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REFRIGERATION USING WASTE HEAT FROM AN ENGINE
A PROJECT REPORT
Submitted by
PRASHANT KUMAR SARMA (U07ME092) SUBHASISH DAS (U07ME124) SWARUP SENAPATI (U07ME131) UJJAL JYOTI BARUAH (U07ME133) UMESH KUMAR SAH (U07ME134)
in partial fulfillment for the award of the degree
Of
BACHELOR OF TECHNOLOGY
IN
MECHANICAL ENGINEERING
UNDER THE GUIDANCE OF Mr.P.UDAYAKUMAR
LECTURER, BIST
BHARATH UNIVERSITY : CHENNAI 600 073
MARCH 2011 1
DEPARTMENT OF MECHANICAL ENGINEERINGBHARATH INSTITUTE OF SCIENCE AND
TECHNOLOGYBHARATH UNIVERSITY CHENNAI-600073
MARCH 2011
BONAFIDE CERTIFICATE
Certified that this report “REFRIGERATION USING WASTE HEAT
FROM AN ENGINE” is the bonafide work of “PRASHANT KUMAR
SARMA (U07ME092), SUBHASISH DAS (U07ME124), SWARUP
SENAPATI (U07ME131), UJJAL JYOTI BARUAH (U07ME133),
UMESH KUMAR SAH (U07ME134)” who carried out the project
under my supervision.
SIGNATURE SIGNATURE
Dr.T.JAYACHANDRA PRABHU Mr.P.UDAYAKUMAR
HEAD OF THE DEPARTMENT GUIDE LECTURER
DEPARTMENT OF MECHANICAL DEPARTMENT OF
MECHANICAL ENGINEERING MECHANICAL ENGINEERING
BHARATH UNIVERSITY BHARATH UNIVERSITY
CHENNAI- 73 CHENNAI- 73
2
ACKNOWLEDGEMENT
We wish to express our thanks to our guide Mr.P.UDAYAKUMAR,
LECTURER, Department of Mechanical Engineering, for his valuable guidance in
completing our project.
We express our kind gratitude to respected Dr. T.JAYACHANDRA
PRABHU, H.O.D. of Mechanical Engineering.
We would like to convey our heartful gratitude to the project co-ordinator
Mr. A.KUMARASWAMY.
We like to convey our heartiest thanks to MR. SHAKTHI of SAI SAKTHI
ENTERPRISES, AVADI, for his technical assistance in completing our project.
It is our bounded duty to pay accolades to all the staff members of Mechanical
Engineering Department for their assistance and kind co-operation in completing our
project.
3
TABLE OF CONTENTS
CHAPTER NO. TITLE PAGE NO.
ABSTRACT iii
LIST OF FIGURES iv
1. INTRODUCTION 1 1.1 REFRIGERATION 1
1.1.1 First Refrigeration Systems 2
1.1.2 Current Application of Refrigeration 3
1.2 METHODS OF REFRIGERATION 4
1.2.1 Non-Cyclic Refrigeration 4
1.2.2 Cyclic Refrigeration 4
1.3 CYCLIC REFRIGERATION CLASSIFICATION 5
1.3.1 Vapor–cycle Classification 5
1.3.2 Vapor-Compression cycle 5
1.4 VAPOR ABSORPTION CYCLE 6
1.5 GAS REFRIGERATION CYCLE 6
1.6 THERMOELECTRIC REFRIGERATION 7
1.6.1 Magnetic Refrigeration 7
2. LITERATURE REVIEW 9
2.1 VAPOR ABSORPTION IN ROAD TRANSPORT
VEHICLES 9
2.2 AIR-CONDITIONING USING WASTE HEAT
FROM DIESEL ENGINE OF CAR 10
2.3 WASTE-HEAT DRIVEN ABSORPTION
TRANSPORT REFRIGERATOR 11
3. ELECTROLUX REFRIGERATION SYSTEM 12
3.1 ELECTROLUX REFRIGERATION SYSTEM 12
4
3.1.1 HISTORY 12
3.1.2 HOW IT WORKS 14
3.2 VAPOR COMPRESSION REFRIGERATION
SYSTEM 15
3.2.1 Vapor Compression Cycle 16
3.2.2 Condensation 16
3.2.3 Expansion 17
3.2.4 Vaporization 17
. 3.3 PRINCIPLE PARTS OF A VAPOR COMPRESSION
SYSTEM 17
3.3.1 Evaporator 17
3.3.2 Sution Line 17
3.3.3 Compressor 19
3.3.4 Discharge Line 19
3.3.5 Condenser 19
3.3.6 Receiver Tank 19
3.3.7 Liquid Line 19
3.3.8 Expansion Valve 20
3.4 ADVANTAGES AND DISADVANTAGES 20
3.5 WATER COOLER 21
3.6 RADIATOR 22
3.6.1 Radiator Matrix Or Core 23
3.7 FAN 24
3.8 COMPRESSOR 24
3.8.1 Introduction 24
3.8.2 Reciprocrating Compressor 25
3.8.3 Specifications of The Compressor 29
3.8.4 Power of The Compressor 29
5
3.8.5 Compressor Drive 29
3.8.6 Lubricration 29
3.9 CONDENSER 30
3.9.1 Introduction 30
3.9.2 Classification Of Condenser 30
3.9.3 Fin and Tube Condenser 32
3.10 INTERNAL COMBUSTION ENGINE 32
3.10.1 Two-Stroke Engine 33
3.10.2 Application 34
4. CONSTRUCTION 35
4.1 IRON RODS 35
4.2 WELDING 35
4.2.1 Arc-Welding 36
4.3 SHEET METAL 36
4.3.1 Aluminium Sheet 37
4.4 FUEL KIT 38
4.5 IGNITION COIL 38
4.5.1 Magneto Ignition Coil 38
4.6 SPARKPLUG 39
4.6.1 Operations of a Sparkplug 39
5. REFRIGERATION AND ACCESSORIES 41
5.1 RECEIVERS 41
5.2 DRIERS 41
5.2.1 Type of Driers 42
5.3 INSULATION 42
5.3.1 Selection of Insulation Materials 42
5.4 TUBING 43
5.4.1 Soft Copper Tubing 43
5.5 SOLDERING 43
6
5.6 PROPERTIES OF COPPER 43
6. WORKING PRINCIPLE 45
7. PHOTOGRAPHS 48
8. CONCLUSION 53
9. REFERENCES 54
7
SL.NO FIG.
NO.
TITLE PAGE
NO.
1 3.1 ABSORPTION SYSTEM 13
2 3.2 VAPOR COMPRESSION CYCLE 16
3 3.3 PRESSURE ENTHALPY DIAGRAM 18
4 3.4 TRUNK TYPE PISTON 27
5 3.5 SIMPLE ACTING
RECIPROCATING
COMPRESSOR
28
6 3.6 AIR COOLED CONDENSER 31
8
ABSTRACT
The objective of the project “Refrigeration Using the Waste Heat from an Engine” is
to carry out an experimental investigation of an Electrolux Refrigeration System
using waste heat of an engine. This would provide an alternative to the conventional
vapor compression refrigeration system used generally. While considering the power
utilization of refrigerators in vehicles, an effort has been made to drive the
refrigerator with the use of heat energy (non-conventional energy) which will be
economical without use of any electrical power. Mostly used refrigerator system are
vapor absorption and vapor compression of which vapor absorption system is more
effective when heat is used as energy input. With the minimal requirement of heat
energy Electrolux Vapor Absorption System is best suitable to the project. It also
suggested that, with careful design, inserting the Electrolux Refrigerating System into
the main engine exhaust system need not impair the performance of the vehicle
propulsion unit. Design of the heat recovery system are reported and discussed.
