Lab mannual of thermal engg.updated 1

IPS Academy, Institute of Engineering & Science
3th Semester Thermal Engineering Lab Session 2019-20
IPS Academy, Indore
Institute of Engineering & Science
Mechanical Engineering Department
LAB MANUAL
Thermal Engineering Lab
(ME-306)
Name ……………………………………………
Session ……………Semester …………………….
Enrollment No. ……………..

Contents
1. Vision Mission of the Institute
2. Vision Mission of the Department
3. PEOs
4. POs
5. COs
6. Content beyond Syllabus.
7. Laboratory Regulations and Safety Rules
8. Index
9. Experiments

Vision of the Institute
To be the fountainhead of novel ideas & innovations in science & technology & persist to be a
foundation of pride for all Indians.
Mission of the Institute
M1: To provide value based broad Engineering, Technology and Science where education in
students are urged to develop their professional skills.
M2: To inculcate dedication, hard work, sincerity, integrity and ethics in building up overall
professional personality of our student and faculty.
M3: To inculcate a spirit of entrepreneurship and innovation in passing out students.
M4: To instigate sponsored research and provide consultancy services in technical, educational
and industrial areas.
Vision of the Department
To be a nationally recognized, excellent in education, training, research and innovation that
attracts, rewards, and retains outstanding faculty, students, and staff to build a Just and Peaceful
Society.
Mission of the Department
M1: Imparting quality education to the students and maintaining vital, state-of-art research
facilities for faculty, staff and students.
M2: Create, interpret, apply and disseminate knowledge for learning to be an entrepreneur and
to compete successfully in today’s competitive market.
M3: To inculcate Ethical, Social values and Environment awareness.

Program Education Objectives (PEOs)
PEO1: To enrich graduates with fundamental knowledge of Physics, Chemistry and advanced
mathematics for their solid foundation in Basic Engineering science.
PEO2: To provide graduates to design the solution of engineering problems relevant to
mechanical engineering design through the process of formulating, executing & evaluating a
design solution as per need with socio-economic impact consideration and related constraints.
PEO3: To provide graduates with experience in learning and applying tools to solve theoretical
and open ended mechanical engineering problems.
PEO4: To provide a contemporary grounding in professional responsibility including ethics,
global economy, emerging technologies and job related skills such as written and oral
communication skills and to work in multidisciplinary team.
PEO5: Prepare graduates to be interested, motivated, and capable of pursuing continued life-
long learning through beyond curriculum education, short term courses and other training
programme in interdisciplinary areas.

Program Outcomes (POs)
Engineering Graduates will be able to:
PO1: Engineering knowledge: Apply the knowledge of mathematics, science, engineering
fundamentals, and an engineering specialization to the solution of Mechanical
engineering problems.
PO2: Problem analysis: Identify, formulate, and analyze mechanical engineering problems to
arrive at substantiated conclusions using the principles of mathematics, and engineering
sciences.
PO3: Design/development of solutions: Design solutions for mechanical engineering
problems and design system components, processes to meet the specifications with
consideration for the public health and safety, and the cultural, societal, and
environmental considerations.
PO4: Conduct investigations of complex problems: An ability to design and conduct
experiments, as well as to analyze and interpret data.
PO5: Modern tool usage: Create, select, and apply appropriate techniques, resources, and
modern engineering and IT tools including prediction and modeling to mechanical
engineering problems with an understanding of the limitations.
PO6: The engineer and society: Apply critical reasoning by the contextual knowledge to
assess societal, health, safety, legal and cultural issues and the consequent
responsibilities relevant to the Mechanical engineering practice.
PO7: Environment and sustainability: Understand the impact of the Mechanical engineering
solutions in societal and environmental contexts, and demonstrate the knowledge of, and
need for sustainable development.
PO8: Ethics: An understanding of professional and ethical responsibility.
PO9: Individual and teamwork: Function effectively as an individual, and as a member or
leader in teams, and in multidisciplinary settings.
PO10: Communication: Ability to communicate effectively. Be able to comprehend and write
effective reports documentation.

PO11: Project management and finance: Demonstrate knowledge and understanding of
engineering and management principles and apply this to Mechanical engineering
problem.
PO12: Life-long learning: ability to engage in life-long learning in the broadest context of
technological change.
Program Specific Outcomes (PSOs)
PSO1: Engage professionally in industries or as an entrepreneur by applying manufacturing and
management practices.
PSO2: Ability to implement the learned principles of mechanical engineering to analyze,
evaluate and create advanced mechanical system or processes.
Course Outcomes (COs)
 Demonstrate the Working principle of Low pressure boiler and High Pressure Boiler.
[BT-01]
 Understand Boiler Performance and their applications. [BT-02]
 Identify the applications of First Law of thermodynamics. [BT-02]
 Identify the compressor types and their performance.[BT-02]
 Evaluate the Quality of steam by using Combined Separating and Throttling
Calorimeter. [BT-03]

Laboratory Regulations and Safety Rules
1. Read the instructions mentioned in the manual carefully and then proceed for the experiment.
2. Mishandling of lab equipment will not be tolerated at all. If any student is found guilty;
he/she should be punished/ discarded from the lab.
3. Care must be taken while dealing with electrical connections.
4. Issued the needed/ supporting equipments by the concerned teacher/lab.technician & return
the same duly before leaving the lab.
5. If any defect or discrepancy noticed in the particular instrument/equipment while the students
are using, they will be fined/ punished for the same.
6. Put your bags on the rack outside the lab before entering in lab.
7. Switch off the lights, fans and all the equipments used, before leaving lab.
8. Students will replace their chairs to its specific position before leaving the lab.

INDEX
S.No. Experiment Date Grade Signature
1. Study of Boiler Terminology and their Classification.
2.
Study of working of Low pressure and High Pressure
Boiler with demonstrate model.
3.
Study of Boiler Mountings & Accessories and Boiler
Performance.
4. Study of two stage air compressor with intercooler.
5.
Verify Joule’s Experiments on Mechanical Equivalent
of Heat
6.
Determine volumetric and isothermal efficiencies of a
single acting, Double stage reciprocating Air
compressor
7.
Study of Temperature Measuring devices
8.
To Calculate the dryness fraction of Steam using
Combined separating Throttling calorimeter.
9. Study and experiments on ORSAT apparatus
10.
Study of Bomb Calorimeter and find the calorific
value of fuel by using Bomb Calorimeter

