design and fabrication of parabolic solar collector …

i

DESIGN AND FABRICATION OF PARABOLIC SOLAR COLLECTOR

AND TO STUDY THE HEAT TRANSFER CHARACTERISTICS OF

ZnO NANOFLUID

(Funded by KSCST)

A Report Submitted to

R.I.T.

Bangalore

For Partial Requirement of Award of Degree of

Bachelor of Engineering in Mechanical Engineering

By

NIKHIL SINGH PUNDIR 1MS13ME108

PAVAN KUMAR A. 1MS13ME120

PAVAN PAYANI 1MS13ME121

PAVAN PRASAD H.G. 1MS13ME122

Under the guidance of

Dr. A.T.Venkatesh

Professor,

Dept. of Mechanical Engineering

R.I.T.

DEPARTMENT OF MECHANICAL ENGINERING

RAMAIAH INSTITUTE OF TECHNOLOGY

(Autonomous institute, Affiliated to VTU)

Bangalore, 560054

ii

May 2017




Bangalore, 560054

CERTIFICATE

This is to certify that the following Students, who were working under our guidance, have

completed their project work as per our satisfaction with the topic “DESIGN AND

FABRICATION OF PARABOLIC SOLAR COLLECTOR AND TO

STUDY THE HEAT TRANSFER CHARACTERISTICS OF ZnO

NANOFLUID”.

By

NIKHIL SINGH PUNDIR 1MS13ME108

PAVAN KUMAR A. 1MS13ME120

PAVAN PAYANI 1MS13ME121

PAVAN PRASAD H.G. 1MS13ME122

Under the guidance of

Dr. A.T.Venkatesh

Professor,

Dept. of Mechanical Engineering

R.I.T.

Signature of

Guide: HOD: Principle:

Dr. A.T.Venkatesh Dr. D. Ramesh Rao Dr. NVR Naidu

iii




Bangalore, 560054

Project Report 2016-2017

DECLARATION

We hereby declare that the entire work embodied in this project has been carried out by us at

RAMAIAH INSTITUTE OF TECHNOLOGY under the supervision ofDr. A.T.Venkatesh.

This report has not been submitted in part or full for the award of any diploma or degree of

this or any other university.

By

NIKHIL SINGH PUNDIR PAVAN KUMAR A.

PAVAN PAYANI PAVAN PRASAD H.G.

iv

ACKNOWLEDGEMENT

The satisfaction and euphoria that accompany a successful completion of any task would be

incomplete without mention of the people who made it possible with constant guidance and

encouragement, crowned our efforts with success.

This project would not have been possible without the support of the management of our

esteemed institution, RAMAIAH INSTITUTE OF TECHNOLOGY for encouraging us to do

this project.

We would like to give special thanks to Dr. NVR Naidu, Principle RAMAIAH INSTITUTE

OF TECHNOLOGY and Dr. D. Ramesh Rao, Head of department, Mechanical engineering

for offering an innovative environment.

We sincerely like to thank Karnataka State Council for Science and Technology (KSCST,

IISc Bangalore) for funding and supporting our project work. This gave us the

encouragement to go ahead and complete the project successfully.

Our heartiest indebtedness to Dr. A.T.Venkatesh, Professor, Dept. of Mechanical Engineering

and Dr. Veeranna B. Nasi, Associate Professor, Dept. of Mechanical Engineering who has

been involved in this project from day one. Their guidance has not been restricted to project

implementation alone but has offered a lot of guidance in the project. They have been

available to us whenever we needed the help and direction.

We would also like to thank K.F.Baby and Jayarame Gowda, Instructors in mechanical

engineering department for his constant support and guidance during our project.

We are extremely thankful to our parents and people who are directly and indirectly

supported us throughout the project at RIT, Bangalore.

v

PROBLEM STATEMENT

Our world is shrinking as we are becoming more connected but the demand of energy is

increasing exponentially. More than 80% of world’s population still depends on conventional

fuels but the problems related to conventional energy sources are, they are non-renewable and

polluting in nature. The burning of fossil fuels produces around 21.3 billion tons of carbon-

dioxide per year but still around 1.2 billion (16% of world’s population) do not have access to

electricity and many more suffer from supply that is of poor quality. Therefore the dire need

of the situation is energy, which is renewable, sustainable, reliable, non-polluting and readily

available.

OBJECTIVE OF THE PROJECT

Many researchers have conducted extensive studies on aluminium oxide and copper oxide

nanoparticles dispersed in water or ethylene glycol base fluids to understand the effect of

these particles on the thermal conductivity of base fluid. Aluminium oxide and copper oxide

nanoparticles are less stable when compared to zinc oxide nanoparticles. Zinc oxide

nanoparticles are lighter and can be easily dispersed in base fluid.

The main objective of our project is

• To enhance the heat transfer in a parabolic trough solar collector by using Zn-O/water

as nanofluid with different volumetric concentrations and flow rates, in free and

forced convection system.

• To determine the empirical correlation for both free and forced convection

vi

ABSTRACT

A solar collector is a device that transforms solar radiation from the Sun into heat, which is

then transferred to working fluid. The use of solar collectors reduces energy costs over time

as they do not use fossil fuels or electricity like that as in traditional water heating. As well as

in domestic settings, a large number of these collectors can be combined in an array and used

to generate electricity in solar thermal power plants.

There are a number of different types of solar collector designs that use the energy of the sun

to heat working fluid. Each design whether a basic blackened flat panel collector or a more

advanced evacuated tube collector all have their own advantages and disadvantages.Parabolic

trough reflector provides a better alternative way in order to generate higher temperatures

with better efficiency. The parabolic trough reflector is a solar energy collector designed to

capture the sun’s direct solar radiation over a large surface area and focus or “concentrate it”

onto a small focal point area, increasing the solar energy received by more than a factor of

two.

Connecting together parabolic troughs to form collector fields requires large areas of land for

the installation. Also, parabolic troughs have a small absorber area and have efficiencies of

around 12% with smaller angle of view.

Convective heat transfer can be enhanced passively by enhancing thermal conductivity of the

fluid. Modern nanotechnology provides new possibilities to enhance heat transfer

performance compared to pure liquids.

Nanofluids are engineered colloidal suspension of Nano meter sized particles called Nano

particles in a base fluid. Metals, oxides, carbides or carbon nanotubes are the general

precursors for nanoparticles. Common base fluids include water, ethylene glycol and oil.

Nanofluids exhibit enhanced thermal conductivity due to large area to volume ratio and high

turbulence properties.

Due to its novel properties nanofluidfind their applications inmany fields of heat transfer,

including microelectronics, fuel cells, pharmaceutical processes, and hybrid-powered

engines, , in grinding, machining ,engine cooling/vehicle thermal management, domestic

refrigerator, chiller, heat exchanger and in boiler flue gas temperature reduction. Knowledge

of the rheological behaviour of Nanofluids is found to be very critical in deciding their

suitability for convective heat transfer applications.

vii

LIST OF FIGURES

1. Fig 1: Path of parallel rays at a parabolic mirror

2. Fig 2: Parabolic trough Parameters

3. Fig 3: Aperture width / focal length vs Rim angle

4. Fig 4: Parabola with Dimensions

5. Fig 5: Final CAD model

6. Fig 6 : Hydraulic circuit

7. Fig 7: Final Setup

8. Fig 8: Parts of parabolic collector

9. Fig 9: Final assembled collector

viii

LIST OF TABLES

Deionized Water Readings

Table 1: Free convection, 1st Trail

Table 2: Free convection, 2nd Trail

Table 3: Forced Convection, 2.2 lit/min

0.4% ZnO nanofluid

Table 4: Free convection



0.2% ZnO nanofluid

Table 7: Free convection



Deionized Water

Table 10: Heat flux (Q) in Watt (W)

Table 11: Heat Transfer Coefficient (h) in W/m2K

0.4% ZnO nanofluid



Table 14: Nusselt number (Nu) vs. Rayleigh number (Ra)

0.2% ZnO nanofluid



Table 17: Nusselt number (Nu) vs. Rayleigh number(Ra)

ix

LIST OF GRAPHS

Deionized Water

Graph 1: Reservoir temperature (T) vs. Time (t)

Graph 2: Heat flux (Q) vs. Time (t)

Graph 3: Heat Transfer Coefficient (h)vs. Time (t)

0.4% ZnO nanofluid




Graph 7: Nusselt number (Nu) vs. Rayleigh number (Ra)