9
CHAPTER 1
INTRODUCTION
If the heat energy possesses the advantage to be "clean", free and renewable, this last
is probably, considered like an adapted potential solution, that answers in even time at
an economic preoccupation and ecological problems. Among the main research done
it is found that it is the use of this free source to operate system of refrigeration. Since
among the domestic appliances used today, refrigerators consume a considerable
amount of energy, using heat energy to run refrigerator is of great practical relevance
nowadays.
The diffusion absorption refrigerator cycle invented in the 1920s is based on
ammonia (refrigerant) and water (absorbent) as the working fluids together with
hydrogen as an auxiliary inert gas. Since there are no moving parts in the unit, the
diffusion absorption refrigerator system is both quiet and reliable. The system is,
therefore, often used in hotel rooms and offices. The absorption diffusion
refrigerating machine is designed according to the operation principle of the
refrigerating machine mono pressure invented by PLATERN and MUNTER. This
machine uses three operation fluids, water (absorbent), the ammonia (refrigerant) and
hydrogen as an inert gas used in order to maintain the total pressure control.
1.1 REFRIGERATION
Refrigeration is the process of removing heat from an enclosed space, or from a
substance, and moving it to a place where it is unobjectionable. The primary purpose
of refrigeration is lowering the temperature of the enclosed space or substance and
then maintaining that lower temperature. The term cooling refers generally to any
natural or artificial process by which heat is dissipated. The process of artificially
producing extreme cold temperatures is referred to as cryogenics.
10
Cold is the absence of heat, hence in order to decrease a temperature, one "removes
heat", rather than "adding cold." In order to satisfy the Second Law of
Thermodynamics, some form of work must be performed to accomplish this. This
work is traditionally done by mechanical work but can also be done by magnetism,
laser or other means.
The first known method of artificial refrigeration was demonstrated by William
Cullen at the University of Glasgow in Scotland in 1756. Cullen used a pump to
create a partial vacuum over a container of diethyl ether, which then boiled, absorbing
heat from the surrounding air. The experiment even created a small amount of ice, but
had no practical application at that time.
In 1805, American inventor Oliver Evans designed but never built a refrigeration
system based on the vapor-compression refrigeration cycle rather than chemical
solutions or volatile liquids such as ethyl ether.
In 1820, the British scientist Michael Faraday liquefied ammonia and other gases by
using high pressures and low temperatures.
1.1.1 First Refrigeration Systems
The first known method of artificial refrigeration was demonstrated by William
Cullen at the University of Glasgow in Scotland in 1756. Cullen used a pump to
create a partial vacuum over a container of diethyl ether, which then boiled, absorbing
heat from the surrounding air. The experiment even created a small amount of ice, but
had no practical application at that time. In 1805, American inventor Oliver Evans
designed but never built a refrigeration system based on the vapor-compression
refrigeration cycle rather than chemical solutions or volatile liquids such as ethyl
ether. In 1820, the British scientist Michael Faraday liquefied ammonia and other
gases by using high pressures and low temperatures. An American living in Great
Britain, Jacob Perkins, obtained the first patent for a vapor-compression refrigeration
11
system in 1834. Perkins built a prototype system and it actually worked, although it
did not succeed commercially.
The first gas absorption refrigeration system using gaseous ammonia dissolved in
water (referred to as "aqua ammonia") was developed by Ferdinand Carré of France
in 1859 and patented in 1860. Due to the toxicity of ammonia, such systems were not
developed for use in homes, but were used to manufacture ice for sale. In the United
States, the consumer public at that time still used the ice box with ice brought in from
commercial suppliers, many of whom were still harvesting ice and storing it in an
icehouse.
1.1.2 Current Application of Refrigeration
Probably the most widely-used current applications of refrigeration are for the air-
conditioning of private homes and public buildings, and the refrigeration of foodstuffs
in homes, restaurants and large storage warehouses. The use of refrigerators in our
kitchens for the storage of fruits and vegetables has allowed us to add fresh salads to
our diets year round, and to store fish and meats safely for long periods.
In commerce and manufacturing, there are many uses for refrigeration. Refrigeration
is used to liquefy gases like oxygen, nitrogen, propane and methane for example. In
compressed air purification, it is used to condense water vapor from compressed air to
reduce its moisture content. In oil refineries, chemical plants, and petrochemical
plants, refrigeration is used to maintain certain processes at their required low
temperatures (for example, in the alkylation of butene and butane to produce a high
octane gasoline component). Metal workers use refrigeration to temper steel and
cutlery. In transporting temperature-sensitive foodstuffs and other materials by trucks,
trains, airplanes and sea-going vessels, refrigeration is a necessity.
Dairy products are constantly in need of refrigeration, and it was only discovered in
the past few decades that eggs needed to be refrigerated during shipment rather than
12
waiting to be refrigerated after arrival at the grocery store. Meats, poultry and fish all
must be kept in climate-controlled environments before being sold. Refrigeration also
helps keep fruits and vegetables edible longer.
1.2 METHODS OF REFRIGERATION
Methods of refrigeration can be classified as non-cyclic, cyclic and thermoelectric.
1.2.1 Non-cyclic refrigeration
In these methods, refrigeration can be accomplished by melting ice or by subliming
dry ice. These methods are used for small-scale refrigeration such as in laboratories
and workshops, or in portable coolers.
1.2.2 Cyclic refrigeration
This consists of a refrigeration cycle, where heat is removed from a low-temperature
space or source and rejected to a high-temperature sink with the help of external
work, and its inverse, the thermodynamic power cycle. In the power cycle, heat is
supplied from a high-temperature source to the engine, part of the heat being used to
produce work and the rest being rejected to a low-temperature sink. This satisfies the
thermodynamics. Heat naturally flows from hot to cold. Work is applied to cool a
living space or storage volume by pumping heat from a lower temperature heat source
into a higher temperature heat sink. Insulation is used to reduce the work and energy
required to achieve and maintain a lower temperature in the cooled space. The
operating principle of the refrigeration cycle was described mathematically by Sadi
Carnot in 1824 as a heat engine.
The most common types of refrigeration systems use the Reverse-Rankine vapor-
compression refrigeration cycle although absorption heat pumps are used in a
minority of applications.
13
1.3 CYCLIC REFRIGERATION SYSTEM
1. Vapor cycle, and
2. Gas cycle
1.3.1 Vapor cycle refrigeration classification
1. Vapor compression refrigeration
2. Vapor absorption refrigeration
1.3.2 Vapor-compression cycle
The vapor-compression cycle is used in most household refrigerators as well as in
many large commercial and industrial refrigeration systems. Figure 1 provides a
schematic diagram of the components of a typical vapor-compression refrigeration
system.
The thermodynamics of the cycle can be analyzed on a diagram as shown in Figure 2.
In this cycle, a circulating refrigerant such as Freon enters the compressor as a vapor.
From point 1 to point 2, the vapor is compressed at constant entropy and exits the
compressor superheated. From point 2 to point 3 and on to point 4, the superheated
vapor travels through the condenser which first cools and removes the superheat and
then condenses the vapor into a liquid by removing additional heat at constant
pressure and temperature. Between points 4 and 5, the liquid refrigerant goes through
the expansion valve (also called a throttle valve) where its pressure abruptly
decreases, causing flash evaporation and auto-refrigeration of, typically, less than half
of the liquid.
That results in a mixture of liquid and vapor at a lower temperature and pressure as
shown at point 5. The cold liquid-vapor mixture then travels through the evaporator
coil or tubes and is completely vaporized by cooling the warm air (from the space
14
being refrigerated) being blown by a fan across the evaporator coil or tubes. The
resulting refrigerant vapor returns to the compressor inlet at point 1 to complete the
thermodynamic cycle.
