heat Transfer by Radiation: Heat transfer due to emission of electromagnetic waves is known as thermal radiation. Heat transfer through radiation takes place in form of electromagnetic waves mainly in infrared region. Radiation emitted by a body is a consequence of thermal agitation of its composing molecules.

TYPES OF FLOWS: Three different types of fluid flow are 1. 2. 3. 4. 5. 6. 7.

Laminar flow Turbulent flow Transitional flow Steady flow and unsteady flow Compressible and incompressible flow Viscous and non-viscous flow Rotational and irrotational flow

1. Laminar flow: Occurs when the fluid flows in parallel layers, with no mixing between the layers. Where the center part of the pipe flow the fastest and the cylinder touching the pipe isn’t moving at all. Page | 11 The flow is laminar when Reynolds number is less than 2300.

2. Turbulent flow: In turbulent flow occurs when the liquid is moving fast with mixing between layers. The speed of the fluid at a point is continuously undergoing changes in both magnitude and direction. The flow is turbulent when Reynolds number greater than 4000.

3. Transitional flow: Transitional flow is a mixture of laminar and turbulent flow, with turbulence flow in the center of Page | 12 the pipe and laminar flow near the edges of the pipe. Each of these flows behaves in different

manners in terms of their frictional energy loss while flowing and have different equations that predict their behavior. The flow is transitional when Reynolds number is in between 2300 and 4000.

4. Steady and Unsteady Flow: Fluid flow can be steady or unsteady, depending on the fluid’s velocity: 

Steady. In steady fluid flow, the velocity of the fluid is constant at any point.



Unsteady. When the flow is unsteady, the fluid’s velocity can differ between any two points.

For example, suppose you’re sitting by the side of a stream and note that the water flow is not steady: You see eddies and backwash and all kinds of swirling. Imagine velocity vectors for a hundred points in the water, and you get a good picture of unsteady flow — the velocity vectors can be pointing all over the map, although the velocity vectors generally follow the stream’s overall average flow.

5. Compressible and Incompressible Flow: Fluid flow can be compressible or incompressible, depending on whether you can easily compress the fluid. Liquids are usually nearly impossible to compress, whereas gases (also considered a fluid) are very compressible. A hydraulic system works only because liquids are incompressible — that is, when you increase the pressure in one location in the hydraulic system, the pressure increases to match everywhere in the whole system. Gases, on the other hand, are very compressible — even when your bike tire

is stretched to its limit, you can still pump more air into it by pushing down on the plunger and squeezing it in. Page | 13

6. Viscous and Non-Viscous flow: Liquid flow can be viscous or non-viscous. Viscosity is a measure of the thickness of a fluid, and very gloppy fluids such as motor oil or shampoo are called viscous fluids. Viscosity is actually a measure of friction in the fluid. When a fluid flows, the layers of fluid rub against one another, and in very viscous fluids, the friction is so great that the layers of flow pull against one other and hamper that flow. Viscosity usually varies with temperature, because when the molecules of a fluid are moving faster (when the fluid is warmer), the molecules can more easily slide over each other. So when you pour pancake syrup, for example, you may notice that it’s very thick in the bottle, but the syrup becomes quite runny when it spreads over the warm pancakes and heats up.

7. Rotational and Irrotational flow: Fluid flow can be rotational or irrotational. If, as you travel in a closed loop, you add up all the components of the fluid velocity vectors along your path and the end result is not zero, then the flow is rotational. To test whether a flow has a rotational component, you can put a small object in the flow and let the flow carry it. If the small object spins, the flow is rotational; if the object doesn’t spin, the flow is irrotational. For example, look at the water flowing in a brook. It eddies around stones, curling around obstacles. At such locations, the water flow has a rotational component.Some flows that you may think are rotational are actually irrotational. For example, away from the center, a vortex is actually an irrotational flow! You can see this if you look at the water draining from your bathtub. If you

place a small floating object in the flow, it goes around the plug hole, but it does not spin about itself; therefore, the flow is irrotational. Page | 14 On the other hand, flows that have no apparent rotation can actually be rotational. Take a shear

flow, for example. In a shear flow, all the fluid is moving in the same direction, but the fluid is moving faster on one side. Suppose the fluid is moving faster on the left than on the right. The fluid isn’t moving in a circle at all, but if you place a small floating object in this flow, the flow on the left side of the object is slightly faster, so the object begins to spin. The flow is rotational.

HEAT EXCHANGERS: 

A heat exchanger is a device used to transfer heat between two or more fluids. Heat exchangers are used in both cooling and heating process.



The fluids may be separated by a solid wall to prevent mixing or they may be in direct contact. They are widely used in space heating, refrigeration, air conditioning, power stations, chemical plants, petrochemical plants, petroleum refineries, natural-gas processing, and sewage treatment.