Experiment No.1
Aim: Study of Boiler Terminology and their Classification
Introduction: A steam generator or boiler is, usually a closed vessel made of steel. Its function
is to transfer the heat produced by the combustion of fuel (solid, liquid or gaseous) to water, and
ultimately to generate steam. The steam produced may be supplied
1. To an external combustion engine, i.e. steam engines and turbines.
2. At low pressures for industrial process work in cotton mills, sugar factories, breweries, etc.
3. For producing hot water, this can be used for heating installations at much lower pressure.
Important terms:
1. Boiler shell: It is made up of steel plates bent into cylindrical form and riveted or welded
together. The ends of the shell are closed by means of end plates. A boiler shell should have
sufficient capacity to contain water and steam.
2. Combustion chamber: It is the space, generally below the boiler shell, meant for burning
fuel in order to produce steam from the water contained in the shell.
3. Grate: It is a platform, in the combustion chamber, upon which fuel (coal or wood) is burnt.
The great, generally, consists of cast iron bars which are spaced apart so that air (required for
combustion) can pas through them. The surface area of the grate, over which the fire takes
place, is called great surface.
4. Furnace: It is the space, above the grate and below the boiler shell, in which the fuel is
actually burnt. The furnace is also called fire box.
5. Heating surface: It is that part of boiler surface, which is exposed to the fire (or hot gases
from the fire).
6. Mountings: These are the fittings which are mounted on the boiler for its proper functioning.
They include water level indicator, pressure gauge, safety valve etc. It may be noted that a
boiler cannot function safely without the mountings.
7. Accessories: These are the devices, which form an integral part of a boiler, but are not
mounted on it. They include super heater, economizer, feed pump etc. It may be noted that the
accessories help in controlling and running the boiler efficiently.
2) Classification of Steam Boilers.
Though there are many classifications of steam boilers, yet the following are important from
the subject point of view.

1. According to the contents in the tube: The steam boilers, according to the contents in the
tube may be classified as:-
(a) Fire tube or smoke tube boiler,
(b) Water tube boiler.
In fire tube steam boilers, the flames and hot gasses, produced by the combustion of fuels,
pass through the tubes (called multi-tubes) which are surrounded by water. The heat is
conducted through the walls of the tubes from the hot gases to the surrounding water. Examples
of fire tube boilers are: Simple vertical boiler, Cochran boiler, Lancashire boiler, Cornish boiler,
Scotch marine boiler, Locomotive boiler, and Velox boiler.
In Water tube steam boilers, the water is contained inside the tubes (called water tubes) which
are surrounded by flames and hot gases from outside. Examples of water tube boilers are
Babcock and Wilcox boiler, Stirling boiler, La-Mont boiler, Benson boiler, Yarrow boiler and
Loeffler boiler.
2. According to the position of the furnace: The steam boilers, according to the position of the
furnace are classified as:
(a) Internally fired boilers
(b) Externally boilers.
In Internally fired steam boilers, the furnace is located inside the boiler shell. Most of the fire
tube steam boilers are internally fired.
In externally fired steam boilers, the furnace is arranged underneath in a brick work setting.
Water tube steam boilers are always externally fired.
3. According to the axis of the shell: The steam boilers, according to the axis of the shell, may
be classified as:
(c) Vertical boilers
(b) Horizontal boilers.
In vertical steam boilers, the axis of the shell is vertical. Simple vertical boiler and Cochran
boiler are vertical boilers.
In horizontal steam boilers, the axis of the shell is horizontal. Lancashire boiler, Locomotive
boiler and Babcock and Wilcox boiler are horizontal boilers.
4. According to the number of tubes: The steam boilers, according to the number of tubes,
may be classified as:

(a) Single tube boilers
(b) Multi tubular boilers.
In single tube steam boilers, there is only one fire tube or water tube. Simple vertical boiler
and Cornish boiler are single tube boilers.
In multi tubular steam boilers, there are two or more fire tubes or water tubes. Lancashire
boiler, Locomotive boiler, Cochran boiler, Babcock and Wilcox boiler are Multitubular boilers.
5. According to the method of circulation of water and steam: The steam boilers, according
to the method of circulation of water and steam, may be classified as:
(a) Natural circulation boilers
(b) Forced circulation boilers.
In Natural circulation steam boilers, the circulation of water is by natural convection currents,
which are set up during the heating of water. In most of the steam boilers, there is a natural
circulation of water.
In forced circulation steam boilers, there is a forced circulation of water by a centrifugal pump
driven by some external power. Use of forced circulation is made in high pressure boilers such
as La-Mont boiler, Benson Boiler, Loeffler boiler and Velox boiler.
7. According to the use: The steam boilers, according to their use, may be classified as:
(a) Stationary boilers
(b) Mobile boilers.
The Stationary steam boilers are used in power plants, and in industrial process work. These
are called stationary because they do not move from one place to another.
The mobile steam boilers are those which move from one place to another. These boilers are
locomotive and marine boilers.
8. According to the source of heat: The steam boilers may also be classified according to the
source of heat supplied for producing steam. These sources may be the combustion of solid,
liquid or gaseous fuel, hot waste gases as byproducts of other chemical processes, electrical
energy or nuclear energy etc.

Questions.
1. Write the classification of Boiler.
2. What are the characteristics of a good Boiler?

Experiment No.2
Aim: Study of working of Low pressure and High Pressure Boiler with Demonstrate model
Working of Low pressure Boiler
To Study the working of Lancashire Boiler
This boiler works on the basic principle of heat ex-changer. It is basically a shell and tube type
heat ex-changer in which the flue gases flow through the tubes and the water flows through
shell. The heat is transfer from flue gases to the water through convection. It is a natural
circulation boiler which uses natural current to flow the water inside the boiler. The low
pressure boilers are those boilers which is generally produces a steam below the 20 bar pressure.
Construction:
As we discussed, this boiler is similar a shell and tube type heat ex-changer. It consist a large
drum of diameter up to 4-6 meter and length up to 9-10 meter. This drum consist two fire tube
of diameter up to 40% of the diameter of shell. The water drum is placed over the bricks works.
Three spaces create between the drum and the bricks, one is at bottom and two are in sides as
shown in figure. Flue gases passes through the fire tubes and side and bottom space. The water
level inside the drum is always above the side channels of flue gases, so more heat transfer to
the water. The drum is half filled with water and the upper half space for steam. The Furnace is
located at one end of the fire tubes inside the boiler. The low brick is situated at the grates
(space where fuel burns) which does not allow to un-burned fuel and ash to flow in fire tubes.
The boiler also consist other necessary mountings and accessories like economizer, super
heater, safety valve, pressure gauge, water gauge, etc. to perform better.
Working:
The Lancashire boiler is a shell and tube type heat ex-changer. The fuel is burn at the grate. The
water is pumped into the shell through the economizer which increases the temperature of
water. Now the shell is half filled with water. The fire tube is fully immersed into the water. The
fuel is charged at the grate which produces flue gases. These flue gases first passes through the
fire tube from one end to another. This fire tubes transfer 80-90% of total heat to the water. The
backward flue gases passes from the bottom passage where it transfer 8-10% heat to water. The
remaining flue gases passes from the side passage where it transfer 6-8% of heat to water. The
brick is the lower conductor of heat, so work as heat insulator. The steam produces in drum
shell it taken out from the upper side where it flows through super heater if required. So the
steam produce is taken by out for process work.

Figure: Lancashire Boiler
Advantages & Disadvantages:
Advantage:
1. This boiler is easy to clean and inspect.
2. It is more reliable and can generate large amount of steam.
3. It required less maintenance.
4. This boiler is a natural circulation boiler so lower electricity consumption than
other boilers.
5. It can easily operate.
6. It can easily meet with load requirement.
7. Lancashire boiler has high thermal efficiency about 80-90%.
Disadvantages:
1. This boiler required more floor space.
2. This boiler has leakage problem.
3. It requires more time to generate steam.

