Investigations Of Mechanical Properties Of Aisi 1018 Steel Quenched In Al2o3 Nano Fluids

INVESTIGATIONS OF MECHANICAL PROPERTIES OF AISI 1018 STEEL QUENCHED IN AL2O3 NANO FLUIDS

A PROJECT REPORT

Submitted by

JAWAKAR D MOHANRAJ K GOWTHAMRAJ K NAGA MARIYAPPAN S in partial fulfillment of the requirement for the award of the degree of

BACHELOR OF ENGINEERING in

MECHATRONICS ENGINEERING

K.S. RANGASAMY COLLEGE OF TECHNOLOGY (An Autonomous Institution, affiliated to Anna University Chennai and Approved by AICTE, New Delhi)

TIRUCHENGODE – 637 215

APRIL 2019

K.S. RANGASAMY COLLEGE OF TECHNOLOGY TIRUCHENGODE - 637 215 BONAFIDE CERTIFICATE Certified that this project report titled “INVESTIGATIONS OF MECHANICAL PROPERTIES OF AISI 1018 STEEL QUENCHED IN AL2O3 NANO FLUIDS” is the bonafide work of JAWAKAR.D (1515120), MOHANRAJ.K (1515132), GOWTHAMRAJ.K(1515118) and NAGA MARIYAPPAN.S (1515134) who

carried out the project under my supervision. Certified further, that to the best of my knowledge the work reported herein does not form part of any other project report or dissertation on the basis of which a degree or award was conferred on an earlier occasion on this or any other candidate.

SIGNATURE HEAD OF THE DEPARTMENT

SIGNATURE Dr.M.Baskaran, M.E.,Ph.D. SUPERVISOR

Professor Department of Mechatronics K.S. Rangasamy College of Technology Tiruchengode - 637 215

Assistant professor Department of Mechatronics K.S. Rangasamy College of Technology Tiruchengode - 637 215

Dr.M.Ilangkumaran, M.E.,Ph.D.

Submitted for the viva-voce examination held on ………………

Internal Examiner

External Examiner

II

DECLARATION We jointly declare that the project report on “INVESTIGATIONS OF MECHANICAL PROPERTIES OF AISI 1018 STEEL QUENCHED IN AL2O3 NANO FLUIDS” is the result of original work done by us and best of our knowledge, similar work has not been submitted to “ANNA UNIVERSITY CHENNAI” for the requirement of Degree of B.E. This project report is submitted on the partial fulfilment of the requirement of the award of Degree of B.E.

Signature ____________________ JAWAKAR D. ____________________ MOHANRAJ K. ____________________ GOWTHAMRAJ K. ____________________ NAGA MARIYAPPAN S.

Place: Tiruchengode Date:

III

ACKNOWLEDGEMENT We wish to express our sincere gratitude to our honourable Correspondent LION Dr. K. S. RANGASAMY, M.J.F., for providing immense facilities at our institution. We would like to express special thanks of gratitude to our Chief Executive Officer Dr.K.THYAGARAJAH, M.E., Ph.D., who has been the key spring of motivation to us throughout the completion of our course and project work. We are very proudly rendering our thanks

to

our

Principal

Dr.A.KUMARAVEL, M.TECH., Ph.D., for the facilities and the encouragement given by him to the progress and completion of our project. We proudly render our immense gratitude to the Head of the Department Dr.M.ILANGKUMARAN, M.E., Ph.D., for his effective leadership, encouragement and guidance in the project. We are highly indebted to provide our heart full thanks to our supervisor Dr.M.BASKARAN,M.E.,Ph.D., Assistant professor for his valuable ideas, encouragement and supportive guidance throughout the project. We wish to extend our sincere thanks to all faculty members of our Mechatronics Department for their valuable suggestions, kind co-operation and constant encouragement for successful completion of this project. We wish to acknowledge the help received from various Departments and various individuals during the preparation and editing stages of the manuscript.

IV

ABSTRACT Quenching is the commonly used heat treatment process is manufacturing industry to obtain certain material properties of the specimen, whereas the rate of cooling plays a major role on mechanical properties. The specimen used for the quenching is AISI 1080 carbon steel, which is used to make forged motor shafts, hydraulics shafts, pump shafts and as well as machinery parts. In order to improve the heat transfer characteristics of quenching medium nanoparticles are used. In this alumina is used as the nano particles. Alumina (Al2O3) nanofluids are to be prepared at five different volume fraction such as 0.01%, 0.02%, 0.03%, 0.04%, 0.05% using deionized water. It is prepared by two step process using ultrasonication process followed by magnetic stirrer. standard.

Then

the

machined

The specimen is machined as per ASTM A370

specimen

was

heated

to

the

recrystallization

temperature(930°C) and quenched in DI water and Al2O3 nanofluids of different concentration. During the quenching, cooling rate was recorded using K-type thermocouple, which is mounted inside the specimen and their data is taken with the help of Arduino UNO. Finally the mechanical properties such as tensile strength, yield strength, elongation, reduction in area and hardness of the specimen is obtained and compared with each other. From the test results it was found that heat transfer rate increased with nanoparticle concentration. This shows that the percentage of nanoparticle concentration in the base fluid affects the heat transfer and the mechanical properties of the AISI 1018 steel. Moreover this was observed in mechanical properties such as tensile strength, yield strength and the hardness of the specimen is increased by 47% as a peak. It also clearly observed through the microstructure of the specimen.

V

TABLE OF CONTENTS CHAPTER

TITLE

Page No.

ABSTRACT

v

LIST OF TABLES

viii

LIST OF FIGURES

viii

LIST OF SYMBOLS AND ABBREVIATIONS

1

ix & x

INTRODUCTION

1

1.1 HEAT TREATMENT

1

1.1.A HEAT TREATMENT PROCESSES

1

1.1.1 Annealing

1

1.1.2 Normalizing

2

1.1.3 Stress Relieving

2

1.1.4 Aging

2

1.1.5 Quenching

3

1.1.6 Tempering

3

1.1.7 Flame Hardening

4

1.1.8 Induction Hardening

4

1.1.9 Case Hardening

4

1.1.10 Cold and Cryogenic Treating

5 5

1.2 NANOFLUIDS 1.2.A SYNTHESIS OF NANOFLUIDS

6

1.2.1

Two-Step Method

6

1.2.2

One-Step Method

6 8

1.2.B APPLICATIONS OF NANOFLUIDS 1.3 MECHANICAL PROPERTIES

11

1.3.1 Tensile Properties

12

1.3.2 Hardness

18

VI

2

LITERATURE REVIEW

20

2.1 ALUMINA NANOFLUID BASED EXPERIMENTS

20

2.2 OTHER NANOFLUID BASED EXPERIMENTS

21 28

2.3 SUMMARY OF LITERATURE REVIEW 3

METHODOLOGY

29

4

EXPERIMENTAL SETUP AND PROCEDURE

31

4.1 SELECTION OF MATERIALS

32

4.2 NANOFLUID PREPARATION

33

4.2.1 Alumina Nanoparticle

33

4.2.2 Preparation of Nanofluid

33

4.3 MUFFLE FURNACE

35 35

4.4 THERMOCOUPLE 5

4.5 DATA ACQUISITION SYSTEM

36

RESULTS AND DISCUSSION

38

5.1 EFFECT OF QUENCHING ON MECHANICAL PROPERTIES 5.1.1 Mechanical Properties of AISI 1018 steel 5.1.2 Micro structure of AISI 1018 carbon steel 5.1.3 Energy-dispersive X-ray spectroscopy of AISI 1018 steel 5.2 RATE OF COOLING

38

38 42 45

47

6

CONCLUSION

48

7

SCOPE OF FUTURE WORK

49

APPENDIX 1

50

REFERENCE

51

VII

LIST OF TABLES Table No.

NAME OF THE TABLE

Page No.

1.1

Hardness testing methods and their indenters

19

4.1

Thermo-physical Properties

32

4.2

ASTM A370 Standard

32

4.3

Specimen ASTM A370 Specifications

32

4.4

Nanoparticle specification

33

5.1

Mechanical properties of AISI 1018 steel

38

VIII

LIST OF FIGURES Figure No.

NAME OF THE FIGURE

Page No.