The classic example of a heat exchanger is found in an internal combustion engine in which a circulating fluid known as engine coolant flows through radiator coils and air flows past the coils, which cools the coolant and heats the incoming air. Another example is the heat sink, which is a passive heat exchanger that transfers the heat generated by an electronic or a mechanical device to a fluid medium, often air or a liquid coolant.

TYPES OF HEAT EXCHANGERS:    

Shell and Tube Heat Exchanger Plate Heat Exchanger Regenerative Heat Exchanger Adiabatic Wheel Heat Exchanger

 Shell and Tube Heat Exchanger: Shell and tube heat exchangers are comprised of multiple tubes through which liquid flows. The tubes are divided into two sets: the first set contains the liquid to be heated or cooled. The second set contains the liquid responsible for triggering the heat exchange, and either removes heat from the first set of tubes by absorbing and transmitting heat away—in essence, cooling the liquid—or

warms the set by transmitting its own heat to the liquid inside. When designing this type of exchanger, care must be taken in determining the correct tube wall thickness as well as tube diameter, to allow optimum heat exchange. In terms of flow, shell and tube heat exchangers can assume any of three flow path patterns. Page | 15

Shell and tube heat exchanger design There can be many variations on the shell and tube design. Typically, the ends of each tube are connected to plenums (sometimes called water boxes) through holes in tube sheets. The tubes may be straight or bent in the shape of a U, called U-tubes.

In nuclear power plants called pressurized water reactors, large heat exchangers called steam generators are two-phase, shell-and-tube heat exchangers which typically have U-tubes. They are used to boil water recycled from a surface condenser into steam to drive a turbine to produce power. Most shell-and-tube heat exchangers are either 1, 2, or 4 pass designs on the tube side. This refers to the number of times the fluid in the tubes passes through the fluid in the shell. In a single pass heat exchanger, the fluid goes in one end of each tube and out the other.

Types of Heat-Transfer Fluids The following are some of the most commonly used heat-transfer fluids and their properties. Consult a solar heating professional or the local authority having jurisdiction to determine the requirements for heat transfer fluid in solar water heating systems in your area. 

Air Air will not freeze or boil, and is non-corrosive. However, it has a very low heat capacity, and tends to leak out of collectors, ducts, and dampers.



Page | 16



Water Water is nontoxic and inexpensive. With a high specific heat, and a very low viscosity, it's easy to pump. Unfortunately, water has a relatively low boiling point and a high freezing point. It can also be corrosive if the pH (acidity/alkalinity level) is not maintained at a neutral level. Water with a high mineral content (i.e., "hard" water) can cause mineral deposits to form in collector tubing and system plumbing. Glycol/water mixtures Glycol/water mixtures have a 50/50 or 60/40 glycol-to-water ratio. Ethylene and propylene glycol are "antifreezes." These mixtures provide effective freeze protection as long as the proper antifreeze concentration is maintained. Antifreeze fluids degrade over time and normally should be changed every 3–5 years. These types of systems are pressurized, and should only be serviced by a qualified solar heating professional.



Hydrocarbon oils Hydrocarbon oils have a higher viscosity and lower specific heat than water. They require more energy to pump. These oils are relatively inexpensive and have a low freezing point. The basic categories of hydrocarbon oils are synthetic hydrocarbons, paraffin hydrocarbons, and aromatic refined mineral oils. Synthetic hydrocarbons are relatively nontoxic and require little maintenance. Paraffin hydrocarbons have a wider temperature range between freezing and boiling points than water, but they are toxic and require a double-walled, closed-loop heat exchanger. Aromatic oils are the least viscous of the hydrocarbon oils.



Refrigerants/phase change fluids These are commonly used as the heat transfer fluid in refrigerators, air conditioners, and heat pumps. They generally have a low boiling point and a high heat capacity. This enables a small amount of the refrigerant to transfer a large amount of heat very efficiently. Refrigerants respond quickly to solar heat, making them more effective on cloudy days than other transfer fluids. Heat absorption occurs when the refrigerant boils (changes phase from liquid to gas) in the solar collector. Release of the collected heat takes place when the now-gaseous refrigerant condenses to a liquid again in a heat exchanger or condenser.



Silicones Silicones have a very low freezing point, and a very high boiling point. They are noncorrosive and long-lasting. Because silicones have a high viscosity and low heat capacities, they require more energy to pump. Silicones also leak easily, even though microscopic holes in a solar loop.

REVIEW OF LITERATURE The addition of nanoparticles to improve the thermo physical properties of fluids has been studied

Page | 17 since the mid- 1990s, but it was only in the early 2000s the first experimental study on Nano-fluids

heat transfer was published. Since then, around 2000 publications on experimental studies with Nano-fluids have been presented, of which nearly 50% belong to the last 3 years.

The compilation of data which is presented here, is based on an under-development database which collects experimental data of several thermo physical properties, isobaric heat capacity, thermal conductivity k, and dynamic viscosity for a number of Nano-fluids consisting of a pure fluid or binary mixture, and a single type of nanoparticles. As a function of the studied property, nanoparticle, and base fluid. As it can be observed, the number of studies on aqueous Nano-fluids exceeds the rest, in the same way that the most studied nanoparticles are Al2O3 and CuO, which could be a consequence of their lower cost.