4. It cannot generate high pressure steam if required.
5. Grates are situated at the inlet of fire tube, which has small diameter. So the grate area is
limited in this boiler.
Working of High pressure Boiler
To Study the working of Benson Boiler
Introduction: Benson Boiler is a water tube high pressure boiler having forced circulation. It
works on the principle that if the boiler pressure is raised to critical pressure (225 kg/cm^2) then
there is no formation of steam bubbles because the steam and water at this pressure will have
the same Density. To achieve this water is fed to the boiler at critical pressure. At this pressure
water will be directly converted to superheated steam as the latent heat at critical pressure is
zero. Overall efficiency of plant is decreased as a lot of energy is consumed by feed water.
Operating the boiler at a slightly lower pressure than the critical pressure efficiency can be
increased. Thermal efficiency up to 90% can be achieved.
Working Principle of Benson Boiler:
This boiler has a unique characteristic of absence of steam separating drum. The entire
process of heating, steam generation and superheating is done in a single continuous tube.
Economizer
The feed water by means of the feed pump is circulated through the economiser tubes. Hot flue
gases pass over the economizer tubes and the feed water is preheated.
Radiant evaporator
The feed water from the economizer flows into the radiant evaporator with radiant parallel tube
sections. The radiant evaporator receives heat from the burning fuel through radiation process
and Majority of water is converted into steam in it.
Convection Evaporator
The remaining water is evaporated in the convection evaporator, absorbing the heat from the hot
gases by convection. Thus the saturated high pressure steam at a pressure of 210 kg/sq.cm is
produced.
Convection super heater
The saturated steam is now passed through the convection superheated where the saturated
steam as superheated to 650’C. The radiant evaporator, the convection evaporator and the
convection super heater are all arranged in the path of the flue gases.

Capacity
Capacity of Benson boiler is about 150 tonnnes/hr, at a pressure of 210 kgf/sq.cm, and at a
temperature of 650’C. (Efficiency may be improved by running the boiler at a pressure slightly
Lower than the critical pressure).
Figure: Benson Boiler
Salient features of BensonBoiler
1. As there are no drums, the total weight of Benson boiler is 20% less than other boilers. This also
reduces the cost of the boilers.
2. As no drums are required, the transfer of the Benson parts is easy. Majority of the parts may be
carried to the site without pre-assembly.
3. Since no drum is used, this is an once-through boiler and the feed water entering at one end is
discharged as superheated steam at the other end.
4. Circulating pump and down comers are dispensed with.

Advantages:-
1. As the generation of steam is carried out in the evaporating tubes at pressure higher than critical
pressure it doesn’t require any evaporating drum.
2. The boiler can be started in short time in 10 to 15 minutes only.
3. Benson boiler is lighter in weight with high generation rate of steam.
4. Due to absence of the evaporating drum the total weight is 20% less than other boilers.
5. The super heater of the Benson boiler is the integral part of forced circulation system therefore
no special starting arrangement for super heater is required.
6. The cost of the boiler is reduces as there is no evaporating drum.7.Bubble formation
is eliminated in Benson boiler which is critical problem in Lamont boiler.
Disadvantages:-
1. The evaporation process will leave small deposits during conversion of water into steam due
to which it requires frequent cleaning. To obviate this problem, the water softening plant is
require.
2. Tubes are likely to be overheated in case of water flow is insufficient.
Questions.
1. Difference between low pressure boiler and high pressure boiler.
2. Write the difference between fire tube and water tub boiler.(Any 7)

Experiment No. 3
Aim:- Study of Boiler Mountings & Accessories with Boiler Performance.
Theory
Boiler: - A steam boiler is a closed vessel in which steam is produced from water by
combustion of fuel.
Boiler Mountings: -
The components which are fitted on the surface of the boiler for complete safety and control of
steam generation process are known as boiler mountings. The following are the various
important mountings of a boiler.
1. Pressure Gauge- It is usually mounted on the front top of the boiler shell. It is mounted on
each boiler to show the pressure of the steam. Its dial is graduated to read the pressure in
Kilograms per sq. centimeter. Bourdon’s pressure gauge is commonly used as shown in Fig.
The essential elements of this gauge are the elliptical spring tube which is made of bronze
and is solid drawn. One end of this tube is attached by lines to a toothed quadrant and the
other end is connected to a steam space.
Figure: Pressure Gauge
2. Safety Valves- They are needed to blow off the steam when pressure of the steam in the
boiler exceeds the working pressure. These are placed on the top of the boiler. There are
four types of safety valves:
i. Dead weight safety valve
ii. Lever safety valve
iii. Spring loaded safety valve
iv. Low water high steam safety valve

Spring loaded safety valve- A spring loaded safety valve is mainly used for locomotives and
marine boilers. In this type the valve is loaded by means of a spring, instead of dead weight.
It consists of two valves, resting on their seats. Valve seats are mounted on the upper ends of
two hallow valve chests, which are connected by a bridge. The lower end of these valves
chests have common passage which may be connected to the boiler. There is a lever which
has two pivots, one of which is integral with it and the other is pin jointed to the lever. This
pivot rests on the valves and forces them to rest on their respective seats with the help of a
helical spring.
Figure: Spring loaded safety valve
3. Feed Check Valve- A feed check valve is shown in Fig. The function of the feed check
valve is to allow the supply of water to the boiler at high pressure continuously and to
prevent the back flow the boiler when the pump pressure is less than boiler pressure or
when pump fails. Feed check valve is fitted to the shell slightly below the normal water
level of the boiler.
Figure: Feed Check Valve

4. Fusible Plug- It is fitted to the crown plate of the furnace of the fire. The function of
fusible plug is to extinguish the fire in the fire box, when water level in the boiler comes
down the limit and it prevents from blasting the boiler, melting the tube and overheating
the fire-box crown plate. A fusible plug is shown in fig. It is located in water space of
the boiler. The fusible metal is protected from direct contact of water by gun metal plug
and copper plug. When water level comes down, the fusible metal melts due to high heat
and copper plug drops down and is held by gun metal ribs. Steam comes in contact with
fire and distinguishes it. Thus it prevents boiler from damages.
Figure: Fusible Plug
5. Blow Off Cock- The blow off cock as shown in fig., is fitted to the bottom of a boiler
drum and consists of a conical plug fitted to body or casing. The casing is packed, with
asbestos packing, in groves round the top and bottom of the plug. The asbestos packing
is made tight and plug bears on the packing. Blow off cock has to principle function are:
 To empty the boiler whenever required.
 To discharge the mud, scale or sedimentation which are accumulated at the bottom
of the boiler.
Figure: Blow Off Cock

6. Water Level Indicator- It is an important fitting, which indicates the water level inside
the boiler to an observer. It is a safety device, up on which the correct working of the
boiler depends. This fitting may be seen in froth of the boiler, and are generally two in
number. The upper end of the valve opens in steam space while the lower end opens in
the water. The valve consists of a strong glass tube. The end of the tube pass through
stuffing boxes formed in the hollow casting. These casting are flanged and bolted to the
boiler. It has three cocks; two of them control the passage between the boiler and glass
tube, while the third one (the drain cock) remains closed.
Figure: Water Level Indicator
7. Steam Stop Valve- A valve placed directly on a boiler and connected to the steam pipe
which carries steam to the engine or turbine is called stop valve or junction valve. It is
the largest valve on the steam boiler. It is, usually, fitted to the highest part of the shell
by means of a flange.
The principal functions of a stop valve are:
 To control the flow of steam from the boiler to the main steam pipe.
 To shut off the steam completely when required.
The body of the stop valve is made of cast iron or cast steel. The valve seat and the nut
through which the valve spindle works, are made of brass or gun metal.