0.2% ZnO nanofluid




Graph 11: Nusselt number (Nu) vs. Rayleigh number (Ra)

Graphs comparing water and nanofluid



x

CONTENTS

1. INTRODUCTION .............................................................................................................................. 1

1.1 HEAT TRANSFER ...................................................................................................................... 2

1.2 SOLAR COLLECTORS ............................................................................................................... 4

1.2.1 Application of solar collectors ............................................................................................... 5

1.3 DIMENSIONLESS NUMBERS................................................................................................... 6

1.4 NANOFLUID ............................................................................................................................... 8

1.4.1 HEAT TRANSFER IN NANOFLUIDS: ............................................................................... 8

1.4.2 SYNTHESIS: ......................................................................................................................... 8

1.4.3 PRODUCTION OF NANOPARTICLES .............................................................................. 8

1.4.4 APPLICATIONS: .................................................................................................................. 9

2. LITERATURE SURVEY ................................................................................................................. 11

3. DESIGNING OF COLLECTOR ...................................................................................................... 13

3.1 Geometry of Parabolic Trough Solar Collector .......................................................................... 14

3.2 Dimensions: ................................................................................................................................ 16

3.3 Constructing the parabola ........................................................................................................... 17

3.4 Final CAD design of the setup .................................................................................................... 17

4. FABRICATION ................................................................................................................................ 18

5. EXPERIMENTATION METHODOLOGY ..................................................................................... 21

5.1 Components: ............................................................................................................................... 22

5.2 Methodology ............................................................................................................................... 23

6. FORMULAE USED ......................................................................................................................... 25

7. OBSERVATION .............................................................................................................................. 29

7.1 Tabulation of Deionised water .................................................................................................... 30

7.2 Tabulation of 0.4% ZnO nanofluid ............................................................................................. 32

7.3 Tabulation of 0.2% ZnO Nanofluid ............................................................................................ 34

xi

8. CALCULATION .............................................................................................................................. 36

8.1 Calculations of water .................................................................................................................. 37

8.2 Calculations of 0.4% ZnO nanofluid .......................................................................................... 38

a) Nanofluid properties ............................................................................................................. 38

b) Dimensionless numbers ........................................................................................................ 39

8.3 Calculations of 0.2% ZnO nanofluid .......................................................................................... 42

a) Nanofluid properties ............................................................................................................. 42

b) Dimensionless numbers ........................................................................................................ 43

9. RESULTS ......................................................................................................................................... 46

9.1 TABULATION OF DEIONISED WATER ............................................................................... 47

9.2 TABULATION OF 0.4% ZnO NANOFLUID ........................................................................... 48

9.3 TABULATION OF 0.2% ZnO NANOFLUID ........................................................................... 50

9.4 Graphs of deionised water .......................................................................................................... 52

9.5 Graphs of 0.4% ZnO nanofluid ................................................................................................... 54

9.6 Graphs of 0.2% ZnO nanofluid ................................................................................................... 56

9.7 Graphs comparing nanofluid and water ...................................................................................... 58

PROJECT OUTCOMES AND CONCLUSIONS ................................................................................ 59

FUTURE SCOPE.................................................................................................................................. 60

REFERENCES ..................................................................................................................................... 61

1

CHAPTER 1

INTRODUCTION

2

INTRODUCTION

1.1HEAT TRANSFER

Heat transfer is the exchange of thermal energy between physical systems. The rate of

heat transfer is dependent on the temperatures of the systems and the properties of the

intervening medium through which the heat is transferred.

The fundamental modes of heat transfer are conduction, convection and radiation.

CONDUCTION

Conduction is the mode of heat transfer occurs from one part of a substance to another part of

within the substance itself or with another substance which is placed in physical contact. In

conduction, there is no noticeable movement of molecules. The heat transfer occurs here by

the two mechanisms:

1. By the transfer of free electrons.

2. The atoms and molecules having energy will pass that energy they have with their

adjacent atoms or molecules by means of lattice vibrations.

Fourier Law of Conduction:

𝑄 = −𝐾𝐴 𝑑𝑇

𝑑𝑥

Where: Q is the heat flow rate by conduction

K is the thermal conductivity of the material

A is the cross sectional area normal to direction of heat flow and

𝑑𝑇

𝑑𝑥is the temperature gradient of the section.

CONVECTION:

Convective heat transfer occurs due to actual movement of molecules and heat is carried out

by transfer of one fraction of the fluid to the remaining portion. Since movement of particles

constitutes convection, it is the macro form of heat transfer. Also convection is only possible

in fluids where the particles can moved easily and the rate of convective heat transfer

depends on the rate of flow to a great extent. Convection can be of two types:

1. Natural convection: In this type of convection, the movement of particles which

constitutes convection occurs by the variation in densities of the fluids. As we already

know, as temperature increases, the density decreases and this variation in density will

force the fluid to move through the volume. This cause convection to occur.

3

2. Forced Convection: The difference between natural convection and forced

convection is that in forced convection, a work is done to make movement in the

fluid. This is done using a pump or blower.

Newton’s Law of Cooling:

Q = h A (Ts-T∞)

Where: Ts is the surface temperature

T∞is the fluid temperature

h is the heat transfer coefficient

RADIATION

Radiation is the third mode of heat transfer. This mode of heat transfer doesn’t require any

medium to occur. Every matter having a temperature above absolute zero will emit energy in

the form of electromagnetic waves and called radiation. It is the same way by which the

energy of the sun reaches us.

The Stefan-Boltzmann equation, which describes the rate of transfer of radiant energy, is as

follows for an object in a vacuum:

𝑄 = 𝜖𝜎(T4)

Where, Q is the heat flux, ε is the emissivity (unity for a black body), σ is the Stefan-

Boltzmann constant, and T is the absolute temperature (in Kelvin or Rankin).

4

1.2 SOLAR COLLECTORS

“Solar collector is a mechanical device which captures the radiant solar energy for use as a

source of energy for the heating of water or the production of electricity.”

There are 4 main categories of Solar Collectors:

● Low Temperature Unglazed ● Concentrating ● Flat Plate ● Evacuated Tube

1. Low Temperature Unglazed Collectors

Consists of black colour matting or tubes made from rubber or plastic based materials.If it is

not insulated it can't efficiently operate in cooler conditions or when hot water (showering

temperature) is required. They are often referred to as "unglazed" as they don’t have a glass

cover like flat plate or evacuated tube collectors.

2. Flat Plate Collectors

The design is very simply an insulated box with an absorber sheet welded to copper pipe

through which the heat transfer liquid circulates through. No insulation above the absorber is

an inherent disadvantage of the design and leads to high heat loss. This heat loss means flat

plates are unable to deliver hot efficiently at higher temperatures (>70oC / 160

oF), and

performance is greatly reduced in cold weather.

3. Evacuated Tube Collectors

Comprised of an array of single or twin wall glass tubes with a vacuum that provides

excellent insulation against heat loss. The design is very similar to a glass hot water flask

used to keep hot water. Single wall evacuated tubes normally have a fin that has the absorber

coating, similar to that used in the flat plate collector. Twin wall evacuated tubes have

absorber coating on the inner tube and the space between the two tubes is “evacuated” to

form the vacuum.

4. Concentrating Collectors

A concentrating collector uses mirrors to concentrate the sunlight onto an absorber tube or

panel, allowing much higher temperatures to be reached. Such collectors normally require 1

or 2 axis tracking to follow the sun and ensure optimal reflection angle. Due to the size and

complexity of these systems they are primarily used for large scale projects.

Parabolic trough collectors

A parabolic trough consists of a linear parabolic reflector that concentrates light onto a

receiver positioned along the reflector's focal line. The receiver is a tube positioned directly

above the middle of the parabolic mirror and filled with a working fluid. The reflector

follows the sun during the daylight hours by tracking along a single axis. A working fluid

5

(e.g. water) is heated to 150–350 °C (300–660 °F) as it flows through the receiver and is then

used as a heat source for a power generation system.

Classification of solar collectors according to concentration degree

Category Example Temperature range,

ºC

Efficiency, %

No concentration Flat-plate

Evacuated tube

75-200 30 – 50

Medium concentration Parabolic cylinder 150 - 500 50 – 70

High concentration

Parabodial

1500 and more 60 – 75

1.2.1 Application of solar collectors

Solar energy can be used by three processes chemical, electrical and thermal.