Reynolds number: Reynolds number is the ratio of inertial forces to viscous forces within a fluid which is subjected to relative internal movement due to different fluid velocities, which is known as a boundary layer in the case of a bounding surface such as the interior of a pipe. A similar effect is created by the introduction of a stream of higher velocity fluid, such as the hot gases from a flame in air. This relative movement generates fluid friction, which is a factor in developing turbulent flow.  

laminar flow occurs at low Reynolds numbers, where viscous forces are dominant, and is characterized by smooth, constant fluid motion; Turbulent flow occurs at high Reynolds numbers and is dominated by inertial forces, which tend to produce chaotic eddies, vortices and other flow instabilities. The Reynolds number is defined as

Nusselt Number: The Nusselt number is a dimensionless number, The Nusselt number is used to describe the ratio of the thermal energy convected to the fluid to the thermal energy conducted within the fluid. Nusselt number is equal to the dimensionless temperature gradient at the surface, and it Page | 18 provides a measure of the convection heat transfer occurring at the surface. The conductive component is measured under the same conditions as the heat convection but with a stagnant fluid. Thus, the Nusselt number is defined as:

Prandtl Number: 

Depends only on fluid & its properties.  It is the ratio of momentum diffusivity to heat diffusivity of the fluid.  It is also the ratio of velocity boundary layer to thermal boundary layer.  Pr = small, implies that rate of thermal diffusion (heat) is more than the rate of momentum diffusion (velocity). Also the thickness of thermal boundary layer is much larger than the velocity boundary layer.

Grashof Number: 

Ratio of Buoyancy force to viscous force in natural convection.  Reynolds number is used in forced convection of fluid flow, whereas Grashof number is used in natural convection

.

ABOUT NANO FLUIDS •

A Nano-fluid is a fluid containing nanometer-sized particles, called nanoparticles. These fluids are engineered colloidal suspensions of nanoparticles in a base fluid. The nanoparticles used in Nano-fluids are typically made of metals, oxides, carbides, or carbon nanotubes. Common

•

Base fluids include water, ethylene glycol and oil.

•

Nano-fluids have novel properties that make them potentially useful in many applications in heat transfer,[4] including microelectronics, fuel cells, pharmaceutical processes, and hybrid-powered engines,[5] engine cooling/vehicle thermal management, domestic refrigerator, chiller, heat exchanger, in grinding, machining and in boiler flue gas temperature reduction. They exhibit enhanced thermal conductivity and the convective heat transfer coefficient compared to the base fluid. Knowledge of the rheological behavior of Nano-fluids is found to be critical in deciding their suitability for convective heat transfer applications. Nano-fluids also have special acoustical properties and in ultrasonic fields display additional shear-wave reconversion of an incident compressional wave; the effect becomes more pronounced as concentration increases.

•

In analysis such as computational fluid dynamics (CFD), Nano-fluids can be assumed to be single phase fluids; however, almost all new academic papers use a two-phase assumption. Classical theory of single phase fluids can be applied, where physical properties of Nano-fluid is taken as a function of properties of both constituents and their concentrations. An alternative approach simulates Nano-fluids using a two-component model.

•

The spreading of a Nano-fluid droplet is enhanced by the solid-like ordering structure of nanoparticles assembled near the contact line by diffusion, which gives rise to a structural disjoining pressure in the vicinity of the contact line. However, such enhancement is not observed for small droplets with diameter of nanometer scale, because the wetting time scale is much smaller than the diffusion time scale

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 TYPES OF NANO FLUIDS Nano-fluid, which is a term used to describe fluids containing dispersed particles of nano scale, can be formed from nanoparticles of single element (e.g., Cu, Fe, and Ag), single element oxide (e.g., CuO, Cu2O, Al2O3, and TiO2,), alloys (e.g., Cu-Zn, Fe-Ni, and Ag-Cu), multi element oxides (e.g., CuZnFe4O4, NiFe2O4, and ZnFe2O4), metal carbides (e.g., SiC, B4C, and ZrC), metal nitrides (e.g., SiN, TiN, and AlN), and carbon materials (e.g., graphite, carbon nanotubes,

and diamond) suspended in water, ethanol, EG, oil, and refrigerants. They can be classified into two main categories: single material Nano-fluids and hybrid Nano-fluids. Single Material Nano-fluids Page | 20 This category of Nano-fluid was first proposed by Choi, in 1995, and is considered as the

conventional form of Nano-fluids used, where a single type of nanoparticles is used to produce the suspension via different preparation methods [5]. It was reported by many authors that Nano-fluids of such category are superior in performance, due to having much more favorable thermo physical properties than their base fluid.