1.4 VAPOR ABSORPTION CYCLE
In the early years of the twentieth century, the vapor absorption cycle using water-
ammonia systems was popular and widely used. After the development of the vapor
compression cycle, the vapor absorption cycle lost much of its importance because of
its low coefficient of performance (about one fifth of that of the vapor compression
cycle). Today, the vapor absorption cycle is used mainly where fuel for heating is
available but electricity is not, such as in recreational vehicles that carry LP gas. It's
also used in industrial environments where plentiful waste heat overcomes its
inefficiency.
The absorption cycle is similar to the compression cycle, except for the method of
raising the pressure of the refrigerant vapor. In the absorption system, the compressor
is replaced by an absorber which dissolves the refrigerant in a suitable liquid, a liquid
pump which raises the pressure and a generator which, on heat addition, drives off the
refrigerant vapor from the high-pressure liquid. Some work is required by the liquid
pump but, for a given quantity of refrigerant, it is much smaller than needed by the
compressor in the vapor compression cycle. In an absorption refrigerator, a suitable
combination of refrigerant and absorbent is used. The most common combinations are
ammonia (refrigerant) and water (absorber) and water (refrigerant) and lithium
bromide (absorber).
1.5 GAS REFRIGERATION CYCLE
When the working fluid is a gas that is compressed and expanded but doesn't change
phase, the refrigeration cycle is called a gas cycle. Air is most often this working
fluid. As there is no condensation and evaporation intended in a gas cycle
15
components corresponding to the condenser and evaporator in a vapor compression
cycle are the hot and cold gas-to-gas heat exchangers in gas cycles.
The gas cycle is less efficient than the vapor compression cycle because the gas cycle
works on the reverse Brayton cycle instead of the reverse Rankine cycle. As such the
working fluid does not receive and reject heat at constant temperature. Because of
their lower efficiency and larger bulk, air cycle coolers are not often used nowadays
in terrestrial cooling devices. The air cycle machine is very common, however, on gas
turbine-powered jet aircraft because compressed air is readily available from the
engines' compressor sections.
1.6 THERMOELECTRIC REFRIGERATION
1.6.1 Magnetic refrigeration
Magnetic refrigeration, or adiabatic demagnetization, is a cooling technology based
on the magneto caloric effect, an intrinsic property of magnetic solids. The refrigerant
is often a paramagnetic salt, such as cerium magnesium nitrate. The active magnetic
dipoles in this case are those of the electron shells of the paramagnetic atoms. A
strong magnetic field is applied to the refrigerant, forcing its various magnetic dipoles
to align and putting these degrees of freedom of the refrigerant into a state of lowered
entropy. A heat sink then absorbs the heat released by the refrigerant due to its loss of
entropy. Thermal contact with the heat sink is then broken so that the system is
insulated, and the magnetic field is switched off. This increases the heat capacity of
the refrigerant, thus decreasing its temperature below the temperature of the heat sink.
Other methods
Other methods of refrigeration include the air cycle machine used in aircraft; the
vortex tube used for spot cooling, when compressed air is available; and thermo-
16
acoustic refrigeration using sound waves in a pressurised gas to drive heat transfer
and heat exchange.
CHAPTER 2
LITERATURE REVIEW
2.1 VAPOR ABSORPTION REFRIGERATION IN ROAD
TRANSPORT VEHICLES
17
by I.HORUZ (Assoc. Prof., Dept. of Mechanical Engineering, Faculty of
Engg. and Arch., Univ. of Uludag, 16059, Bursa, (Turkey).
Abstract
This study includes an experimental investigation into the use of vapor absorption
refrigeration (VAR) systems in road transport vehicles using the waste heat in the
exhaust gases of the main propulsion unit as the energy source. This would provide
an alternative to the conventional vapor compression refrigeration system and its
associated internal combustion engine. The performance of a VAR system fired by
natural gas is compared with that of the same system driven by engine exhaust gases.
This showed that the exhaust-gas-driven system produced the same performance
characteristics as the gas-fired system. It also suggested that, with careful design,
inserting the VAR system generator into the main engine exhaust system need not
impair the performance of the vehicle propulsion unit. A comparison of the capital
and running costs of the conventional and proposed alternative system is made.
Suggestions are also made regarding operation of the VAR system during
off-road/slow running conditions.
2.2 AIR-CONDITIONING USING WASTE HEAT FROM DIESEL
ENGINE OF CAR.
18
DESHPANDE,A.C. PILLAI,R.M
Jr. Res. Fellow at SVNIT, Surat under BARC, Surat, India
Abstract
According to a cautious estimate, approximately 10% of the energy available at the
crankshaft in a diesel operated vehicle is used for operating the compressor of the
vehicle's air-conditioning system. This is a huge loss if one takes into account the fact
that the thermal efficiencies of most diesel operated vehicles range from 20-30%
when in pristine condition. The bottom line is that a great deal of diesel is consumed
to generate electricity. In addition to this, alternating current via an alternator is
necessary for the operation of the conventional a/c system. The refrigerant, usually
R12 or R22 leaks easily. Being a secondary refrigerant, it is also harmful to the
environment. Conventional air conditioning systems are also questioned due to the
ODP (ozone depletion potential) and GWP (global warming potential) caused by the
CFCs or HCFCs. Increasing recognition of environmental problems associated with
CFCs and HCFCs has opened favorable opportunities for the development of green
air conditioning technologies. This project report presents a revolutionary silica gel-
water adsorption system for air conditioning in automobiles. The cooling effect is
achieved by recovering waste thermal energy from the exhaust gases. The system is
cheap and easy to fabricate. The refrigerant, being water, is environment friendly. The
report provides the details regarding the construction of a prototype fabricated on this
technology, by the co-authors. The design of the generator, which is the focal part of
the system, is novel yet simple. The experimental results obtained, while conducting
tests on a four stroke diesel engine from Mahindra have been include.
19
2.3 WASTE-HEAT DRIVEN ABSORPTION TRANSPORT
REFRIGERATOR
Title: Waste-Heat Driven Absorption Transport Refrigerator.
Investigators: GARRABRANT MICHAEL .A
Abstract
An exhaust energy powered Absorption Transport Refrigerator (ATR) is proposed
that can provide a controlled, below ambient environment to a refrigerated trailer
using significantly less fuel than current technology. An ATR utilizes an absorption
refrigeration cycle that is powered primarily by waste heat from the transport vehicle
(truck) engine. Supplemental fuel is required only during periods of no or reduced
truck engine load. Current technology utilizes a vapor-compression refrigeration
system consisting of a trailer mounted refrigeration unit with the compressor driven
by a small combustion engine (typically diesel). Capacities of these systems range
from 20,000 - 50,000 Btu/hr (5.9 - 14.6 kW). Primary disadvantages of diesel/gas
engine driven systems include:
1. Low combustion engine operating efficiencies of approximately 35%.
2. Combustion of gasoline or diesel fuel, contributing to air pollution, greenhouse
effects, and the national trade imbalance. Over 350,000 refrigerated trailers are in use
in the U.S. today, consuming more than 245 million gallons of fuel per year.
3. Use of environmentally unfriendly CFC or HCFC refrigerants.
4. High number of moving parts requiring extensive maintenance and
environmentally unfriendly lubricants and coolants.