1. Chemical process, through photosynthesis, maintains life on earth by producing food

and converting CO2 to O2.

2. Electrical process, using photovoltaic converters, provides power for spacecraft and is

used in many terrestrial applications.

3. Thermal process, can be used to provide much of the thermal energy required for

solar water heating and building heating.

6

1.3DIMENSIONLESS NUMBERS

1. Reynolds Number:

The dimensionless number that gives the measure of the ratio of inertial forces to viscous

forces for a particular fluid stream.

Re =ρUL

µ=

UL

V

Where:

Re = Reynolds number ρ = Density of the fluid u = mean velocity of fluid object

L = is a characteristic length or linear dimension (internal diameter for flow in pipe or sphere

moving in pipe, length or width for aircraft or ship moving in fluid, equivalent diameter for

rectangular pipe and non-spherical object in fluid)

µ = viscosity of fluid

Physical significance

1. Reynolds number gives the information, whether the flow is inertial or viscous force

dominant. It tells us whether the flow is laminar or turbulent.

2. If Re is smaller, the fluid will be more viscous & less inertial forces will exist in the

fluid inverse will be true for greater value of Re.

2. Prandtl Number

The dimensionless number that gives the ratio between momentum diffusivity to thermal

diffusivity.

Pr =v

α=

cpµ

k

Where:

Pr = Prandtl number ν = momentum diffusivity α = thermal diffusivity µ = viscosity

ρ = density k = thermal conductivity cp = specific heat capacity at constant pressure


1. If a fluid has low Pr, its thermal diffusivity will be higher and momentum diffusivity

will be lower.

2. It depends on only the state of fluid and the type of fluid, it is independent of any

length dimension (as Re depends).

3. Prandtl number gives the information about the type of fluid. Also it provides

the information about the thickness of thermal and hydrodynamic boundary layer.

https://image.slidesharecdn.com/somedimensionlessnumbersinheattransfer-130415115400-phpapp02/95/some-dimensionless-numbers-in-heat-transfer-2-638.jpg?cb=1366026877

7

3. Nusselt Number

The dimensionless number which gives the ratio of convective heat transfer across (normal

to) the boundary layer of the fluid to the conductive heat transfer.

Nu =hl

k

Where:

Nu = Nusselt number h = convective heat transfer coefficient of fluid

k = thermal conductivity of fluid

L = characteristic length (outer diameter of cylinder, length of vertical plate, diameter of

sphere, volume of fluid object per surface area for complex shapes).


Nusselt number gives the comparison between the conduction and convection heat

transfer rates.

4. Grashof Number

The dimensionless number which gives the ratio of product of inertia force and buoyancy

force to the square of viscous force.

Controls the ratio of length scale to natural convection boundary layer thickness

Gr =gρ2βΔTL3

µ2

Where

Gr- Grashof Number β =inverse of temperature in kelvin.

ΔT- change in temperature. ρ = Density of the fluid. µ = viscosity.


1. Higher Grashoff number means high buoyancy which means higher flow movement.

2. Grashoff number is significant in cases of fluid flow due to natural convection. This

means that the fluid motion is caused not due to an external source but due to the

difference in densities between two points.

3. Just as Reynolds number is used to categorize the flow (laminar, turbulent, transition)

in case of forced convection, Grashoff number is used in case of natural convection.

8

1.4 NANOFLUID

A nanofluid 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 nanofluid are typically made of metals, oxides, carbides, or carbon nanotubes. Common

base fluids include water, ethylene glycol and oil.

Due to its novel properties nanofluid find their applications in many fields of heat transfer,

including microelectronics, fuel cells, pharmaceutical processes, and hybrid-powered

engines, , in grinding, machining ,engine cooling/vehicle thermal management, domestic

refrigerator, chiller, heat exchanger and in boiler flue gas temperature reduction. They have

better thermal conductivity and the convective heat transfer coefficient as that of the fluid in

which it is made of. Knowledge of the rheological behaviour of nanofluids is found to be

very critical in deciding their suitability for convective heat transfer applications

1.4.1 HEAT TRANSFER IN NANOFLUIDS:

Suspended nanoparticles in conventional fluids, called nanofluids, have been the subject of

intensive study worldwide since pioneering researchers recently discovered the anomalous

thermal behaviour of these fluids. Existing theories could not explain the enhanced thermal

conductivity of these fluids with small-particle concentration. Micrometre-sized particle-fluid

suspensions exhibit no such dramatic enhancement. This difference has led to studies of other

modes of heat transfer and efforts to develop a comprehensive theory.

1.4.2 SYNTHESIS:

Nanofluids are produced by several techniques they are,

1. Direct Evaporation (1 step)

2. Gas condensation/dispersion (2 steps)

3. Chemical vapour condensation (1 step)

4. Chemical precipitation (1 step)

Although stabilization can be a challenge, on-going research indicates that it is possible.

Nano-materials used so far in nanofluid synthesis include metallic particles, oxide particles,

carbon nanotubes, graphene nano-flakes and ceramic particles.

1.4.3 PRODUCTION OF NANOPARTICLES

Production of nanoparticles can be divided into two main categories, namely, physical

synthesis and chemical synthesis. The common production techniques of nanofluids as

follows.

Physical Synthesis: Mechanical grinding, inert-gas-condensation technique.

Chemical Synthesis: Chemical precipitation, chemical vapour deposition, micro-emulsions,

spray pyrolysis, thermal spraying.

https://en.wikipedia.org/wiki/Nanometer

https://en.wikipedia.org/wiki/Nanoparticle

https://en.wikipedia.org/wiki/Colloid

https://en.wikipedia.org/wiki/Fluid

https://en.wikipedia.org/wiki/Carbon_nanotube

https://en.wikipedia.org/wiki/Ethylene_glycol

https://en.wikipedia.org/wiki/Thermal_conductivity

https://en.wikipedia.org/wiki/Heat_transfer_coefficient

https://en.wikipedia.org/wiki/Rheology

9

Production of Nanofluids-There is mainly two methods of nanofluid production, namely,

two-step technique and one-step technique.

In one-step technique, combines the production of nanoparticles and dispersion of

nanoparticles in the base fluid into a single step. There are some variations of this technique.

In one of the common methods, named direct evaporation one-step method, the Nano-fluid is

produced by the solidification of the nanoparticles, which are initially gas phase, inside the

base fluid. The dispersion characteristics of Nano-fluids produced with one step techniques

are better than those produced with two-step technique. The main drawback of one-step

techniques is that they are not proper for mass production, which limits their

commercialization.

In the two-step technique, the first step is the production of nanoparticles and the second step

is the dispersion of the nanoparticles in a base fluid. Two-step technique is advantageous

when mass 4 production of Nano-fluids is considered, because at present, nanoparticles can

be produced in large quantities by utilizing the technique of inert gas condensation. The main

disadvantage of the two-step technique is that the nanoparticles form clusters during the

preparation of the Nano-fluid which prevents the proper dispersion of nanoparticles inside the

base fluid.

1.4.4 APPLICATIONS:

Nanofluids are primarily used for their enhanced thermal properties as coolants in heat

transfer equipment such as heat exchangers, electronic cooling system (such as flat plate) and

radiators. Heat transfer over flat plate has been analysed by many researchers. However, they

are also useful for their controlled optical properties. Graphene based nanofluid has been

found to enhance polymerase chain reaction efficiency. Nanofluids in solar collectors is

another application where Nanofluids are employed for their tuneable optical properties.

https://en.wikipedia.org/wiki/Nanofluids_in_solar_collectors

10

CHAPTER 2

LITERATURE SURVEY

11

LITERATURE SURVEY

Although the costs of solar energy have gone down and continue to fall, the levelized costs of

solar energy are still much higher than conventional energy. The levelized cost of solar

concentrated power (CSP) is four times than that of supercritical coal without carbon capture

and storage [1].

Cost is one of the major factors inhibiting development of trough collectors. Increasing the

efficiency of the solar collector systems can in part alleviate this problem. Many attempts

have been made to improve the performance of these systems [2–5].

Heat transfer can be enhanced by increasing the thermal conductivity of the heat transfer fluid

(HTF). Thermal conductivity of metallic particles, metallic oxides and nanotubes is relatively

higher than that of liquids. Addition of fine particles into heat transfer fluids (thus forming

nanofluids) can significantly increase the heat transfer rate [6–8].