Hybrid Nano-fluids Hybrid Nano-fluids are an advanced category of Nano-fluids which are made of a combination of more than one type of nanoparticles suspended in a base fluid. This type of fluids was first studied experimentally by Jana et al., in 2007, in order to enhance the fluid thermal conductivity beyond that of a conventional single material type Nano-fluid. In their study, Cu nanoparticles, carbon nanotubes (CNTs), and Au nanoparticles dispersed in water, as well as their hybrids (CNT– Cu/H2O and CNT–Au/H2O) were examined. The results showed that the thermal conductivity of Cu/H2O Nano-fluid was the highest among the tested samples and increased linearly with the rise of particle concentration. Nevertheless, the stability of the CNT–Cu/H2O Nano-fluid achieved longer settling time than the other types of Nano-fluids. This enables the fluid to conserve its thermal conductivity much longer before degrading.

Table 3 A selection of thermal conductivity measurements from several Nano-fluid studies.

Nanoparticle

Metals

Particle Size (nm)

Thermal Working Fluid

Fraction

Enhancement (%)

Reference

Nanoparticle

Particle Size (nm)

Thermal Working Fluid

Fraction

Enhancement

Reference

(%)

Page | 21

Ag

<100

Water

Ag

100–500

Ethylene Glycol

Cu

50–100

Water

Cu

<10

Ethylene Glycol

1Fe

10

Ethylene Glycol

9

Water

0.3–0.9 vol %

0.1–1.0 vol %

0.1 vol %

0.01–0.05 vol %

0.1–0.55 vol %

30 at 50 °C

[50]

18

[205]

24

[206]

41

[67]

18

[103]

29

[207]

Metal Oxides

Al2O3

2–10 vol %

Nanoparticle

Particle Size (nm)

Thermal Working Fluid

Fraction

Enhancement

Reference

(%)

Page | 22

Water/Ethylene

Al2O3

28

Al2O3

650–1000

Transformer oil

CuO

100

Water

TiO2

15

Water

SiO2

12

Ethylene Glycol

190

Water

Glycol

3–8 vol %

0.5–4 vol %

7.5 vol %

0.5–5 vol %

1–4 vol %

41

[100]

20

[208]

52

[209]

30

[159]

23

[210]

10 at 35 °C

[55]

Carbons

Carbon Black

4.4–7.7 vol %

Nanoparticle

Particle Size (nm)

Thermal Working Fluid

Fraction

Not

oxide

specified

Ethylene Glycol

Dia. 10–50 SWCNT

Len. 0.3–

Diesel Oil

10 µm

MWCNT

25 nm × 50 µm

Dia. 10 MWCNT

Len. 5–15 µm

Reference

(%)

Page | 23

carbon/graphene

Enhancement

0–0.06 wt %

0.25–1 vol %

Oil

1 vol %

Gum Arabic &

0.14-0.24

Water

vol %

6.47 at 40 °C

[211]

10–46

[212]

150

[79]

10

[213]

Carbon Nanomaterial Based Nano-fluids:  Carbon Nano-materials Carbon is one of the most abundant elements in the Earths biosphere. Nature has used this element, coupled predominantly with oxygen and hydrogen to form a diverse range of organic compounds. Furthermore, carbon atoms can bond with themselves in a number of different ways to form a variety of carbon materials or allotropes of carbon. Each of these allotropes has differences in their respective material properties. Typical carbon allotropes include amorphous carbon, diamond and graphite. Carbon allotropes can also have a variety of structures and morphologies such as crystalline (i.e., diamond, three dimensional, 3D), graphite sheets (2D) and carbon nanotubes (1D).

Moreover, the discovery of Buckminster-fullerenes, or Bucky balls by Kroto et al. in the mid1980s, stimulated the search for new forms of carbonaceous materials. Carbon Nano-materials are of particular interest, since they are black in color, which makes them ideal for solar absorption applications. In addition, their very high thermal conductivity also makes them ideal additives for Nano-fluids. Page | 24

A selection of carbon allotropes that have been examined for use in Nano-fluids.

 Carbon Nanotube-Based Nano-fluid Carbon nanotubes (CNTs) are one-dimensional carbon-based cylinders with high aspect ratios. The cylindrical structure is composed of either single walled or multi-walled configurations. CNTs synthesis was first reported by Iijima in 1991 and since then the unique thermo-physical properties of these materials have been extensively studied.

Nano-Diamond Nano-fluids In recent years, several researchers have appraised the thermal conductivity properties of Nanodiamond Nano-fluids. Studies by Ghazvini et al. investigated Nano-fluids composed of water/engine oil mixtures and small quantities of Nano-diamonds (ND). They found the addition of small mass fractions (~1.0 wt %) could produce thermal conductivity enhancements of around 25%. While studies by Ma et al. found the addition of small quantities of NDs (0.01 vol %) to water-based Nano-fluids increased the pure waters thermal conductivity from 0.581 W m−1K−1 to 1.003 W m−1K−1.