20
Chapter 3
ELECTROLUX REFRIGERATION SYSTEM
3.1 ELECTROLUX REFRIGERATION SYSTEM
3.1.1 History
In 1922, two young engineers, Baltzar von Platen and Carl Munters from the Royal
Institute of Technology in Stockholm, submitted a degree project that gained them
much attention. It was a refrigeration machine that employed a simple application of
the absorption process to transform heat to cold. The heat source that initiated the
process could be fueled by electricity, gas or kerosene, making the system extremely
flexible.
The two inventors needed money to develop and market their product, however. By
1923, they had come as far as establishing two companies, AB Arctic and Platen-
Munters Refrigeration System. Refrigerator production got under way now, albeit on
a small scale, at the new Arctic factory in Motala. The absorption refrigeration
machine was far from fully developed when Wenner Gnan began to take an interest in
it. It was, then, a bold move when he made an offer for the two companies, which
meant Electrolux's future would depend on the success of the refrigerator. In 1925,
Electrolux introduced its first refrigerators on the market. Intense efforts to develop
refrigeration technology were under way at a refrigeration lab that had been set up in
Stockholm. The primary goal was to develop an air-cooled system. Platen-Munters'
first appliance was water-cooled an fairly impractical solution. This was one of the
reasons for bringing physicist John Tandberg to the lab. Tandberg was one of the
specialists who played a key role in the development of refrigeration technology at
Electrolux, making contributions to improving the control of corrosion and rust and
much more.
21
22
FIG.3.1
3.1.2 How it worksThe continuous absorption type of cooling unit is operated by the application of a
limited amount of heat furnished by gas, electricity or kerosene. No moving parts are
employed.
The unit consists of four main parts - the boiler, condenser, evaporator and absorber.
The unit can be run on electricity, kerosene or gas. When the unit operates on
kerosene or gas the heat is supplied by a burner which is fitted underneath the central
tube (A) and when the unit operates on electricity the heat is supplied by a heating
element inserted in the pocket (B).The unit charge consists of a quantity of ammonia,
water and hydrogen at a sufficient pressure to condense ammonia at the room
temperature for which the unit is designed. When heat is supplied to the boiler
system, bubbles of ammonia gas are produced which rise and carry with them
quantities of weak ammonia solution through the siphon pump (C). This weak
solution passes into the tube (D), whilst the ammonia vapor passes into the vapor pipe
(E) and on to the water separator. Here any water vapor is condensed and runs back
into the boiler system leaving the dry ammonia vapor to pass to the condenser. Air
circulating over the fins of the condenser removes heat from the ammonia vapor to
cause it to condense to liquid ammonia in which state it flows into the evaporator.
The evaporator is supplied with hydrogen. The hydrogen passes across the surface of
the ammonia and lowers the ammonia vapor pressure sufficiently to allow the liquid
ammonia to evaporate.
The evaporation of the ammonia extracts heat from the food storage space, as
described above, thereby lowers the temperature inside the refrigerator. The mixture
of ammonia and hydrogen vapor passes from the evaporator to the absorber. Entering
the upper portion of the absorber is a continuous trickle of weak ammonia solution
fed by gravity from the tube (D). This weak solution, flowing down through the
absorber comes into contact with the mixed ammonia and hydrogen gases which
23
readily absorbs the ammonia from the mixture, leaving the hydrogen free to rise
through the absorber coil and to return to the evaporator. The hydrogen thus circulates
continuously between the absorber and the evaporator. The strong ammonia solution
produced in the absorber flows down to the absorber vessel and thence to the boiler
system, thus completing the full cycle of operation. The liquid circulation of the unit
is purely gravitational. Heat is generated in the absorber by the process of absorption.
This heat must be dissipated into the surrounding air. Heat must also be dissipated
from the condenser in order to cool the ammonia vapor sufficiently for it to liquefy.
Free air circulation is therefore necessary over the absorber and condenser. The whole
unit operates by the heat applied to the boiler system and it is of paramount
importance that this heat is kept within the necessary limits and is properly applied.
A liquid seal is required at the end of the condenser to prevent the entry of hydrogen
gas into the condenser. Commercial Platen-Munters systems are made of all steel
with welded joints. Additives are added to minimize corrosion and rust formation and
also to improve absorption.
Since there are no flared joints and if the quality of the welding is good, then these
systems become extremely rugged and reliable. The Platen-Munters systems offer
low COP due to energy requirement in the bubble pump and also due to losses in the
evaporator because of the presence of hydrogen gas. In addition, since the circulation
of fluids inside the system is due to buoyancy and gravity, the heat and mass transfer
coefficients are relatively small, further reducing the efficiency.
3.2 VAPOUR COMPRESSION REFRIGERATION CYCLE
The low pressure vapor in dry state is drawn from the evaporator during the suction
stroke of the compressor. During compression stroke the pressure and temperature
increases until the vapor temperature is greater than the temperature of condenser
cooling medium.
24
3.2.1 Vapor Compression Cycle
EVAPORATOR COIL
EXPANSION
VALVE
FIG.3.2
3.2.2 Condensation
25
CO
MP
RES
CONDENSER
When the high pressure refrigerant vapour enters the condenser heat flows from
condenser to cooling medium thus allowing vaporized refrigerant to return to liquid
state.
3.2.3 Expansion
After condenser the liquid refrigerant is stored in the liquid receives until needed.
From the receiver it passes through an expansion value where the pressure is reduced
sufficiently to allow the vaporization of liquid at a low temperature of about – 10
degree centigrade.
3.2.4 Vaporization
The low pressure refrigerant vapour after expansion in the expansion valve enters the
evaporator on refrigerated space where a considerable amount of heat is absorbed by
it and refrigeration is furnished.
3.3 PRINCIPLE PARTS OF A SIMPLE VAPOUR COMPRESSION
SYSTEM
The principle part of a simple vapour compression refrigeration system is as follows.
3.3.1 Evaporator
Its function is to provide a heat transfer surface through which heat can pass from the
refrigerated space into the vaporizing refrigerant.
3.3.2 Suction LineIt carries the low pressure vapor from the evaporator to the suction inlet of the
compressor.
26
27
FIG.3.3
3.3.3 CompressorA compressor is considered to be the heart of the vapour compression refrigeration
system it pumps the refrigerant through the system and circulates it again and again in
cycles. It produces high pressure and hence high temperature to enable the
refrigerants to reject its heat in the condenser. It also helps to produce low pressure in
the evaporator to make the refrigerant to pick up maximum amount of heat from the
space to be refrigerated.
The compressors used in the modern vapor compression system can be either of
positive displacement or non-positive displacement type.
3.3.4 Discharge Line
It conveys the high pressure and high temperature refrigerant from the compressor to
the condenser.
3.3.5 Condenser
The function of the condenser is to provide a heat transfer surface through which heat
passes from the refrigerant to the condenser medium which is either water of air.
3.3.6 Receiver Tank
It acts as a reservoir which stores the liquid refrigerant coming from the condenser
and supplies it to the evaporator according to the requirement.
3.3.7 Liquid Line
It carries the liquid refrigerant from the receiver and conveys it to the expansion
valve.
3.3.8 Expansion Valve
28
Its function is to supply a proper amount of refrigerant to the evaporator after
reducing its pressure considerably so that the refrigerant may take sufficient amount
of heat from the refrigerating during evaporation.
3.4 ADVANTAGES AND DISADVANTAGES OF VAPOUR
COMPRESSION REFRIGERATION SYSTEM OVER AIR
REFRIGERATION SYSTEM
Advantages
The coefficient of performance is quite high as the working cycle of this
system is near the Carnot cycle
The among of refrigerant circulated is less per ton of refrigeration than air
refrigeration system because the heat carried away by the refrigerant is the
latent heat. As a result of this, the size of evaporator is smaller for the
same refrigerating effect.