Many studies have been carried out on the performances of PTCs using synthetic oils and

nanofluids as heat transfer fluid. The latter are formed by suspending nanoparticles (1nm-

100nm) in a traditional heat transfer fluid. These so-called nanofluids display good thermal

properties compared with fluids conventionally used [9]

Choi is the first who used the nanofluid term at the 1995 annual winter meeting of the

American Society of Mechanical Engineers as he presented the possibility of doubling the

convection heat transfer coefficients using nano-fluids. In addition to this work, researchers

in Japan and Germany have published articles concerning similar fluids (Massuda et al 1993,

Grimm 1993) [10].

Heris et al conducted experiments with the Al2O3 and CuO nanoparticles suspended in water

under laminar flow. They found that the heat transfers could increase of about 40% while the

improvement of thermal conductivity doesn’t exceed 15% [11].

Tyagi et al studied theoretically the efficiency of a low-temperature nanofluid-based direct

absorption solar collector using a mixture of water and aluminium, where the nanoparticle

volume fraction varies from 0.1 % to 5%. They found that the efficiency increases

significantly for low volume fractions of nanoparticles, whereas for values higher than 2%

the efficiency levels off. They also investigated the size of nanoparticles (1nm-20nm) at the

volume fraction of 0.8%: the efficiency increases slightly with increasing size of

nanoparticles [12].

In 2010, Otanicar et al studied both experimentally and numerically the effect of different

nanofluids (carbon nanotubes, graphite and silver) on the performances of a micro scale

direct absorption solar collector. Their results showed that the suspension of a slight amount

(less than 0.5%) of nanoparticles improves remarkably the efficiency. However, for a volume

fraction higher than 0.5%, the efficiency remains constant and even begins to decrease with

12

increasing volume fraction. They also found that the efficiency increases with decreasing size

of nanoparticles [13].

Khular et al investigated theoretically in 2012 thermal efficiency of a nanofluid-based direct

absorption solar parabolic trough collector. They used aluminium nanoparticles at the volume

fraction of 0.05% suspended in the base fluid Therminol-VP1. Their results showed that

thermal efficiency increases compared to a conventional PTC by 10 % at low temperatures

and by 5% at high temperatures. [14]

13

CHAPTER 3

DESIGNING OF COLLECTOR

14

3.1 Geometry of Parabolic Trough Solar Collector

Parabolic Trough Solar Collector (PTSC) which is also called cylindrical parabolic collector

employs linear imaging concentration. These collectors are comprised of a cylindrical

concentrator of parabolic cross – sectional shape, and a circular cylindrical receiver located

along the focal line of the parabola.

Basically it consists of (i) a parabolic reflector of about 1-6 m aperture width, (ii) an absorber

tube made of steel or copper with diameter 1-5 cm and coated with selective coating, and (iii)

a concentric tubular glass cover surrounding receiver with a gap of about 1- 2 cm.The

cylindrical parabolic reflector focuses all the incident sunlight onto a metallic tubular receiver

placed along its length in the focal plane. The heat transfer fluid is allowed to flow through

the receiver.

Radiation concentration at a parabolic trough

Parabolic troughs have a focal line, which consists of the focal points of the parabolic cross-

sections. Radiation that enters in a plane parallel to the optical plane is reflected in such a

way that it passes through the focal line.

Fig 1 : Path of parallel rays at a parabolic mirror

The following four parameters are commonly used to characterize the form and size of a

parabolic trough: trough length, focal length, aperture width, i.e. the distance between

one rim and the other, and rim angle, i.e. the angle between the optical axis and the line

between the focal point and the mirror rim:

15

Fig 2: Parabolic trough Parameters

The focal length, i.e. the distance between the focal point and the vertex of a parabola, is a

parameter that determines the parabola completely

The rim angle, i.e. the angle between the optical axis and the line between the focal point and

the mirror rim, has the interesting characteristics that it alone determines the shape of the

cross-section of a parabolic trough. That means that the cross-sections of parabolic troughs

with the same rim angle are geometrically similar. The cross-sections of one parabolic trough

with a given rim angle can be made congruent to the cross-section of another parabolic

trough with the same rim angle by a uniform scaling (enlarging or shrinking). If only the

shape of a collector cross-section is of interest, but not the absolute size, then it is sufficient

to indicate the rim angle. Two of the three parameters rim angle, aperture width and focal

length are sufficient to determine the cross-section of a parabolic trough completely, i.e.

shape and size. This also means that two of them are sufficient to calculate the third one.

Figure 3: Aperture width / focal length vs Rim angle

16

Geometrical parameters of real parabolic troughs

We see that the rim angle should neither be too small nor too large. The rim angle is related

to the distance between the different parts of the mirrors and the focal line.

The rim angle is a very important constructive trait of collectors. For instance, it has an

effect on the concentration ratio and on the total irradiance per meter absorber tube [W/m].

Qualitatively, we can understand in the following way that there must be some ideal rim

angle range and that it should neither be too small nor too large. If the rim angle is very

small, then the mirror is very narrow and it is obvious that a broader mirror (with a larger rim

angle) would enhance the power projected onto the absorber tube. If the rim angle is very big,

then the way of the reflected radiation from the outer parts of the mirror is very long and the

beam spread is very big, hencereducingthe concentration ratio. A mirror with a smaller rim

angle and the same aperture width would permit a higher concentration ratio.

Last but not least there is an economical aspect that limits the reasonable rim angle: At high

rim angles the outer parts have a low contribution to the energy yield in relation to the mirror

area. That means a high investment is necessary, which contributes only little to the energy

yield. So, there are several criteria, which together determine the rim angle.

3.2 Dimensions:

After conducting more research on solar energy and solar collection, the decision

was made to have:

Trough Length = 1m, So that data can easily be extrapolated for multiple parabolic troughs

placed together as a single unit.

Absorber tube diameter = 1.27cm,

Parabola angle = 120deg, to obtain greater viewing area.

Aperture width = 0.7m

Focal length = 0.303221m

Equation of parabola:y2 = 1.21284 x

Concentration ratio = 55.1181

17

3.3 Constructing the parabola: (by tangent method)

Fig 4: Parabola with Dimensions

3.4 Final CAD design of the setup

Fig 5: Final CAD model

18

CHAPTER 4

FABRICATION

19

The parabolic collector is a closed box composing of following principle parts

Fig 8: Parts of parabolic collector

The basic materials generally used for construction of the collector are galvanized iron sheet,

stainless steel sheet, mirrors and acrylic mirror sheet of late. The reason for choosing acrylic

mirror sheet over others were due to its ease of handling, higher reflectiveness and cost

effectiveness

To create the reflecting surface fist we fabricated the supporting structure. To fabricate the

supporting structure we used metal strips of 25mm width and 3mm thickness. The strips were

cut and hammered into required shape of the parabola.

Then the ¾ inch square pipe was cut according to the design to form the supports for the side

plates and top plate. 1 inch square pipe was cut to form the bottom support of the parabolic

trough. Edges of all the pieces were ground and welded according to the design.

The holes on the top supports were drilled to fix acrylic transparent sheet. The acrylic mirror

sheet was fixed onto the supporting structure by means of araldite. To fix the copper pipe

exactly on the focus, a mechanism was created by means of nuts, bolts and PVC pipe. It is hard for a manually made collector to match the efficiency lifetime cost effectiveness

and water tightness standard of an industrial product.

20

Fig 8: Final assembled collector

21

CHAPTER 5

EXPERIMENTATION METHODOLOGY

22

5.1 Components:

1. Parabolic trough collector

2. Nanofluid / Water tank (Reservoir)

3. Water tank (Sink)

4. Connecting tubes

5. Copper Tubes

6. Copper Fittings

7. Thermocouple

8. DigitalRead-out meter

9. Pump

10. Plastic tube (Manometer)

11. Thermometer

12. Nanofluid (Concentration - 0.2% and 0.4%)

Fig 6 : Hydraulic circuit

23

5.2 Methodology

Forced Convection: Forced convection occurs when the streams and currents in the fluid are

induced by external means such as fans, stirrers, and pumps creating an artificially induced

convection current.

Method:

Different components are connected accordingly.

The pump is switched on and any leakage is checked

The ball valve is adjusted to required position and flow rate is measured.

Initial temperatures of fluid in reservoir and sink tanks are measured.

The temperature of fluids is again measured at regular interval.

The experiment is conducted for 6-8 hrs.