1.1

Stress-strain curve

14

1.2

Measure of Ductility

18

3.1

Working Methodology

29

3.2

Heat transfer Mechanism

30

4.1

Experimental Procedure

31

4.2

Specimen ASTM A370 (D=16)

32

4.3

Nanofluid preparation

34

4.4

Magnetic stirrer

34

4.5

Muffle furnace

35

4.6

K-Type thermocouple

36

4.7

Data acquisition system setup

36

4.8

Arduino program

37

5.1

AISI 1018 steel specimen

38

5.2

Tensile Strength of AISI 1018 steel

39

5.3

Yield Strength of AISI 1018 steel

39

5.4

Hardness of AISI 1018 steel

40

5.5

Elongation of AISI 1018 steel

40

5.6

Reduction in area of AISI 1018 steel

41

5.7

Microstructure of AISI 1018 steel in 2.5KX

42

5.8

Microstructure of AISI 1018 steel in 5KX

43

5.9

EDX analysis of AISI 1018 steel

46

5.10

Cooling curve of AISI 1018 steel

47

IX

LIST OF SYMBOLS AND ABBREVIATIONS

SYMBOLS D

-

Gripping end diameter

mm

D

-

Gauge Diameter

mm

Lc

-

Parallel length

mm

GE

-

Gripping end length

mm

R

-

Transition radius

mm

Lt

-

Total Length

mm

T

-

Temperature

K

-

Thermal Conductivity

o

C or oF

W/mK

ABBREVATIONS PVP

-

Poly Vinyl Pyrrolidone

ODA

-

Octa Decyl Amine

GON

-

Graphene Oxide Nano sheets

CHF

-

Critical Heat Flux

MEMS

-

Micro Electro Mechanical Systems

UTS

-

Ultimate Tensile Strength

TS

-

Tensile Strength

BHN

-

Brinell Hardness Number

VHN

-

Vicker Hardness Number

CNT

-

Carbon Nano Tubes

SDBS

-

Sodium Dodecyl Benzoic Sulfate

X

CHAPTER 1 INTRODUCTION 1.1 HEAT TREATMENT Heat treatment is the heating and cooling of metals to change their physical and mechanical properties, without letting it change its shape. Heat treatment could be said to be a method for strengthening materials but could also be used to alter some mechanical properties such as improving formability, machining, etc. The most common application is metallurgical but heat treatment can also be used in manufacture of glass, aluminium, steel and many more materials. The process of heat treatment involves the use of heating or cooling, usually to extreme temperatures to achieve the wanted result. It is very important manufacturing processes that can not only help manufacturing process but can also improve product, its performance, and its characteristics in many ways.

1.1.A HEAT TREATMENT PROCESSES 1.1.1 Annealing Annealing is the process for softening materials or to bring about required changes in properties, such as machinability, mechanical or electrical properties, or dimensional stability. The annealing process consists of heating the steel to or near the critical temperature (temperature at which crystalline phase change occurs) to make it suitable for fabrication. Annealing is performed to soften steel after cold rolling, before surface coating and rolling, after drawing wired rod or cold drawing seamless tube. Stainless steels and high alloy steels generally require annealing because these steels are more resistant to rolling. A material can be annealed by heating it to a specific temperature and then letting the material slowly cool to room temperature in an oven. This process is expensive because the oven is unusable during the cool down process.

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1.1.2 Normalizing Normalizing is a heat treatment process for making material softer but does not produce the uniform material properties of annealing. A material can be normalized by heating it to a specific temperature and then letting the material cool to room temperature outside of the oven. This treatment refines the grain size and improves the uniformity of microstructure and properties of hot rolled steel. Normalizing is used in some plate mills, in the production of large forgings such as railroad wheels and axles, some bar products. This process is less expensive than annealing. 1.1.3 Stress Relieving Stress Relieving consists of heating the steel to a temperature below the critical range to relieve the stresses resulting from cold working, shearing, or gas cutting. It is not intended to alter the microstructure or mechanical properties significantly. Also a process for making material softer. However, stress relieving does not change the material properties as does annealing and normalizing. A material can be stress relieved by heating it to a specific temperature that is lower than that of annealing or normalizing and letting it cool to room temperature inside or outside of the oven. This heat treatment is typically used on parts that have been severely stressed during fabrication. It is worth noting that many heat treatments and welding processes cause stresses in the material that can lead to warpage either after the heat treating process or during subsequent machining operations. Of specific concern is the stress induced by welding. If a weldment is to be machined it should almost always be stress relieved or normalized before the machining process. This is because machining chunks of material from a stressed weldment redistributes the internal stresses and can cause the part to warp. If the stresses are first relaxed, then abrupt changes in geometry after machining are reduced. 1.1.4 Aging Some metals are classified as precipitation hardening metals. When a precipitation hardening alloy is quenched, its alloying elements will be trapped in solution, resulting in a soft metal. Aging a "solutionized" metal will allow the alloying elements to diffuse through the microstructure and form intermetallic particles. These intermetallic particles will nucleate 2

and fall out of solution and act as a reinforcing phase, thereby increasing the strength of the alloy. Alloys may age "naturally" meaning that the precipitates form at room temperature, or they may age "artificially" when precipitates only form at elevated temperatures. In some applications, naturally aging alloys may be stored in a freezer to prevent hardening until after further operations - assembly of rivets, for example, may be easier with a softer part.Examples of precipitation hardening alloys include 2000 series, 6000 series, and 7000 series aluminium alloy, as well as some super alloys and some stainless steels. Steels that harden by aging are typically referred to as maraging steels, from a combination of the term marten site aging. 1.1.5 Quenching Quenching is a process of cooling a metal at a rapid rate. This is most often done to produce a marten site transformation. In ferrous alloys, this will often produce a harder metal, while non-ferrous alloys will usually become softer than normal. To harden by quenching, a metal (usually steel or cast iron) must be heated above the upper critical temperature and then quickly cooled. Depending on the alloy and other considerations (such as concern for maximum hardness vs. cracking and distortion), cooling may be done with forced air or other gases, (such as nitrogen). Liquids may be used, due to their better thermal conductivity, such as oil, water, a polymer dissolved in water, or a brine. Upon being rapidly cooled, a portion of austenite (dependent on alloy composition) will transform to marten site, a hard, brittle crystalline structure. The quenched hardness of a metal depends on its chemical composition and quenching method. Cooling speeds, from fastest to slowest, go from brine, polymer (i.e. mixtures of water + glycol polymers), fresh water, oil, and forced air. Some Beta titanium based alloys have also shown similar trends of increased strength through rapid cooling. However, most non-ferrous metals, like alloys of copper, aluminium, or nickel, and some high alloy steels such as austenitic stainless steel (304, 316), produce an opposite effect when these are quenched: they soften. Austenitic stainless steels must be quenched to become fully corrosion resistant, as they work-harden significantly. 1.1.6 Tempering Untempered martensitic steel, while very hard, is too brittle to be useful for most applications. A method for alleviating this problem is called tempering. Most applications require that quenched parts be tempered. Tempering consists of heating steel below the lower critical temperature, (often from 400 to 1105 ˚F or 205 to 595 ˚C, depending on the desired 3

results), to impart some toughness. Higher tempering temperatures (may be up to 1,300 ˚F or 700 ˚C, depending on the alloy and application) are sometimes used to impart further ductility, although some yield strength is lost. Tempering may also be performed on normalized steels. Other methods of tempering consist of quenching to a specific temperature, which is above the martensite start temperature, and then holding it there until pure bainite can form or internal stresses can be relieved. These include austempering and martempering. 1.1.7 Flame Hardening Flame hardening is used to harden only a portion of a metal. Unlike differential hardening, where the entire piece is heated and then cooled at different rates, in flame hardening, only a portion of the metal is heated before quenching. This is usually easier than differential hardening, but often produces an extremely brittle zone between the heated metal and the unheated metal, as cooling at the edge of this heat-affected zone is extremely rapid. 1.1.8 Induction Hardening Induction hardening is a surface hardening technique in which the surface of the metal is heated very quickly, using a no-contact method of induction heating. The alloy is then quenched, producing a martensite transformation at the surface while leaving the underlying metal unchanged. This creates a very hard, wear resistant surface while maintaining the proper toughness in the majority of the object. Crankshaft journals are a good example of an induction hardened surface. 1.1.9 Case Hardening Case hardening is a thermochemical diffusion process in which an alloying element, most commonly carbon or nitrogen, diffuses into the surface of a monolithic metal. The resulting interstitial solid solution is harder than the base material, which improves wear resistance without sacrificing toughness. Laser surface engineering is a surface treatment with high versatility, selectivity and novel properties. Since the cooling rate is very high in laser treatment, metastable even metallic glass can be obtained by this method.

4

1.1.10 Cold and Cryogenic Treating Although quenching steel causes the austenite to transform into martensite, all of the austenite usually does not transform. Some austenite crystals will remain unchanged even after quenching below the martensite finish (Mf) temperature. Further transformation of the austenite into martensite can be induced by slowly cooling the metal to extremely low temperatures. Cold treating generally consists of cooling the steel to around -115 ˚F (-81 ˚C), but does not eliminate all of the austenite. Cryogenic treating usually consists of cooling to much lower temperatures, often in the range of -315 ˚F (-192 ˚C), to transform most of the austenite into martensite. Cold and cryogenic treatments are typically done immediately after quenching, before any tempering, and will increase the hardness, wear resistance, and reduce the internal stresses in the metal but, because it is really an extension of the quenching process, it may increase the chances of cracking during the procedure. The process is often used for tools, bearings, or other items that require good wear resistance. However, it is usually only effective in high-carbon or high-alloy steels in which more than 10% austenite is retained after quenching.

1.2 NANOFULIDS A nanofluid is a fluid containing nanometre-sized particles, called nanoparticles. These fluids are engineered colloidal suspensions of nanoparticles in a base fluid. The nanoparticles used in nanofluids are typically made of metals, oxides, carbides, or carbon nanotubes. Common base fluids include water, ethylene glycol and oil. Nanofluids have novel properties that make them potentially useful in many applications in heat transfer, including microelectronics, fuel cells, pharmaceutical processes, and hybrid-powered engines, 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 behaviour of nanofluids is found to be critical in deciding their suitability for convective heat transfer applications. Nanofluids 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.

