Basic Civil And Mechanical Engineering Question Bank

Department of Mechanical Engineering, SNSCE
Page 1 of 60 Prepared by: R.Govindaraj AP/Mech
SNS COLLEGE OF ENGINEERING
COIMBATORE – 641 107
DEPARTMENT OF MECHANICAL ENGINEERING
GE 2152- BASIC CIVIL AND MECHANICAL ENGINEERING
QUESTION BANK
(COMMON FOR ECE, CSE, EEE & IT)
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PREPARED BY
R.GOVINDARAJ, ASSISTANT PROFESSOR/MECHANICAL ENGINEERING

UNIT –III - POWER PLANT ENGINEERING
2 MARK QUESTIONS
1. What is the difference between renewable and non-renewable sources of energy?
Renewable sources of energy are not consumed and are inexhaustible.
Example: solar, wind energy
Non-Renewable sources of energy are either consumed or converted in to other forms.
Example: coal and petrol
2. Classify the power plants based on energy sources.
i) Renewable energy sources
a) Solar power plant
b) Wind power plant
c) Tidal power plant
d) Hydel power plant
e) Geothermal power plant
ii) Non-Renewable energy sources
a) Thermal power plant
b) Nuclear power plant
c) Diesel power plant
d) Gas turbine power plant
3. List out the important circuits in the thermal power plant.
i) Coal and ash circuit
ii) Water and steam circuit
iii) Air and flue gas circuit
iv) Cooling water circuit
4. How you can classify the hydro electric power plant?
i) High head power plant
ii) Medium head power plant
iii) Low head power plant
5. List out the main components of a hydel power plant.
i) Water reservoir
ii) Dam
iii) Pressure tunnel
iv) Surge tank
v) Penstock
vi) Inlet valve
vii) Hydraulic turbine
viii) Draft tube
ix) Tail race

6. What is meant by tail race?
Tail race is a water way to lead the water discharged from the turbine to the river. The water
held in the tail race is called tail race water level.
7. What is the function of a surge tank?
Surge tank regulates the water supply to the turbine according to the load on the turbine.
When the load on the turbine decreases, the extra water starts flowing into the surge tank and the
level of water in the surge tank increase when the load on the turbine increase the reverse
happens.
8. What is the purpose of using Surge Tank?
Surge tank is a water storage tank that is located between the dam and the turbine. It helps in
arresting the sudden rise in water pressure (called as water hammer) in penstock.
9. Give short notes on draft Tube?
Draft tube is a metallic pipe or concrete tunnel. It is connected to the outlet of the turbine. It
has increasing cross sectional area.
10. List out any three application of Diesel power plant.
(i) They are suitable for mobile power generation and widely used in railways and ships
(ii) They can be used as stand by plant to hydro-electric plant and steam power Plant.
(iii) They can be used as continuous supply such as hospitals, telephone exchange, radio
station and cinema theatre’s.
11. List out the main components of Diesel power plant.
(i)Diesel engine
(ii)Engine starting system
(iii) Fuel system
(iv)Air in-take system
(v)Exhaust system
(vi)Engine cooling system
12. List out the types of nuclear power plant.
(i)Boiling water reactor
(ii) Pressurized water reactor
(iii)Heavy water cooled reactor
13. List out the main components of nuclear power plant.
(i)Nuclear reactor
(ii)Radiation shield
(iii)Heat exchanger
(iv) Turbine
(v)Coolant pump, Feed pump
(vii)Condenser

14. What is the difference between nuclear fission and nuclear fusion?
NUCLEAR FUSSION NUCLEAR FUSION
1) Nuclear energy is released by breaking up
Heavy nuclei into two pieces of equal size.
1) Nuclear energy is released by combining
Light nuclei such as hydrogen and helium.
2) It is used for constructive purpose (For
Power generation).
2) It is used for destructive purpose (nuclear
Bomb).
3)Heat energy released is less than fusion
process
3) Heat energy release is more than fission
process.
15. What is the function of moderator?
Moderators are used to reduce the speed of neutrons and thus sustain the chain reaction.
16. Name some materials used as moderators.
Heavy water, beryllium and graphite.
17. What are the functions of control rods? Give example.
Control rods are used to regulate the chain reaction; they are made of boron, Cadmium.
18. List out the elements of Gas Turbine power plant.
1. Starting monitor
2. Low pressure compressor
3. Intercooler
4. High pressure compressor
5. Regenerator
6. Combustion chamber
19. Write the applications of Gas Turbine power plant.
(i) Gas Turbine power plant is used to supply peak load in steam or hydro
plants. (ii) Gas Turbine power plant is used in jet, aircraft and ships.
20. How can you classify the steam Turbine?
1. According to the type of energy at inlet
a) Impulse turbine
b) Reaction turbine
2. According to the direction of low
a) Tangential flow turbine
b) Radial flow turbine
c) Axial flow turbine
3. According to the head of the inlet of the turbine
a) High, Medium, Low head turbine
21. How the gas turbines are classified?
a) Open cycle gas turbine
b) Closed cycle gas turbine

22. Define reaction turbine.
If at the inlet of the turbine, the water possesses kinetic energy as well as
potential energy, the turbine is known as reaction turbine.
23. Difference between impulse and reaction turbine.
IMPULSE TURBINE REACTION TURBINE
1)Power is obtained due to striking force of the
steam jet
1)Power is obtained due to the pressure of the
steam acting on the turbine blade
2) It has fixed nozzle and moving blade. 2) It has fixed blade and moving blades.
3)The blades used in the rotor are symmetrical 3) Blades are not symmetrical. Like aerofoil
type.
24. List out of the main parts of centrifugal pump.
(i) Casing
(ii) Impeller
(iii) Suction pipe with foot value and strainer
(iv) Delivery pipe and delivery value
(v) Shaft
(vi) Stuffing box
25. What are the types of casing?
(i)Volute casing
(ii) Vortex
casing
(iii) Diffuser casing
26. Classify the pumps.
(i) Positive displacement pump Example: Reciprocating pump
(ii) Roto dynamic pump Example: Centrifugal pump
27. List out the main parts of a reciprocating pump.
(i) Cylinder, Piston, Piston rod, Connecting rod and Crank
(ii) Suction pipe
(iii) Suction value
(iv) Delivery pipe
(v) Delivery
value
28. Define coefficient of discharge.
The ratio between the actual discharge and the theoretical discharge is defined
as coefficient of discharge (Cd) of the pump.
Cd=Qa/Qh
29. Define slip of a reciprocating pump.
The difference of the theoretical discharge and actual discharge of fluid is defined as slip of
a reciprocating pump.
Slip = Theoretical discharge – Actual discharge

30. Define negative slip of the reciprocating pump.
If the actual discharge is more than the theoretical discharge, the slip of the pump is
negative. Negative slip occurs when the suction pipe is longer than delivery pipe and pump is
running at high speed.
31. What is the purpose of fitting the air vessels?
(i)To obtain a uniform and continuous discharge from a reciprocating pump.
(ii) To save considerable amount of work in overcoming the frictional resistance.
(iii)To run the pump at high speed.
32. Define Static Head.
The pressure at any point in liquid contain in a vertical column of that the liquid is caused by
the weight of that liquid in the column above the point in question. The height of the column of
the liquid is called Static Head
33. Define Suction Head.
Suction head is defined as the vertical distance in meter from the liquid supply level to the
pump centre line with the pump physically located below the liquid supply level.
34. Design specific speed of centrifugal pump (Ns)
The specific speed of a centrifugal pump is define of the speed in revolutions per minute at
which a geometrically similar impeller would deliver are cubic meter of liquid per second a
delivery head of one meter.
35. How you can classify the centrifugal pumps
According to the types of casting
1. Volute casing
2. Vortex casing
3. Diffuser casing.
According to the number of stages
1. Single stage
2. Multi stage
According to the types of impellers
1. Single suction impellers
2. Double suction impellers.
According to the shape of the vanes of the impeller
1. Radial flow.
2. Axial flow
36. Define priming of a centrifugal pump
Priming in a centrifugal pump, means removal of air, gas or vapour from the pump casing
and from its suction line.
Priming is defined as the operation in which the suction pipe, casing of the pump and a
portion of the delivery pipe up to delivery value is completely filled up from outside source
which the liquid to be lifted by the pump. Priming is done before starting the pump.

37. Write a short note on Cavitations.
When a liquid is subjected to a pressure lower than its vapour pressure, it boils and vapour
bubbles produced. These bubbles collapse violently when subject to high pressure. If the
collapse of the bubbles is nearer to a solid surface, then due to localized pressures, noise and
vibrations are produced. This phenomenon eats away the metal where it occurs. It is known as
Cavitation.
38. What are the effects of Cavitations?
a. Metallic surfaces are damaged.
b. Due to sudden collapse of vapour bubbles, considerable noise and vibration are produced.
c. Efficiency of the pump decreases due to cavitations.
39. Define compounding of steam turbines.
The velocity of steam at the exit of the turbine is very high, hence considerable loss of
kinetic energy. Also the speed of the rotor is high about 30,000 rpm. To reduce the high
speed of the rotor and loss of kinetic energy, several blade rings are used to absorb the
available energy in the steam. This method of absorbing the jet velocity in stages when the
steam flows over the moving blades is known as compounding.
It is classified as
1. Velocity compounding
2. Pressure compounding
3. Pressure – velocity compounding
12 MARK QUESTION AND ANSWERS
1. Explain in details the layout of steam power plant with a neat sketch. Also mention its
merits and demerits.
Working Principle
A thermal power plant is also known as steam power plant, which uses steam as the working
fluid. Steam power plant works based on the Rankine cycle. Steam is produced in a boiler
using coal as fuel and is used to drive the steam turbine; heat energy is converted into
mechanical energy by the steam turbine and that mechanical energy is used for generating
power with the help of generator. The steam coming out of the turbine is condensed in the
condenser and the condensate is supplied back to the boiler with the help of feed pump.
The layout of the steam power plant consists of four main circuits. These are
1. Coal and ash circuit
2. Air and flue gas circuit
3. Water and steam circuit
4. Cooling water circuit
1. Coal and ash circuit
This circuit consists of coal delivery, preparation, coal handling, boiler furnace, ash handling
and ash storage. Coal from the storage yard is transferred to the boiler furnace by means of coal
handling equipment like belt conveyor, bucket elevator, etc. This coal is sized by crushers,