For next trail, the position of ball valve is changed to vary the flow rate.

The experiment is repeated and observations are tabulated.

Free Convection: In this type of convection, the movement of particles which constitutes

convection occurs by the variation in density of the fluid. As we already know, as

temperature increases, the density decreases and this variation in density will force the fluid

to move through the volume. This causes convection to occur.

Method:

Different components are connected accordingly.

Both ball valves should be in fully open position.

Initial temperatures of fluid in reservoir and sink tanks are measured.

The temperatures of fluids are again measured at regular interval.

The experiment is conducted for 6-8 hrs.

The experiment is repeated and observations are tabulated.

Both forced and free convection is carried out for different fluids and at required flow rates.

24

Fig 7: Final Experimental Setup

25

CHAPTER 6

FORMULAE USED

26

1. 𝑄 =𝑚∗𝐶𝑝∗(𝑇𝑜−𝑇𝑖)

𝑡

Where,

Q = Heat in W

m = Mass of water (5 kg)

Cp = Specific heat of water (4184 J/kg-K )

To = Outlet temperature of water

Ti = Inlet temperature of water

t = Time taken (1 hour)

2. 𝑄 = 𝑕 ∗ 𝐴 ∗ (𝑇𝑤 − 𝑇𝑏)

Where,

Q = Heat in W

h = Heat transfer coefficient in W/m2K

A = πdL = Area of the receiver pipe (d = 0.5 inch; L = 1m)

Tw = Surface temperature of receiver pipe

𝑇𝑏 =𝑇𝑖 + 𝑇𝑜

2

3. VOLUME FRACTION (𝝋𝒁𝒏𝑶)

𝜑𝑍𝑛𝑂 =

𝑊𝑍𝑛𝑂𝜌𝑍𝑛𝑂


+𝑊𝑏𝑓

𝜌𝑏𝑓

[16]

𝑊 = 𝑤𝑒𝑖𝑔𝑕𝑡 𝑜𝑓 𝑡𝑕𝑒 𝑠𝑢𝑏𝑠𝑡𝑎𝑛𝑐𝑒

𝜌 = 𝑑𝑒𝑛𝑠𝑖𝑡𝑦 𝑜𝑓 𝑡𝑕𝑒 𝑠𝑢𝑏𝑠𝑡𝑎𝑛𝑐𝑒

ZnO = Zinc Oxide

bf = base fluid

4. DENSITY OF NANOFLUID (𝝆𝒏𝒂𝒏𝒐)

𝜌𝑛𝑎𝑛𝑜 = 1 − 𝜑𝑍𝑛𝑂 𝜌𝑏𝑓 + 𝜑𝑍𝑛𝑂𝜌𝑍𝑛𝑂 [16]

27

5. SPECIFIC HEAT ( 𝑪𝒑𝒆𝒇𝒇 )

𝐶𝑝𝑒𝑓𝑓 =

1−𝜑𝑍𝑛𝑂 𝜌𝐶𝑍𝑛𝑂 𝑏𝑓 +𝜑𝑍𝑛𝑂 (𝜌𝐶𝑝 )𝑍𝑛𝑂

𝜌𝑛𝑎𝑛𝑜 [16]

6. THERMAL CONDUCTIVITY (𝑲𝒆𝒇𝒇)

𝐾𝑒𝑓𝑓 = 𝐾𝑏𝑓 ∗ 𝐾𝑍𝑛𝑂 +2𝐾𝑏𝑓 +2𝜑(𝐾𝑍𝑛𝑂 +𝐾𝑏𝑓 )

𝐾𝑍𝑛𝑜 +2𝐾𝑏𝑓 −(𝐾𝑍𝑛𝑂 − 𝐾𝑏𝑓 )𝜑 (Maxwell’s Equation) [16]

𝐾𝑍𝑛𝑂 = 50 𝑊𝑚𝐾

𝐾𝑤𝑎𝑡𝑒𝑟 = 0.6305 𝑊 𝑚𝐾

7. DYNAMIC VISCOSITY ( 𝝁)

𝜇 = (1 + 2.5𝜑𝑍𝑛𝑂 )𝜇𝑏𝑓 [16] [17](𝐸𝑖𝑛𝑠𝑡𝑒𝑖𝑛′𝑠 𝐸𝑞𝑢𝑎𝑡𝑖𝑜𝑛)

8. REYNOLDS NUMBER:

𝑅𝑒 =ρUL

µ=

𝑈𝐿

𝑉

Re - Reynolds number

ρ - Density of the fluid

u - Mean velocity of fluid object

L - Characteristic length

µ - Dynamic Viscosity of fluid

9. PRANDTL NUMBER

𝑃𝑟 =𝑣

α=

µ𝑐𝑝𝑘

Pr - Prandtl number

ν - Momentum diffusivity of the fluid

α - Thermal diffusivity of the fluid

µ - Dynamic Viscosity of the fluid

ρ - Density of the fluid

k - Thermal conductivity of the fluid

Cp - specific heat capacity at constant pressure.

https://image.slidesharecdn.com/somedimensionlessnumbersinheattransfer-130415115400-phpapp02/95/some-dimensionless-numbers-in-heat-transfer-2-638.jpg?cb=1366026877

28

10. NUSSELT NUMBER

𝑁𝑢 =𝑕𝑙

𝑘

Nu - Nusselt number

h - Convective heat transfer coefficient of fluid

k - Thermal conductivity of fluid

L - Characteristic length

11. GRASHOF NUMBER

𝐺𝑟 =𝑔ρ2βΔT𝐿3

µ2

Where

Gr- Grashof Number

β - Inverse of temperature in kelvin.

ΔT -Change in temperature.

ρ - Density of the fluid.

µ -Dynamic Viscosity.

29

CHAPTER 7

OBSERVATION

30

7.1 Tabulation of Deionised water

1. Day 1: 19 April 2017

Fluid: Deionized Water

Method: Free convection

2. Day 2: 20 April 2017



Sl. No. Time Temperature(oC)

1 10:00 am 27

2 10:30 am 29

3 11:00 am 31

4 11:30 am 32

5 12:00 pm 33

6 12:30 pm 34

7 1:00 pm 35

8 1:30 pm 36

9 2:00 pm 36

10 2:30 pm 36.5

11 3:00 pm 36.5

12 3:30 pm 37

13 4:00 pm 37.5


1 10:00 am 28

2 10:30 am 28

3 11:00 am 31

4 11:30 am 32

5 12:00 pm 34

6 12:30 pm 35

7 2:00 pm 35

8 2:40 pm 35.5

9 3:00 pm 36

10 3:30 pm 36.5

11 3:45 pm 37

12 4:00 pm 37.5

31

3. Day 3: 21 April 2017


Method: Forced convection

Flow rate: 2.2 litres/min.


1 10:15 am 28

2 11:00 am 31

3 11:20 am 34

4 11:45 am 35.5

5 12:00 pm 37

6 12:15 pm 37.5

7 12:30 pm 38

8 12:45 pm 39

9 1:00 pm 39.5

10 1:15 pm 39.5

11 1:35 pm 40

12 1:45 pm 40

13 2:00 pm 40.5

14 2:15 pm 40.5

15 2:30 pm 41

16 2:45 pm 41.5

17 3:00 pm 40.5

32

7.2 Tabulation of 0.4% ZnO nanofluid

4. Day 4: 22 April 2017

Fluid: ZnO Nanofluid 0.4% conc


Sl. No. Time Temperature of

reservoir(oC)

Temperature of

collector(oC)

1 10:00 am 28 29

2 10:30 am 34 39

3 11:00 am 38 45

4 11:30 am 41 51

5 12:00 pm 43 55

6 12:30 pm 44.5 59

7 1:00 pm 45.5 63

8 1:30 pm 47 67.5

9 2:00 pm 48.5 71

10 2:30 pm 49.5 73

11 3:00 pm 50 74.5

12 3:30 pm 50.5 76

13 4:00 pm 50.5 76.5

14 4:30 pm 49.5 76

5. Day 5: 24 April 2017



Flow rate: 2.2 litres/min.


reservoir(oC)

Temperature of

collector(oC)

1 10:00 am 29 29

2 10:30 am 34.5 39.5

3 11:00 am 38.5 45

4 11:30 am 42 51.5

5 12:00 pm 43.5 55

6 12:30 pm 45 59

7 1:00 pm 46.5 63.5

8 1:30 pm 48 67.5

9 2:00 pm 49 71

10 2:30 pm 50.5 73.5

11 3:00 pm 51 74.5

12 3:30 pm 51.5 75

13 4:00 pm 52 75.5

14 4:30 pm 51 75

33

6. Day 6: 27 April 2017



Flow rate: 0.66 litres/min


reservoir(oC)