5

In analysis such as computational fluid dynamics (CFD), nanofluids 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 nanofluid is taken as a function of properties of both constituents and their concentrations. An alternative approach simulates nanofluids using a two-component model. The spreading of a nanofluid 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 nanometre scale, because the wetting time scale is much smaller than the diffusion time scale. 1.2.1 SYNTHESIS OF NANOFLUIDS 1.2.1.1 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 dry powders by chemical or physical methods. Then, the nanosized powder will be dispersed into a fluid in the second processing step with the help of intensive magnetic force agitation, ultrasonic agitation, high-shear mixing, homogenizing, and ball milling. Twostep method is the most economic method to produce nanofluids in large scale, because nanopowder synthesis techniques have already been scaled up to industrial production levels. Due to the high surface area and surface activity, nanoparticles have the tendency to aggregate. The important technique to enhance the stability of nanoparticles in fluids is the use of surfactants. However, the functionality of the surfactants under high temperature is also a big concern, especially for high-temperature applications. Due to the difficulty in preparing stable nanofluids by two-step method, several advanced techniques are developed to produce nanofluids, including one-step method. In the following part, we will introduce one-step method in detail. 1.2.1.2 One-Step Method To reduce the agglomeration of nanoparticles, Eastman et al. developed a one-step physical vapor condensation method to prepare Cu/ethylene glycol nanofluids]. The one-step process consists of simultaneously making and dispersing the particles in the fluid. In this method, the processes of drying, storage, transportation, and dispersion of nanoparticles are avoided, so the agglomeration of nanoparticles is minimized, and the stability of fluids is 6

increased. The one-step processes can prepare uniformly dispersed nanoparticles, and the particles can be stably suspended in the base fluid. The vacuum-SANSS (submerged arc nanoparticle synthesis system) is another efficient method to prepare nanofluids using different dielectric liquids The different morphologies are mainly influenced and determined by various thermal conductivity properties of the dielectric liquids. The nanoparticles prepared exhibit needle-like, polygonal, square, and circular morphological shapes. The method avoids the undesired particle aggregation fairly well. One-step physical method cannot synthesize nanofluids in large scale, and the cost is also high, so the one-step chemical method is developing rapidly. Zhu et al. presented a novel one-step chemical method for preparing copper nanofluids by reducing C u S O4⋅ 5 H2O with NaH2P O2⋅ H2O in ethylene glycol under microwave irradiation. Well-dispersed and stably suspended copper nanofluids were obtained. Mineral oil-based nanofluids containing silver nanoparticles with a narrow-size distribution were also prepared by this method. The particles could be stabilized by Korantin, which coordinated to the silver particle surfaces via two oxygen atoms forming a dense layer around the particles. The silver nanoparticle suspensions were stable for about 1 month. Stable ethanol-based nanofluids containing silver Nanoparticles could be prepared by microwave-assisted one-step method. In the method, poly vinyl pyrrolidone (PVP) was employed as the stabilizer of colloidal silver and reducing agent for silver in solution. The cationic surfactant octadecylamine (ODA) is also an efficient phase-transfer agent to synthesize silver colloids. The phase transfer of the silver nanoparticles arises due to coupling of the silver nanoparticles with the ODA molecules present in organic phase via either coordination bond formation or weak covalent interaction. Phase transfer method has been developed for preparing homogeneous and stable graphene oxide colloids. Graphene oxide nanosheets (GONs) were successfully transferred from water to n-octane after modification by oleylamine, and the schematic illustration of the phase transfer process is shown However, there are some disadvantages for one-step method. The most important one is that there reactants are left in the nanofluids due to incomplete reaction or stabilization. It is difficult to elucidate the nanoparticle effect without eliminating this impurity effect.

7

1.2.2 APPLICATIONS OF NANOFLUIDS 1.2.2.1 Industrial Cooling Applications Routbort started a project in 2008 that employed nanofluids for industrial cooling that could result in great energy savings and resulting emissions reductions. ForU.S. industry, there placement of cooling and heating water with nanofluids has the potential to conserve1trillion BTU of energy. For the U.S. electric power industry, using nanofluids in closed-loop cooling cycles could save about 10–30 trillion BTU per year (equivalent to the annual energy consumption of about 50,000–150,000 households). The associated emissions reductions would be approximately 5.6 million metric tons of carbon dioxide; 8,600 metric tons of nitrogen oxides; and 21,000 metric tons of sulphur dioxide. For Michelin North America tire plants, the productivity of numerous industrial processes is constrained by the lack of facility to cool the rubber efficiently as it is being processed. This requires the use of over 2 million gallons of heat transfer fluids for Michelin's North American plants. It is Michelin's goal in this project to obtain a 10% productivity increase in its rubber processing plants if suitable water-based nanofluids can be developed and commercially produced in a cost-effective manner. Han et al. have used phase change materials as nanoparticles in nanofluids to simultaneously enhance the effective thermal conductivity and specific heat of the fluids. As an example, a suspension of indium nanoparticles (melting temperature, 157∘C) in polyalphaolefin has been synthesized using a one-step, nano emulsification method. The fluid's thermos physical properties, that is, thermal conductivity, viscosity, and specific heat, and their temperature dependence were measured experimentally. The observed meltingfreezing phase transition of the indium nanoparticles significantly augmented the fluid's effective specific heat. This work is one of the few to address thermal diffusivity; similar studies allow industrial cooling applications to continue without thorough understanding of all the heat transfer mechanisms in nanofluids.

8

1.2.2.2 Smart Fluids In this new age of energy awareness, our lack of abundant sources of clean energy and the widespread dissemination of battery operated devices, such as cell-phones and laptops, have accented the necessity for a smart technological handling of energetic resources. Nanofluids have been demonstrated to be able to handle this role in some instances as a smart fluid. In a recent paper published in the March 2009 issue of Physical Review Letters, Donzelli et al. showed that a particular class of nanofluids can be used as a smart material working as a heat valve to control the flow of heat. The nanofluid can be readily configured either in a “low” state, where it conducts heat poorly, or in a “high” state, where the dissipation is more efficient. To leap the chasm to heating and cooling technologies, the researchers will have to show more evidence of a stable operating system that responds to a larger range of heat flux inputs. 1.2.2.3 Nuclear Reactors Kim et al. at the Nuclear Science and Engineering Department of the Massachusetts Institute of Technology (MIT), performed a study to assess the feasibility of nanofluids in nuclear applications by improving the performance of any water-cooled nuclear system that is heat removal limited. Possible applications include pressurized water reactor (PWR) primary coolant, standby safety systems, accelerator targets, plasma diverters, and so forth. In a pressurized water reactor (PWR) nuclear power plant system, the limiting process in the generation of steam is critical heat flux (CHF) between the fuels rods and the water—when vapour bubbles that end up covering the surface of the fuel rods conduct very little heat as opposed to liquid water. Using nanofluids instead of water, the fuel rods become coated with nanoparticles such as alumina, which actually push newly formed bubbles away, preventing the formation of a layer of vapour around the rod and subsequently increasing the CHF significantly. After testing in MIT's Nuclear Research Reactor, preliminary experiments have shown promising success where it is seen that PWR is significantly more productive. The use of nanofluids as a coolant could also be used in emergency cooling systems, where they could cool down overheat surfaces more quickly leading to an improvement in power plant safety.

9

Some issues regarding the use of nanofluids in a power plant system include the unpredictability of the amount of nanoparticles that are carried away by the boiling vapour. One other concern is what extra safety measures that have to be taken in the disposal of the nanofluid. The application of nanofluid coolant to boiling water reactors (BWR) is predicted to be minimal because nanoparticle carryover to the turbine and condenser would raise erosion and fouling concerns. From Jackson's study, it was observed that considerable enhancement in the critical heat flux can be achieved by creating a structured surface from the deposition of nanofluids. If the deposition film characteristics such as the structure and thickness can be controlled, it may be possible to increase the CHF with little decrease in the heat transfer. Whereas the nanoparticles themselves cause no significant difference in the pool-boiling characteristics of water, the boiling of nanofluids shows promise as a simple way to create an enhanced surface. The use of nanofluids in nuclear power plants seems like a potential future application. Several significant gaps in knowledge are evident at this time, including, demonstration of the nanofluid thermal-hydraulic performance at prototypical reactor conditions and the compatibility of the nanofluid chemistry with the reactor materials. Another possible application of nanofluids in nuclear systems is the alleviation of postulated severe accidents during which the core melts and relocates to the bottom of the reactor vessel. If such accidents were to occur, it is desirable to retain the molten fuel within the vessel by removing the decay heat through the vessel wall. This process is limited by the occurrence of CHF on the vessel outer surface, but analysis indicates that the use of nanofluid can increase the in-vessel retention capabilities of nuclear reactors by as much as 40%. Many water-cooled nuclear power systems are CHF-limited, but the application of nanofluid can greatly improve the CHF of the coolant so that there is a bottom-line economic benefit while also raising the safety standard of the power plant system. 1.2.2.4 Extraction of Geothermal Power and Other Energy Sources The world's total geothermal energy resources were calculated to be over 13000ZJ in a report from MIT. Currently only 200 ZJ would be extractable, however, with technological improvements, over 2,000 ZJ could be extracted and supply the world's energy needs for several millennia. When extracting energy from the earth's crust that varies in length between 5 to 10 km and temperature between 5000O C and 1000O C, nanofluids can be 10

employed to cool the pipes exposed to such high temperatures. When drilling, nanofluids can serve in cooling the machinery and equipment working in high friction and high temperature environment. As a “fluid superconductor,” nanofluids could be used as a working fluid to extract energy from the earth core and processed in a PWR power plant system producing large amounts of work energy. In the sub-area of drilling technology, so fundamental to geothermal power, improved sensors and electronics cooled by nanofluids capable of operating at higher temperature in downhole tools, and revolutionary improvements utilizing new methods of rock penetration cooled and lubricated by nanofluids will lower production costs. Such improvements will enable access to deeper, hotter regions in high grade formations or to economically acceptable temperatures in lower-grade formations. In the sub-area of power conversion technology, improving heat-transfer performance for lower-temperature nanofluids, and developing plant designs for higher resource temperatures to the supercritical water region would lead to an order of magnitude (or more) gain in both reservoir performance and heat-to power conversion efficiency. Tran et al.

funded by the United States Department of Energy (USDOE),

performed research targeted at developing a new class of highly specialized drilling fluids that may have superior performance in high temperature drilling. This research is applicable to high pressure high temperature drilling, which may be pivotal in opening up large quantities of previously unrecoverable domestic fuel resources. Commercialization would be the bottleneck of progress in this sub-area.