breakers, etc. The coal is burnt in the boiler furnace and ash is formed by burning of coal. Ash
coming out of the furnace to hot, dusty and accompanied by some poisonous gases. The ash is
transferred to ash storage. The Indian coal contains 30 to 40% of ash. A power plant of 100
MW capacities produces 20 to 25 tones of hot ash per hour. Hence the space needed for the
storage of ash is also very high.
2. Air and Flue Gas Circuit
It consist of force draught fan, air preheated, boiler furnace, super heater, economizer, dust
collector, induced draught fan, chimney, etc. Air is taken from the atmosphere by the action of a
forced draught fan. It is passed through an air preheated. The air is preheated by the flue gas in
the preheated. This preheated air is supplied to the furnace to aid the combustion of fuel. Due to
combustion of fuel, hot gases (flue gases) are formed.
The flue gases from the furnace pass over boiler tubes and super heater tubes. In boiler, wet
steam is generated is converted in to super heated steam by means of flue gases. Then the flue
gases pass through the economizer to heat the feed water. After that, it passes through the air
preheated to pre heat the incoming air. Finally, the hot flue gases leave to the atmosphere
through chimney.
5. Water and steam circuit:
It consists of feed pump, economizer, boiler drum, super heater, turbine, condenser etc.
Feed water is pumped to the economizer from the hot well. This water is preheated by the flue
gases in the economizer. This pre heated water is then supplied to the boiler drum. Heat is
transferred to the water by the burning of coal. Due to this, water is converted in to steam.
The steam raised in boiler is passed through a super heater. It is super heated by the flue gases.
The super heated steam is then expanded in a turbine to do work. The turbine drives a generated
to produce electric power. The exhaust steam is then passed through the condenser. In

condenser, the steam is condensed in to water and re circulated.
6. Cooling water circuit
This circuit consists of a pump, condenser, cooling tower etc. cooling water is required to
condense the steam in the condenser. Large quantity of water is required for the purpose. Such
large quantity of water is taken either from river or lake, provided adequate water supply is
available from the river or lake through out the year.
If adequate quantity of water is not available at the plant site, the hot water from the
condenser is cooled in the cooling tower or cooling ponds and circulated again.
Advantages
1. The Coal used as fuel is cheap.
2 .The power plants can be located near load centre, so the transmission cost and
transmission losses are considerably reduced.
3. The power production does not depend on nature mercy.
4. The initial cost of construction of the plant is low compared to hydro electric plant.
5. Suitable for varying load conditions.
6. There are no transmission losses since they are located near load centre.
7. It takes less time for its construction as compared to hydel power plant.
8. Life of the plant is more (25-30 years) as compared to diesel plant (2-5 years).
Disadvantages
1. Thermal power plant discharges large quantities of sulphur dioxide (SO2) which may
cause acid rain.
2. Ash disposal is a serious problem in thermal plant and large areas are needed for ash
storage.
3. Cooling water required is more.
4. Fuel transportation, handling and storage charges are more.
5. Power generation is considerably high when compared to hydro plant.
6. Cannot be used during peak load.
7. High cost of transmission and distribution if the planet is located far away from load
centres.
8. Coal reserves are depleting continuously.
2. Explain in details the layout of hydro-electric power plant. What are the pros and cons of
hydro –electric power plant?
Working principle
The source of energy used in hydroelectric power plant is water. Water at higher altitude
possesses potential energy. Moving water, such as a river or a waterfall, has mechanical
energy.
‘Mechanical energy is the energy that is possessed by an object due to its motion or stored energy of
position.’ This means that an object has mechanical energy if it’s in motion or has the
potential to do work (the movement of matter from one location to another,) based on its
position. The energy of motion is called kinetic energy and the stored energy of position is
called potential energy. Water has both the ability and the potential to do work. Therefore, water

contains mechanical energy (the ability to do work), kinetic energy (in moving water, the
energy based on movement), and potential energy (the potential to do work.)
When the water falls from a higher level to a lower level, its potential energy is converted in
to kinetic energy and this kinetic energy is converted into mechanical energy by allowing the
water to flow through hydraulic turbine. This mechanical energy is utilized to run an electric
generator which is coupled to the turbine shaft.
Components of hydroelectric power plant:
1. Water reservoir:
The area behind the dam where water is stored is called the reservoir. The water there is
called gravitational potential energy. The main purpose of reservoir is to store water during
rainy season and supply it during dry season. Continuous availability of water is a basic
necessity for a hydroelectric plant. The level of water surface in the reservoir is called head
water level.
2. Dam:
The dam is used to increase the height of water level and thereby it increases the capacity of
reservoir. The dam is usually built on a large river that has a drop in elevation, so as to use
the forces of gravity to aid in the process of creating electricity. A dam is built to trap water,
usually in a valley where there is an existing lake. An artificial storage reservoir is formed by
constructing a dam across a river. Notice that the dam is much thicker at the bottom than at the
top, because the pressure of the water increases with depth.
3. Spillway:
Spillway is constructed to act as a safety valve. It discharges the overflow water to the
downs tream side when the reservoir is full. These are generally constructed of concrete
and provided with water discharge opening, shut off by metal control gates. By changing the
degree to which the gates are opened, the discharge of the head water to the tail race can be
regulated in order to maintain water level in reservoir.
4. Gate:
A gate is used to regulate or control the flow of water from the dam.
5. Pressure tunnel:

It carries water from the reservoir to surge tank.
6. Penstock:
Pipes which carry water from the reservoir to the hydraulic turbine are known as penstock.
Penstock is made up of steel or reinforced concrete pipes.
7. Surge tank:
When the load on the generator decreases, the gates admitting water must be closed. Due to
sudden decrease in the rate of flow of water to the turbine, pressure in the penstock increases
suddenly. This sudden increase in pressure causes hammering action on the penstock. This
hammering action is known as water hammer. A surge tank is provided to avoid water
hammer in the penstock.
8. Water turbine:
Water through the penstock enters into the turbine through an inlet valve. The Pelton wheel,
Francis turbine, Kaplan turbine are the commonly used hydraulic turbines. The potential energy
of water entering the turbine is converted to mechanical energy. The mechanical energy
available at the turbine shaft is used to run the electric generator. The water is then discharged
through the draft tube.
9. Draft Tube:
It is connected to the outlet of the turbine. It allows the turbine to be placed over tailrace
level. Draft tube is a metallic pipe or concrete tunnel. Draft tube has increasing cross sectional
area towards outlet.
10. Tail race:
Tail race is a passage for discharging water leaving the turbine into the river. The water held
in the tail race is called tail race water level.
11. Electric generator, step-up transformer:
As the water rushes through the turbine, it spins the turbine shaft, which is coupled to the
electric generator. The generator has a rotating electromagnet called a rotor and a stationary part
called a stator. The rotor creates a magnetic field that produces an electric charge in the stator.
The charge is transmitted as electricity. The step-up transformer increases the voltage of the
current from the stator. The electricity is distributed through power lines to consumers.
Classification of hydro-electric power plants
Hydro-electric power plants are usually classified according to the available head of water.
1. High head power plants:
In these power plants the head of water is more than 300 meters. The turbine used in
such plants is Pelton wheel.
2. Medium head power plants:
In these power plants the head of water ranges from 30 to 300 meters. The turbine
used in such plants is Francis turbine.
3. Low head power plants:

In these power plants the head of water ranges from 3 to 30 meters. The turbine used
in such plants is Kaplan turbine and Francis turbine.
Merits of the hydro-electric power plant:
1. Water is a renewable source of energy. Water which is the operating fluid hence
pollution free.
2. Water is the cheapest source of energy because it exists as a free gift of nature hence
there is no fuel cost.
3. Hydro-electric power plant is highly reliable.
4. Running cost of the plant is low.
5. Variable load do not affect the efficiency in the case of hydro-electric power plant.
6. There is no ash disposal problem as in the case of thermal power plants.
7. Water stored in the hydro-electric power plant can also be used for domestic water
supply.
8. It requires less supervising staff.
9. Maintenance cost is low.
10. Number of operations required to run a hydro-electric power plant is less, compared to
thermal power plant.
Demerits of the hydro-electric power plant:
1. The hydro-electric power plant are often far away from the load center and require long
transmission lines to deliver power.
2. Initial cost of the plant is high.
3. It takes long time for the erection of such plants and the construction of a dam, compared
to thermal power plant.
4. Power generation is dependent on the quantity of water available, which may vary
season to season and year to year.
5. Water in the reservoir is lost by evaporation.
3. Briefly explain the working principle of gas turbine power plant with a neat sketch.
Also mention its advantages and disadvantages.
Working principle of gas turbine power plant
Gas turbines are described thermodynamically by the Brayton cycle, in which air is
compressed isentropically, combustion occurs at constant pressure, and expansion over the
turbine occurs isentropically back to the starting pressure. The atmospheric air enters the
compressor where it is compressed to a high pressure. This high pressure air then enters