This system can be employed over a large range of temperatures. By
adjusting the expansion valve of the same unit, the required temperature in
the evaporator can be achieved.
The running cost of this system is less than air refrigerating system. The
air refrigeration system requires five times more power than a vapour
compression refrigeration system of the same capacity.
Disadvantages
Prevention of leakage of refrigerant in this system is the major problem.
First investment cost is high than the air refrigeration system.
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3.5 WATER COOLERWater cooler is a device which is used to cool the water. It consists of four
components. They are as follows
Compressor
Condenser
Expansion Valve
Evaporator
The water cooler works under vapour compression cycle. The vapour compression
cycle is explained below.
In this system the same old principle “the liquid when evaporates absorbs heat” is
employed. The only specialty of this method is that same refrigerant is used again
and again in a cycle. The refrigerant continues changing from liquid to vapour state,
when absorbing heat and from vapour to liquid state, when giving out heat.
The refrigerant picks up heat from the space to be cooled and takes it to a distant
point and rejects it there. In other words in this care heat is transferred from a lower
temperature to a higher temperature. According to second law of thermodynamics
this can only be accomplished by the expenditure of energy from some external
source.
Vapour compression refrigeration system was refrigeration sealed in an airtight and
leak proof mechanism. The refrigerant is circulated through the system and it
undergoes a number of changes in its state while passing through various components
of the system. Each such change in the state of vapour is called a process. The
system repeats over and over again this process. The process of repetition of a similar
order of operation is called cycle.
The compression cycle is given this name because it is the compression of the
refrigerant by the compressor which permits transfer of heat energy. The refrigerant
absorbs heat from one place and releases it to another place. In other words the
compressor is used to put the heat latent refrigerant vapour in such a condition that it
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may dissipate the heat it absorbed at low pressure from the refrigerated space, to an
easily available cooling medium.
3.6 RADIATORThe function of the radiator is to reject coolant heat to the outside air. The name
radiator is a misnomer because the heat transfer from coolant to the air is by
conduction and forced convection instead of by radiation. But in our project the heat
is rejected from the atmospheric air to the water in the radiator tubes. The cooling
effect in a radiator is achieved by dispersing the heated coolant into fine streams
through the radiator matrix so that relatively small quantities of coolant are brought in
contact with large metal surface areas which in turn are cooled by a stream of air.
It should be noted that it is easier to transfer heat from water to the metal surfaces
than from metal surfaces to air. For the same metal exposure surface, the heat
transfer from coolant to fins is as much as sever times faster than the heat transfer
from fins to air. Due to its high specific heat water allows a given amount of heat
transfer a higher mean temperature differential compared to that of air. This means
that the air will require a larger surface area of metal than that needed for the water.
This additional surface area is provided by fins. Not only that, the additional or
secondary heat transfer surfaces are so arranged that some turbulence is generated in
air passages which further assists the heat transfer process.
In the down flow type water flows from top to bottom. The radiator has a supply or
header tank at the top and a collector tank at the bottom of the main radiator core or
matrix. The header tank receives hot coolant from the engine, accommodates
expansion of water, and also acts as a water reserve against coolant loss. A
submerged horizontal baffle is provided to reduce mixing of the incoming coolant
with air so that aeration, which impairs the radiator heat transfer efficiency, is
avoided. Some modern designs use a separate header tank for this purpose.
In the cross flow type of radiator the hot coolant is supplied to the top of the supply
tank, it flows across the radiator and is taken out from the bottom of the collector
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tank. A separate header tank is usually provided at the upper end of the collector tank
to prevent aeration and also to provide a coolant reserve. Availability of space
generally dictates the choice of the radiator both cross flow and down flow types
being equally efficient.
3.6.1 Radiator Matrix Or Core
The radiator core is divided into two separate and complicated parts-one acts as a
water passage and the other as an air passage. Earliest radiator used a honeycomb
block which was made by using a large number of circular tubes upset at each end to
hexagonal shape. The hexagons were packed in contact and bonded the shoulder.
This provided a continuous water passage between the circular parts of the tube. The
cooling air was passed through the circular tubes. This type of radiator matrix is now
obsolete because the absence of any secondary heat transfer surface and air
turbulence makes its heat transfer efficiency quite poor.
Ribbon-cellular matrix consists of a pair of thin metal ribbons soldered together along
their edges so as to form a waterway running from header tank to the collector tank.
Between two waterways is a zigzag copper ribbon forming air passages. The copper
ribbon acts as air fins. Water flows from top to bottom and gives up its heat to the
fins across which air flows from top to bottom and gives up its heat to the fins across
which air flows from front to back and ultimately takes away their heat. Due to the
zigzag ribbon the metal surface area is significantly increased the turbulence is also
created. The shape of the fins is such that a smooth layer of air flow that would
insulate their surface is not allowed to form and the turbulence generated in breaking
the pattern creates turbulence which further increases the heat transfer.
In the tube and fin type of matrix a series of long tubes extending from top to bottom
of the radiator are surrounded by straight metallic fins which form the secondary heat
transfer surfaces. Coolant passes through the tubes and the air passes between the
fins around the tubes. An advantage of this type of matrix is its greater structural
strength compared to the film type matrix.
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An improvement over the tube and fin type of matrix is tube and corrugated fin type
matrix. The water tubes are made of flattened oval shaped section and Zigzag copper
ribbons are used to provide secondary heat transfer areas and air turbulence. The tube
and corrugated type of matrix combines the good heat transfer of film type matrix and
the structural strength of the tube and fin type matrix.
The material used for radiators must have good corrosion resistance in
addition to good thermal conductivity. They must also possess the required strength
and be easily formable. Yellow brass and copper meet all these requirements and are
widely used. These materials can also be radiators where weight is very critical.
Radiators headers are also made of copper while the supporting sides are usually
made of steel.
The heat dissipated by radiator depends on
Relative air velocity
Air density @ humidity
Water @ air temperature
Surface provided
Ratio of tube depth to diameter
The thermal conductivity of
Aluminium 754 KJ/m-hr-k
Cast iron – 214 KJ/m-hr-k
Steel – 251 KJ/m-hr-k
3.7 FANIt continuously moves the mass of air at a desired velocity by the action of its rotor.
3.8 COMPRESSOR
3.8.1 Introduction
The vapour compression machine consists of the compressor, condenser, expansion
device, and evaporator. Out of all these components of the system the compressor is
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the only moving part in the system and its functions is to raise the pressure of the
vapour refrigerant coming form the evaporator, high enough so that the temperature
of the leaving gas is higher than that of the condensing medium. Hence, the same
refrigerant can be liquefied back and expanded to the evaporator suction conditions in
a cycle.
The compressors are classified as follows.
1. According to method of operation
Reciprocating compressor
Rotary compressor
Centrifugal compressor
Screw compressor
2. According to drive employed
Open type (belt drive)
Semi-hermetic or Semi-sealed (direct drive, motor and compressor in separate
housings)
Hermetic or Sealed compressor (direct drive, motor and compressor in same
housings)
3.8.2 Reciprocating Compressor
The reciprocating compressor sucks the low pressure and low temperature refrigerant
during its suction stroke and delivers it as high pressure and high temperature. The
reciprocating compressors are built in sizes ranging from a fraction horse power to
several hundred horse power. These are used of refrigerant plant ranging in sizes from
0.25 ton to 1000 tons capacity per unit. The reciprocating compressors are
satisfactorily used with the refrigerant as Dichloro difluro methane (CCl2F2) and most
of the freons. This is preferable for high compression ration and low specific volume
refrigerant.