1.3 MECHANICAL PROPERTIES The metal specimen of required dimension is heat treated and quenched using nanofluids. Due to quenching using nanofluids there is change in physical properties of the metal specimen. The properties such as tensile strength, hardness and wear strength are measured. The tensile strength of a material is the maximum amount of tensile stress that it can be subjected to before failure. The definition of failure can vary according to material type and design methodology. Hardness is a measure of how resistant solid matter is to various kinds of permanent shape change when a compressive force is applied. Some materials, such as metal, are harder than others. Macroscopic hardness is generally characterized by strong intermolecular bonds, but the behaviour of solid materials under force 11

is complex; therefore, there are different measurements of hardness: scratch hardness, indentation hardness, and rebound hardness. Wear is related to interactions between surfaces and more specifically the removal and deformation of material on a surface as a result of mechanical action of the opposite surface. The need for relative motion between two surfaces and initial mechanical contact between asperities is an important distinction between mechanical wear compared to other processes with similar outcomes. These mechanical properties of the metal specimen is calculated using suitable methods and investigated. 1.3.1 Tensile Properties Tensile properties indicate how the material will react to forces being applied in tension. A tensile test is a fundamental mechanical test where a carefully prepared specimen is loaded in a very controlled manner while measuring the applied load and the elongation of the specimen over some distance. Tensile tests are used to determine the modulus of elasticity, elastic limit, elongation, proportional limit, and reduction in area, tensile strength, yield point, yield strength and other tensile properties The main product of a tensile test is a load versus elongation curve which is then converted into a stress versus strain curve. Since both the engineering stress and the engineering strain are obtained by dividing the load and elongation by constant values (specimen geometry information), the load-elongation curve will have the same shape as the engineering stress-strain curve. The stress-strain curve relates the applied stress to the resulting strain and each material has its own unique stress-strain curve. A typical engineering stress-strain curve is shown below. If the true stress, based on the actual crosssectional area of the specimen, is used, it is found that the stress-strain curve increases continuously up to fracture. 1.3.1.1 Linear-Elastic Region and Elastic Constants As can be seen in the figure, the stress and strain initially increase with a linear relationship. This is the linear-elastic portion of the curve and it indicates that no plastic deformation has occurred. In this region of the curve, when the stress is reduced, the material will return to its original shape. In this linear region, the line obeys the relationship defined as Hooke's Law where the ratio of stress to strain is a constant. The slope of the line in this region where stress is proportional to strain and is called the modulus of elasticity or Young's modulus. The modulus of elasticity (E) defines the properties of a material as it undergoes stress, deforms, and then returns to its original shape after the stress is removed. It is a measure of the stiffness of a given material. To compute 12

the modulus of elastic, simply divide the stress by the strain in the material. Since strain is unit less, the modulus will have the same units as the stress, such as MPa. The modulus of elasticity applies specifically to the situation of a component being stretched with a tensile force. This modulus is of interest when it is necessary to compute how much a rod or wire stretches under a tensile load.

Fig 1.1 Stress-Strain Curve There are several different kinds of moduli depending on the way the material is being stretched, bent, or otherwise distorted. When a component is subjected to pure shear, for instance, a cylindrical bar under torsion, the shear modulus describes the linear-elastic stressstrain relationship. Axial strain is always accompanied by lateral strains of opposite sign in the two directions mutually perpendicular to the axial strain. Strains that result from an increase in length are designated as positive (+) and those that result in a decrease in length are designated as negative (-). Poisson's ratio is defined as the negative of the ratio of the lateral strain to the axial strain for a uniaxial stress state.

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Poisson's ratio is sometimes also defined as the ratio of the absolute values of lateral and axial strain. This ratio, like strain, is unit less since both strains are unit less. For stresses within the elastic range, this ratio is approximately constant. For a perfectly isotropic elastic material, Poisson's Ratio is 0.25, but for most materials the value lies in the range of 0.28 to 0.33. Generally, for steels, Poisson’s ratio will have a value of approximately 0.3. This means that if there is one inch per inch of deformation in the direction that stress is applied, there will be 0.3 inches per inch of deformation perpendicular to the direction that force is applied. Only two of the elastic constants are independent so if two constants are known, the third can be calculated using the following formula: E = 2 (1 +µ) G. Where:

E = modulus of elasticity (Young's modulus) µ = Poisson's ratio G = Modulus of rigidity (shear modulus).

A couple of additional elastic constants that may be encountered include the bulk modulus (K), and Lame's constants (m and l). The bulk modulus is used describe the situation where a piece of material is subjected to a pressure increase on all sides. The relationship between the change in pressure and the resulting strain produced is the bulk modulus. Lame's constants are derived from modulus of elasticity and Poisson's ratio. 1.3.1.2 Yield Point In ductile materials, at some point, the stress-strain curve deviates from the straightline relationship and Law no longer applies as the strain increases faster than the stress. From this point on in the tensile test, some permanent deformation occurs in the specimen and the material is said to react plastically to any further increase in load or stress. The material will not return to its original, unstressed condition when the load is removed. In brittle materials, little or no plastic deformation occurs and the material fractures near the end of the linearelastic portion of the curve. 14

With most materials there is a gradual transition from elastic to plastic behaviour, and the exact point at which plastic deformation begins to occur is hard to determine. Therefore, various criteria for the initiation of yielding are used depending on the sensitivity of the strain measurements and the intended use of the data. (See Table) For most engineering design and specification applications, the yield strength is used. The yield strength is defined as the stress required to produce a small, amount of plastic deformation. The offset yield strength is the stress corresponding to the intersection of the stress-strain curve and a line parallel to the elastic part of the curve offset by a specified strain (in the US the offset is typically 0.2% for metals and 2% for plastics). To determine the yield strength using this offset, the point is found on the strain axis (x-axis) of 0.002, and then a line parallel to the stress-strain line is drawn. This line will intersect the stress-strain line slightly after it begins to curve, and that intersection is defined as the yield strength with a 0.2% offset. A good way of looking at offset yield strength is that after a specimen has been loaded to its 0.2 percent offset yield strength and then unloaded it will be 0.2 percent longer than before the test. Even though the yield strength is meant to represent the exact point at which the material becomes permanently deformed, 0.2% elongation is considered to be a tolerable amount of sacrifice for the ease it creates in defining the yield strength. Some materials such as grey cast iron or soft copper exhibit essentially no linearelastic behaviour. For these materials the usual practice is to define the yield strength as the stress required to produce some total amount of strain. 

True elastic limit is a very low value and is related to the motion of a few hundred dislocations. Micro strain measurements are required to detect strain on order of 2 x 10-6 in/in.



Proportional limit is the highest stress at which stress is directly proportional to strain. It is obtained by observing the deviation from the straight-line portion of the stressstrain curve.



Elastic limit is the greatest stress the material can withstand without any measurable permanent strain remaining on the complete release of load. It is determined using a tedious incremental loading-unloading test procedure. With the sensitivity of strain measurements usually employed in engineering studies (10-4in/in), the elastic limit is greater than the proportional limit. With increasing sensitivity of strain measurement,

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the value of the elastic limit decreases until it eventually equals the true elastic limit determined from micro strain measurements. Yield strength is the stress required to produce a small-specified amount of plastic deformation. The yield strength obtained by an offset method is commonly used for engineering purposes because it avoids the practical difficulties of measuring the elastic limit or proportional limit.

1.3.1.3 Ultimate Tensile Strength The ultimate tensile strength (UTS) or, more simply, the tensile strength, is the maximum engineering stress level reached in a tension test. The strength of a material is its ability to withstand external forces without breaking. In brittle materials, the UTS will at the end of the linear-elastic portion of the stress-strain curve or close to the elastic limit. In ductile materials, the UTS will be well outside of the elastic portion into the plastic portion of the stress-strain curve. On the stress-strain curve above, the UTS is the highest point where the line is momentarily flat. Since the UTS is based on the engineering stress, it is often not the same as the breaking strength. In ductile materials strain hardening occurs and the stress will continue to increase until fracture occurs, but the engineering stress-strain curve may show a decline in the stress level before fracture occurs. This is the result of engineering stress being based on the original cross-section area and not accounting for the necking that commonly occurs in the test specimen. The UTS may not be completely representative of the highest level of stress that a material can support, but the value is not typically used in the design of components anyway. For ductile metals the current design practice is to use the yield strength for sizing static components. However, since the UTS is easy to determine and quite reproducible, it is useful for the purposes of specifying a material and for quality control purposes. On the other hand, for brittle materials the design of a component may be based on the tensile strength of the material.