Temperature of

collector(oC)

1 10:00 am 29 29

2 10:30 am 34.5 38.5

3 11:00 am 38.5 44

4 11:30 am 42 49.5

5 12:00 pm 43.5 54

6 12:30 pm 45 57

7 1:00 pm 46.5 60.5

8 1:30 pm 47.5 64.5

9 2:00 pm 48 69

10 2:30 pm 48.5 71.5

11 3:00 pm 49 72.5

12 3:30 pm 50 73

13 4:00 pm 50.5 73

14 4:30 pm 50.5 73

34

7.3 Tabulationof 0.2% ZnO Nanofluid

7. Day 7: 28 April 2017




reservoir(oC)

Temperature of

collector(oC)

1 10:00 am 28 29

2 10:30 am 34 39

3 11:00 am 37 45

4 11:30 am 40 51

5 12:00 pm 42.5 55

6 12:30 pm 43.5 59

7 1:00 pm 44.5 63

8 1:30 pm 46 67.5

9 2:00 pm 47 71

10 2:30 pm 47.5 73

11 3:00 pm 48 74.5

12 3:30 pm 48.5 76

13 4:00 pm 49 76.5

14 4:30 pm 49.5 76

8. Day 8: 2 May 2017





reservoir(oC)

Temperature of

collector(oC)

1 10:00 am 27 28

2 10:30 am 32.5 38.5

3 11:00 am 36.5 45

4 11:30 am 39 52

5 12:00 pm 41.5 55.5

6 12:30 pm 43.5 58.5

7 1:00 pm 45 64.5

8 1:30 pm 46.5 66.5

9 2:00 pm 47.5 70.5

10 2:30 pm 48 73.5

11 3:00 pm 49 74.5

12 3:30 pm 49.5 74.5

13 4:00 pm 49.5 74

35

9. Day 9: 3 May 2017





reservoir(oC)

Temperature of

collector(oC)

1 10:00 am 27 28

2 10:30 am 32 39.5

3 11:00 am 35.5 44

4 11:30 am 38 50.5

5 12:00 pm 40.5 54

6 12:30 pm 42 58

7 1:00 pm 44 63

8 1:30 pm 45.5 65.5

9 2:00 pm 46 68

10 2:30 pm 47 71

11 3:00 pm 48.5 72.5

12 3:30 pm 49 74

13 4:00 pm 48.5 73.5

36

CHAPTER 8

CALCULATION

37

8.1 Calculations of water

1. 𝑚 =𝑉

𝜌

𝑚 =5000

1000

𝒎 = 𝟓 𝒌𝒈

2. 𝑄 =𝑚∗𝐶𝑝∗(𝑇𝑜−𝑇𝑖)

𝑡

𝑄 =5 ∗ 4187 ∗ (31 − 28)

3600

𝑸 = 𝟏𝟕. 𝟒𝟑𝟑 𝑾

3. 𝑄 = 𝑕 ∗ 𝐴 ∗ (𝑇𝑤 − 𝑇𝑏)

𝑕 =𝑄

𝐴 ∗ (𝑇𝑤 − 𝑇𝑏)

𝑕 =17.433

0.039898 ∗ (37 − 33)

𝒉 = 𝟏𝟒𝟓. 𝟔𝟒𝟗 𝑾/𝒎𝟐𝑲

38

8.2 Calculations of 0.4% ZnO nanofluid

a) Nanofluid properties

1. 𝜑𝑍𝑛𝑂 =



+𝑊𝑏𝑓

𝜌𝑏𝑓

𝜑𝑍𝑛𝑂 =

112.2

5610112.2

5610+

4980

992.2

𝝋𝒁𝒏𝑶 = 𝟎. 𝟎𝟎𝟑𝟗𝟕𝟗𝟒𝟗

2. 𝜌𝑛𝑎𝑛𝑜 = 1 − 𝜑𝑍𝑛𝑂 𝜌𝑏𝑓 + 𝜑𝑍𝑛𝑂𝜌𝑍𝑛𝑂

𝜌𝑛𝑎𝑛𝑜 = 1 − 0.00397949 992.2 + (0.00397949 ∗ 5610)

𝝆𝒏𝒂𝒏𝒐 = 𝟏𝟎𝟏𝟎.𝟓𝟕𝟔𝟒𝟖𝟗 𝒌𝒈/𝒎𝟑

3. 𝐶𝑝𝑒𝑓𝑓 =


𝜌𝑛𝑎𝑛𝑜


1 − 0.00397949 992.2 ∗ 4187 + 0.00397949(5610 ∗ 495.207667)

1010.576489

𝑪𝒑𝒆𝒇𝒇 = 𝟒𝟏𝟎𝟓.𝟒𝟒𝟑𝟗 𝑱/𝒌𝒈− 𝑲

4. 𝐾𝑒𝑓𝑓 = 𝐾𝑏𝑓 ∗ 𝐾𝑍𝑛𝑂 +2𝐾𝑏𝑓 +2𝜑(𝐾𝑍𝑛𝑂 +𝐾𝑏𝑓 )

𝐾𝑍𝑛𝑜 +2𝐾𝑏𝑓 −(𝐾𝑍𝑛𝑂 − 𝐾𝑏𝑓 )𝜑

𝐾𝑒𝑓𝑓 = 0.6305 ∗ 50 + 2 ∗ 0.6305 + 2 ∗ 0.00397949(50 + 0.6305)

50 + 2 ∗ 0.6305 − 50 − 0.6305 0.00397949

𝑲𝒆𝒇𝒇 = 𝟎. 𝟔𝟑𝟕𝟕𝟕 𝑾/𝒎𝑲

5. 𝜇 = (1 + 2.5𝜑𝑍𝑛𝑂 )𝜇𝑏𝑓

𝜇 = 1 + 2.5 ∗ 0.00397949 6531 ∗ 10−3

𝝁 = 𝟎. 𝟔𝟓𝟗𝟓𝟗𝟕 ∗ 𝟏𝟎−𝟑 𝑵𝒔𝒎−𝟐

39

b) Dimensionless numbers

1. 𝑅𝑒 =ρUL

µ=

𝑈𝐿

𝑉

𝑅𝑒1 =0.46685 ∗ 0.01

6.5269 ∗ 10−7

𝑹𝒆𝟏 = 7152.7065

𝑅𝑒2 =0.14 ∗ 0.01

6.5269 ∗ 10−7

𝑹𝒆𝟐 = 𝟐𝟏𝟒𝟓. 𝟖𝟑𝟐𝟑

2. 𝑃𝑟 =𝑣

α=

µ𝑐𝑝

𝑘

𝑃𝑟 =0.659597 ∗ 10−3 ∗ 4105.4439

0.63777

𝑷𝒓 = 𝟒. 𝟐𝟒𝟓𝟗𝟒𝟖

3. 𝐺𝑟 =𝑔ρ2βΔT𝐿3

µ2

𝐺𝑟 =0.003187 ∗ 9.81 ∗ 26 ∗ 10−6

6.5269 ∗ 10−7 2

𝑮𝒓 = 𝟏𝟗𝟎𝟖𝟏𝟏𝟖.𝟗𝟗𝟗

4. 𝑁𝑢

m = ρ*v

m = 1010.576489 * 5000 * 10-6

m = 5.05288 kg

Cp = 4015.4439𝐽/𝑘𝑔 − 𝐾

40

Day - 1 (2.2 litres/min.)

ΔT = 52 – 29 = 23

𝑄𝑡𝑜𝑡𝑎𝑙 = 5.05288 ∗ 4105.4439 ∗ (52 − 29)

3600

𝑸𝒕𝒐𝒕𝒂𝒍= 133.533126 W

𝑕𝑡𝑜𝑡𝑎𝑙 = 𝑄

𝐴∆𝑇

𝑕𝑡𝑜𝑡𝑎𝑙 = 133.533126

0.039898 ∗ (75.5 − 52)

𝒉𝒕𝒐𝒕𝒂𝒍 = 𝟏𝟒𝟏. 𝟑𝟓𝟑𝟏𝟑𝟖 𝑾/𝒎𝟐𝒌

𝑁𝑢 =𝑕𝑙

𝑘

𝑁𝑢 =141.353138 ∗ 0.01

0.63777

𝑵𝒖𝟏 = 𝟐. 𝟐𝟏𝟔𝟑𝟔

Day – 2 (0.66 litres/min.)