Graphite and Graphene Nano-fluids Several researchers have investigated the change in thermal properties of fluids after the addition of small quantities of graphite or graphene. Ladjevardi et al. have used numerical modelling and

experimental studies to examine the influence of particle size and volume fractions on the performance of graphite Nano-fluids in direct absorption solar collectors. Their study found small volume fractions (~0.25 × 10−5 vol %) of nanometer-scale graphite in water absorbed 50% of all incident solar irradiation, while pure water absorbed only 27%. Studies by Taylor et al. have also examined the influence of adding small quantities of graphite nanoparticles to water-based NanoPage | 25 fluids designed for solar collectors. Their studies demonstrated that it was possible to achieve collector performance improvements of around 10%. Whereas, Eswaraiah et al., have examined the mechanical properties resulting from the addition of graphene to engine oil-based Nano-fluids.

Preparation of Nano-fluids Uniformity of the particle dispersion depends mainly on the preparation method used and can have a significant effect on the thermo physical properties of the Nano-fluid. Meaning that if two similar Nano-fluids were to be prepared using different preparation methods, their thermo physical properties and tendency to agglomeration are most likely to vary from each other. This is because Nano-fluids are not simply formed from a solid-liquid mixture but requires special conditions to be present in the suspension such as homogeneity, physical and chemical stability, durability, and dispersibility. There are mainly two techniques used to fabricate Nano-fluids, namely, the bottom-up approach known as the one-step method and the top-down approach identified as the two-step method.

Stability of Nano-fluids Part of the challenges that faces commercializing Nano-fluids is their poor stability due to the interaction between the particles themselves and between the particles and the surrounding liquid. This kind of behavior can be linked to two opposing forces: the well-known Van der Waals attractive forces on the particles surface which causes the particles to be attracted to each other into forming clusters or agglomerations of particles and then separate from the base-fluid and settle at the bottom due to gravitational force and the electrical double layer repulsive force which tends to separate the particles from each other via steric and electrostatic repulsion mechanisms.

NANOFLUID PREPARATION AND STABILIZATION The process of preparation of Nano-fluid and stabilization is an important activity since extracting the benefits of nanoparticle in thermal cycle needs proper preparation and stabilization. Page | 26 Poorly prepared Nano-fluids results in biphasic heat transfer (i.e. solid–liquid). Particle instability results in particle fouling in reservoir, pipes, pumps and other equipment of thermal cycle, as well as reduced pressure, all of which are considered undesirable factors in our experiment. The nanoparticles used in this study were Silver oxide and copper oxide nanoparticles of approximately 15 nm in diameter and 95% purity. As for the AG+/Water Nano-fluid, samples of 0.1% to 0.3%, fluid were prepared without surfactants solely with magnetic stirring for 1 h and subsequent ultrasonic irradiation for 2 h. These samples proved highly appropriate in terms of homogenous dispersion and long term stability. As for the CuO/EG Nano-fluid, samples of 0.1% to 0.3% weight copper oxide in base fluid (EG) were prepared using the surfactant sodium dodecyl sulfate (SDS) alongside magnetic stirring for 1 h and subsequent ultrasonic irradiation for 2 h. These samples proved appropriate for a cyclic system in terms of homogenous dispersion and long term stability. The fig 1 (a) and (b) shows the SEM image of CuO and DI/AG+ Nano-fluid. The particles are homogenously dispersed throughout the base-fluid in an acceptable fashion.

pH Control of Nano-fluids: Manipulating the pH value of Nano-fluids changes the nanoparticles surface and can strongly improve the stability of the dispersed nanoparticles. This is because the stability of a Nano-fluid is directly related to its electro kinetic properties. Therefore, the zeta potential can be increased/decreased by changing the pH value of the Nano-fluid and as mentioned previously, zeta potential values of Nano-fluids above +30 mV or below −30 mV are considered to be more stable because of the high repulsive force generated between the charged nanoparticles. The pH value of a Nano-fluid can be increased or decreased by adding an appropriate nonreactive alkaline or acidic solution, respectively. Many studies were carried out to demonstrate the effect of pH level on the stability of Nano-fluids. Witharana et al. examined the settling and aggregation behavior of alumina (Al 2O3)/H2O Nanofluid of 0.5 wt%, 46 nm particle size, and of spherical particle shape at pH values of 6.3 and 7.8. They discovered that the suspensions were stable at a pH value of 6.3 for more than 30 min compared with the pH value of 7.8 which had endured a complete particle separation and settlement after 30 min. Manjula et al. studied in their work the effect of added surfactants and pH level on the dispersion behavior of water based alumina Nano fluid through its sedimentations. Their results showed that adding surfactant and optimizing the pH level maximized the stability of the Nano-suspension. Zhu et al. investigated the influence of different concentrations of SDBS and pH values on the behavior of Al2O3/H2O suspension. They found out that the effective thermal conductivity and stability of their Nano-fluid were significantly dependent on the SDBS concentration and pH value of the fluid, where the effective thermal conductivity was increased by 10.1% at a pH value of 8 and particle concentration of 0.15 wt%.