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1.3.1.4 Measure of Ductility (Elongation and Reduction of Area) The ductility of a material is a measure of the extent to which a material will deform before fracture. The amount of ductility is an important factor when considering forming operations such as rolling and extrusion. It also provides an indication of how visible overload damage to a component might become before the component fractures. Ductility is also used a quality control measure to assess the level of impurities and proper processing of a material. The conventional measures of ductility are the engineering strain at fracture (usually called the elongation) and the reduction of area at fracture. Both of these properties are obtained by fitting the specimen back together after fracture and measuring the change in length and cross-sectional area. Elongation is the change in axial length divided by the original length of the specimen or portion of the specimen. It is expressed as a percentage. Because an appreciable fraction of the plastic deformation will be concentrated in the necked region of the tensile specimen, the value of elongation will depend on the gage length over which the measurement is taken. The smaller the gage length the greater the large localized strain in the necked region will factor into the calculation. Therefore, when reporting values of elongation, the gage length should be given.

Fig 1.2 Measure of Ductility One way to avoid the complication from necking is to base the elongation measurement on the uniform strain out to the point at which necking begins. This works well at times but some engineering stress-strain curve are often quite flat in the vicinity of

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maximum loading and it is difficult to precisely establish the strain when necking starts to occur. Reduction of area is the change in cross-sectional area divided by the original crosssectional area. This change is measured in the necked down region of the specimen. Like elongation, it is usually expressed as a percentage. 1.3.2 Hardness Hardness is regarded as the resistance of a material to indentations and scratching. This is generally determined by forcing an indenter on to the surface. The resultant deformation in steel is both elastic and plastic. There are several methods using which the hardness of a metal could be found out. They basically differ in the form of the indenter, which is used on to the surface. In all the above cases, hardness number is related to the ratio of the applied load to the surface area of the indentation formed. The testing procedure involves forcing the indenter on to the surface at a particular road. On removal, the size of indentation is measured using a microscope. Based on the size of the indentation hardness is worked out. For example, Brinell hardness (BHN) is given by the ratio of the applied load and spherical area of the indentation i.e. Table 1.1 Hardness testing methods and their indenters Hardness Testing Method

Indenter

a)

Brinell hardness

Steel ball

b)

Vickers hardness

Square based diamond pyramids of 135o included angle

c)

Rockwell hardness

Diamond core with 120o included angle

Note: Rockwell hardness testing is not normally used for structural steels.

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BHN = 2 P / (π D (D - (D2 - d2)1/2)) where BHN = Brinell hardness number P = load on the indenting tool (kg) D = diameter of steel ball (mm) d = measure diameter at the rim of the impression (mm) VHN= Vickers hardness value The Vickers test gives a similar hardness value (VHN) as given by VHN = 1.854 P / L2 Where L is the diagonal length of the indent. Both the BHN and VHN for steel range from 150 to 190.

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CHAPTER 2 LITERATURE REVIEW 2.1 ALUMINA NANOFLUID BASED EXPERIMENTS 2.1.1 An experimental analysis of quenching of continuously heated vertical rod with aqueous Al2O3nanofluid (Nirupama Patra , Vivek Gupta , Ravi Singh , R.S. Singh , Pradyumna Ghosh , Arun Nayak) The quenching tests have been performed using nanofluids as well as DI water. A more enhanced cooling performance is observed in the case of nanofluid quenching. The enhanced cooling performance is due to high wettability of a thin layer formed on a heating surface by a deposition of nanoparticles during evaporation of liquid droplets. This phenomenon is more prominent in case of a long rod. The quenching performance is enhanced more than 10 s for Al2O3water nanofluid in comparison to DI water at higher initial rod temperature. The effect of decay heat is more significant at higher initial rod temperature. The effect of flow rate on quenching time is not significant for both water and nanofluid. however, the study can be conducted at higher value of initial rod temperature and wide range of flow rate to conclude in a better way. The heat transfer coefficient is enhanced in case of nanofluids as compared to DI water in both the cases, with or without decay heat. The effect of decay heat is not significant because the heat transfer coefficient mainly depends on stored heat which is dependent on initial rod temperature.

2.1.2 Heat transfer enhancement using air-atomized spray cooling with water A𝐥𝟐 𝐎𝟑 nanofluid ( Satya V. Ravikumar, and Krishnayan Haldar) The study deals with the air-atomized spray cooling using nanofluid as the cooling media for high heat flux applications. The nanofluid has been prepared by commercial Al2 O3 particles of diameter less than 13 nm and water. Heat transfer study has been carried out on a pre-heated steel specimen of dimensions 100 mmx100 mm x6 mm. The initial temperature of the plate which was subjected to air-atomized spray cooling was over 900 C. The results obtained using nanofluid coolants are compared with that of the results where pure water (filtered potable water) is used as a coolant. The analyses reveal that the cooling rate, critical heat flux and heat transfer coefficients are significantly enhanced when nanofluids are used as coolants in air-atomized spray process. Also, the nanofluid coolants with dispersing agent shows a better enhancement of heat transfer over that of the nanofluid without the dispersing 20

media Overall, the percentage enhancement in cooling rate of all these nanofluids compared with pure water (filtered potable water) is 10.2% for water A l2 O3 , 18.6% for water Al2 O3 SDS, and upto 32.3% for water Al2 O3 between 20.

2.2 OTHER NANOFLUID BASED EXPERIMENTS 2.2.1 ATOMIZED SPRAY QUENCHING AS AN ALTERNATIVE QUENCHING METHOD FOR DEFINED ADJUSTMENT OF HEAT TRANSFER (Frank Puschmann and Eckehard Specht) Schematically illustrates the quenching of a hot solid from a temperature higher than Leidenfrost temperature. Water Spray Quenching and Atomized Spray Quenching are compared. In Water Spray Quenching a vapour layer forms. The heat is mainly transferred by conduction through the vapour. Excrescent water discharges sideways. At the edges, the vapour layer collapses immediately. Thus Nucleate Boiling occurs at these locations. An amount of only 1/10 to 1/20 of water is sprayed onto the surface to achieve the same heat transfer with Atomized Spray Quenching. The water is atomized to a fine spray with compressed air. The drops impinge onto the hot surface, evaporate partially and rebound. Afterwards they are taken away with the strong air stream superposed. Thus a water layer is not able to form. The required distribution of impingement density can be created by choosing an adapted twin fluid nozzle. With Atomized Spray Quenching the heat transfer coefficient is directly proportional to the impingement density over the whole surface width. With Water Spray Quenching nucleate boiling occurs at the edges with the same impingement density profile. The heat transfer coefficient is also nearly proportional to the impingement density, but at the edges it jumps up because of the change in boiling regime. Thus the borders cool down strongly. With Atomized Spray Quenching, the temperature profile is more even. It is shown that by evening out the temperature profile, especially by raising the temperature at the borders, the quality is significantly improved. This improvement is caused by the evening out of hardness, the reduction of residual stress at edges and a decrease in warping.

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2.2.2 Comparative study on different additives with a jet array on cooling of a hot steel surface (Ishita Sarkar, Samarshi Chakraborty, Avinash Ashok, Iman Sengupta, Surjya K. Palb, Sudipto Chakraborty) The heat transfer performance of a jet array by using different coolants has been investigated in the current study. The experiments have been conducted on a stainless steel plate having surface temperature above 900 °C. The water flow rate and impingement height of the jet array have been optimized based on maximum cooling rate attained. The effect of different surfactant, polymer and nanofluid based additives on the cooling rate of the hot steel plate have been studied. The key findings of the study can be summarized as follows: The rate of heat transfer was found to increase with water flow rate up to 16 lpm, and thereafter it decreased. The cooling rate increased with impingement height up to 15 cm after which it declined. Almost uniform cooling can be achieved throughout the steel plate using jet array due to formation of several forced convection zones unlike a single jet where there is nonuniformity of temperature in the surface, Maximum average cooling rate of 111.73 °C/s was achieved for a water flow rate of 16 lpm and impingement height of 15 cm. The cooling rate of a jet array is increased by 60% as compared to that of a single free falling jet at the same water flow rate and impingement height. Maximum critical heat flux of 2.44 MW/𝑚2 was achieved for a water flow rate of 16 lpm with impingement height of 15 cm.Maximum cooling rate of 143 °C/s was obtained for PVP based coolant for an optimized impingement height and coolant flow rate, which is 28% more than that achieved for pure water. The highest cooling rate attained indicates that ultrafast cooling can be obtained using additive based jet array impingement.