Figure: Steam Stop Valve
Boiler Accessories:-The appliances installed to increase the efficiency of the boiler are known
as the boiler accessories. The commonly used accessories are:
1. Economiser- Economiser is a one type of heat exchange which exchanges the some
parts of the waste heat of flue gas to the feed water. It is placed between the exit of the
furnace and entry into the chimney. Generally economiser is placed after the feed pump
because in economiser water may transfer into vapour partially, which creates a priming
problem in feed pump water into the boiler drum. If economiser is used before feed
pump it limits the temperature rise of water .It consists of vertical cast iron tubes
attached with scraper. The function of scraper is to remove the root deposited on the
tube, mechanically.
Figure: Economiser

2. Super Heater- An element of steam generating unit in which the steam is super heated,
is known is super heater. A super heater is used to increase the temperature of saturated
steam at constant pressure. It is usually placed in the path of hot flue gases and heat of
the flue gases is first used to superheat the steam as shown in figure. The steam enters in
the down-steam tube and leaves at the front header. The overheating of super heater tube
is prevented by the use of a balanced damper which controls the flue gas. Steam
consumption of turbine is reduced by about 1% for each 5.5°C of superheat.
Figure: Super Heater
3. Air Pre-heater- The function of air pre-heater is to increase the temperature of air
before it enters the furnace. It is installed between the economiser and the chimney. The
air required for the purpose of combustion is drawn through the air pre-heater and its
temperature is raised when passed through ducts. The preheated air gives higher furnace
temperature which results in more heat transfer to the water and reduces the fuel
consumption. There are three types of pre-heaters:
1. Tubular type 2. Plate type 3. Regenerative type

Figure: Air Pre-heater
Questions.
1. Write the function of Boiler accessories also show their position in boiler plant with
Block Diagram.
2. What is Equivalent Evaporation of a Boiler and Boiler Efficiency?
3. What are the types of heat losses in boiler Pant?

Experiment No. 4
Aim:- Study of two stage air compressor with intercooler
Introduction:- An air compressor is a machine to compress the air and to raise its pressure. The
air compressor sucks air from the atmosphere, compresses it and then delivers the same under a
high pressure to a storage vessel. From the storage vessel, it may be conveyed by the pipeline to
a place where the supply of compressed air is required. Since the compression of air requires
some work to be done on it, therefore a compressor must be driven by some prime mover. The
compressed air is used for many purposes such as for operating pneumatic drills, riveters, road
drills, paint spraying, in starting and supercharging of internal combustion engines, in gas
turbine plants, jet engines and air motors etc. It is also utilized in the operation of lifts, rams,
pumps etc
 Single Stage Reciprocating Air Compressor
 Multistage Reciprocating Air Compressors
Multistage Reciprocating Air Compressors:
In a single stage air compressor if the compression ratio is increased, the final temperature
increases and the volumetric efficiency decreases. In such conditions leakage past the piston
starts and high compression requires robust cylinder construction. A high compression
temperature also affects the operation of the delivery valves, diminishes the lubricating
properties of the oil and increases the risk of ignition in pipe line. For these reasons if a higher
compression ratio (above 6 to 8) is needed, the overall compression ratio is subdivided into two
or more stages with lower compression ratios. Usually the maximum compression ratio for
small single stage compressors is 8 and for large machines it is 5. In practice, delivery pressure
up to5.6 bar in single stage, 5.6 to 35 bar in two stage and from 35 to 84 bar in three stages are
used. An intercooler between the two stages cools down compressed air from the first stage
before it enters the second stage. The temperature of the cooled air is nearly equal to initial
temperature of first stage. By cooling the air in between stages in this way, the compression is
made to approach isothermal. Thus the final temperature is appreciably lowered and the work
required for compression is reduced.

Figure: PV Diagram for two stage air compressor
Two-stage Reciprocating Air Compressor with Intercooler:
A schematic arrangement for a two-stage reciprocating air compressor with water cooled
intercooler is shown in figure. In its operation, the fresh air is sucked from the atmosphere in the
low pressure (L.P.) cylinder during its suction stroke at intake pressure P1 and temperature T l.
The air, after compression in the L.P. cylinder (i.e. first stage) from1 to 2, is delivered to the
intercooler at pressure P2 and temperature T2. The air is cooled in the intercooler from 2 to 3 at
constant pressure P2 and from temperature.T2 to T3. After that, the air is sucked in the high
pressure (H.P.) cylinder during its suction stroke. Finally, the air, after further compression in
the H.P. cylinder (i.e. second stage) from 3 to 4, is delivered by the compressor at pressure P3
and temperature T4
Figure: Two-stage Reciprocating Air Compressor with Intercooler

Advantages of Two-stage Reciprocating Air compressor
1. Piston type compressors are available in wide range of capacity and pressure
2. Very high air pressure (250 bar) and air volume flow rate is possible with multi-staging.
3. Better mechanical balancing is possible by multistage compressor by proper cylinder
arrangement.
4. High overall efficiency compared to other compressor
Disadvantages of Two-stage Reciprocating Air compressor
1. Reciprocating piston compressors generate inertia forces that shake the machine. Therefore, a
rigid frame, fixed to solid foundation is often required
2. Reciprocating piston machines deliver a pulsating flow of air. Properly sized pulsation
damping chambers or receiver tanks are required.
3. They are suited for small volumes of air at high pressures.
Questions.
1. Write the Classification and applications of Air Compressors.
2. Write the Advantages of multistage compression.

Experiment No. 5
Aim:- To study about two cylinder Two stage Reciprocating air compressor and find out
isothermal efficiency and volumetric efficiency.
Theory:- This may be regarded as a machine which compresses or which is used to increase
the pressure of air by reducing its volume.
Reciprocating compressor:- This is a machine which compresses air by means of piston
reciprocating inside a cylinder.
Working:- It consist a piston which is enclosed within a cylinder and equipped with
suction and discharge valve. The piston receives the power from the main shaft through a
crank shaft and connecting rod. A fly wheel is fitted on the main shaft to ensure turning
moment to be supplied throughout the cycle of operations.
Description: Two stage compressors is reciprocating type driven by a prime mover AC motor
through belt. The test rig consists of a base on which the tank (air reservoir) is mounted. The
electrical safety valve & mechanical safety valves are provided. The suction side of low
pressure cylinder is connected to the air tank with an orifice plate. The pressure drop across the
orifice plate can be measured by water manometer. The output of the motor is recorded by the
swinging field arrangement. The input of the motor can be measured by an energy meter .
Compressor Details & Parameters :
Diam. of L.P Cylinder D = 70mm
Stroke Length l = 85mm
Procedure:
1. Close the outlet valve.
2. Check the manometer connections. The manometer is filled with water up to the half
level.
3. Start the compressor and note down initial energy meter reading and spring balance
reading.
4. Read the tank pressure gauge for a particular pressure.
5. Note down the RPM of the compressor from the digital speed indicator.
6. Note down the manometer readings.
7. Note down the spring balance reading.
8. Note down the reading of energy meter for a given no of revolutions.