the combustion chamber where it mixes with the fuel (natural gas or petrol) and combustion
takes place. The high pressure and high temperature combustion gases expand in the gas
turbine and thus mechanical energy is produced. Part of this mechanical energy is used in
driving the compressor which is usually mounted on the same shaft as that of the turbine
shaft and the remaining part of this mechanical energy is utilized for producing electric power.
Uses of gas power plant
1. Gas turbine plants are used in jet, aircraft and ships.
2. They are used as standby plants for hydro-electric power plants.
Elements of a gas turbine power plant
The gas turbine plant consists of
1. Starting motor
2. Low pressure compressor (LPC)
3. Intercooler
4. High pressure compressor (HPC)
5. Regenerator
7. Gas turbine
8. Reheating unit
1. Starting motor
Gas turbines are not self starting. They require a starting motor to first bring the turbine to
the minimum speed called coming in speed, for this purpose a starting motor is required
2. Low pressure Compressor (LPC)
In gas turbine plant, the axial and centrifugal flow compressors are used. The major function
of the compressor is to compress the air. Atmospheric air is drawn in and passed through the air
filter. It then flows into the low pressure compressor. Major percentage of power developed (66
%) by the turbine is used to run the compressor. The power required to run the compressor can
be reduced by compressing the air in two stages, i.e., in low pressure and high pressure
compressors and also by incorporating an intercooler between the two.
3. Intercooler
Intercooler is used to reduce the work of the compressor and increase the efficiency. The air
after compression in the LPC is hot. It is cooled by the intercooler. The intercooler is circulated

with cooling water. An intercooler is provided in between the two stages of compression in
order to minimize the power required for compression at the higher stages.
4. High pressure compressor (HPC)
The cooled air coming out of the intercooler is further compressed in the high pressure
compressor. The pressure and temperature of air further increases in the high pressure
compressor.
5. Regenerator
The air from the H.P compressor enters a regenerator which is a type of heat exchanger.
Here the air is preheated by the exhaust gases from the low pressure turbine before it enters the
combustion chamber. The main objective of preheating the compressed air is to reduce the fuel
consumption and to increase the efficiency.
As the name suggests, it is a chamber where combustion takes place. For any combustion,
fuel and air is required. The fuel used in gas power plants may be natural gas, coal gas,
kerosene or gasoline. Hot air from regenerator flows to the combustion chamber; fuel is injected
into the combustion chamber. After the fuel injection, the combustion takes place. These
high pressures, high temperature products of combustion are passed through the turbine.
7. Gas turbine
Two types of gas turbines are used in the gas turbine plant. 1. High pressure turbine. 2. Low
pressure turbine. The products of combustion from the combustion chamber are first expanded
in high pressure turbine and then in low pressure turbine. The part of the work developed by the
gases passing through the turbine is used to run the compressor and the remaining about (34 %)
is used to generate electric power.
8. Reheating unit
The output of the plant can be further improved by providing a reheating combustion
chamber between high pressure and low pressure turbines. In this, fuel added to reheat the
exhaust gases of high pressure turbine. The addition of the regenerator, intercooler and
reheating combustion chamber are to increase the overall efficiency of the plant.
Advantages of Gas Turbine power plant
1. The initial cost is lower than an equivalent thermal plant.
2. Very high power-to weight ratio, compared to reciprocating engines.
3. Natural gas is a very suitable fuel and where this is available cheap, it is an ideal source
of power in gas turbine.
4. Gas turbine plant is small and compact in size as compared to steam power plants.
5. It can be started quickly and can be put on load in a very short time.
6. It requires less water as compared to a steam power plant.
7. Moves in one direction only, with far less vibration than a reciprocating engine.
8. Fewer moving parts than reciprocating engines.
9. High operation speeds.(40,000 to 100,000 rpm)
10. The exhaust of the gas turbine is free from smoke.
Disadvantages of Gas Turbine power plant
1. 66% of the power developed is used to drive the compressor; the gas turbine unit has a
low thermal efficiency.

2. It requires special metals and alloys for deferent components because the operating
temperature (2000 0
C) and speed (100,000) are very high.
3. Life of the gas turbine power plant is less.
4. Part load efficiency is poor.
5. Gas turbine power plant creates more noise in it operation
4. with a schematic diagram, explain the working principle of diesel power plant. What are its
merits and demerits?
Working principle of diesel power plant
Diesel generating plants have an important role in power plants as well as in industries and
commercial installations to meet continuous and emergency standby power requirements for day
to- day use. A diesel power plant may use two stroke or four stoke engine. Diesel engine
works on diesel cycle this cycle is also known as constant pressure cycle. Diesel engine is
mostly employed in Stationary Power plants, Ships, Heavy Motor Vehicles. In diesel engine,
diesel oil and light and heavy oil used as fuel. This fuel is ignited by being injected into the
engine cylinder containing air compressed to a very high pressure; the temperature of this air is
sufficiently high to ignite the fuel. That is why there is no spark plug used in diesel engine. This
high temperature compressed air used in the form of very fine spray is injected at a controlled
rate so that the combustion of fuel proceeds at constant pressure.
Main Components of Diesel Power Plant
The essential components of a diesel power plant are
1. Diesel engine
2. Starting systems
3. Fuel supply systems
4. Air intake system
5. Exhaust system
6. Cooling system
7. Lubricating system
Layout of diesel power plant

1. Diesel Engine
A diesel engine is a compression ignition (C.I) engine. The main component of a diesel
power plant is diesel engine which is used to produce power. A diesel engine may be four stroke
or two stroke cycle engine. The two stroke engine is more favored for diesel power plant. Air is
admitted into the cylinder of the engine and is compressed; fuel (diesel) is injected into the
cylinder through fuel injectors. Due to the high temperature and pressure obtained during
compression, it ignites. The fuel burns and the burnt gases expand to do work on the moving
part inside the cylinder called piston. This movement of the piston rotates a flywheel. The
engine is directly coupled to the electric generator. The gases after expansion inside the cylinder
are exhausted into the atmosphere and passes through a silencer in order to reduce the noise.
The fuel for the diesel engine is drawn through a filter from the all day tank. The air required
for the diesel engine is drawn through the air filter from the atmosphere.
2. Starting System:
This includes air compressor and starting air tank. Diesel engine used in diesel power plants
is not self starting. The engine is started from cold condition with the help of an air compressor.
3. Fuel supply system:
It includes the storage tank, fuel pump, fuel transfer pump strainers and heaters. Pump draws
diesel from storage tank and suppliers it to the small day tank through the filter. Day tank
supplies the daily fuel need of the engine. The day tank is usually placed high so that diesel
flows to engine under gravity. Diesel is again filtered before being injected into the engine by
the fuel injection pump. The fuel is supplied to the engine according to the load on the plant.
4. Air intake system:
The air required for the combustion of fuel inside the diesel engine cylinder is drawn
through the air filter. The purpose of the filter is to remove dust from the incoming air. The
dry filter used may be made of felt, wood or cloth. In wet filter, oil bath is used, in this the air

passes over a bath of oil where the dust particles get coated on the oil.
5. Exhaust system
An exhaust manifold is provided to the diesel engine for conveying the exhaust gases to the
atmosphere. The exhaust system should silence the exhaust noise to requisite levels. The
muffling of the exhaust noise is met by using silencers. The gases must be discharged
sufficiently high above the ground level to avoid low level pollution of air.
6. Cooling system
The primary purpose of cooling system is to carry the heat from engine cylinder and to keep the
temperature of the cylinder within safe limits. The temperature of the burning fuel inside the
engine cylinder is in the order of 1500o
Cto 2000o
C. If the excess heat is not removed, it would
overheat the engine and may damage the piston, piston rings and cylinder walls of the engine.
Small engine are cooled by air. Large stationary engines are cooled by water.
Cooling of engines is done by circulating water through jackets. In this, raw water is made
to flow through the heat exchanger when it takes up the excess of heat of jacket water and then
is returned back to the cooling tower.
7. Lubricating system:
This circuit includes lubricating oil tank, oil pump and oil cooler. The purpose of the
lubrication system is to reduce the wear of the engine moving parts. Part of the cylinder such as
piston, shafts, and valves must be lubricated. Lubrication also helps to cool the engine.
In the lubrication system the oil is pumped from the lubricating oil tank through the oil
cooler where the oil is cooled by the cold water entering the engine. The hot oil after cooling
the moving parts and return to the lubrication oil tank.
Advantages of diesel power plant
1. Plant layout is simple
2. Diesel engine power plant can be located near the load centre.
3. Quick starting and easy pick-up load in a short time.
4. Fuel handling is easier and no problem of ash disposal exists.
5. It occupies less space.
6. It requires less quantity of water for cooling purposes.
7. Diesel power plants operate at high overall efficiency than steam power plant.
8. It can respond to varying load without any difficulty
9. The operating of the plant is easy and requires less number of personnel
Disadvantages of diesel power plant
1. Plant capacity is limited to about 50 MW of power.
2. Diesel fuel is much more expansive than coal.
3. High maintenance and lubrication cost.
4. In a plant noise is a serious problem.
5. Life of the plant is low when compared to thermal plants.
6. Diesel engines are not guaranteed for operation under continuous overloads, while steam
turbine can work under 25 % of overload continuously

5. Draw the neat sketch of nuclear power plant and explain its working principle. Also
mention its advantages and disadvantages.
1. Fuel:
The fuel which is used in the nuclear reactors are U235
, Pu239
and U233
2. Nuclear reactor:
It consists of reactor core, reflector, shield etc. It may be regarded as a substitute for the
boiler fire box of a steam power plant. During the fission the large amount of heat is liberated by
U235
, This large amount of heat is absorbed by the coolant and it is circulated through the core.
The various types of reactors used in nuclear power plant is
a. Boiling water reactor (BWR)
b. Pressurized water reactor (PWR)
c. Heavy Water-cooled reactor (HWR)
3. Steam Generator:
The steam generator is fed with feed water which is converted into steam by the heat of the
hot coolant. The purpose of the coolant is to transfer the heat generated in the reactor core and
use it for steam generation. Ordinary water of heavy water is a common coolant.
4. Steam turbine:
Steam turbine is used to convert the heat energy into mechanical (rotational) energy. The
steam produced in the steam generator is allowed to expand inside the steam turbine by which
the turbine blades (fixed and movable) are made to rotate. Since the turbine blades are fitted
around the turbine shaft, the turbine shaft is rotated. The turbine shaft in turn is coupled to a
generator at the other end that generates electricity.
5. Moderator
It is a material which reduces the speed of fast moving neutrons. During the chain reaction,
neutrons moving with high velocity are produced. Fast moving neutrons try to escape from the
reactor without causing fission of U235
. Hence, their speed is reduced. This is done by
colliding them with the nuclei of other light material (moderator) which does not capture the
neutrons but scatters them. During collision the kinetic energy is lost and the speed of fast
moving neutrons is reduced. The slow neutrons thus produced are easily absorbed by the nuclear
fuel and chain reaction takes places smoothly. Beryllium, graphite or heavy water is normally
used as a moderator.