2.2.3 Enhancement of heat transfer rate in air-atomized spray cooling of a hot steel plate by using an aqueous solution of non-ionic surfactant and ethanol (Satya V. Ravi Kumar a, Jay M. Jha, Ishita Sarkar , Surjya K. Pal , Sudipto Chakraborty) In this paper, the enhancement of spray cooling heat transfers of a hot stainless steel plate by using ethanol and surfactant as the additives was investigated experimentally. The surface tension and heat transfer characteristics of working fluid with different additives were tested and analysed. This research has been carried out to enhance the ultrafast cooling process within the experimental range, which is needed for the production of advanced high strength steels on ROT of a hot strip mill in steel industries. A slight increase in the cooling rate is also relatively very important for metallurgical transformations in steel. On the basis of 22

the current experimental results, the following conclusions can be drawn: Upon the addition of 100 ppm ethanol to water, the spray cooling heat transfer is enhanced and the effect becomes stronger by increasing the concentration up to an optimal level. In the experiments, it was seen that the enhancement in cooling rate of the hot plate is highest at an ethanol concentration of 300 ppm, whereas the enhancement is low between 300 and 500 ppm and decreases beyond 500 ppm concentration. The addition of higher amounts of ethanol stabilizes the bubbles on the hot surface, which restricts the spread ability of the wetting front. Hence the cooling rate decreases. The enhancements in cooling rate with pure water with all the three concentrations of the ethanol are 3, 6.7 and 9.6 percent, respectively. The pure water working fluid can give a cooling rate of 167 C/s; whereas with the addition of ethanol, the maximum cooling rate is found to be 183 C/s. In the presence of the surface active agent, the cooling rate of ethanol water mixture (at 500 ppm concentration) increases further by 28.4 percent. However, surfactant alone can enhance the cooling rate of pure water by 28 percent. Overall, the maximum cooling rates of pure water, surfactant water, ethanol water mixture and ethanol water surfactant mixture are 167 C/s, 183 C/s, 214 C/s, and 235 C/s respectively. Hence, the resulting cooling rates indicate that ethanol water surfactant mixture is the best coolant with a higher cooling rate falling in the ultrafast cooling regime about 235 C/s, and corresponds to a maximum cooling power of 3.66 MW/𝑚2 on a 6 mm thick AISI 304 stainless steel plate. Ethanol and surfactant have a significant effect on the surface tension reduction and the rate of decrease in surface tension increases with an increase in ethanol concentration. The ethanol water surfactant mixture shows a high degree of reduction in the surface tension. The decrease in surface tension increases the solid liquid contact by decreasing the wetting angle. Moreover, ethanol promotes the bubble nucleation and this effect is high in the surfactant water medium. The enhancement in heat transfer with ethanol water and ethanol/water/surfactant mixtures is due to the suppression of surface tension which promotes the liquid to spread on the surface at a faster rate. The decrease in surface tension makes a better solid liquid contact, such that the wettability of the surface increases. As a result, the evaporation rate of droplets from the surface increases. Moreover, a decrease in surface tension leads to formation of droplets of finer size. Therefore, the droplets of lower size can evaporate quickly from the surface so that the thickness of the vapour layer decreases. In the boiling curves, the CHF of ethanol is higher than that of pure water, and it is increasing with an increase in ethanol concentration. Similarly, surfactant also increases the CHF of pure water. The maximum CHF values have been found while working with ethanol/water/surfactant mixtures. The heat transfer coefficient of the additives at 200 °C (i.e., in nucleate boiling heat transfer regime) is 23

higher than that of pure water. For comparing the surface heat transfer coefficients of working fluid with all the additives, the enhancement factor was introduced. According to this, in the nucleate boiling regime, the HTC increases to 1.21 times for ethanol water mixture, 1.32 times for surfactant water and 1.47 times for ethanol water surfactant mixtures. Thus, this paper also proposes the enhancement of the air-atomized spray cooling heat transfer by alcohols, surfactants and their mixtures for application in metallurgical industries to design the ultra-high strength martensitic steels.

2.2.4 Experimental study of heat transfer coefficient on hot steel plate during water jet impingement cooling (Hemu Wang, Wei Yu, Qingwu Cai) The surface temperature has a significant effect on heat transfer coefficient during water jet impingement cooling. With decreasing surface temperature, the heat transfer coefficient gradually increases at above 300 °C Below this surface temperature, the heat transfer coefficient increases drastically faster at stagnation line Within 70 mm distance from stagnation line, the cooling water flow rate in the range of 15–35 L/min has no effect on heat transfer coefficient and surface temperature. Beyond surface temperature of 300 °C, the heat transfer coefficient increases with increasing initial test surface temperature. Within 70 mm distance from stagnation line, the heat transfer coefficient ratio changes slightly from 0.87 to 0.97. The heat transfer coefficient ratio decreases with increasing distance from stagnation line at above 350 °C.

2.2.5 Experimental study on heat-transfer characteristics of circular water jet impinging on high-temperature stainless steel plate (Ruifeng Dou, Zhi Wen, Gang Zhou, Xunliang Liu, Xiaohong Feng) The heat-transfer characteristics of the water jet on stainless steel plate have been successfully determined by inverse heat conduction method. The verification indicated that the test facility and the data filter method are suitable to evaluate the heat flux on a test plate. The experiment method in this study greatly reduces the number of thermocouples needed for the test of heat flux at one location. The roughness of the test plate can alter the heat-transfer intensity. The higher surface roughness results in higher heat flux. According to the method of Hauksson and Xu, the heat-transfer mode can be identified by surface temperature fluctuations of the test plate. 24

In this study, the heat-transfer modes at the point near the stagnation are hard to be identified, because the arrival time of the wetting front is too short after water jet impinging. However, the outer point gives a clear division of the heat-transfer modes.

2.2.6 Heat transfer characteristic research during jet impinging on top/bottom hot steel plate (Bingxing Wang, Xitao Guo, Qian Xie, Zhaodong Wang, Guodong Wang) The present study was focused on the heat transfer characteristics during jet impinging on the top or bottom of hot steel plates for industrial application. The heat transfer difference between these two types of cooling processes was analysed using the inverse heat conduction method. The critical parameters, such as the water flow rate and nozzle-to-surface distance, were studied. The results demonstrate that the difference in top and bottom heat transfer performance and the wetting front propagation phenomenon are significant. The top surface heat flux is slightly higher than that of the bottom one for the measured cooling region. However, the top surface wetting front propagation is significantly slower than that of the bottom surface. The heat transfer performance is increased with the water flow rate for the top and bottom surface. At the impinging point, the tMHF is approximately 0.8 s, and it increases with the distance to the impinging point for all experimental conditions. The top surface tMHF, for each measured point outside the impact region, is higher than that of the bottom surface, when the water flow rate is above 2 l/min. The shorter nozzle-to-surface distance will result in higher heat transfer performance. The wetting delay time increases with the nozzle-to-surface distance for both experimental conditions.

2.2.7 Heat transfer characteristics during jet impingement on a high-temperature plate surface (Bingxing Wang, Dong Lin, Qian Xie, Zhaodong Wang, Guodong Wang) The heat transfer characteristics during water jet impingement on a hot plate surface were systematically investigated. Moreover, the factors that influenced the rewetting front propagation and maximum heat flux were studied in detail. The main conclusions are as follows: The heat transfer process and region distribution were studied by the cooling curves and digital graphs during water jet impingement on a hot surface. The cooling curves indicated the initial plate temperature had a significant effect on both the impact and parallel regions, but the water temperature and jet velocity merely showed the remarkable effect in the parallel region. 25

The rewetting temperature depended highly on the initial plate temperature, depended slightly on the water temperature and was almost unaffected by the jet velocity. The wetting velocity initially increased and then declined with the increasing radial distance. The rewetting front propagation was significantly affected by the growth and detachment of the bubbles in the rewetting front region. The qmax of the measurement points in the impinging region was larger than that in the parallel region. The local qmax reduced with the rewetting front propagated outward, and the equations were regressed to estimate qmax. Meanwhile, the factors of higher initial temperature, lower water temperature, and larger jet velocity were contributed to a higher heat flux.

2.2.8 Heat transfer enhancement using air-atomized spray cooling with water Al2O3nanofluid (Satya V. Ravi Kumar, Krishnayan Haldar, Jay M. Jha, Samarshi Chakraborty, Ishita Sarkar , Surjya K. Pal , Sudipto Chakraborty) Air-atomized spray cooling of a high temperature steel plate using water based alumina nanofluids has been experimentally studied. The results are compared with those obtained using pure water (filtered potable water) spray. The heat transfer analysis depicts that the heat flux shifts to higher values both in transition and nucleate boiling regimes using nanofluid coolants as compared to that of pure water (filtered potable water). The results show that a quick shift from transition boiling to nucleate boiling occurs when the nanofluid are used as the coolants. The enhanced heat transfer by nanofluid is attributed due to the deposition phenomenon of nanoparticles on the heated surface during cooling. Moreover, increases in thermal conductivity of base fluid also contribute significantly for high heat transfer rates. As concluded by Liu and Qiu that the deterioration of nanofluid jet boiling heat transfer is due to decrease in surface roughness by adherence of deposited nanoparticles on the heated surface. However, in the air-atomized spray cooling, before the nanoparticles adhere and completely cover the heated surface, they are disintegrating from the plate surface by a high velocity superposed air flow, and hence preventing the formation of stable nanoparticle sorption layer unlike the nanofluid jet impingement cooling. The alumina nanofluid with presence of surfactant (SDS or Tween 20) shows enhanced heat transfer results compared to that without a surfactant. This is due to decrease in surface tension by a surfactant which in turn promotes the surface wettability and surface bubble nuclei density. Moreover, during transition boiling, decrease in surface tension is the reason for vapour film instability and heat 26

transfer augmentation. The Tween 20 surfactant has the best enhancement performance compared to that of SDS due to effective decrease in surface tension and viscosity of the base fluid. The high value of critical heat flux (3.33 MW/m2) has been obtained using water A𝑙2 𝑜3 Tween 20 nanofluid, which is 21.5% higher than the critical heat flux of pure water (filtered potable water). The achieved cooling rate for watereAl2O3 spray is 184 C/s, whereas this cooling rate for water A𝑙2 𝑜3 SDS nanofluid is 198 C/ s and it is even much higher in the case of water A𝑙2 𝑜3 Tween 20 nanofluid as 221 C/s. The percentage enhancement in cooling rate of all these nanofluid with pure water (filtered potable water) is 10.2% for water A𝑙2 𝑜3 18.6% for water A𝑙2 𝑜3 SDS, and up to 32.3% for water A𝑙2 𝑜3 Tween 20 nanofluid. The enhanced heat transfer results obtained using water based alumina nanofluid coolants can be applicable for run-out table cooling of a hot strip mill in steel industry.