ΔT = 50.5 – 29 = 21.5

𝑄𝑡𝑜𝑡𝑎𝑙 = 5.05288 ∗ 4105.4439 ∗ (50.5 − 29)

3600

𝑸𝒕𝒐𝒕𝒂𝒍= 123.8897 W


𝐴∆𝑇

𝑕𝑡𝑜𝑡𝑎𝑙 = 123.8897

0.039898 ∗ (73 − 50.5)

𝒉𝒕𝒐𝒕𝒂𝒍 = 𝟏𝟑𝟖. 𝟎𝟎𝟕𝟎𝟑 𝑾/𝒎𝟐𝒌

𝑁𝑢 =𝑕𝑙

𝑘

𝑁𝑢 =138.00703 ∗ 0.01

0.63777

𝑵𝒖𝟐 = 𝟐. 𝟏𝟔𝟑𝟗

41

𝑁𝑢 = c (𝑅𝑒)𝑚(𝑃𝑟)1/3

2.1639 = c (2145.8323)𝑚(4.245948)1/3

2.21636 = c(7152.7065)𝑚(4.245948)1/3

Dividing both equations

2.21636

2.1639=

7152.7065

2145.8323 𝑚

1.024243 = 3.3333𝑚

Taking logarithm on both sides

log (1.024243) = m log 3.3333

0.0239538 = m * 1.20397

m = 0.019895

2.21636 = C (7152.7065)0.019895 (4.245948)1/3

c =1.17498769

𝑵𝒖 = 𝟏. 𝟏𝟕𝟒𝟗𝟖𝟕𝟔𝟗 (𝑹𝒆)𝟎.𝟎𝟏𝟗𝟖𝟗𝟓𝑷𝒓𝟏/𝟑

42

8.3 Calculations of 0.2% ZnO nanofluid

a) Nanofluid properties

1. 𝜑𝑍𝑛𝑂 =



+𝑊𝑏𝑓

𝜌𝑏𝑓

𝜑𝑍𝑛𝑂 =

56.1

561056.1

5610+

4980

992.2

𝝋𝒁𝒏𝑶 = 𝟎. 𝟎𝟎𝟏𝟗𝟖𝟒𝟒𝟑

2. 𝜌𝑛𝑎𝑛𝑜 = 1 − 𝜑𝑍𝑛𝑂 𝜌𝑏𝑓 + 𝜑𝑍𝑛𝑂𝜌𝑍𝑛𝑂

𝜌𝑛𝑎𝑛𝑜 = 1 − 0.00198443 992.2 + (0.00198443 ∗ 5610)

𝝆𝒏𝒂𝒏𝒐 = 𝟏𝟎𝟎𝟏.𝟔𝟑𝟔𝟕𝟎𝟏 𝒌𝒈/𝒎𝟑

3. 𝐶𝑝𝑒𝑓𝑓 =


𝜌𝑛𝑎𝑛𝑜


1 − 0.00198443 992.2 ∗ 4187 + 0.00198443(5610 ∗ 495.207667)

1010.576489

𝑪𝒑𝒆𝒇𝒇 = 𝟒𝟏𝟎𝟓.𝟒𝟒𝟑𝟗 𝑱/𝒌𝒈− 𝑲

4. 𝐾𝑒𝑓𝑓 = 𝐾𝑏𝑓 ∗ 𝐾𝑍𝑛𝑂 +2𝐾𝑏𝑓 +2𝜑(𝐾𝑍𝑛𝑂 +𝐾𝑏𝑓 )

𝐾𝑍𝑛𝑜 +2𝐾𝑏𝑓 −(𝐾𝑍𝑛𝑂 − 𝐾𝑏𝑓 )𝜑

𝐾𝑒𝑓𝑓 = 0.6305 ∗ 50 + 2 ∗ 0.6305 + 2 ∗ 0.00198443(50 + 0.6305)

50 + 2 ∗ 0.6305 − 50 − 0.6305 0.00198443

𝑲𝒆𝒇𝒇 = 𝟎. 𝟔𝟑𝟒𝟏𝟐𝟏𝟗𝟕 𝑾/𝒎𝑲

5. 𝜇 = (1 + 2.5𝜑𝑍𝑛𝑂 )𝜇𝑏𝑓

𝜇 = 1 + 2.5 ∗ 0.00198443 6531 ∗ 10−3

𝝁 = 𝟎. 𝟔𝟓𝟔𝟑𝟒 ∗ 𝟏𝟎−𝟑 𝑵𝒔𝒎−𝟐

43

b) Dimensionless numbers

1. 𝑅𝑒 =ρUL

µ=

𝑈𝐿

𝑉

𝑅𝑒1 =0.46685 ∗ 0.01

6.5269 ∗ 10−7

𝑹𝒆𝟏 = 7152.7065

𝑅𝑒2 =0.14 ∗ 0.01

6.5269 ∗ 10−7

𝑹𝒆𝟐 = 𝟐𝟏𝟒𝟓. 𝟖𝟑𝟐𝟑

2. 𝑃𝑟 =𝑣

α=

µ𝑐𝑝

𝑘

𝑃𝑟 =0.65634 ∗ 10−3 ∗ 4108.160461

0.63412197

𝑷𝒓 = 𝟒. 𝟐𝟓𝟐𝟏

3. 𝐺𝑟 =𝑔ρ2βΔT𝐿3

µ2

𝐺𝑟 =0.003187 ∗ 9.81 ∗ 27 ∗ 10−6

(6.55446 ∗ 10−7)2

𝑮𝒓 = 𝟏𝟕𝟒𝟔𝟓𝟕𝟗.𝟗𝟖

4. 𝑁𝑢

m = ρ*v

m = 1001.363701* 5000 * 10-6

m = 5.006818 kg

Cp = 4108.160461𝐽/𝑘𝑔 − 𝐾

44

Day - 1 (2.2 litres/min.)

ΔT = 49.5 – 27 = 22.5

𝑄𝑡𝑜𝑡𝑎𝑙 = 5.006818 ∗ 4108.160463 ∗ (49.5−27)

3600

𝑸𝒕𝒐𝒕𝒂𝒍= 128.555 W


𝐴∆𝑇

𝑕𝑡𝑜𝑡𝑎𝑙 = 128.555

0.039898 ∗ (75.5 − 52)

𝒉𝒕𝒐𝒕𝒂𝒍 = 𝟏𝟐𝟖. 𝟖𝟖𝟑𝟔𝑾/𝒎𝟐𝒌

𝑁𝑢 =𝑕𝑙

𝑘

𝑁𝑢 =128.8836 ∗ 0.01

0.63412197

𝑵𝒖𝟏 = 𝟐. 𝟎𝟑𝟐𝟒𝟒𝟕𝟑𝟑

Day – 2 (0.66 litres/min.)

ΔT = 49 – 27 = 22

𝑄𝑡𝑜𝑡𝑎𝑙 = 5.006818 ∗ 4108.160463 ∗ (49− 27)

3600

𝑸𝒕𝒐𝒕𝒂𝒍= 125.69829W


𝐴∆𝑇

𝑕𝑡𝑜𝑡𝑎𝑙 = 125.69829

0.039898 ∗ (74 − 49)

𝒉𝒕𝒐𝒕𝒂𝒍 = 𝟏𝟐𝟔. 𝟎𝟏𝟗𝟎𝟒 𝑾/𝒎𝟐𝒌

45

𝑁𝑢 =𝑕𝑙

𝑘

𝑁𝑢 =126.01904 ∗ 0.01

0.63412197

𝑵𝒖𝟐 = 𝟏. 𝟗𝟖𝟕𝟑𝟎

𝑁𝑢 = c (𝑅𝑒)𝑚(𝑃𝑟)1/3

2.0324733 = c (7152.7065)𝑚(4.245948)1/3

1.98730 = c(2145.8323)𝑚(4.245948)1/3

Dividing both equations

2.0324733

1.98730=

7152.7065

2145.8323 𝑚

1.024243 = 3.3333𝑚

Taking logarithm on both sides

log (1.022726) = m log 3.3333

0.02247161 = m * 1.20397

m = 0.0186647

2.0324733 = c(7152.7045)0.0186647 (4.2521)1/3

c =1.0630356

𝑵𝒖 = 𝟏. 𝟎𝟔𝟑𝟎𝟑𝟓𝟔 (𝑹𝒆)𝟎.𝟎𝟏𝟖𝟔𝟔𝟒𝟕𝑷𝒓𝟏/𝟑

46

CHAPTER 9

RESULTS

47

9.1 TABULATION OF DEIONISED WATER

10. Heat flux(Q) in Watt(W)

11. Heat Transfer Coefficient(h) in W/m2K

Time Day 1(Free

convection)