6. Reflector:
The neutrons produced by fission process are absorbed by fuel rods, moderator, coolant or
the surrounding construction. Some neutrons may escape from the reactor core without
absorption. This is a loss and should be eliminated. This loss can be minimized by surrounding
the reactor core with a material called reflector. The reflector material reflects the escaping
neutrons back into the core. The reflected neutrons cause more fission and improve the neutrons
economy of the reactor. Water, carbon, graphite, beryllium are generally used as reflectors.
7. Control rods:
The control of chain reaction is carried out by removing the fuel rod or the neutrons. It is
easy to absorb neutrons. Absorbing of neutrons is done by inserting neutron absorbing material
rods known as control rods in the reactor core. The control rods must be able to absorb excess
neutrons. The position of these rods are regulated by electronic or electro – mechanical devices.
The material used for control rods are boron, cadmium, hafnium etc.
8. Coolant pump and Feed Pump:
The steam from the turbine flows to the condenser where cooling water is circulated.
Coolant pump and feed pump are provided to maintain the flow of coolant and feed water
respectively.
9. Biological shield (Radiation shield):
The reactor produces intense radio activity and these radiations are very harmful to the
human life. The common radiations from the reactors are alpha rays, beta rays, gamma rays and
fast moving neutrons. These radiations must be absorbed before emitted to atmosphere. Thick
layers of lead concrete or steel are provided all around the reactor. These layers absorb the
gamma rays, neutrons etc. Concrete and steel are used as shielding material.
Advantages of nuclear power plant:
1. The nuclear power plant requires very small quantity of fuel. Hence fuel
transportation cost is less.
2. Space requirement is less when compared with other power plants of equal
capacity.
3. It is not affected by adverse weather conditions.
4. Suitable for large power generation.
5. Very large amount of heat is liberated by a very small quantity of fuel.
6. Fuel storage facilities are not needed as in the case of the thermal power plant.
7. Conserve the fossil fuel (coal, oil, gas etc.) for other energy requirements.
8. Reliability of operation.
9. Does not require large quantities of water for cooling.
Disadvantages of nuclear power plant:
1. Nuclear radiation can be extremely dangerous.
2. Radioactive wastes should be disposed carefully, Otherwise it may have bad effect on
the health of workers and the environment as a hole.
3. It requires high initial cost.
4. Availability of nuclear fuel is scarce and cost is high.
5. Maintenance cost is higher.

6. It is not suited for varying load conditions.
7. It requires well-trained personnel.
6. Explain the working principle of single acting reciprocating pump.
If a reciprocating pump uses one side of the piston for pumping liquid, then it is known as a
Single Acting Reciprocating Pump.
The main parts of a single acting reciprocating pump are:
1. Cylinder, Piston, Piston Rod, Connecting Rod and Crank.
2. Suction Pipe
3. Suction Valve
4. Delivery Pipe
5. Delivery Valve
1. Cylinder, Piston, Piston Rod, Connecting Rod and Crank
A single acting reciprocating pump consists of a piston, which moves forwards and
backwards inside a close fitting cylinder. The movement of the piston is obtained by connecting the
piston rod to the crank by means of a connecting rod. The crank is rotated by an electric motor.
2. Suction Pipe
A suction pipe connects the lower sump and the cylinder. At the bottom end of the suction
pipe, strainer and foot valve are provided. Foot valve (non-return valve) allows water to flow in the
upward direction only.
3. Suction Valve:
Suction valve is one way valve or a non-return valve. It allows the liquid to flow in one
direction only. That is, it allows the liquid from the suction pipe to the cylinder.
4. Delivery Pipe:
A delivery pipe connects the cylinder and the upper sump and water is discharged from the
cylinder into the delivery pipe.
5. Delivery Valve:
Delivery valve is also one way valve or non-return valve. It allows the liquid to flow in one
direction only. That is, it allows the liquid from the cylinder to the delivery pipe.
Working Principle:

It consists of a piston which moves forwards and backwards in a close fitting
cylinder. The movement of the piston is obtained by connection the piston rod to crank by means of
a connecting rod. The crank is rotated by means of an electric motor. Suction and delivery pipes
with suction valve and delivery valve are connected to the cylinder. The suction and delivery valves
are one way valves or non-return valves, which allow the water to flow in one direction only.
Suction valve allows water from suction pipe to the cylinder which delivery valve allows water
form cylinder to delivery pipe only.
When crank starts rotating, the piston moves to and fro in the cylinder. When crank is at A.,
the piston is at the extreme left position in the cylinder. As the crank is rotating from A to C, (i.e.,
from θ = 0 to θ = 1800
), the piston is moving towards right in the cylinder. The movement of the
piston towards right creates a partial vacuum in the cylinder. But on the surface of the liquid in the
sump atmospheric pressure is acting, which is more than the pressure inside the cylinder. Thus the
liquid is forced in the suction pipe from the sump. This liquid opens the suction valve and enters the
cylinder. When crank is rotating from C to A (i.e., from θ = 1800
to θ = 3600
), the piston from its
extreme right position starts moving towards left in the cylinder. The movement of the piston
towards left increases the pressure of the liquid inside the cylinder more than atmospheric pressure.
Hence suction valve closes and delivery valve opens. The liquid is forced into the delivery pipe and
is raised to a required height.
7. Briefly explain the types of reciprocating pumps.
If the mechanical energy is converted into hydraulic energy (pressure energy) by sucking the
liquid into a cylinder, in which a piston is reciprocating, the pump is known as Reciprocating Pump.
Reciprocating pump uses piston or plunger to positively displace a given volume of liquid during
each stroke of the piston. The piston is moving backwards and forwards, exerting a thrust on the
liquid, thereby increasing its pressure energy.
Classification of Reciprocating Pump:
According to the liquid contact on sides of the piston, reciprocating pumps are classified as
1. Single acting reciprocating pump
2. Double acting reciprocating pump.
According to the number of cylinder
1. Single Cylinder Reciprocating Pump
2. Double Cylinder Reciprocating Pump
3. Triple Cylinder Reciprocating Pump
4. Duplex Double Acting Pump
5. Quintuplex Pump
Single Acting Reciprocating Pump
If a reciprocating pump uses one side of the piston for pumping liquid, then it is known as a
Single Acting Reciprocating Pump.

The main parts of a single acting reciprocating pump are:
1. Cylinder, Piston, Piston Rod, Connecting Rod and Crank.
2. Suction Pipe
3. Suction Valve
4. Delivery Pipe
5. Delivery Valve
1. Cylinder, Piston, Piston Rod, Connecting Rod and Crank
A single acting reciprocating pump consists of a piston, which moves forwards and
backwards inside a close fitting cylinder. The movement of the piston is obtained by connecting the
piston rod to the crank by means of a connecting rod. The crank is rotated by an electric motor.
2. Suction Pipe
A suction pipe connects the lower sump and the cylinder. At the bottom end of the suction
pipe, strainer and foot valve are provided. Foot valve (non-return valve) allows water to flow in the
upward direction only.
3. Suction Valve:
Suction valve is one way valve or a non-return valve. It allows the liquid to flow in one
direction only. That is, it allows the liquid from the suction pipe to the cylinder.
4. Delivery Pipe:
A delivery pipe connects the cylinder and the upper sump and water is discharged from the
cylinder into the delivery pipe.
5. Delivery Valve:
Delivery valve is also one way valve or non-return valve. It allows the liquid to flow in one
direction only. That is, it allows the liquid from the cylinder to the delivery pipe.
Working Principle:
It consists of a piston which moves forwards and backwards in a close fitting
cylinder. The movement of the piston is obtained by connection the piston rod to crank by means of
a connecting rod. The crank is rotated by means of an electric motor. Suction and delivery pipes
with suction valve and delivery valve are connected to the cylinder. The suction and delivery valves
are one way valves or non-return valves, which allow the water to flow in one direction only.
Suction valve allows water from suction pipe to the cylinder which delivery valve allows water

form cylinder to delivery pipe only.
When crank starts rotating, the piston moves to and fro in the cylinder. When crank is at A.,
the piston is at the extreme left position in the cylinder. As the crank is rotating from A to C, (i.e.,
from θ = 0 to θ = 1800
), the piston is moving towards right in the cylinder. The movement of the
piston towards right creates a partial vacuum in the cylinder. But on the surface of the liquid in the
sump atmospheric pressure is acting, which is more than the pressure inside the cylinder. Thus the
liquid is forced in the suction pipe from the sump. This liquid opens the suction valve and enters the
cylinder.
When crank is rotating from C to A (i.e., from θ = 1800
to θ = 3600
), the piston from its
extreme right position starts moving towards left in the cylinder. The movement of the piston
towards left increases the pressure of the liquid inside the cylinder more than atmospheric pressure.
Hence suction valve closes and delivery valve opens. The liquid is forced into the delivery pipe and
is raised to a required height.
Double Acting Reciprocating Pump:
If the liquid is in contact with both the sides of the piston, it is known as Double Acting
Reciprocating Pump. A double acting reciprocating pump consists of the following main parts.
1. Cylinder:
The cylinder consists of a piston which moves forwards and backwards. The cylinder is a
closely fitted one and the suction and delivery pipes with one-way valves are connected with the
cylinder. The piston inside the cylinder is connected with a piston rod.
2. Connecting Rod and Crank:
The movement of the piston is obtained by connecting the piston rod to a crank by means of
a connecting rod. The crank is rotated clockwise by means of an electric motor. The crank, by its
rotary movement provides the to and fro movement of the piston and connecting rod.
3. Suction and Delivery Pipes:
The suction and delivery pipes are connected with the cylinder. Two suction pipes and two
delivery pipes are used with suction and delivery valves respectively.
Working Principle
A double acting reciprocating pump has two suction ant two delivery pipes with suction and
delivery valves as shown.
During each stroke, when suction takes place on one side of the piston, the other side
delivers the liquid. In this way, in the case of a double acting pump, in one complete revolution of
the crank, there are two suction strokes and two delivery strokes. Therefore, the liquid is delivered