2.2.9 Heat transfer in jet impingement on a hot steel surface using surfactant based Cu– Al layered double hydroxide nanofluid (A.M. Tiar, Samarshi Chakraborty , Ishita Sarkar , Surjya K. Pal, Sudipto Chakraborty) The current research work encompasses the jet impingement cooling of an AISI 304 steel plate using Cu–Al LDH based nanofluid with different additives. The different types of additives employed in this study are SDS, CTAB, Tween 20 and PVP surfactants. The additive based nanofluid system was characterized and its thermal properties were investigated. The effects of the additives on thermal properties of the nanofluid system and its subsequent effect on the heat transfer rates have been studied and the findings are summed up as below: The thermal properties including thermal conductivity, surface tension and viscosity were investigated for different additives based Nano fluid system and it was found that Tween 20 based Nano fluid exhibited the maximum thermal conductivity enhancement and the highest reduction in surface tension. The minimum thermal conductivity enhancement was displayed by SDS based Nano fluid system along with the least reduction in surface tension. PVP based Nano fluid exhibited a cooling rate better than that of CTAB surfactant due to higher enhancement in thermal conductivity. The viscosity shows a decrease upon addition of Tween-20 surfactant in comparison to other surfactants. It was observed that the cooling rates increased from 117 C/ s in the case of SDS surfactant to 154 C/s in the case of

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Tween 20 surfactant. Also, the CHF value was highest for Tween 20 at 3.06 MW/m2, whereas it was lowest in the case of SDS based Nano fluid at 1.95 MW/m2. The heat transfer coefficient showed an increasing trend with a decrease in surface temperatures in case of all the additives. The ultrafast cooling rate was achieved in case of the non-ionic surfactant (Tween 20) based Nano fluid, making it the best additive to be used alongside with Cu–Al LDH system for jet impingement cooling. Deposition of Nano fluid on the test surface is verified by the presence of a thin sorption layer of nanoparticle on the plate surface after jet impingement, as shown by SEM and EDAX analysis.

2.3 SUMMARY OF LITERATURE REVIEW 

The use of nanofluids in quenching process improves heat transfer efficiency



Among many nanoparticles used, oxides of metals and metal nanoparticles have positive results.



Using nanofluids as quenching media will help in effective disruption of the vapour phase of boiling when the quenching medium comes into contact with very hot specimen.



Nanoparticle coating done manually and due to repetitive quenching of the same specimen in nanofluids improve heat transfer to greater extent.

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CHAPTER 3 METHODOLOGY

Fig 3.1 Working Methodology

The rods selected for quenching experiments are mild steel and EN8 steel. Nanofluids were prepared using deionized (D.I) water as base fluid under sonication for required time period proportional to concentration of nanoparticles in the base fluid, which acts as quenching medium. Then the specimens are heated up to recrystallization temperature using muffle furnace and the specimens are immersed into quenching medium. To measure the temperature at the centre of the rod and the cooling fluid temperature, K type thermocouples are used. The temperature-time data is recorded using data acquisition system during quenching. In order to investigate a possible change in mechanical properties due to quenching process, the quenching tests are conducted on each specimen with nanofluids of different volume fraction. The K type thermocouple constantly senses the temperature of the specimen 29

and it gives the analog value of the temperature to data acquisition system, then it converts the analog to digital value to the Arduino installed computer. During quenching of specimen in nanofluids, the heat transfer mechanism is complex. It involves both conduction and convection in alternative manner. The convection between nanoparticles and base fluid disrupts the vapour phase of boiling leading to enhanced heat transfer in the form of nucleate boiling.

Fig 3.2 Heat transfer Mechanism

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CHAPTER 4 EXPERIMENTAL SETUP AND PROCEDURE

Fig 4.1 Experimental Procedure The Experimental setup consists of Muffle furnace, steel specimens, Nano-fluid, Quench tray, thermocouple, Arduino, MAX6675 Module and PC for data acquisition. The muffle furnace used is rated for maximum temperature of 900oC is used to heat the specimen. The machined carbon steel specimens were taken. The prepared nano-fluids at different concentrations were kept ready in the quench tray for quenching. The quench tray was prepared to the dimensions required to quench the specimens along the axis. The thermocouple used is K-type and can handle temperatures up to 1200oC. The computer with Arduino was kept ready and interfaced with MAX6675 Module. The carbon steel specimens were used for each experiment. The muffle furnace was used for heating up the specimen. The specimen with thermocouple fixed into it was placed inside the muffle furnace. The specimen was heated to 930oC which are the re-crystallization temperature and left inside so that the temperature across the cross section of the specimen became uniform. The specimen was then quickly immersed, with the specimen axis being vertical into the quench tray containing distilled water maintained at 30o C (room temperature). The experiment was repeated in five nanofluids filled and maintaining their temperatures at 30o C. The time–temperature data was recorded for regular interval of time using a computer assisted data acquisition system using Arduino.

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4.1 SELECTION OF MATERIALS The materials selected for the experiment are AISI carbon steel (C-0.14 to 0.20%, Fe98.81 to 99.26%, Mn-0.60 to 0.90%, S-less than 0.04%, P- less than 0.040%. steels are used for low tensile applications. The general thermo-physical properties of AISI carbon steels are as follows. Table 4.1 Thermo-physical properties Material

Thermal Conductivity W/mK

Melting Temperature oC

Density

52

1280

7.9

AISI carbon steel

g/cm3

Fig 4.2 Specimen ASTM A370 (D=16) Table 4.2 ASTM A370 Standard S.No

Material Diameter/Thickness, mm

Dimension, mm D

d

Lc (min)

GE(min)

R

Lt (min)

1

6

6

4.00+0.02 25

25

1

77

2

10

10

6.25+0.03 30

30

5

100

3

10

10

6.25+0.03 30

60

5

160

4

16

16

8.75+0.04 50

50

8

166

5

20& above

20

12.5+0.04 70

60

10

210

32

Table 4.3 Specimen ASTM A370 Specification SYMBOLS AND DESIGNATION D

Gripping end diameter

D

Gauge Diameter

Lc

Parallel length

GE

Gripping end length

R

Transition radius

Lt

Total Length

4.2 NANOFLUID PREPARATION 4.2.1 ALUMINA NANOPARTICLE The following table lists the properties of Alumina Nanoparticles Table 4.4 Nanoparticle Specification Purity

99.8%

Colour

White nanopowder

APS

30-60nm (TEM)

SSA

30-50m2/g

Morphology

Spherical

Density

1.06 g/cm3

4.2.2 PREPARATION OF NANOFLUIDS Two-step method is the most widely used method for preparing nanofluids. Nanoparticles, nanofibers, nanotubes, or other nano materials used in this method are first produced as dry powders by chemical or physical methods. Then, the nano sized powder will be dispersed into a fluid in the second processing step with the help of intensive magnetic force agitation, ultrasonic agitation. Two-step method is the most economic method to produce nanofluids in large scale, because nanopowder synthesis techniques have already been scaled up to industrial productions levels.

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Fig 4.3 Nanofluid preparation

Fig 4.4 Magnetic Stirrer The alumina nanofluids are prepared as follows. The required quantity of the nano powder is measured for needed volume fraction. Then it is mixed with the required quantity of base fluid which is water in this case. This mixture is stirred in a magnetic stirrer for required period and to further improve the stability the stirrer mixture is sonicated for required time period based on the volume fraction of the mixture. The sonication process is carried out at the maximum power of 70% and cycles range at 8-9. Thus the nanofluid is prepared.

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4.3 MUFFLE FURNACE

Fig 4.5 Muffle Furnace A muffle furnace is front-loading box type oven for high-temperature application such as fusing glass, creating enamel coating, ceramics and soldering and brazing articles. They are also used in many research facilities, for example by chemists in order to determine what proportion of a sample is non-combustible and non-volatile. The specimen is placed inside the furnace and heated to recrystallization temperature. 4.4 THERMOCOUPLE A thermocouple is an electrical device consisting of two dissimilar electrical conductors forming electrical junctions at differing temperatures. A thermocouple produces a temperature-dependent voltage as a result of the thermoelectric effect, and this voltage can be interpreted to measure temperature. Thermocouples are a widely used type of temperature sensor. Commercial thermocouples are inexpensive, interchangeable, are supplied with standard connectors, and can measure a wide range of temperatures. In contrast to most other methods of temperature measurement, thermocouples are self-powered and require no external form of excitation. The main limitation with thermocouples is precision; system errors of less than one degree Celsius (°C) can be difficult to achieve. Type K (chromel– alumel) is the most common general-purpose thermocouple with a sensitivity of approximately 41 µV/°C.[10] It is inexpensive, and a wide variety of probes are available in its −200 °C to +1350 °C (−330 °F to +2460 °F) range. Type K was specified at a time when metallurgy was less advanced than it is today, and consequently characteristics may vary considerably between samples. One of the constituent metals, nickel, is magnetic; a characteristic of thermocouples made with magnetic material is that they undergo a deviation in output when the material reaches its Curie point, which occurs for type K thermocouples at 35

around 185 °C. The thermocouple is fitted to the specimen to be heated so the cooling rate can be determined.