Low capacity compressors are cooled just by providing the fins on the cylinder head.
This type of cooling is more effective and sufficient for low capacity compressor
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when F-12 is used as refrigerant because of the low temperature of gas at high
pressure.
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FIG.3.4
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FIG.3.5
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3.8.3 Specifications of the Compressor
1. Number of cylinders One
2. Working position Vertical
3. Method of compression Single acting
4. Number of times of compression of gas Single stage
5. Cooling system Air-cooled
6. Capacity 0.5 ton
7. Motor used Single phase
8. Speed of the motor 1400 rpm
3.8.4 Power of the CompressorDuring the compression process, heat is transferred very quickly form the
Refrigerant vapour to the walls of the cylinder initially but as the compression
process is very short and mean effective temperature is almost constant.
It can be safely assumed that the process takes place polytropically with an
Exponent of 1.30.
3.8.5 Compressor DriveSince we have chosen a twin cylinder single acting reciprocating compressor for the
work, it is usually driven by an electric motor which rotates at a speed of 1420 rpm.
3.8.6 LubricationLubrication system ranges from the simplest “splash system” to the most elaborate
“forced feed system” with filters, vents and equalizers. The type of lubrication
required depends largely on bearings. It is conventional to use splash lubrication in
reciprocating compressor in order to get a good performance and excellent service.
The splash system in turn consists of special dippers or slingers fastened to the crank
to tank.
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The suction pressure on the compressor is 25 - 35 psi.
The delivery pressure on the compressor is 150 – 180 psi.
3.9 CONDENSER
3.9.1 IntroductionThe condenser is an important device, used in the high pressure side of a refrigeration
system. Its function is to remove heat of the vapour refrigerant discharged form the
compressor. The hot vapour refrigerant consists of the heat absorbed by the
evaporator and the heat of compression added by the mechanical energy of the
compressor motor. The heat form the hot vapour refrigerant in a condenser is
removed first by transferring it to walls of the condenser tubes and then form the
tubes to the condensing or cooling medium.
3.9.2 Classification Of CondensersThe common forms of condensers may be broadly classified on the basis of the
cooling medium as
1. Water cooled condenser
2. Air cooled condenser
3. Evaporative (air and water cooled) condenser
4. In the work Fin and Tube condenser (air cooled) is used.
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40
FIG.3.6
3.9.3 Fin and Tube CondensersThe fin and tube condenser is one in which the removal of heat is done by air. It consists of steel
or copper tubing through which the refrigerant flows. The size of tube usually ranges from 6mm
to 18mm outside diameter, depending upon of the size of the condenser. Generally copper tubes
are used because of its excellent heat transfer ability. The tubes are usually provided with plate
type fins to increase the surface area for heat transfer. The fins are usually made from aluminium
because of its light weight.
The condensers with the single row of tubing provide the most efficient heat transfer. This is
because the air temperature rises as it passes through each row of tubing. The temperature
difference between the air and the vapour refrigerant decreases in each row of tubing and
therefore each row becomes low effective. However single row condensers required more space
than multi row condensers.
3.10 INTERNAL COMBUSTION ENGINE
Internal combustion engines are generally used for propulsion in vehicles. A internal
combustion engine is any engine that uses the explosive combustion of fuels to push a piston
within a cylinder. A practical Internal combustion engine was first successfully invented by
Nicolaus Otto a German scientist in 1876 called “Otto Cycle Engine”.
Generally internal combustion engine uses fossil fuel ( mainly petroleum) to run ,these engine
have been extensively used in every vehicles like trucks, cars, buses etc. and in a wide variety of
aircraft and locomotives.
Advantages of Internal Combustion Engine :
1. Overall efficiency is high.
2. Greater mechanical simplicity.
3. Weight to power ratio is generally low.
4. Generally lower cost.
5. Easy starting from cold conditions.
Classification of I.C. Engines
Internal Combustion engines may be classified as given below:
1. According to cycle of operation:
Two-stroke cycle engine.
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Four-stroke cycle engines.
2. According to cycle of combustion:
Otto cycle engine (combustion at constant volume).
Diesel cycle engine (combustion at constant pressure).
Dual combustion cycle engine (combustion partly at constant volume and partly
at constant pressure).
3. According to arrangement of cylinder:
Horizontal engine.
Vertical engine.
V-type engine
Radial engine etc.
4. According to their uses:
Stationary engine.
Portable engine.
Marine engine.
Automobile engine.
5. According to the fuel employed and the method of fuel supply to the engine cylinder:
Oil engine.
Petrol engine.
Gas engine.
Kerosene engine.
Our project has been carried out with the use of a two-stroke engine.
3.10.1 TWO-STROKE ENGINE:
Following are the details about two-stroke engine
Two-stroke engine is a internal combustion engine that complete the process in two strokes of the
piston or in one revolution of crankshaft. Thus one power stroke is obtained in each revolution of the
crankshaft. In this engine suction and exhaust strokes are eliminated. Here instead of valves, ports
are used. The exhaust gases are driven out from engine cylinder by the fresh entering the cylinder
nearly at the end of the working stroke. Because of one power stroke for one revolution, power
produced for one revolution. Power produced for same size of engine in more or for the same power
the engine is light and compact. Because of one power stroke in one revolution greater cooling and
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lubrication required. Great rate of wear and tear. In two-stroke petrol engine some fuel is exhausted
during scavenging. Two-stroke petrol engines used in very small sizes only.
Invention of two-stroke engine cycle is attributed to Dugald Clerk who in 1881patented his design.
3.10.2 Application
Two-stroke engines continue to be commonly used in high-power, handheld applications such as
trimmers and chainsaws.The light overall weight, and light-weight spinning parts give important
operational and even safety advantages.These engines are still used for small, portable, or
specialized machine applications such as outboard motors, motorcycles, mopeds, scooters, tuk-tuk
and lawnmowers.
CHAPTER 4
CONSTRUCTION
4.0 CONSTRUCTIONThe following materials were required for the construction and assembly process-
4.1 IRON RODSIron rods is a type of wrought iron, which is generally used for building heavy construction.
We have arranged few numbers of iron rods from the market. The iron pieces were cut and
reshaped according to our model specifications, in a welding shop.
4.2 WELDING
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Welding is a fabrication or sculptural process that joins materials,
usually metals or thermoplastics, by causing coalescence. This is often done by melting the work
pieces and adding a filler material to form a pool of molten material (the weld pool) that cools to
become a strong joint, with pressure sometimes used in conjunction with heat, or by itself, to
produce the weld. This is in contrast with soldering and brazing, which involve melting a lower-
melting-point material between the work pieces to form a bond between them, without melting
the workpieces.
Many different energy sources can be used for welding, including a gas flame, an electric arc,
a laser, an electron beam, friction, and ultrasound. While often an industrial process, welding can
be done in many different environments, including open air, under water and in outer space.
Regardless of location, welding remains dangerous, and precautions are taken to avoid
burns, electric shock, eye damage, poisonous fumes, and overexposure to ultraviolet light.
Until the end of the 19th century, the only welding process was forge welding, which
blacksmiths had used for centuries to join iron and steel by heating and hammering them. Arc
welding and oxy-fuel welding were among the first processes to develop late in the century, and
resistance welding followed soon after. Welding technology advanced quickly during the early
20th century as World War I and World War II drove the demand for reliable and inexpensive
joining methods. Following the wars, several modern welding techniques were developed,
including manual methods like shielded metal arc welding, now one of the most popular welding
methods, as well as semi-automatic and automatic processes such as gas metal arc
welding, submerged arc welding, flux-cored arc welding and electro-slag welding.