Repeat the experiment for various discharge pressures.
Calculations:
1. Actual volume flow rate of air :
Va = Cd A VA X 3600 m3/hr
= Cd A 2gha X 3600 m3/hr
2ghw D of water
= CdA ---------- X ------------------ X 3600 m3/hr
1000 D of Air
where Cd is co-efficient of discharge = 0.62
3.14* d2
A is Aera of orifice = --------- m2
4
d = dia of orifice = 15 mm ( 0.015 m)
Density of Water = 1000 kg/m cu
Density of Air = 1.293 kg/ m cu
hw = pressure drop across orifice plate in mm of water
2. Swept Volume = Vs (m3/hr)
3.14 D2 Nc X 60
Vs = ------------ X L X ---------------- in m3/hr.
4
D is diam. of piston = 70 mm = 0.07 m
L is stroke length = 85 mm = 0.085 m
Nc is speed of the compressor in RPM.
3. Volumetric Efficiency
Va
Volumetric Efficiency = -------- X 100
Vs
4 . Isothermal efficiency of the compressor

I n p2/p1 p2 discharge Pressure Isotherm.
Efficiency = --------------------------------- when ------ = ------------------------------------
[ n / (n-1)] [ (p2/p1) n-1 /n - 1] p1 inlet Pressure
Observations:
Readings are noted in the tabular column given below.
Graphs:
Graphs of Volumetric efficiency and isothermal efficiency are drawn for
various discharge pressures of air form the compressor.
S.No
Inlet
pressures
Discharge
Pressure
p2 =
p1 Nc Nm
hw,
mm Volum.
Isoth.
p1 Kg/cm2 P2

Questions.
1. Write the difference between axial flow compressor and Centrifugal compressor.
2. What is Volumetric Efficiency of Compressor?

Experiment No. 6
Aim:- To verify Joule’s Experiments on Mechanical Equivalent of Heat.
Introduction Accurate investigation of the relationship between heat developed and mechanical
work spent was taken up by the British Scientist James Prescott Joule. The main aim of his
investigations was to determine exactly the ratio between the work done and the quantity of heat
produced.
Joule used different arrangements for doing the work, W in different ways and measured the
corresponding amount of heat, H produced in each case. In all the cases he found that the
expenditure of the same amount of work always produced the same amount of heat. Every time
he found that 4186 joule of work was spent to produce the same amount of heat which could
raise the temperature of one kg of water through 10C. He established the relation, W/H to be a
constant quantity. The constant relation W/H was represented symbolically by the letter ‘J’. J is
known as Joule's mechanical equivalent of heat. ‘Symbolically, we can write :
W/H = J or W = JH
Thus he established that heat is a form of energy.
Joule’s Method for Experimental Determination of J.
Details of Apparatus: The apparatus consists of a specially designed calorimeter placed in a
wooden box C with felt lining to avoid heat losses to the surroundings. A number of vanes
projects from the walls of the calorimeter in its interior. A spindle carrying a number of m.s.
paddles P, P acts as a churner and it is so pivoted at the bottom that the paddles P, P are
capable of turning between the fixed vanes V. The spindle can be attached to a motor. The
spindle rotates by the motor.
Working: The K.E.is given by motor to turn the spindle and there by turn the paddles P, P
immersed in a known mass (m) of water contained in the calorimeter. The water is thus
churned but not allowed to rotate due to fixed vanes and the electrical energy of the Motor is
converted into kinetic energy of paddles. Due to friction offered by paddles KE is changed
into heat and as a result of it, the temperature of the water in the calorimeter rises. The rise in
temperature is measured by an accurate thermometer T inserted in the calorimeter. The
process is rapidly repeated several times (every time varies the speed of the motor) such that
there is an accurately measurable rise in the temperature of water.
Requirements :
1. Water =1Kg = 1.04166 Lt
2.Stop Watch
Constants Values:

The specific heat of water is 1 calorie/gram °C = 4.186 Kj/Kg °C
Formula for finding work done:
Work Done = V x I x T Joule
Observation:
Sl. No.
Volt Meter
Reading
(V)
Ammeter
Reading
(A)
Time
(sec)
Temp(Water)
( ̊C)
1.
2.
3.
Calculation
H=mw Cp(Tf-Ti)
= Joules
Analysis:
Graph the results of work done (w) vs Temp.

Importance of Joule’s Experiments
1. Joule’s experiments conclusively established that heat is a form of energy. It is not a
material substance like caloric fluid.
2. Always the same amount of heat was produced by spending a given amount of
mechanical work. It is immaterial what type of arrangement is used for doing
mechanical work. Other alternative ways used by Joule for conversion of mechanical
work into heat were
(i) By mechanically stirring mercury, and
(ii) By rubbing two iron rings together. Every time he found that W/H is a
constant quantity, i.e., when 4.186 Joule converted to heat the temperature of 1
kg of water will rise by 10C.
3. Terms Used
4. J = joule’s (Mechanical heat equivalent)
5. W= work done
6. H = heat developed
7. Mw = mass of the water
8. Ti=initial temp. of water
9. Tf= final temp. of water
10. Cp= specific heat
Questions
1. Write First Law of Thermodynamics for cyclic Process.
2. Explain Zeroth law of Thermodynamics.
3. Write Limitations of Thermodynamics.

Experiment No. 7
Aim: To Study Temperature Measuring Instruments
(a) Mercury – in glass thermometer &
(b) Thermocouple
Apparatus used: Mercury thermometer, Thermocouple setup
Theory
(a) Mercury – in glass thermometer:
A liquid-in-glass thermometer is widely used due to its accuracy for the temperature range -200
to 600°C. Compared to other thermometers, it is simple and no other equipment beyond the
human eye is required. The LIG thermometer is one of the earliest thermometers. It has been
used in medicine, metrology and industry. In the LIG thermometer the thermally sensitive
element is a liquid contained in a graduated glass envelope. The principle used to measure
temperature is that of the apparent thermal expansion of the liquid. It is the difference between
the volumetric reversible thermal expansion of the liquid and its glass container that makes it
possible to measure temperature.
The liquid-in-glass thermometer comprises of
1. A bulb, a reservoir in which the working liquid can expand or contract in volume.
2. A stem, a glass tube containing a tiny capillary connected to the bulb and enlarged at the
bottom into a bulb that is partially filled with a working liquid. The tube's bore is extremely
small - less than 0.02 inch (0.5 millimeter) in diameter.
3. A temperature scale is fixed or engraved on the stem supporting the capillary tube to indicate
the range and the value of the temperature. It is the case for the precision thermometers whereas
for the low accurate thermometers such as industrial thermometer, the scale is printed on a
separate card and then protected from the environment. The liquid-in-glass thermometers are
usually calibrated against a standard thermometer and at the melting point of water.
4. A reference point, a calibration point, the most common being the ice point.
5. A working liquid, usually mercury or alcohol.
6. An inert gas is used for mercury intended to high temperature. The thermometer is filled with
an inert gas such as argon or nitrogen above the mercury to reduce its volatilization.
The response of the thermometer depends on the bulb volume, bulb thickness, total weight and
type of thermometer. The sensitivity depends on the reversible thermal expansion of the liquid
compared to the glass. The greater the fluid expansion, the more sensitive the thermometer.
Mercury was the liquid the most often used because of its good reaction time, repeatability,