WORKING OF DI/AG+ NANO FLUID: Silver nanoparticles have unique optical, electrical, and thermal properties and are being incorporated into products that range from photo-voltaics to biological and chemical sensors. Page | 27 Examples include conductive inks, pastes and fillers which utilize silver nanoparticles for their high electrical conductivity, stability, and low sintering temperatures. Additional applications include molecular diagnostics and photonic devices, which take advantage of the novel optical properties of these Nano-materials. An increasingly common application is the use of silver nanoparticles for antimicrobial coatings, and many textiles, keyboards, wound dressings, and biomedical devices now contain silver nanoparticles that continuously release a low level of silver ions to provide protection against bacteria.

Figure 1: Transmission electron microscopy (TEM) images of silver nanoparticles with diameters of 20 nm, 60 nm, and 100 nm respectively. Scale bars are 50 nm. Understanding how the size, shape, surface, and aggregation state of the silver nanoparticles change after integration into a target application is critical for optimizing performance. We offer precisely manufactured mono-disperse silver nanoparticles that are free from agglomeration, making them ideal for research, development, and use in a variety of innovative applications (Figure 1). Each batch of nanoparticles is extensively characterized using transmission electron microscopy (TEM) images, dynamic light scattering (for particle size analysis), Zeta potential measurements, and UV/Visible spectral analysis to ensure consistent materials in every order.

Silver Nanoparticle Optical Properties: There is growing interest in utilizing the optical properties of silver nanoparticles as the functional component in various products and sensors. Silver nanoparticles are extraordinarily efficient at absorbing and scattering light and, unlike many dyes and pigments, have a color that depends upon the size and the shape of the particle. The strong interaction of the silver nanoparticles with light occurs because the conduction electrons on the metal surface undergo a collective oscillation when excited by light at specific wavelengths (Figure 2, left). Known as a surface plasmon resonance (SPR), this oscillation results in unusually strong scattering and absorption properties. In fact,

silver nanoparticles can have effective extinction (scattering + absorption) cross sections up to ten times larger than their physical cross section. The strong scattering cross section allows for sub 100 nm nanoparticles to be easily visualized with a conventional microscope. When 60 nm silver nanoparticles are illuminated with white light they appear as bright blue point source scatterers under a dark field microscope (Figure 2, right). The bright blue color is due to an SPR that is Page | 28 peaked at a 450 nm wavelength. A unique property of spherical silver nanoparticles is that this SPR peak wavelength can be tuned from 400 nm (violet light) to 530 nm (green light) by changing the particle size and the local refractive index near the particle surface. Even larger shifts of the SPR peak wavelength out into the infrared region of the electromagnetic spectrum can be achieved by producing silver nanoparticles with rod or plate shapes.

Figure 2: (Left) Surface plasmon resonance where the free electrons in the metal nanoparticle are driven into oscillation due to a strong coupling with a specific wavelength of incident light. (Right) Dark field microscopy image of 60 nm silver nanoparticles.

Silver Nanoparticle Characterization: The size and shape of metal nanoparticles are typically measured by analytical techniques such as TEM, scanning electron microscopy (SEM) or atomic force microscopy (AFM). Measuring the aggregation state of the particles requires a technique to measure the effective size of the particles in solution such as dynamic light scattering (DLS) or analytical disc centrifugation. However, due to the unique optical properties of silver nanoparticles, a great deal of information about the physical state of the nanoparticles can be obtained by analyzing the spectral properties of silver nanoparticles in solution. The spectral response of silver nanoparticles as a function of diameter is shown in Figure 3, left. As the diameter increases, the peak plasmon resonance shifts to longer wavelengths and broadens. At diameters greater than 80 nm, a second peak becomes visible at a shorter wavelength than the primary peak. This secondary peak is due to a quadrupole resonance that has a different electron oscillation pattern than the primary dipole resonance. The peak wavelength, the peak width, and the effect of secondary resonances yield a unique spectral fingerprint for a plasmonic nanoparticle with a specific size and shape. Additionally, UV-Visible spectroscopy provides a mechanism to monitor how the nanoparticles change over time. When silver nanoparticles aggregate, the metal particles become electronically coupled and this coupled system has a different SPR than the individual particles. For the case of a multi-nanoparticle

aggregate, the plasmon resonance will be red-shifted to a longer wavelength than the resonance of an individual nanoparticle, and aggregation is observable as an intensity increase in the red/infrared region of the spectrum. This effect can be observed in Figure 3, right, which displays the optical response of a silver nanoparticle solution destabilized by the addition of saline. Carefully monitoring the UV-Visible spectrum of the silver nanoparticles with time is a sensitive Page | 29 technique used in determining if any nanoparticle aggregation has occurred.