Day 2(Free

convection)

Day 3(Forced

convection)

11:00am 145.649 145.649 291.298

12:00pm 45.994 36.4122 203.909

1:00pm 18.2061 20.51396

2:00pm 13.5943 6.4733 7.28246

3:00pm 8.3227 6.4733 7.6657

4:00pm 10.7888 6.77438

Time Day 1(Free

convection)

Day 2(Free

convection)

Day 3(Forced

convection)

11:00am 17.433 23.244 17.433

12:00pm 17.433 11.622 40.677

1:00pm 11.622 14.5277

2:00pm 5.8111 5.8111 5.8111

3:00pm 5.8111 5.8111 5.8111

4:00pm 8.71667 5.8111

48

9.2 TABULATION OF 0.4% ZnO NANOFLUID


Time Day 1(Free

convection)

Day 2(Forced

convection)

Day 3(Forced

convection)

11:00am 57.62306 54.74194 54.74194

12:00pm 28.81139 28.81139 28.81139

1:00pm 14.40556 17.28667 17.28667

2:00pm 17.28667 14.40556 8.643333

3:00pm 8.643333 11.52444 5.762222

4:00pm 2.881111 5.762222 8.643333


Time Day 1(Free

convection)

Day 2(Forced

convection)

Day 3(Forced

convection)

11:00am 361.0639 422.1667 422.1667

12:00pm 76.01328 80.23611 80.23611

1:00pm 24.47861 30.405 30.405

2:00pm 21.66358 18.05278 12.37861

3:00pm 9.218333 12.69639 6.490833

4:00pm

2.859889 6.145694 9.418944

49

14. NUSSELT NUMBER(Nu) Vs. RAYLEIGH NUMBER(Ra)

Time Nu Gr Ra=Gr*Pr

11:00am

5.661338 293560 1246441

12:00pm

1.191858 697205 2960296

1:00pm

0.383815 1082503 4596250

2:00pm

0.339676 1467800 6232203

3:00pm

0.14454 1724665 7322838

4:00pm

0.044842 1853098 7868156

50

9.3 TABULATION OF 0.2% ZnO NANOFLUID



Time Day 1(Free

convection)

Day 2(Forced

convection)

Day 3(Forced

convection)

11:00am 286.4078 286.4078 256.2602

12:00pm 76.83889 66.60639 65.09417

1:00pm 18.49417 29.92278 30.84403

2:00pm 16.8475 16.8475 13.97092

3:00pm 5.671111 8.857778 15.56556

4:00pm 5.303647 2.870278 -

Time Day 1(Free

convection)

Day 2(Forced

convection)

Day 3(Forced

convection)

11:00am 51.42194 54.27861 48.56528

12:00pm 31.42444 28.56778 28.56778

1:00pm 11.42694 19.99722 19.99722

2:00pm 14.28389 14.28389 11.42694

3:00pm 5.713333 8.570336 14.28389

4:00pm 5.713333 2.891778 0

51

17. Nusselt Number (Nu) Vs. Rayleigh Number (Ra)

Time Nu Gr Ra=Gr*Pr

11:00am

4.516594 327483.7 1392494

12:00pm

1.211734 745935.2 3171791

1:00pm

0.291649 1128000 4796367

2:00pm

0.265682 1546451 6575664

3:00pm

0.089432 1837548 7813437

4:00pm

0.083637 1964902 8354962

52

9.4 Graphs of deionised water

1. Reservoir temperature vs. Time

2. Heat Flux (Q) vs. Time

20

25

30

35

40

45

10:00 AM 11:00 AM 12:00 PM 1:00 PM 2:00 PM 3:00 PM 4:00 PM

Day 1 (Free convection)


Day 3 (Forced convection)

0

5

10

15

20

25

30

35

40

45

11:00am 12:00pm 1:00pm 2:00pm 3:00pm 4:00pm

Day 1(Free convection)


Day 3(Forced convection)

53

3. Heat transfer Coefficient (h) vs. Time

0

50

100

150

200

250

300

350

11:00 AM 12:00 PM 1:00 PM 2:00 PM 3:00 PM 4:00 PM

Day 1 (Free Convection)

Day 2 ( Free convection)

Day 3 (Forced Convection)

54

9.5 Graphs of 0.4% ZnO nanofluid


5. Heat transfer coefficient (h) vs. Time

20

25

30

35

40

45

50

55




0

50

100

150

200

250

300

350

400

450

11:00am 12:00pm 1:00pm 2:00pm 3:00pm 4:00pm




55

6. Heat Flux (Q) vs. Time

7. Nusselt number (Nu) vs. Rayleigh number (Ra)

0

10

20

30

40

50

60

70

11:00am 12:00pm 1:00pm 2:00pm 3:00pm 4:00pm




56

9.6 Graphs of 0.2% ZnO nanofluid


9. Heat flux (Q) vs. Time

20

25

30

35

40

45

50

55




0

10

20

30

40

50

60

11:00am 12:00pm 1:00pm 2:00pm 3:00pm 4:00pm




57


11. Nusselt number (Nu) vs. Rayleigh Number (Ra)

0

50

100

150

200

250

300

350

11:00am 12:00pm 1:00pm 2:00pm 3:00pm 4:00pm




58

9.7 Graphs comparing nanofluid and water



20

25

30

35

40

45

50

55

Water

0.4 % ZnO Nanofluid

0.2% ZnO Nanofluid

0

50

100

150

200

250

300

350

400

450

11:00am 12:00pm 1:00pm 2:00pm 3:00pm 4:00pm

Water

0.4% ZnO nanofluid

0.2% ZnO nanofluid

59

PROJECT OUTCOMES AND CONCLUSIONS

The empirical correlations between dimensionless numbers of convection were found and are

as in the table given below:

FLUID RELATION

0.4% ZnO nanofluid Free

Convection 𝑵𝒖 = 𝟐. 𝟎𝟐𝟒𝟔𝟕𝟏 ∗ 𝟏𝟎𝟏𝟐(𝑮𝒓.𝑷𝒓)−𝟏.𝟖𝟗𝟓𝟐𝟓𝟕

0.4% ZnO nanofluid Forced

Convection 𝑵𝒖 = 𝟏. 𝟏𝟕𝟒𝟗𝟖𝟕𝟔𝟗 (𝑹𝒆)𝟎.𝟎𝟏𝟗𝟖𝟗𝟓𝑷𝒓

𝟏/𝟑

0.2% ZnO nanofluid Free

Convection 𝑵𝒖 = 𝟕. 𝟓𝟖𝟎𝟏𝟖𝟓 ∗ 𝟏𝟎𝟏𝟏(𝑮𝒓.𝑷𝒓)−𝟏.𝟖𝟐𝟔𝟕𝟑𝟖

0.2% ZnO nanofluid Forced

Convection 𝑵𝒖 = 𝟏. 𝟎𝟔𝟑𝟎𝟑𝟓𝟔 (𝑹𝒆)𝟎.𝟎𝟏𝟖𝟔𝟔𝟒𝟕𝑷𝒓

𝟏/𝟑

From the experimentation it was found that there was an increase of 34.6% in the final

temperature reached by the reservoir. By water it was seen that the maximum temperature

reached was 41.5oC but by using nanofluid temperatures up to 52

oC was reached.

By the addition of nanoparticles to the base fluid the thermal conductivity value of the base

fluid is increased as shown in the calculations where as the specific heat value decreases i.e.

there is increase in heat conduction but at the same time the temperature rise and fall takes

place at a faster rate.

60

FUTURE SCOPE

Tracking Mechanism

Graphene Coating On Collector

Other Concentrations of ZnO nanofluid

Different nanofluids

Different flow rates in order to determine optimum flow rate

Multiple Collectors

Structural Analysis Of Nano Particles

CFD Analysis

61

REFERENCES

62

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