linear coefficient of expansion and large temperature range. But it is poisonous and so other
working liquids are used.
Figure: Liquid in Glass Thermometer
A mercury-in-glass thermometer, also known as a mercury thermometer, consisting of
mercury in a glass tube. Calibrated marks on the tube allow the temperature to be read by the
length of the mercury within the tube, which varies according to the heat given to it. To increase
the sensitivity, there is usually a bulb of mercury at the end of the thermometer which contains
most of the mercury; expansion and contraction of this volume of mercury is then amplified in
the much narrower bore of the tube. The response time of the thermometer is nothing but as
time constant or the time of consideration for measuring particular temperature.
(b) Thermocouple:
An electric current flows in a closed circuit of two dissimilar metals if their two junctions are at
different temperatures. The thermoelectric voltage produced depends on the metals used and on
the temperature relationship between the junctions. If the same temperature exists at the two
junctions, the voltage produced at each junction cancel each other out and no current flows in
the circuit. With different temperatures at each junction, different voltage is produced and
current flows in the circuit. A thermocouple can therefore only measure temperature differences
between the two junctions.
Figure:Thermocouple
Thermocouples response time is measured as a “time constant.” The time constant is defined as
the time required for a thermocouple’s voltage to reach 63.2% of its final value in response to a
sudden change in temperature. It takes five time constants for the voltage to approach 100% of

the new temperature value. Thermocouples attached to a heavy mass will respond much slower
than one that is left free standing because its value is governed by the temperature of the large
mass. A free standing (exposed or bare wire) thermocouple’s response time is a function of the
wire size (or mass of the thermocouple bead) and the conducting medium. A thermocouple of a
given size will react much faster if the conducting medium is water compared to still air.
Conclusion: Hence the study of various temperatures measuring instruments.
Questions
1. Write the answer of following Questions.
2. What is Peltier effect & Thomson effect?
3. Give 5 example were Thermocouple and Mercury – in glass thermometer is used
4. Write Down the Material used in Thermocouple

Experiment No. 8
Aim: To calculate the dryness fraction of Steam using combined separating Throttling
calorimeter.
Introduction: The dryness fraction of steam is determined by four methods. These are
 Separating Calorimeter.
 Throttling Calorimeter.
The Process of Throttling is similar to free expansion process with only the difference that free
expansion is a non-flow process, where as in Throttling of steam, the steam is taken
continuously & hence here we are dealing with flow process during which Enthalpy of system
remains constant. The process is utilized to determine experimentally the value of dryness
fraction of steam.
It was stated that only separating calorimeter suffers from the disadvantage that the
steam passing out after water separation may not be completely dry or it may have higher
dryness fraction. And for only throttling calorimeter it was found that the dryness fraction of
the order about 93% can be found out. Hence, for better results combined separating &
throttling calorimeter is used.
This separating & throttling calorimeter is designed for non-IBR boiler of capacity @ 20
to 25 Kg/hr. & pressure 2 to 2.5 Kg/Cm2 for throttling process orifice diameter is 0.5”
The very wet steam at pressure P1 from the steam main through sampling pipe first
enters the separating calorimeter via valve A., to insure that there is no throttling of steam
hence, the valve must be fully open. The wet steam in the metal basket B is subjected to sudden
reversal of direction of motion. Since the basket is provided with a number of perforations all
around but not at the bottom consequently the water particles due to grater inertia are thrown
out of suspension (mixture of dry steam, & water). The quantity of water thus separated is
collected in to the inner chamber provided with a graduated scale which indicates the quantity
of water separated.
The fairly dry steam moving upwards from the inner chamber is subsequently passed
on the throttling calorimeter where it undergoes throttling due to orifice
The pressure gauges are provided one at steam main & other before orifice plate. Valve C is
provided to drain the water from basket B. Valve D is provided to release the exhaust
condensed. Manometer is provided to take the pressure difference between atmosphere & after
throttling process of steam.

Calculations :
1. Dryness fraction of Steam (Separating Calorimeter):
Mm
mX

1
Let,
M = Mass of dry steam read from the gauge of condenser.
m = Mass of water separated in separating calorimeter.
2. Dryness fraction of steam (Throttling Calorimeter)
1
12sup2
2
(
gf
fspg
h
httCh
X


Where ,
hg 2 = Enthalpy of steam at final pressure ( P2 )
hfg 1 = Enthalpy of Vapors at initial pressure ( P1 )
hf 1 = Enthalpy of water at initial pressure ( P1 )
tSu p 2 = Super heated Steam Temp ( T1 )
ts2 = Saturated Steam Temp at pressure ( P2 )
Cp = Specific heat of super heated steam after throttling= 4.186 KJ/Kg.
Atmospheric Pressure = 1.0133 Kg/Cm2
.
3. Dryness fraction of Steam / Quality of given steam.
21 XXX 

Observation Table:
Sr. No Observations 1 2
1 Steam Pressure in separating Calorimeter( P1 ) Kg/Cm2
2 Steam Pressure in Throttling Calorimeter( P2 ) Kg/Cm2
3 Steam Temp. in Throttling Calorimeter o
C
4 Mass of Water separated in separating Calorimeter ( M ) ml
5 Mass of Water condensed in condenser ( m ) ml
Conclusion:
Dryness Fraction of Steam will vary according to steam Pressure.
Questions
1. What is Pure Substance?
2. Define Critical and Triple point of water?
3. What do understand by the degree of Superheat and the degree of sub cooling?