Figure 3. (Left) Extinction (scattering + absorption) spectra of silver nanoparticles with diameters ranging from 10-100 nm at mass concentrations of 0.02 mg/mL. (Right) Extinction spectra of silver nanoparticles after the addition of a destabilizing salt solution. For silver nanoparticle solutions that have not agglomerated and have a spectral shape that is identical to the as-received suspension, the UV/Visible extinction spectra can be used to quantify the nanoparticle concentration. The concentration of silver nanoparticle solutions is calculated using the Beer-Lambert law, which correlates the optical density (OD, a measure of the amount of light transmitted through a solution) with concentration. Due to the linear relationship between OD and concentration, these values can be used to quantify the concentration of nanoparticle solutions.

Silver Nanoparticle Applications: Silver nanoparticles are being used in numerous technologies and incorporated into a wide array of consumer products that take advantage of their desirable optical, conductive, and antibacterial properties. 

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Diagnostic Applications: Silver nanoparticles are used in biosensors and numerous assays where the silver nanoparticle materials can be used as biological tags for quantitative detection. Antibacterial Applications: Silver nanoparticles are incorporated in apparel, footwear, paints, wound dressings, appliances, cosmetics, and plastics for their antibacterial properties. Conductive Applications: Silver nanoparticles are used in conductive inks and integrated into composites to enhance thermal and electrical conductivity.

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Optical Applications: Silver nanoparticles are used to efficiently harvest light and for enhanced optical spectroscopies including metal-enhanced fluorescence (MEF) and surface-enhanced Raman scattering (SERS).

WORKING OF DI/ALUM NANOPARTICLES: Metal oxide nanoparticles have been extensively developed in the past decades. They have been widely used in many applications such as catalysts, sensors, semiconductors, medical science, capacitors, and batteries. Among them, aluminum oxide (Al2O3) and its compounds have long been known for more than a century, for example, aluminum oxide hydroxide (AlOOH) and aluminum tri-hydroxide (Al (OH) 3). Al2O3 or alumina generally refers to corundum. It is a white oxide. Alumina has several phases such as gamma, delta, theta, and alpha. However, the alpha alumina phase is the most thermodynamically stable phase. In general, alumina has many interesting properties, for example high hardness, high stability, high insulation, and transparency. Alumina is also widely used in the fire retard, catalyst, insulator, surface protective coating, and composite materials. Al2O3 nanoparticles can be synthesized by many techniques including ball milling, sol-gel, pyrolysis, sputtering, hydrothermal, and laser ablation. Among them, the laser ablation is a widely used technique for the synthesis of nanoparticles since it can be synthesized in gas, vacuum or liquid. This technique offers several advantages such as rapid and high purity process compared with other methods. Furthermore, nanoparticles prepared by the laser ablation of materials in liquid are easier to be collected than those of in gas atmosphere. In the recent years, Al2O3 nanoparticles were synthesized in liquid using a short pulse laser with the pulse width in the range of nanosecond. Furthermore, Al target was used as a starting material for laser ablation in those works. Therefore, in this study we reported the synthesis 2 Journal of Nanomaterials Glass vessel Deionized water Focusing lens Aluminum pellet Mirror Nd:YAG laser λ = 1064 nm Figure 1: Experimental setup for synthesizing Al2O3 nanoparticles by laser ablation of Al in deionized water. of Al2O3 from Al powders using laser ablation in deionized water with a long pulsed Nd:YAG laser. The laser pulse widths adopted in this work were 2.5, 6, and 9.5 ms to obtain the output laser energies of 1, 3, and 5 J, respectively. The particle size and morphology of synthesized nanoparticles obtained at different laser energies were investigated by field emission scanning electron microscopy (FESEM). The optical property of synthesized nanoparticles was carried out using UV-visible spectroscopy. The structure of the synthesized nanoparticles was investigated using X-ray diffraction (XRD) technique.

THERMAL ANALYSIS EXCHANGER:

OF

HEAT

TRANSFER

USING

HEAT

THEORITICAL ANALYSIS: Page | 31 Shell and tube type heat exchangers are designed normally by using Kern’s method. Kern’s method