Fig 4.6 K-Type thermocouple 4.5 DATA ACQUISITION SYSTEM Data acquisition is the process of sampling signals that measures real world physical condition and converting the resulting samples into digital numeric values that can be manipulated by a computer. Data acquisition system typically convert analog wave form into digital values for processing. The components of the data acquisitions systems include. Sensors that converts physical parameters to electrical signal. Signals conditioning circuitry to convert sensor signals into a form that can be converted to digital values.

Fig 4.7 Data acquisition system setup 36

Fig 4.8 Arduino program

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CHAPTER 5 RESULTS AND DISCUSSION

5.1 EFFECT OF QUENCHING ON MECHANICAL PROPERTIES The effect of Quenching on the mechanical properties (ultimate tensile strength, hardness, toughness, percentage elongation, and percentage reduction) of the samples quenched using nano fluid and water is shown in table.

5.1.1 Mechanical Properties of AISI 1018 steel Table 5.1 Mechanical properties of AISI 1018 steel S.No

Specimen

Tensile

Yield

%

%

Strength

Strength

Elongation

Reduction

N/mm2

N/mm2

Hardness (BHN)

in Area

1

AISI 1018- untreated

480

293

48

72

25

2

AISI 1018- DI

520

320

44

68

28

3

AISI 1018- 0.01 vol%

545

390

40

64

32

4

AISI 1018- 0.02 vol%

603

415

39

69

37

5

AISI 1018- 0.03 vol%

689

487

38

51

45

6

AISI 1018- 0.04 vol%

628

453

38

48

40

7

AISI 1018- 0.05 vol%

595

392

39

70

37

The Tensile strength of the AISI 1018 steel is 480 N/mm2 when it is untreated or in normal condition. when it involves in quenching process its tensile strength gets increased. Tensile strength of the DI water quenched AISI 1018 steel is higher than the untreated, it gets 38

increased till the 0.03 vol% of about 689 N/mm2 and it gets decreased in 0.04 vol% and 0.05 vol% . From this 0.03 vol % of AISI 1018 steel having the higher tensile than the others.

Fig 5.2 Tensile Strength of AISI 1018 steel The yield strength of the AISI 1018 steel is 293 N/mm2 when it is untreated or in normal condition. But the specimen involves in quenching process its tensile strength gets increased. From this 0.03 vol % of AISI 1018 steel having the higher yield strength of about 487 N/mm2 than others volume concentration.

Fig 5.3 Yield Strength of AISI 1018 steel 39

The hardness of the AISI 1018 steel quenched in the different volume concentration is 25, 28, 32, 37, 45, 40, 37 of untreated, DI water, 0.01%, 0.02%, 0.03%, 0.04% and 0.05%. The below graph clearly represent 0.03% volume concentration specimen is having the hardness of very high when comparing with others.

Fig 5.4 Hardness of AISI 1018 steel

. Fig 5.5 Elongation of AISI 1018 steel

40

Elongation of the AISI 1018 steel quenched in the different concentration is less comparing to the untreated specimen. Due to the hardness increases, elongation decreases. This is proved by above graph where quenching in normal untreated water having the higher elongation percentage compared to quenching in nanofluids. The concentrations we experimented with 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, and 0.03% concentration having the lowest of all.

Fig 5.6 Reduction in Area of AISI 1018 steel Percent reduction in area is often used in other engineering equations for stress and strain. The equation takes as input the initial area and the changed area to calculate and return the delta change in the area. When the change in area is due to deforming strain applied to solids, there is no negative value for this concept. No strain results in an expansion of the material. The formula for percent change in area is: PC = (Af - Ai)/Ai Whereas PC is the percent change in area, Af is the final area, Ai is the initial area From the below graph the untreated AISI 1018 steel having the higher percentage of reduction in area and 0.04 vol % having the lowest of all.

41

5.1.2 Micro structure of AISI 1018 carbon steel

Fig 5.7 Microstructure of AISI 1018 steel in 2.5KX

42

Fig 5.8 Microstructure of AISI 1018 steel in 5KX

43

The above images are representing the microstructure of AISI 1018 carbon steel quenched in nanofluids in different concentration of Al2O3 nanoparticles. This having the magnification of 2.5KX and 5KX. For the metallographic analysis, the polished samples were etching in order to reveal the microstructure. Subsequently, the samples were cleaned with alcohol and observed in the metallographic microscope Images with different scales were obtained in order to observe the microstructure and identify the phases involved in each of the thermal treatments, according to ASTM E112 (ASTM E112, 2013) and ASM. The microstructure resulting from the heat treatment of quenching is observed in Fig 5.7 and 5.8 that is, a metal matrix of ferrite and perlite in the steel. This contains martensite and ferrite grain. where a metal matrix of ferrite can be seen, as well as in the limits of grain, perlite. It should be noted that the formation of 100% martensite is only possible in very thin sections, as well as with a rapid cooling. On the other hand, diameter of the order of 2 to 3 µm can be observed in both samples. whereby the control sample is assumed to have a condition of normalized.

44

5.1.3 Energy-dispersive X-Ray spectroscopy of AISI 1018 Energy-dispersive X-ray spectroscopy (EDS, EDX, EDXS or XEDS), sometimes called energy dispersive X-ray analysis (EDXA) or energy dispersive X-ray microanalysis (EDXMA), is an analytical technique used for the elemental analysis or chemical characterization of a sample. It relies on an interaction of some source of X-ray excitation and a sample. Its characterization capabilities are due in large part to the fundamental principle that each element has a unique atomic structure allowing a unique set of peaks on its electromagnetic emission spectrum (which is the main principle of spectroscopy). To stimulate the emission of characteristic X-rays from a specimen, a high-energy beam of charged particles such as electrons or protons (see PIXE), or a beam of X-rays, is focused into the sample being studied. At rest, an atom within the sample contains ground state (or unexcited) electrons in discrete energy levels or electron shells bound to the nucleus. The incident beam may excite an electron in an inner shell, ejecting it from the shell while creating an electron hole where the electron was. An electron from an outer, higher-energy shell then fills the hole, and the difference in energy between the higher-energy shell and the lower energy shell may be released in the form of an X-ray. The number and energy of the X-rays emitted from a specimen can be measured by an energy-dispersive spectrometer. As the energies of the X-rays are characteristic of the difference in energy between the two shells and of the atomic structure of the emitting element, EDS allows the elemental composition of the specimen to be measured.

45

Fig 5.9 EDX Analysis of AISI 1018 steel

46

5.2 RATE OF COOLING 5.2.1 Cooling curve of AISI 1018 steel

Fig 5.10 Cooling curve of AISI 1018 steel

The characteristics of the cooling curves obtained during quenching process, depicts the following: 

When the sample is quenched in DI water, the cooling curve is recorded using Arduino. DI water is taken to avoid impurities and other salt contents. Then the second sample is quenched using 0.01% concentration Al2O3 nanofluid, the cooling curve is recorded. It is observed that when quenching in this concentration the cooling rate is rapid because of uniform distribution of nanoparticle in the nanofluid.



Then the third sample is quenched in 0.02% concentration of Al2O3 nanofluid, in this, the cooling curve lies before water and 0.01% concentration nanofluid. The cooling rate is lower than 0.01% nanofluid and water. This is because of nano particle agglomeration. So the heat transfer is reduced than 0.01% concentration nanofluid.



Same as, all the remaining samples are quenched in 0.03%, 0.04%, 0.05% concentration of Al2O3 nanofluid and the cooling curve is recorded.

47

CHAPTER 6 CONCLUSION The present experiments were conducted to investigate the effect of nanofluids on quenching heat transfer and in the mechanical properties of the AISI 1018 steel. Considering the nanofluids with different concentrations of nanoparticles the heat transfer changes with the concentration change. Some papers show that there is no very significant change in quenching behaviour of water versus the nanofluids. Some papers show that the increase in concentrations of the nanoparticles in the nanofluid decreased the critical heat flux of the nanofluid. The reason for increase in heat transfer characteristics according to the literature was due to repetitive quenching of the same specimen on which nanoparticles had deposited. This deposited nanoparticles helped in reducing the pool boiling and increased the nucleate boiling which effectively transfers heat. The specimen of ASTM A370 standard is to be heated up to recrystallization temperature and quechenced using nanofluids. The change in properties of the specimen due to quenching is to be tested. From the test results, it is inferred that 

The heat treatment of AISI 1018 carbon steel using nanofluid revealed that as the concentration of the nano particle plays a vital role. When the particle concentration increases cooling rate decreases. As the cooling rate decreases the hardness also decreases.



So with increase or decrease in the heat transfer rate, the mechanical properties of the specimens were affected. Nanofluids with 0.03% concentration of nanoparticles enhanced the mechanical properties as observed. On the other hand as the concentration increases the heat transfer decreased leading to less enhancement comparatively.



The reduction in heat transfer can be attributed to the phenomenon of agglomeration of the nanoparticles. Agglomeration of the nanoparticles can be avoided by using surfactant, however the use of surfactant may lead to hindrance to heat transfer due to high temperatures involved in quenching.

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CHAPTER 7 SCOPE OF FUTURE WORK 

An experimental investigation investigation of quenching process can be carried out using various nanoparticles and their effects can be compared with other results.



A study may be conducted to investigate tribiological properties and corrosion resistance using various nanofluids with varying volume concentration percentage.



A study pertaining to mechanical properties of different materials quenched in different hybrid nanofluids.



A numerical modelling can be carried out to investigate components quenched in different nanofluids.

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APPENDIX 1

50

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