Experiment No. 9
Aim: Study and experiments on ORSAT apparatus.
Introduction:
Flue gas is the mixture of gases resulting from combustion and other reactions in combustion
equipments like engines and boilers, composed largely of nitrogen, carbon dioxide, carbon
monoxide, water vapour, and often sulfur dioxide, excess O2 and sometimes serving as a source
from which carbon dioxide or other compounds are recovered. Based on the fuel composition
flue gases are formed, a fuel having carbon and hydrogen compounds generates flue gas
containing oxides of carbon and hydrogen. To check the combustion efficiency of I.C engines,
it is essential to know the constituents of the flue gases being exhausted. An Orsat gas analyzer
is a piece of laboratory equipment used to analyze a gas sample (typically fossil fuel or flue gas)
for its oxygen, carbon monoxide and carbon dioxide content. Orsat apparatus consists of a
water-jacketed measuring burette, connected in series to a set of three absorption pipettes, each
through a stop-cock to absorb different gases.
Pipette 1: Contains ‘KOH’ (caustic soda or potassium hydroxide; 250g KOH in 500mL of
boiled distilled water) to absorb CO2
Pipette 2: Contains an alkaline solution of ‘pyrogallic acid’ (25g pyrogallic acid + 200g KOH
in 500ml of distilled water) to absorb O2 and CO2
Pipette 3: Contains an acid solution of ‘cuprous chloride’ (100g cuprous chloride + 125 ml
liquor ammonia + 375 ml of water) to absorb CO, O2 and CO2.
The other end is provided with a three-way stop-cock, the free end of which is further connected
to a U-tube packed with glass wool for avoiding the incoming of any smoke particles, etc. The
graduated burette is surrounded by a water jacket to keep the temperature of the gas constant
during the experiment. The lower end of the burette is connected to a water reservoir by means
of long rubber tubing.
Working principle of Orsat analyzer:
Typical flue gas analyzers measure the quantity of carbon dioxide, carbon monoxide and
oxygen by a chemical absorption principle. Based on the absorption factor of these three
components their respective absorbing solutions are selected in three different pipette
compartments. When the gas is passed into these pipettes consecutively, where each component
is separated in sequence, helps to know the volume drop from initial flue gas volume. Water
vapour in flue gas removed by adsorption on solid calcium chloride and then passed into three

pipettes. It is necessary that the flue gas is passed first through potassium hydroxide pipette
where CO2 is absorbed, then through alkaline pyrogallic acid pipette where only O2 will be
absorbed (because CO2 has already been removed) and finally through cuprous chloride pipette,
where only CO will be absorbed (because CO2 and O2 has already been removed). At last the
remaining amount of flue gas is assumed to contain N2 only.
 At first the flue gas is passed into caustic potash (KOH) solution pipette to absorb CO2 to
form potassium carbonate by the reaction: 2KOH + CO2 ↔ K2CO3 + H2O at ambient
conditions.
 Then gas is led to alkaline pyrogallic acid containing pipette to absorb oxygen by the
reaction: 2C6H3(OH)3 (pyrogallol) + 2KOH (saturated alkaline) + O2 ↔ 4H2O +
2C5H3OCOOK and a physical color change is observed.
 Finally the gas is led to cuprous chloride pipette to absorb carbon monoxide by the reaction:
2CuCl + 2CO → [CuCl(CO)]2.
Figure: Orsat analyzer

Procedure:
1. The whole apparatus is thoroughly cleaned, stoppers greased and then tested for air-tightness.
The absorption pipettes are filled with their respective solutions to level just below their rubber
connections.
2. Their stop-cocks are then closed. The jacket and leveling reservoir are filled with water.
3. The three-way stop-cock is opened to the atmosphere and reservoir is raised, till the burette is
completely filled with water and air is excluded from the burette.
4. The three-way stop-cock is now connected to the flue gas supply and the reservoir is lowered
to draw in the flue gas in the burette. The sample gas mixed with some air is present in the
apparatus. So the three-way stop-cock is opened to the atmosphere, and the gas expelled out by
raising the reservoir. This process of sucking and exhausting of gas is repeated 3-4 times, so as
to expel the air from the capillary connecting tubes, etc. Finally, gas is sucked in the burette and
the volume of the flue gas is adjusted to 100 ml at atmospheric pressure.
5. For adjusting final volume, the three-way stop-cock is opened to atmosphere and the
reservoir is carefully raised till the level of water in it is the same as in the burette which stands
at 100 ml mark. The three-way stop-cock is then closed finally.
6. The stopper of the absorption pipette containing caustic potash solution is opened and all the
gas is forced into this pipette by raising the water reservoir.
7. The gas is again sent to the burette by lowering the water reservoir. This process is repeated
several times to ensure complete absorption of CO2 by KOH solution.
8. The unabsorbed gas is finally taken back to the burette, till the level of solution in the CO2
absorption pipette stands at the constant mark and then, its stop-cock is closed.
9. The levels of water in the burette and reservoir are equalized and the volume of residual gas
is noted. The decrease in volume-gives the volume of CO2 in 100 ml of the flue gas sample.
10. The volumes of O2 and CO are similarly determined by passing the remaining gas through
alkaline pyrogallic acid pipette and cuprous chloride pipette respectively.
11. The gas remaining in burette after absorption of CO2, O2 and CO is taken as nitrogen.

Observation table:
S.No. Amount of CO2
(100 – X) ml
Amount of O2
(X – Y) ml
Amount of CO
(Y – Z) ml
Amount of N2
Z ml
Results and discussions:
Amount of flue gas sample = 100 ml
Amount of CO2 = (100 – X) ml; X = Final volume of flue gas taken out from the KOH pipette
Amount of O2 = (X – Y) ml; Y = Final volume of flue gas taken out from the alkaline
pyrogallic pipette
Amount of CO = (Y – Z) ml; Z = Final volume of flue gas taken out from the cuprous chloride
pipette
Amount of N2 = Z ml
Precautions:
a) The reagents in the absorption pipette 1, 2 and 3 should bring to the etched mark levels one-
by-one by operating the reservoir bottle and the valve of each pipette. Then their respective
valves are closed.
b) All the air in the reservoir bottle is expelled to atmosphere by lifting the reservoir bottle and
opening the three-way to atmosphere.
c) It is quite necessary to follow the order of absorbing gases: CO2 first, O2 second and CO last.
Conclusion:
From the above experiment we came to know the working principle of Orsat analyzer and the
very basic principle of measuring CO2, O2, CO and N2 emission parameters.
Questions
1. What will happen if the sequence of flue gas entering the pipettes is altered?
2. What will happen if at beginning of the test atmospheric air will remain in the apparatus?
3. What are the assumptions of the experiment?
4. What are the harmful effects of carbon dioxide and carbon monoxide?

Experiment No. 10
Aim: To find the calorific value of fuel by using Bomb Calorimeter
Apparatus: - Bomb Calorimeter
Introduction:
The calorific value or heating value is the total heat released when a substance (fuel or food)
undergoes complete combustion with oxygen under standard conditions. It may be expressed
with the quantities: energy/mass (KJ/kg) for liquid and solid and energy/volume (KJ/m3) for
gaseous substances. It can be categorized into higher calorific value (HCV) and lower calorific
value (LCV). After combustion, if the products of combustion cooled down to their initial
temperature so that the water vapour produced can condense by releasing the latent heat of
condensation which will be accounted in the total heat released will give HCV and if the
product of combustion does not cooled down and latent heat of condensation will not accounted
in the total heat released will give LCV.
A calorimeter is an object used for measuring the heat of chemical reactions or physical changes
as well as heat capacity. A bomb calorimeter is a type of constant-volume calorimeter used in
measuring the heat released during combustion of a particular reaction carried by a solid and
liquid fuel. Basically, a bomb calorimeter consists of a stainless steel bomb (may be made of
copper also) where the fuel is placed and reaction is occurring, crucible (made of nickel alloy,
quartz, platinum and stainless Steel etc.) to contain the sample fuel, a stirrer, good thermometer
(which can read very low temperature difference), calorimeter vessel (made of copper and is
coated with Ni-Cr to reflect the heat back into the water instead of radiating it) in which the
bomb is placed and is filled with water and ignition circuit connected to the bomb. In the moist,
high pressure oxygen environment inside the bomb, nitrogen present will be oxidized to nitric
acid, sulfur present will be oxidized to sulfuric acid, and chlorine present will be released as a
mixture of chlorine and hydrochloric acid during combustion. These acids combine with the
residual high temperature oxygen to form a corrosive vapour which will etch ordinary metals.
The Bomb body and the lid are machined from an ultra-strong corrosion resistant stainless steel
alloy containing Cr, Ni & Mo which satisfying special ringing and bending tests for inter-
crystalline corrosion. The cover or head of the bomb carries the oxygen valve for admitting
oxygen and a release valve for exhaust gases. Bomb calorimeter always gives the higher