to the pipes by the pump during these two delivery strokes.
In the case of a double acting reciprocating pump, when there is a suction stroke on one side
of the piston, its other side has a delivery stroke. Thus, for one complete revolution of the crank,
there are two delivery strokes. The liquid is delivered by the pump during these two delivery
strokes.
If the speed of the crank is N rpm, then the number of delivery strokes will be 2N per minute
or (N / 30) per second. However, due to the presence of the piston rod on one side, the volumes of
liquid delivered from both the sides of the piston will not be equal.
8. Explain briefly the working of centrifugal pump.
Centrifugal Pump is a Rotodynamic pump which uses the mechanical energy of the rotating
impeller to increase the velocity of a fluid by the application of centrifugal force. The fluid enters
the pump impeller along the rotating axis and gets accelerated, flows radically outwards into a
casing and exits through the piping system. It is generally used for large discharge through smaller
heads.
Main Parts of a Centrifugal Pump:
The following are the main parts of a centrifugal pump:
1. Impeller.
2. Casing
3. Suction pipe with a foot valve and a strainer.
4. Delivery pipe.
5. Shaft
6. Stuffing Box
1. Impeller:
The rotating part of the centrifugal pump is called Impeller. It consists of backward curved
vanes of blades. The impeller is mounted on a shaft. The shaft is coupled to the shaft of an electric
motor. It is enclosed in the casing. The fluid enters in the central portion known as the eye of the
impeller and flows out radially outward and it is then discharged around the entire circumference
into the casing.
Impellers may be classified as:

a. Closed or Shrouded Impeller
b. Semi-Open Impeller
c. Open Impeller
2. Casing:
The centrifugal pump has a stationary outer casing. It is an air-tight passage surrounding the
impeller. Its shape is designed in such a way that the kinetic energy of liquid discharged at the outlet
of the impeller is converted into pressure energy before the liquid leaves the casing and enters the
delivery pipe. Two openings are provided in the casing for suction and delivery of water. The
casing contains bearings for supporting the pump shaft. The following three types of casings are
commonly adopted:
a. Volute casing
b. Vortex casing
c. Casing with guide blades (or) Diffuser casing.
3. Suction pipe with a foot valve and a strainer.
Suction Pipe is a pipe connected at its upper end tot eh inlet of the pump at the center of the
impeller. The center of the impeller is known as Eye of the Impeller. The lower end of the suction
pipe dips into liquid in a suction tank or a sump from which the liquid is to be pumped or lifted up.
A Strainer is fitted at the lower end of the suction pipe. The liquid from the sump first enters
the strainer. The strainer is provided in order to keep the debris (impurities) such as leaves, wooden
pieces and other rubbish away from the pump. It then passes through the foot valve to enter the
suction pipe.
A foot valve is a not-return valve or one-way type of valve. It is fitted at the lower end of the
suction pipe. The foot valve opens only in the upward direction. Therefore, the liquid will pass
through the foot valve only upwards. It will not allow the liquid to flow downwards back to the
sump.
4. Delivery Pipe and Delivery Valve:
A pipe whose one end is connected to the outlet of the pump and the other end delivers the
liquid at the required height is known as Delivery pipe.
Delivery Valve: Just near the outlet of the pump on the delivery pipe, a delivery valve is provided.
A deliver valve is a regulating valve. It is required to be provided to control the flow of the liquid
from the pump into the delivery pipe.
5. Shaft:
A shaft of a pump performs the duties of transferring the torque from the motor to the
impeller, transferring the hydraulically induced radial loading to the journal bearing without undue
deflection, transferring the axial thrust from the impeller to the bearing and providing and
acceptable environment for the shaft seals.
6. Stuffing Box:
It is used to stop leakage of air into the casing when the pressure in the casing is below
atmospheric. It also stops the leakage of liquid under pressure from the casing of the pump. The
stuffing box packing consists of a soft semi-plastic material. This plastic material is cut in rings. It
fits around the shaft or shaft sleeve.

Working Principle:
The first step in the operation of a centrifugal pump is priming. After the pump is primed,
the delivery valve is still kept closed. The electric motor is now started to rotate the impeller. The
delivery valve is kept closed in order to reduce the starting torque for the motor.
The rotation of the impeller in the casing full of liquid produces centrifugal force. This
centrifugal force imparts a centrifugal head to the liquid. This result is an increase of pressure
throughout the liquid mass. Thus, if the speed of the impeller is sufficiently high, the pressure in the
liquid surrounding the impeller is increased. As long as the delivery valve is closed and the impeller
is rotating, it jut churns the liquid in the casing.
When the delivery valve is opened, the liquid is made to flow in an outward radial direction.
And the liquid is leaving the vanes of the impeller at the outer circumference with a high pressure.
In the mean while, a partial vacuum is created at the eye of the impeller due to the centrifugal
action. This causes sucking of the liquid form the sump (which is at atmospheric pressure) to rush
through the suction pipe to the eye of the impeller.
Thus, this rushing liquid is replacing the liquid which is being discharged from the entire
circumference of the impeller. The high pressure of the liquid leaving the impeller is utilized in
lifting the liquid to the required height through the delivery pipe.
Uses of Centrifugal Pumps:
Centrifugal pumps are most commonly employed for pumping large volumes of liquids at
low pressures. However, by multi-staging, it is possible to increase the outlet pressures. The
capacity of the pump depends upon the impeller diameter, its width and speed. The head of the
pump depends upon the impeller diameter and speed.
Centrifugal pumps are sued widely in power plants. They are also used for plumbing,
drainage and marine works. They find applications in residences, agriculture and industries such as
petroleum, sugar paper, pharmaceutical, chemicals, etc.
9. Write a brief note on steam turbine.
In steam turbine, the heat energy of steam is first converted into kinetic energy in nozzles.
This high velocity steam impinges on the curved blades which changes the direction of flow of
steam. The change in the flow direction causes the force to be extorted on the blades which are
attached to the shaft. As a result, the shaft rotates and the turbine produces work.
The main parts of the steam turbine are fixed nozzles, rotor, fixed and moving blades, outer
casing, etc. The rotor is a circular disc fixed to a horizontal shaft. On the periphery of the rotor, a
number of blades are fixed at uniform intervals.
Classification of Steam Turbines:
Steam turbines are classified as follows:
1. According to the method of steam expansion in the turbine.
a. Impulse turbine
b. Reaction turbine
c. Combination of impulse and Reaction turbine
2. According to the steam flow direction:

a. Axial turbine b. Radial turbine c. Tangential turbine d. Mixed flow turbine
3. According to the number of stages
a. Single stage turbine b. Multi state turbine.
4. According to the steam pressure
a. High pressure turbine b. Low pressure turbine c. Medium pressure turbine
Simple Impulse Turbine
Delaval turbine is known as simple impulse turbine. Simple impulse turbine consists of only
one set of nozzles and moving blades.
As the steam expands in the nozzle, velocity of steam increases at the expense of its
pressure. The high velocity steam jet impinges on the moving blades which move in the direction of
the jet. The movement of blades makes the shaft to rotate.
All the kinetic energy of steam is absorbed by one set of moving blades, the velocity of
turbine shaft is too high (25,000 to 30,000 rpm).The speed of the impulse turbine is very high and it
has many practical problems. With this high speed small amount of kinetic energy of steam can be
utilized. These difficulties associated with the use of single stage turbines for large pressure drops
can be solved by compounding, i.e., the use of more than one stage.
Compounding may be of three types:
1. Velocity compounding
2. Pressure compounding
3. Pressure – Velocity compounding
Reaction Turbine
In reaction turbines, there is no sudden pressure drop. Reaction turbines, steam expands as it
flows over the fixed blades which act as nozzles. In this turbine there is a gradual pressure drop
takes place continuously over the fixed and moving blades. In fact this pressure drop gives a
reaction and hence the rotor starts moving. A number of wheels are fixed to the rotating shaft. Fixed

guide ways are provided in between each pair of rotating wheels.
The fixed blades act as guides and also as nozzles. The guide blades serve the following
functions.
1. It changes the direction of steam.
2. It guides the steam to enter the next wheel
3. It allows the steam to expand to a higher velocity as steam flows through them.
Differences between Impulse and Reaction Turbines:
Sl.
No
Impulse Turbines Reaction Turbines
1.
Impulse turbine consist of moving blades
and nozzles
Reaction turbine consists of fixed blades and
moving blades (moving blades act as nozzles)
2.
Steam strikes the blades with kinetic
energy.
Steam passes over the moving blades with
pressure and kinetic energy
3.
Pressure drops in nozzles and not in moving
blades
Pressure drops in fixed bladed (nozzles) as
well as moving blades
4.
Due to sudden and steep reassure drop at the
end (tip) of the nozzle, blade speed and
steam speed increase.
Due to low level pressure drop, blade speed
and steam speed are comparatively less.
5.
Due to more pressure drop, number of
stages required is less.
Number of stages required is more due to
more pressure drop.
6. Overall efficiency is low. Overall efficiency is high.
7.
The amount of space occupied by the
impulse turbine is less.
The amount of space occupied by the reaction
turbine is more.
8.
Very much suitable for small power
generation.
Very much suitable for high power
generation.
10. Compare the differences between centrifugal pump and reciprocating pump.
Sl.
No
Centrifugal Pumps Reciprocating Pumps
1. The discharge is continuous and smooth The discharge is fluctuating and pulsating
2. It can handle large quantity of liquid. It handles small quantity of liquid only.
3.
It can be used for lifting highly viscous
liquids
It is used only for lifting pure water of less
viscous liquids.
4.
It is used for large discharge through
smaller heads.
It is meant for small discharge and high heads.
5.
Cost of centrifugal pump is less as
compared to reciprocating pump.
Cost of reciprocating pump is approximately
four times the cost of centrifugal pump.
6.
Centrifugal pump runs at high speed.
They can be coupled to electric motor.
Reciprocating pump runs at low speed. Speed is
limited due to consideration of separation and
cavitation.
7.
The operation of centrifugal pump is
smooth and without much noise. The
maintenance cost is low.
The operation of reciprocating pump is
complicated and with much noise. The
maintenance cost is high.
8.
Centrifugal pump needs smaller floor area
and installation cost is low.
Reciprocating pump requires large floor area
and installation cost is high.
9. Efficiency is high. Efficiency is low.