is mostly used for the preliminary design. In this we have designed a simple shell and tube type heat exchanger to heat water from 40℃ to 70℃ by using steam at 140℃ temperature by using Kern’s method. The steps of designing are described as follows: a) First we consider the energy balance to find out the values of some unknown temperature values. Certainly some inputs like hot fluid inlet and outlet temperatures, cold fluid inlet temperature, and mass flow rates of the two fluids are needed to serve the purpose. The energy balance equation may be given as: Q = mh Cph (‫ݐ‬ℎ1-‫ݐ‬ℎ2) = mCc (tc2-tc1) b) Then we consider the LMTD expression to find its Value: LMTD = (ΔT1−ΔT2) / In (ΔT1/ΔT2) Where, ΔT1 = th1-tc2 and ΔT2 = tℎ2-tc1. c) Our next step is to calculate the area required of the heat exchanger (on the basis of assumed U0), number of tubes, tube bundle diameter, diameter of shell and its thickness with the help of following expressions: A = Q / (UoΔT) Nt = A / (πdtol) Db = dto (Nt / K1)1/n1 Di = Db + additional clearance Do = Di + 2 × thickness d) Then we calculate the proper baffle dimension viz. its diameter, thickness and baffle spacing. e) Our next step is to find out heat transfer coefficients on the inner and outer surface of the tubes using following correlation: 1/U = (1/Ui) + (/Uo) f) Then by the values obtained by the above equation we calculate the actual value of heat transfer coefficient and check whether the actual value is greater than the assumed one or not. In the present project, the methodology used in the design of the heat exchanger is studied and presented. The thermal design involves the calculation of shell side and tube side heat transfer coefficients, heat transfer surface area and pressure drops on the shell side and tube side. The mechanical design involves the calculations of thickness of pressure parts of the heat exchanger such as the shell, channel, tube etc. to evaluate the rigidity of part under design pressures. The design of the heat exchanger is then modeled in Pro-Engineer and finally analyzed using ANSYS software. In this system oil is taken as hot fluid and cold fluid is water. Where no phase change occurs.

EXPERIMENTAL SETUP:

 Al 7075 T6 ALLOY CYLINDRICAL PIPE WITH ANNULAR PASSAGES: •

A vertical test section was casted by preparing a furnace. The furnace is prepared by using cylindrical steel tin. In that tin insulating material PLASTER OF PARIS is placed at the internal surface of tin. • A hole was prepared at the lower end of tin and a steel pipe was welded at the hole to flow Page | 32 the blower air into the furnace. • The whole internal section was coated with POS. • In forging l, we prepared the pattern by using wooden piece and make it like the annular passage. The wooden piece is placed at centre of cope box and rammed the sand into the box. After completing this process we removed the pipe from box. • During casting process, the aluminum metals were melted by using the furnace. • The molten metal was poured into the cavity of test section. After passage of molten metal by the cavity the test section was prepared. • The test section was prepared by removing the boxes by ramming process. • A number of holes of diameter 6mm are drilled on one side of test section to insert the thermocouples.  FRAME: • By using ¾ sized angular was welded by arc welding process into a closed rectangular shaped frame. The edges are welded and grinded. • At distance of 35cm from one side of frame another rectangular block should be welded to place the Heater inside. • On the side from a distance of 10cm two angulars of size 15mm are welded perpendicular to surface to hold the vertical test section. • Sheet metal process was done by adding screws to the angular and the whole frame was closed by the sheet metal. • A hole is prepared at another side to place the blower hole.

 THERMOCOPLES: • • •

Thermocouples are connected to the aurduno board to visualize the readings of temperatures inside the chamber and test section. Two thermocouples are used to know the temperature at inlet and chamber T1 AND T2. Four thermo couples are used to know the temperature inside the vertical test section T3, T4, T5 andT6.

 CONTROL PANEL: • •

Control panel was made by wooden board, the placements of the switches and plug points, temperature monitors, aurdino board and fuse. Plug point are placed to supply power to heater and blower.

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1. FRAME CVERED WITH SHEET METAL

3. OVERALL EXPERIMENTAL SECTION

2.VERTICAL TEST SECTION & TANK

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5. AURDINO BOARD WITH CONNECTIONS

6. WHOLE CIRCUITS OF COONTROL PANEL

COPPER TUBES AND BRASS PLATE; Copper tubes are placed inside the vertical test section in a circular manner in order to flow the Nano-fluid inside the pipe. Page | 35

Brass plate is inserted in test section to connect the thermocouples and to decrease the temperature inside the tube.

TANK: The Nano-fluid is stored in the tank besides to the vertical test section. Two motors are connected to the copper tubes in order to pump the fluid through pipes in vertical test section.

REFERENCES 1. 2.

3. 4. 5. 6.

Y.M. Xuan, Q. Li, Investigation on convective heat transfer and flow features of nanofluids, ASME J. Heat Transfer, 125 (2003), 151-155. S. Zeinali Heris, M. Nasr Esfahany, S.Gh. Etemad, Numerical investigation of nanofluid laminar convective heat transfer through circular tube, J. Numer. Heat Transfer A: Appl. 52 (2007), 1043–1058. S.U.S. Choi, Developments and Application of NonNewtonian Flows, ASME FEDV.231/MD-V.66, New York, 1995, pp.99–105. S. Lee, S.U.S. Choi, S. Li, J.A. Eastman, Measuring thermal conductivity of fluids containing oxide nanoparticles, J. Heat Transfer, 121 (1999), 280–289. Y. Xuan, Q. Li, Heat transfer enhancement of nanofluids, Int. J. Heat Fluid Flow 21 (2000), 58–64. D. Wen, Y. Ding, Experimental investigation into convective heat transfer of nanofluids at the entrance region under laminar flow conditions, Int. J. Heat Mass Transfer 47 (2004), 5181–5188.