Developments continued with the invention of laser beam welding and electron beam welding in
the latter half of the century. Today, the science continues to advance. Robot welding is
becoming more commonplace in industrial settings, and researchers continue to develop new
welding methods and gain greater understanding of weld quality and properties.
4.2.1 Arc WeldingArc welding is a type of welding that uses a welding power supply to create an electric
arc between an electrode and the base material to melt the metals at the welding point.
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They can use either direct (DC) or alternating (AC) current, and consumable or non-
consumable electrodes. The welding region is sometimes protected by some type of inert or
semi-inert gas, known as a shielding gas, and/or an evaporating filler material.
The process of arc welding is widely used because of its low capital and running costs. Getting
the arc started is called striking the arc. An arc may be struck by either lightly tapping the
electrode against the metal or scratching the electrode against the metal at high speed.
4.3 SHEET METAL
Sheet metal is simply metal formed into thin and flat pieces. It is one of the fundamental forms
used in metalworking, and can be cut and bent into a variety of different shapes. Countless
everyday objects are constructed of the material. Thicknesses can vary significantly, although
extremely thin thicknesses are considered foil or leaf, and pieces thicker than 6 mm (0.25 in) are
considered plate.
Sheet metal is available as flat pieces or as a coiled strip. The coils are formed by running a
continuous sheet of metal through a roll slitter.
The thickness of the sheet metal is called its gauge. The gauge of sheet metal ranges from 30
gauge to about 8 gauge. The higher the gauge, the thinner the metal.There are many different
metals that can be made into sheet metal, such
as aluminum, brass, copper, steel, tin, nickel and titanium. For decorative uses, important sheet
metals include silver, gold, and platinum (platinum sheet metal is also utilized as a catalyst).
Sheet metal has applications in car bodies, airplane wings, medical tables, roofs for buildings and
many other things. Sheet metal of iron and other materials with high magnetic permeability, also
known as laminated steel cores, has applications in transformers and electric machines.
Historically, an important use of sheet metal was in plate armor worn by cavalry, and sheet metal
continues to have many decorative uses, including in horse tack.
4.3.1 Aluminum Sheet
The four most common aluminum grades available as sheet metal are 1100-H14, 3003-H14,
5052-H32, and 6061-T6.
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Grade 1100-H14 is commercially pure aluminum, so it is highly chemical and weather resistant.
It is ductile enough for deep drawing and weld able, but low strength. It is commonly used in
chemical processing equipment, light reflectors, and jewelry.
Grade 3003-H14 is stronger than 1100, while maintaining the same formability and low cost. It
is corrosion resistant and weld able. It is often used in stampings, spun and drawn parts, mail
boxes, cabinets, tanks, and fan blades.
Grade 5052-H32 is much stronger than 3003 while still maintaining good formability.
It maintains high corrosion resistance and weldability. Common applications include electronic
chassis, tanks, and pressure vessels.
Grade 6061-T6 is a common heat treatable structural aluminium alloy. It is weldable, corrosion
resistant, and stronger than 5052, but not as formable. Note that it loses some of its strength
when welded
4.4 FUEL KIT
A fuel kit is provided in the model to store the petrol with an adjustment knob. With the help of
the knob the fuel flow can be regulated in the engine. The capacity of the fuel kit is two liter.
4.5 IGNITION COIL
An ignition coil system is a system for igniting a fuel-air mixture. It is best known in the field
of internal combustion engines but also has other application. The earliest internal combustion
engines used a flame, or a heated tube, for ignition but these were quickly replaced by systems
using an electric spark.
4.5.1 Magneto Ignition System
The simplest form of spark ignition is that using a magnet. The engine spins a magnet inside a
coil, or, in the earlier designs, a coil inside a fixed magnet, and also operates a contact breaker,
interrupting the current and causing the voltage to be increased sufficiently to jump a small gap.
The spark plugs are connected directly from the magneto output. Early magnetos had one coil,
with the contact breaker (sparking plug) inside the combustion chamber.
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In about 1902, Bosch introduced a double-coil magneto, with a fixed sparking plug, and the
contact breaker outside the cylinder.
Magnetos are not used in modern cars, but because they generate their own electricity they are
often found on piston-engine aircraft engines and small engines such as those found
in mopeds, lawnmowers, snow blowers, chainsaws, etc. where a battery-based electrical system
is not present for any combination of necessity, weight, cost, and reliability reasons. Magnetos
were used on the small engine's ancestor, the stationary "hit or miss" engine which was used in
the early twentieth century, on older gasoline or distillate farm tractors before battery starting
and lighting became common, and on aircraft piston engines.
Magnetos were used in these engines because their simplicity and self-contained operation was
more reliable, and because magnetos weighed less than having a battery
and dynamo or alternator.
Aircraft engines usually have multiple magnetos to provide redundancy in the event of a failure.
Some older automobiles had both a magneto system and a battery actuated system (see below)
running simultaneously to ensure proper ignition under all conditions with the limited
performance each system provided at the time. This gave the benefits of easy starting (from the
battery system) with reliable sparking at speed (from the magneto).
4.6 SPARKPLUG
A sparkplug is an electrical device that fits into the cylinder head of some internal combustion
engines and ignites compressed fuels such as aerosol, gasoline, ethanol and liquefied petroleum
gas by means of an electric spark.
Sparkplug have an insulated central electrode which is connected by a heavily insulated wire to
an ignition coil on the outside, forming with a grounded terminal and the base of the plug, a
spark gap inside the cylinder.
4.6.1 Operation of a SparkplugThe plug is connected to the high voltage generated by an ignition coil or magneto. As the
electrons flow from the coil, a voltage difference develops between the central electrode and side
electrode. No current can flow because the fuel and air in the gap is an insulator, but as the
voltage rises further, it begins to change the structure of the gases between the electrodes.
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Once the voltage exceeds the dielectric strength of the gases, the gases become ionized. The
ionized gas becomes a conductor and allows electrons to flow across the gap. Spark plugs
usually require voltage of 12,000–25,000 volts or more to 'fire' properly, although it can go up to
45,000 volts. They supply higher current during the discharge process resulting in a hotter and
longer-duration spark.
As the current of electrons surges across the gap, it raises the temperature of the spark channel to
60,000 K. The intense heat in the spark channel causes the ionized gas to expand very quickly,
like a small explosion. This is the "click" heard when observing a spark, similar to
lightning and thunder.
The heat and pressure force the gases to react with each other, and at the end of the spark event
there should be a small ball of fire in the spark gap as the gases burn on their own.
The size of this fireball or kernel depends on the exact composition of the mixture between the
electrodes and the level of combustion chamber turbulence at the time of the spark. A small
kernel will make the engine run as though the ignition timing was retarded and a large one as
though the timing was advanced.
A frame is constructed out of those rods to hold the engine and the refrigerator box along with
the entire components.
The iron rods are joined with the help of arc-welding and the frame was tested successfully.
An iron pipe was attached to the exhaust of the engine to make an arrangement as proposed.
A magnetic ignition system was provided as the ignition coil for the engine and a spark is
provided there with the help of a spark plug.An insulation is made to cover the generator tubes,
with the help of an aluminium sheet enclosing the fur.
CHAPTER 5
REFRIGERATION AND ACCESSORIES
5.0 REFRIGERATION AND ACCESSORIESA number of accessory items are used in refrigeration circuit for specific purposes and their
requirement in a particular system depends on the application.
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5.1 RECEIVERSIt is that part of open type vapour compression system which receives the liquid refrigerant form
condenser and supplies it to evaporator through refrigerant control device. It is made of cast steel
or cast iron. It is usually located just after condenser in vertical or horizontal positions. It is used
for servicing purposes and for taking care of variations in the amount of liquid refrigerant in the
system. Refrigerant is stored in the receiver when the part of the machine is taken apart for
repairing purposes.