UNIT IV
INTERNAL COMBUSTION ENGINES
2 MARKS QUESTION AND ANSWERS
1. Give short notes on heat engine? And list out the classification.
Heat engine is a uses for converting heat energy in to mechanical energy. In heat engines heat
energy is obtained by combustion of fuel.
Classification: 1.Internal combustion engine 2.External combustion engine
2. What is mean by internal combustion engine?
In I.C engine combustion of fuel takes place inside the cylinder of the engine.
Example: Diesel engine, Petrol engine
3. What are the main parts of an internal combustion engine?
The main parts of an internal combustion engine are cylinder, piston, piston rings, piston pin,
crank shaft, connecting rod, crank case, and fly wheel.
4. How is I.C engines classified?
I.C.Engine is classified as spark ignition (S.I) engines and compression ignition (C.I).
Another classification of engines is based on stroke
1. Four stroke engine. 2. Two stroke engine
Classification of engines is based on thermodynamic cycle
1. Auto cycle 2. Diesel cycle
5. What are the four stroke of an I.C engine?
Suction stroke, compression stroke, expansion [or] power [or] working stroke and exhaust
stroke.
6. What is meant by stroke in an I.C engines?
The stroke refers to the linear distance between the two extreme positions of the piston. This
distance is measured parallel along the axis of the cylinder.
7. Name the important systems in an I.C engine?
Fuel supply system, ignition system, cooling system, lubricating system and air supply system.
8. What is the main purpose of fuel supply system in an I.C engine?
Storage and supply of fuel for combustion of I.C engine is the main purpose of fuel system.
9. What is the basic function of ignition system?
Ignition system is used in a spark ignition engine to ignite the air fuel mixture in the cylinder
for combustion.
10. What are the two types of ignition system?
[1].Battery coil ignition system [2].Magneto coil ignition system.
11. What is the function of spark plug?
Spark plug is used in petrol engine. The function of spark plug is to produce a spark in the

combustion chamber by conducting a high potential electric current from the ignition circuit
across its gap. The spark thus produced ignites compressed air fuel mixture.
.
12. What is the function of carburetor?
Carburetor is a device used in petrol engines to mix petrol and air in correct proportions. This
mixture is sent to the engine for combustion.
13. Why is cooling system necessary in an I.C engine?
Combustion of fuel air mixture in the cylinder produces very high temperature in the range of
1000 - 1500 degree Celsius. This heat may cause expansion of cylinder wall, cylinder head, piston
and other parts resulting in abnormal ignition and seizing of parts. Cooling system is used to
maintain the temperature within limits so that normal ignition occurs.
14. Name the different cooling system
1. Air cooling system 2.Liquid or water cooling system.
15. What is the compression ratio of an I.C engine?
Compression ratio of an I.C engine is defined as the ratio of maximum cylinder volume
to minimum cylinder volume
Maximum cylinder volume
Compression ratio = ----------------------------------
Minimum cylinder volume
16. What is meant by scavenging in I.C engine?
Scavenging refers to the process of removing burnt gases during exhaust stroke with the help
of incoming charge and deflector.
17. What is meant by Top Dead Centre (T D C)?
The extreme position reached by the piston at the top of the cylinder in the vertical engine is
called top dead centre. In horizontal engines, it is called as Inner Dead Centre.
18. What is meant by Bottom Dead Centre (BDC)?
The extreme position reached by the piston at the bottom of the cylinder in the vertical
Engine is called bottom dead centre. In horizontal engines, it is called as Outer Dead Centre.
19. Explain C.I engines?
C.I means compressed ignition engine. The air in the diesel engine cylinder is compressed in
to very high level for the piston upward movement. Finally the diesel from the fuel injector
sprayed as fine droplets. This results the burning inside the chamber.
20. Give the main components of a petrol engine.
Cylinder, Cylinder head, Piston, Connecting rod, Valves, Spark plug, Crank shaft, Cam
shaft and flywheel.
21. Number of working strokes per minute for a four stroke cycle engines are -
The speed of the engine is in rpm. Ans: Half
22. A petrol engine works on cycle.
Ans: Otto

23. is used to mix fuel and air in a petrol engine.
Ans: carburetor
24. What is a four stroke engine?
A four stroke engine, one power stroke is completed for every four stroke of the piston or
during two revolutions of the crank shaft.
25. Diesel engine works on the principle of .
Ans: Diesel cycle.
26. What is the fundamental difference between two stroke four stroke engines?
In two stroke engine, one power stroke is obtained in each revolution of crank shaft.
In four strokes engine one power stroke obtained in two revolutions of crank shaft.
27. Why fuel is injected in a C.I engine?
The fuel used in C.I engine cannot be vaporized and is injected in to the cylinder in the
form of fine spray.
28. State the function of choke in a petrol engine?
Choke is provided for easy starting of the engine. It allows rich mixture in to the cylinder
by reducing the amount of air present in the mixture.
29. Define fuel injector?
Fuel injector is a device used to atomize the fuel and to deliver the fuel to the cylinder of a
diesel engine in the form of fine spray.
30. Mention the types of water cooling on I.C engine?
1. Natural circulation system.
2. Forced circulation system.
31. Carburetor supplies a normal air fuel mixture in the ratio of about
Ans: 15:1
32. is commonly used as fuel in a compression ignition engine
Ans: Diesel.
33. A two stroke cycle engine has power strokes times that of four stoke cycle engine.
Ans: two.
34. In engine, valves are replaced by ports.
Ans: two strokes
35. Define the swept volume?
The volume covered by the piston as it moves from BDC to TDC is known as swept
volume (or) piston displacement.
36. is associated with a SI engine only
Ans: Otto cycle.
37. is associated with a Diesel engine only
Ans: fuel injector

38._ is used to convert rectilinear to fro motion of a piston in to rotary motion
Ans: connecting rod.
39. is used to reduce friction between rubbing surfaces.
Ans: Lubricant.
40. What is Boiler?
Boiler is also known as steam generator. It is a closed vessel in which steam is generated
from water by the application of heat and the pressure being higher than the atmosphere. The main
function of a boiler is to evaporate water into steam at a higher pressure.
45. How are boilers / steam generators are classified?
1. Horizontal, vertical and inclined.
2. Fire tube and water tube.
3. Externally fired and internally fired.
4. Forced circulation and natural circulation.
5. High pressure and low pressure.
6. Stationary and portable boiler.
7. Single tube and multi tube boiler.
8. Natural draught and forced draught.
46. Distinguish between fire tube and water tube boiler?
In a water tube boiler water is circulated through a series of tube and hot flue gases surround
the water tubes.
In a fire tube boiler hot flue gases pass through a series of tubes and tubes are surround by
water.
47. Mention the some boiler accessories?
Economizer, Air preheater, super heater, Steam separator.
46. Mention the boiler mounting?
Pressure gauge, water level indicator, steam stop valve, fusible plug.
47. What is the function at the economizer?
The feed water from the feed tank is supplied to the economizer by the feed pump. Water is
preheated in the economizer by the flue gases. Economizer is a heat exchanger where the heat from
the hot gases is transferred onto the economizer pipe carrying the feed water.
48. Mention two water tube boilers?
Babcock and Wilcox boiler.
ii. La Mont boiler.
49. Mention two fire tube boilers?
a. Cochran boiler. b. Lancashire boiler.
50. State the function of safety valve in a boiler?
A safety valve is a device used to release steam pressure inside the boiler exceeds the safe

working pressure.
51. State the function of steam stop valve in a boiler?
Steam stop valve is used to regulate the flow of steam according to the varying demand.
52. What is the function of blow off cock?
Blow off cock is used to remove the impurities like sand mud and salt deposits that get
collected at the bottom of the boiler shell.
53. What are the main parts of a steam turbine?
Steam nozzles, blades, rotor and casing.
54. What is the function of an air preheater?
Air preheater is a heat exchanger that is used to preheat the air that is sent to the furnace. Air
preheater utilizes the heat of exhaust gas before it is let out through the chimney.
55. What is the function of the super heater?
Super heater is a heat exchanger which is used to super heat the steam. By this process
the moisture present in the steam is removed and the steam temperature is further increased.
56. Distinguish between boiler mountings and boiler accessories.
Boiler mountings Boiler accessories
Mounting are fitted in a boiler for the safety
of boiler and complete control of steam
generation process
Example: pressure gauge, water level
indicator, steam stop valve, fusible plug.
With out mounting the boiler cannot be
operated
Accessories are fitted to increase the efficiency
of the boiler plant or help in the proper of the
boiler
Example: economizer, air pre heater, super
heater, steam separator.
With out accessories the boiler can be operated
12 MARKS QUESTION AND ANSWERS
1. Explain the working principle of two stroke petrol engine and neat
sketches.
Two stroke cycle is very widely employed where small power required for motor cycle, auto
rickshaw, scooters. These types of engines are compact in size, easy for manufacturing and
simple in operations. One drawback is there, Specific Fuel Consumption (S.F.C) is more (means
fuel per Break Horse Power (B.H.P.) per hour is more).
There are no inlet and exhaust valves as in four stroke engine but we have inlet and exhaust ports
only, due to which suction and exhaust stroke are eliminated in two stroke cycle engine. Here the
burnt exhaust gases are forced out through the exhaust port by a fresh charge of fuel which
enters the cylinder nearly at the end of working stroke through inlet port. This process is
called as Scavenging”.
First stroke (suction and compression)
From bottom dead centre, when the piston moves up, it first closes the transfer port and