calorific value of the fuel as the product of combustion condenses releasing the latent heat of
condensation to the surrounding water.
Working principle of bomb calorimeter:
The whole bomb pressurized with excess pure oxygen (typically at 30atm) and containing a
weighed mass of a sample fuel (typically 1-1.5gm) is submerged under a known volume of
water i.e. 2000ml to saturate the internal atmosphere, thus ensuring that all water vapour
produced during reaction is condensed before the charge is electrically ignited. The bomb forms
a closed system so that no gases can escape during the reaction. The weighed reactant put inside
the steel container is then ignited by an electric discharge. Heat released by the combustion will
flow and will raise the temperature of the steel bomb, its contents, and the surrounding water
jacket. The temperature change in the water is then accurately measured with a thermometer. A
small correction is made to account for the electrical energy input, the burning fuse, the burning
thread and acid production (by titration of the residual liquid). Apart from this, the mass of the
bomb, stand, container which also be heated are assumed to be equivalent to equal amount of
water mass to be heated if it is not possible to determine the change in temperature of the
individual components (bomb, stand, container). After the temperature rise has been measured,
the excess pressure in the bomb is released. Based on the energy balance principle i.e. heat
liberated will be equal to heat absorbed the calorific value or the heating value can be found out.
Procedure:
1. Weight the sample fuel. Sample should not be less than 0.9gm not more than 1.5gm.
2. Weight the nichrome wire and cotton thread taken.
3. Connect the nichrome wire (fuse wire) across the electrodes. Tie the cotton thread to the fuse
wire by one end and the other end will touch the sample fuel.
4. Assemble the bomb and charge it slowly with oxygen to a pressure of around 30bar without
displacing the original air present in the bomb.
5. Pour known volume of distilled water (i.e. 2ltr) into calorimeter vessel upto the marked level.
6. Transfer the calorimeter vessel to the water jacket, lower the bomb into the calorimeter vessel
and check that the bomb is gas tight. If gas escapes from the bomb, discard the test.
7. Setup the apparatus and keep the stirrer on.
8. After two minutes fire the charge using a special transformer and firing unit.
9. Record the thermometer reading once the temperature will be steady.

10. Remove the bomb from the calorimeter vessel. The bomb is allowed to remain unopened for
thirty minutes after the charge is fired, to allow the acid mist to settle and release the pressure
and dismantle the bomb.
Figure : Bomb calorimeter
Observation table:
Serial no. Time
Initial
temperature(0C)
Final
temperature(0C)
Observations

Results and discussions:
Let, Mf = Mass of fuel sample burnt in the bomb in kg
Mw = Mass of water filled in the calorimeter; 2kg
WE = Water equivalent of bomb calorimeter in J/°C;
(bomb-2.44kg, stand-0.12kg, container- 0.44kg).
Mtlo = Mass of thread left over after combustion in gm
Mnwlo = Mass of nichrome wire left over after combustion in gm
CVt = Calorific value of cotton thread, 17.55KJ/g
CVnw = Calorific value of nichrome wire, 1.4KJ/g
HCV = Higher calorific value of the fuel sample in KJ/kg
T1 = Initial temperature of water and apparatus in °C
T2 = Final temperature of water and apparatus in °C
CPW = Specific heat constant of water, 4.2KJ/kg-K
Now, Heat liberated by fuel = Mf × HCV
Heat absorbed by water and apparatus = WE × (T2 – T1)
From energy balance, Heat liberated during the reaction = Heat absorbed by water equivalent
mass
Mf × HCV = WE × (T2 – T1)
HCV = WE × (T2 – T1) / Mf
But, for accurate analysis various correction factors should be accounted in the above basic
equation. The correction factors are as bellow-
a) Subtract thread correction factor, Ct (accounts for the heating value of the left over thread
after combustion) = Mtlo x C
b) Subtract fuse wire correction factor, Cf (accounts for the heating value of the left over fuse
wire after combustion) = Mnwlo x CVnw
c) Sulphur and Nitrogen oxidation correction factor, Ca (if can be found out)
Considering above all the correction factors, the modified equation will be-
H.C.V. = [{WE × (T2 – T1)} – (Ca + Ct + Cf)] / Mf

Determination of Water Equivalent of bomb calorimeter:
Before a material with an unknown heat of combustion can be tested in a bomb calorimeter, the
heat capacity of the bomb calorimeter also known as energy equivalent or water equivalent
(WE) must first be determined. The WE of the bomb calorimeter takes into consideration the
sum of the heat capacities of the components in the calorimeter, such as the metal bomb, bucket,
water in the bucket, nichrome wire and cotton thread. The heat capacity of the calorimeter is
determined empirically by burning a sample of a standard material with a known calorific value.
Benzoic acid is used almost exclusively as a reference material because it burns completely in
oxygen, it is not hygroscopic and it is readily available in very pure form. The amount of heat
produced by the reference sample is determined by multiplying the calorific value of the
standard material by the mass of the sample burned. Then, by dividing this value by the
temperature rise in the test, we obtain a resultant heat capacity of the bomb calorimeter known
as water equivalent of bomb calorimeter. The mass of the fuse wire and thread can be decided
by the user, but once decided, it is highly recommended that the same mass and material be
used for all subsequent experiments to be done in the bomb calorimeter. It should also ensure
that the cotton thread and nichrome wire should burn completely. Mathematically, Water
Equivalent can be expressed as-
Water Equivalent (WE) in J/°C = [(Mf x HCV) + (Mt x CVt) + (Mnw x CVnw)]/Δt
Where, M = Mass of fuel sample burnt in the bomb in kg
HCV = Calorific value of the sample fuel; 26.5 kJ/gm for benzoic acid
Mt = Mass of thread in gm
Mnw = Mass of nichrome wire in gm
CVt = Calorific value of cotton thread, 17.55KJ/g
CVnw = Calorific value of nichrome wire, 1.4KJ/g
Conclusion:
From the above experiment we came to know the working principle of the bomb calorimeter
and determined the higher calorific value of the given fuel.

Questions
1. Which type of CV is always found by bomb calorimeter and why?
2. Why bomb calorimeter is not used to determine the CV of gaseous fuels? What is the name of
the calorimeter which is used to determine the CV of gaseous fuel?
3. What will happen if the amount of fuel is very high in bomb calorimeter?
4. Why knowing the correct value of CV is important?
5. What are the values of CV of gasoline and Diesel?

Lab mannual of thermal engg.updated 1

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