Advantages1. It supplies liquid refrigerant to the evaporator.
2. Slightly excess or short of refrigerant does not alter the working of the machine.
3. Gas can be stored in the liquid receiver when the part of the machine is to be
repaired.
4. Gas is stored in the liquid receiver when there is to be stopped for long period, so that
in may not leak out from the system.
5.2 DRIERSA refrigeration system is equipped with a drier to remove moisture as well as minute particles
to have its normal functioning.
The moisture is absorbed by the drier due to the water crystallization. The amount of
absorption of water depends upon the type of desiccant and the size of its granules. The drier
consists of a shell containing desiccant granules with a provision for uniform distribution of
condensation over the entire desiccant particles.
The shell containing desiccant is usually called cartridge which can be filled again and
again. At the exit perforated pipe is provided with a view to prevent the flow of bigger granules.
The filter is incorporated to entrap the fine particles. In order to keep the filter in position, a
spring is used. The driers are usually kept in the liquid line.
5.2.1 Types of DriersThere are two types of driers namely,
1. Throw-away type
2. Refill type
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The refill type is employed in this system. In the refill type the desiccant granules are
replaced by fresh charge after removing the flange. The desiccants for common use are alumina
sulphate, silica-gel, zeolite, etc., with the silica-gel being the best and most common among
them.
5.3 INSULATIONSince heat always flows from higher temperature region to one of lower temperature, there is a
continuous flow of heat form outside to the refrigerated space. To limit the amount of such flow
it becomes necessary to use good insulating material. When the temperature difference between
the outside and refrigerated space is large it becomes absolutely essential to use insulation.
Heat transfer occurs due to conduction, convection and radiation. The heat flow due to
convection can be reduced by use of materials having a low heat conductivity material.
Having very small closed air cells in the insulation material can reduce the heat transfer
through convection. Thus an insulating material should have low heat conductivity and a number
of small closed air cells for good insulation.
5.3.1 Selection of Insulation materialThe following factors are of prime importance in the selection of the insulation material:
1. Low thermal conductivity
2. Vapour permeability.
3. Resistance to fire.
4. Mechanical strength and rigidity of its own
5. Resistance to vermin and fungus.
6. Less moisture absorption
7. Ease of application and cost.
5.4 TUBINGMost tubing used in refrigeration system is made of copper. However, some aluminium, stainless
steel and plastic tubing is used. All tubing used in refrigeration system are carefully processed to
be sure that it is clean and dry inside.
Copper tubing is used in the work to provide good refrigeration work in the system.
Copper tubing is available in soft and hard types. Both are available in tow-wall thickness, K and
L. Type K is a heavy wall, type L is medium thick. Most tubing used at present is of L thickness.
5.4.1 Soft Copper Tubing
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It is used in domestic work and in some commercial refrigeration work. The copper tube is used
in the work of 3/8” outside diameter and 0.032” wall thickness. The copper tube is annealed
(heated and then allowed to cool) So that the bending of the tube is easy and flexible. Soldering
process is carried out to wound the copper tubes around the hot and cold (evaporator) tanks.
5.5 SOLDERINGSoldering is a process of applying molten metal to metals that are heated but are not molten. It is
a n adhesion process. The molten solder flows in to the pores of the surface of the metals being
joined, and as the solder solidifies (hardens) a good bond is obtained.
5.6 PROPERTIES OF COPPER1. Density - 8954 kg/m3
2. Thermal diffusivity - 0.404 m2/hr
3. Specific heat - 0.091 keal/kg 0 c or 0.381 kj/kg k
4. Thermal conductivity - 386 w/mk
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CHAPTER 6
WORKING PRINCIPLE
6.0 WORKING PRINCIPLE:
The project consists of an Electrolux refrigerating system using heat energy as input.
The principle behind Electrolux refrigeration is that it uses three gases to accomplish its
cooling effect namely ammonia (refrigerant) , water (absorbent) & hydrogen.
Here heat input is required at the side tube of the refrigerating unit, where aqua ammonia
is heated to get ammonia vapors.
In this project we are utilizing the non-conventional energy source, which we have taken
from the waste heat from an engine.
Since the Electrolux system has no pump (unlike the simple vapor absorption system) for
its working, the only energy input is in the form of waste heat at the generator pipe.
We bought an old Electrolux refrigeration system from the market and inspected the
system with the help of a professional fridge mechanic and found that the existing system
was working correctly.
We also managed to get obsolete Electrolux refrigeration at a minimal price.
Our next aim was to modify the existing system so that its running cost becomes zero.
For that, we decided to modify the existing system by replacing the heating unit with the
silencer of the exhaust manifold of an engine.
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We also bought a second hand 2-stroke 100cc kinetic engine for the
energy source. We decided to run the Electrolux refrigerating system with the output heat
coming out from the exhaust of the engine.
Experiments showed that for effective liberation of ammonia vapor from ammonia
hydroxide solution, the temp. should be above 88ºC. As the exhaust gas temp. From the
2-stroke engine was above 300ºC so the process was found feasible.
We have prepared a welded frame so as o mount the engine and the refrigerator at a
proper height and alignment.
The next challenge for us was to attach the exhaust gas silencer pipe with the rear side of
the refrigerator unit.
So we have extended the silencer pipe of the exhaust manifold with the help of an iron
rod in such a way that it touches the generating tube of the Electrolux refrigerating
system.
We have provided an aluminum coated insulation enclosing both the silencer rod and the
generating tube, so to assure that no heat is lost to the atmosphere.
After absorbing the heat we are allowing the exhaust gases to flow the atmosphere with
the special arrangement of the silencer.
When we kick start the engine the exhaust gases come out from it passes through the
generator pipe in the refrigerating unit, but it takes considerable time to heat the ammonia
hydroxide solution to form vapors, so as to start the Electrolux refrigerating system.
The Electrolux refrigeration system works with the formation of ammonia vapor which is
then made to pass through the condenser.
Air circulating over the fins of the condenser removes heat from the ammonia vapor to
condense the liquid ammonia in which state it flows in to the evaporator.
The evaporator is supplied with hydrogen which lowers the ammonia vapor pressure
sufficiently to allow the liquid ammonia to evaporate.
Ammonia acting as a refrigerant extracts heat from the food storage space thereby
lowering the temp. inside the refrigerator.
The mixture of ammonia and hydrogen vapor passé from the evaporation to the absorber.
A strong ammonia solution produced in the absorber flows down to the absorber vessel
and then to the generating pipe thus completing the full cycle of refrigerating operation.
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SNAPSHOT 1
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SNAPSHOT 2
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SNAPSHOT 3
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SNAPSHOT 4
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SNAPSHOT 5
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CONCLUSION
The project is mainly utilizing the waste heat from an engine to run the process of vapor
absorption system to produce the cooling effect in an Electrolux Refrigerating System. Also, a
successful implementation of non-conventional form of energy (heat energy) is tested and
achieved in this project. If one utilizes energy which is otherwise wasted, more useful processes
could be carried out. The project is mainly working as a heat recovery system.
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REFERENCES
1. Khurmi, R.S. and Gupta, J.K. (1987) ‘ A Textbook of Refrigeration and Air Conditioning’, S.Chand Publication.Reprint 2009, Multicolor Illustrative Edition.
2. Rajput, R.K. (2004) ‘Thermal Engineering’, Laxmi Publications(P) Ltd.
3. V,Ganesan (2003) ‘Internal Combustion Engine’, Tata McGraw Hill Publications.
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