then exhaust port. The charge of fuel which previously entered in the cylinder is now compressed.
When the piston is nearing the upward movement the inlet port opens and afresh charge of air-fuel
mixture from the carburetor enters the crankcase.
Second stroke (ignition, expansion and exhaust stroke)
The ignition starts due to the spark given by spark plug when the piston is nearing the completion
of its compression stroke. As a result, piston is pushed down performing the working stroke. So
the piston moves from TDC to BDC. During the downward movement it closes the inlet port
and pushes the fresh charges in the crank case towards up by means of transfer port. So the fresh
up going charges reach the combustion chamber and push the burned gases through the exhaust
port.Likewise the cycle is repeated.
2. Explain the working principle of two stroke diesel engine and neat sketches.
A two-stroke diesel engine shares the same operating principles as other internal combustion
engines. It has all of the advantages that other diesel engines have over gasoline engines. A two-
stroke diesel engine does not produce as much power as a four-stroke diesel engine; however, it
runs smoother than the four-stroke diesel. This is because it generates a power stroke each time the
piston moves downward; that is, once for each crankshaft revolution. The two-stroke diesel engine
has a less complicated valve train because it does not use intake valves. Instead, it requires a
supercharger to force air into the cylinder and force exhaust gases out, because the piston cannot do
this naturally as in four-stroke engines. The two-stroke diesel takes in air and discharges
exhaust through a system called scavenging. Scavenging begins with the piston at bottom dead
center. At this point, the intake ports are uncovered in the cylinder wall and the exhaust valve is
open. The supercharger forces air into the cylinder, and, as the air is forced in, the burned gases
from the previous operating cycle are forced out

First stroke (suction, compression):
As the piston moves towards top dead center, it covers the intake ports. The exhaust valves closed.
Due to the piston continues upward movement, the air in the cylinder is tightly compressed As in
the four-stroke cycle diesel, a tremendous amount of heat is generated by the compression. At
the same time the fresh air get entered into the crank case through the inlet port.
Second stroke (ignition, expansion and exhaust):
At the end of the compression stroke, fuel is injected. Due to the compression the air which is
compressed there is in high temperature the burning of fuel taking place. So the force developed due
to the burned gases will push down the piston. This downward movement is taken by the crank
shaft for vehicle movement. During the downward movement the piston close the inlet port and
open the exhaust port. At the same time the piston push the fresh air in the crank case towards up
through the transfer port. So the fresh air goes into the combustion chamber and pushes the burned
gases out through the exhaust port. (I.e. scavenging taking place) Now the engine is ready for next
cycle of operation.
Compression ratio
The amount of compression in an engine cylinder is a ratio of the original volume and the final
volume. A compression ratio of 2:1 means the air has been compressed to half its original volume.
A ratio of 3:1 indicates compression to one-third of the original volume. The compression ratio of a
gasoline engine varies from about 6:1 to 10:1. The compression ratio for a diesel engine varies from
about 12:1 to 24:1. The diesel’s higher compression ratios are necessary to create air temperatures
hot enough to ignite fuel on contact.
3. Explain the working principle of Four Stroke petrol engine and neat sketches
Generally the vehicles using petrol / gasoline engine have four strokes as they are more
efficient than two stroke engine and give complete combustion of fuel to optimum use.
The four-stroke cycle engine has four strokes namely intake (suction), compression, power, and
exhaust strokes.

A) Suction or intake stroke:
Initially when engine is started piston moves downwards towards bottom of the cylinder
which creates low pressure at top. Due to this intake valve opens and the fuel mixture containing
petrol vapors and air are sucked in by the cylinder from the Carburetor.
B) Compression stroke:
After this the inlet valve gets closed. The piston now moves towards the top of cylinder and
compresses the fuel mixture to one tenth of its initial volume. The temperature and pressure inside
the cylinder increases due to compression caused.
C) Power stroke:
During this stroke the inlet and exhaust valve remains closed. As the piston reaches near top
position spark plug produces an electric spark. Due to this the combustion taking place inside the
cylinder of the engine. The spark produced causes explosion of fuel. The hot gases expand and
force the piston to move downwards. The piston is linked to the piston rod and the piston rod to the
crank shaft. They all move each other due to the link between them.
D) Exhaust stroke:
In this stroke the exhaust valve remains open at the start. The piston is forced to move
upwards because of the momentum gained. This forces gases to move through the exhaust valve
into the atmosphere. Now the exhaust valve closes and the intake valve opens. Then the cycle of
operation repeated.
Carburetor

It is the heart of gasoline engine. They meter the fuel and mix it with the air in precise
proportions. Old carburetors do spark advance by measuring the difference in pressure between the
outside and inside of the carburetor. The amount of throttle advance is also measured. The engine's
remains which may be carbon monoxide or unburned hydrocarbons shows how well the carburetor
is working. In new engines, a small computer is used to calculate these parameters and control one
or more electric injectors. Most of the new cars use electronic fuel injection as it allows the engine
computer to precisely control the fuel air mixture which increases energy efficiency and reduces
pollution.
Applications:
These engines are widely used in vehicles, portable power plants to supply the power to run
pumps and other machineries on farms. Many small boats, aero planes, trucks and buses also use it.
4. Explain the working principle of Four Stroke diesel engine and neat sketches.
Suction stroke:-
In this stroke, the piston moves down from the top dead centre. As a result, inlet valve opens and air
is drawn into the cylinder. After sufficient quantity of air with pressure is drawn, suction valve
closes at the end of the stroke. The exhaust valve remains closed during this stroke.
Compression stroke:-
In this stroke, piston moves up from the bottom dead centre. During this stroke both inlet
and exhaust valve are closed. The air drawn into the cylinder during suction stroke is entrapped
inside the cylinder and compressed due to upward movement of the piston. In diesel engine, the
compression ratio used is very high as a result; the air is finally compressed to a very high pressure
and temperature. Finally the fuel is injected and the burning taking place inside the cylinder.
Working or power stroke:-
In this stroke, both inlet and exhaust valve remain closed. The hot gases (which are
produced due to ignition of fuel during compression stroke) and compressed air now expand in the
cylinder pushing the piston down and hence work is done. At the end of stroke, the piston finally
reaches the bottom dead centre.

Exhaust stroke:-
In this stroke, the piston again moves upward. The exhaust valve opens, while inlet and fuel
valve are closed. The upward movement of the piston pushes the gases out through the exhaust
valve. And the engine ready for next cycle.
5. Differentiate 4 stroke engine with 2 stroke engine
S.No Four stroke engine Two stroke engine
1
Two revolution of flywheel having
one power stroke.
One revolution of flywheel having one power
stroke.
2 Valves are provided. Ports are provided.
3 Water cooling arrangement. Air cooling arrangement.
4 More space is required. Less space is required.
5 Heavier flywheel is required. Lighter flywheel is required.
6 Thermal efficiency is more. Thermal efficiency is less.
7 Volumetric efficiency is more. Volumetric efficiency is less.
8 Less fuel consumption. More fuel consumption.
9 Requires more lubrication. Not essential.
10 Torque is not uniform. Torque is uniform.

6. Differentiate petrol engine with diesel engine
S.NO PETROL ENGINE (S.I ENGINE) DIESEL ENGINE (C.I.ENGINE)
1 Operates based on Otto cycle. Operates based on diesel cycle.
2 Spark plug is used for fuel ignition. Fuel is ignited by hot compressed air.
3 Low compression ratio (6 to 8). High compression ratio (15 to 20).
4 Operates at high speed. Operates at low speed.
5 Petrol is the costlier fuel. Diesel is the less cost fuel.
6 Lighter in weight. Heavier in weight.
7 Carburetor is used. Fuel injection pump is used.
8 Fuel consumption is more. Fuel consumption is less.
9 Less vibration. More vibration.
10
Petrol is the high volatile liquid, so
handling is more risk.
Diesel is less volatile liquid. So handling is
less risky.
7. Discuss the working of a Benson boiler?
The presence of steam bubbles in contact with the surface of tubes seriously affects the heat
transfer from flue gases to water. By rising the boiler pressure to the critical level (220 kgf /sq.cm),
the problem is overcome. This was suggested by Mark Benson in 1922.
Here they eliminate the boiler drum and send the water in a single stage. And they use two types of
evaporators (radiant evaporator, convective evaporator).
Economizer: It is used to pre heat the water to the boiler.
Radiant evaporator: They are parallel tubes in construction. This is exactly placed over the grate
area. So the water in the pipe line of radiant evaporator receives the heat energy from the
combustion of fuel in the grate area. Majority of the water converted in to steam in it.
Convection evaporator: The remaining water in the pipe line is fully converted into wet steam in
the convection evaporator by receiving the heat energy from hot flue gases.
Convection super heater: when wet steam used to rotate the turbine blade, it will create corrosion
problems. So for removing the water vapor, they pass the steam through the super heater. Here all
the water particles are removed and the steam becomes super heated steam. This is the steam used
to rotate the blades of turbine for power production.

Super heater, Air pre heater, economizer and evaporator receive heat from flue gases.
Working
The water from the well is treated for boiler usage in the separate plant. Then it’s passed in
to the boiler through a pipe line. The feed pump is used to pump the water to economizer unit.
There the water slightly heated by the hot flue gases from the burned area below. Then the hot water
passes through the radiant evaporator, which is very near to the grate area. Radiant evaporator is
nothing but a series of parallel pipe lines. So the water moving time and exposure to the heating
area will become high. By this most of the water become steam in this area. Here the water in the
pipe line directly in contact with firing of coal. Next the water entered in to convective evaporator;
here the remaining water is converted into saturated steam. For avoiding corrosion problem from
the usage of wet steam, they send the water through super heater. Here the water output becomes
super heated steam. This is the steam required to rotate the blades of the turbine.
Advantages
1. Smaller in size.
2. Less weight.
3. Simple in design compared to la mount boiler.
8. Explain the working principle of La-Mont High Pressure boilers
La mount boiler is a modern high pressure boiler working on forced circulation system. A
forced circulation boiler was introduced by la mount in the year of 1925 which is used in Europe
and America.
Feed water pump : The pump supplies the water to the economizer.
Economizer : This device used to preheat the water before to drum.
Drum : This is for storing water and also steam.

Circulating pump : Centrifugal pump is used to pump the water to evaporator unit.
Evaporator : It is used to convert the hot feed water to wet steam.
Super heater : The moisture in the wet steam will corrode the turbine blades,
So removing the water vapor in steam we pass the wet steam through
the super heater.
Air pre heater : It’s used to preheat the air by means of flue gases from burned area.
Working
Feed water is pumped to the boiler drum by the feed pump through the economizer.
Economizer preheats the incoming water to the boiler drum. Then using the centrifugal pump the
hot water is pumped to evaporator unit. Evaporator used to convert the water from water to wet
steam level by means of burning the coal in the grate area. Then the wet steam is passed through the
super heater to avoid water vapors in the steam content. This is steam required to rotate the blades
of the turbine unit. The economizer and super heater get the heat energy from flue gases.
Advantages
1. Output of the boiler steam is at high pressure.
2. Usage of air pre heater and economizer increase the efficiency of the boiler.
3. Small in size.
4. Forced circulation of water increase the boiler efficiency and heat transfer rate.
Disadvantages
1. Ash removal problem is high it is because of its compact size.
2. Salt sedimentation and cleaning problem.
3. Ash and salt deposition decrease the boiler efficiency.

9. Explain the working principle of Babcock and Wilcox boilers (high pressure boiler) and
neat sketches.
This kind of boiler producing steam at a pressure of more than 80 bar. Mostly water tube
boilers are preferred for high pressure steam production.
It’s a horizontal, externally fired, high pressure, water tube boiler.
Parts
Shell
It’s a horizontal water filled drum. Half portion is filled by water and the remaining is for steam
collection.
Water tubes
Number of water tubes is placed between the drum and furnace with the inclination of 10 to 15
degree. This arrangement is for increasing the water circulation at the time of operation.
Uptake header and down comer
The water tubes are connected to the drum by small pipes at one end is called uptake header
by long pipes at the other end is called down comer.
Furnace
This is the place of burning for the coal. The coal is transferred from the storage area to
furnace by means of conveyers. Fire door is the entrance for the burning area.

Baffles
Baffles are the part used to redirect the flue gases around the water tubes more time. This is
done for increasing better heat transfer.
Mud box
This is placed at the bottom of the entire arrangement. The clay like impurities are collected
in the mud box. And send out through the blow off cock arrangement.
Inspection doors
This is the passage for repair and inspection work for the labors.
Working
Coal from the storage area is transferred to the furnace area by means of conveyor. The
burned gases from the combustion are goes around the water tubes; here the baffle plates are used to
deflect the hot gases more time around the water tubes. This will increase the heat transfer
effectively from flue gas to water. The steam produced due to heating of water is stored in the boiler
drum. The uptake header and uptake header are used to increase the steam and water circulation in
the tubes to the drum. The collected steam passes through the super heater for further processing.
10. Draw and explain any 4 boiler mountings?
For having smooth and safety operation some of the equipments are very essential in
running of boiler unit.
They are,
1. Water level indicator,
2. Pressure gauge,
3. Fusible plug,
4. Safety valve.
Water level indicator
It’s used to show the level of water in the
boiler drum. The indicator made up of glass
material to show the water level.
And it has inlet and outlet as shown in
figure. There are some readings in the body.
This equipment helps to avoid the over
heating of boiler when the level of water
become less in the drum.
Pressure gauge
It’s mainly used to indicate the steam pressure inside the boiler. This is made up of bronze
alloy. The pressure gauge consists of a curved metallic tube (bourdon tube) of elliptical cross
section. One of its ends is connected with toothed sector by a link and the other end is open and is
connected to the steam space of the boiler. There is a pointer which is connected to the sector
arrangement.

When the steam enters into the tube, the elliptical structure tries to expand into a circle. This
causes the free end of the tube to move. This effect is transfer to through the links and the pointer
shows some reading in the gauge.
Fusible plug
Fusible plug used to put off the fire in the boiler furnace, when the water level below on
unsafe limit. It prevents the overheating of tubes and shell thereby avoiding explosion of the boiler.
It consists of gun metal body with a hexagonal flange screwed with the firebox crown plate. A
hollow gun metal plug is screwed into the gun metal body. Another copper plug is locked with the
hollow plug by a low melting point fusible metal (tin or lead).
The fusible plug is submerged in water in water during the normal operation. When the
water level falls below the safe limit, the fusible plug is uncovered from water. The plug gets over
heated and the fusible metal melts by the heat of the furnace. The copper plug drops down and the
water from the put off the fire. Gun metal body prevents the plug from falling into the furnace.
Lever safety valve
Safe valves are sed to maintain a constant safe pressure
inside the boiler. When the pressure inside the boiler exceeds the
safe limit, the valve automatically relieves the excess pressure.
In its body, it has lever, valve seat, valve, fulcrum and
hinges.

The required operating pressure level of weight is added on the lever end. When the pressure
of steam inside the boiler exceeds the normal level, the valve lifted up and the excess pressure of
steam released out.
11. Draw and explain any 4 boiler accessories?
These are the devices used to increase the efficiency of the boiler and also for proper working of
the boiler.
1. Economizer
2. Air preheater
3. Super heater
4. Steam separator
Economizer
This is the device used to pre heat the
water before it goes into the boiler. Water
enters in the lower portion and leaves from
the upper portion to boiler. The hot flue gases
from the boiler used to pre heat the water. By
doing these kind of operations we increase the
boiler efficiency.
Air preheater
The air taken from the atmosphere for
burning of coal in the furnace is sent through a
pre heating arrangement for increasing the boiler
efficiency. Hot air passed in the lower portion of
the unit and leaves out from the top outlet as
shown in figure. The hot flue gases from the
burning area heats the pipe line of the atmosphere
air. Baffle plates are used to deflect the hot air
more time around the tubes. So better heat
transfer takes place in the arrangement. This will increase the efficiency of the boiler.
Super heater
This is the level of steam require to
rotate the blades of the turbine. The structure
of the unit has many tubes. The hot saturated
steam from the evaporator is heated once again
up to super heated level (removing of all water
vapors in the steam content) by means of flue
gases from the burning of coal in the grate
area.

Steam seperator
This is the part used to separate water particles from steam before it is supplied to a steam
engine or turbine. It prevents the damaging of turbine blades
due to moisture present in steam. It is located in the supply
near the turbine or engine.
It has cylindrical container with baffle plates as shown in
figure. A water gauge is fitted to indicate the water collected
in the separator. A drain cock is provided at the bottom of
the separator to drain away the separated water.
During the operation the steam strikes the baffle plates
of the separator and the direction changed. As a result,
heavier water particles in the steam falls down to the bottom of the separator. The separated steam
is free from water particles. It is passed to the turbine through the outlet pipe.

UNIT-V
REFRIGERATION AND AIR CONDITIONING SYSTEM
2 MARK QUESTIONS
1. Define Refrigeration.
Refrigeration is the process of reducing and maintaining the temperature of a body below the
atmosphere temperature.
2. What is Refrigerator?
Refrigerator is an equipment used to reduce and maintain the temperature below the
atmosphere temperature by removing the heat from the space continuously.
3. Define Refrigerant. Give some example.
Refrigerant is a fluid which absorbs the heat from the body and rejects the heat at high temperature.
Example: Ammonia, Carbon di oxide,.Freon-12,Chloro fluoro carbon, Methyl chloride
4. Define COP.
COP is the ratio of heat extracted and work input.
Heat extracted
Coefficient of Performance = ---------------------------
Work input
5. Define refrigeration effect?
It is defined as the ratio of the quantity of heat removed and the time taken.
Heat removed
Refrigeration effect N = ---------------------------
Time taken
6. Name the two types of Refrigerators?
1. Vapour compression refrigerator
2. Vapour absorption refrigerator
7. is commonly used refrigerant.
Ans: Freon (R-12)
8. An example for man made refrigerant is .
Ans: Freon (R-22)
9. The chemical name of R-22 is_ .
Ans: Monochloro difluoro methane.
10. The chemical name of R-717 is .
Ans: Ammonia
11. Mention the types of refrigerators.
1. Primary refrigerators 2. Secondary refrigerators

12. Give some properties of a good refrigerant.
1. It should have low freezing point and boiling point
2. It should be easily liquefied
3. It should have high COP
4. It should absorb high latent heat
13. Mention some application of refrigeration?
1. In preserving food, fruits and drugs 2. Used in refineries
3. Manufacturing of ice 4. In manufacturing industries
14. Define capacity of refrigerator.
Capacity is the rate at which heat can be extracted from the cold body. i.e., the rate at which
refrigeration can be produced. The capacity is expressed in term of tons of refrigeration.
15. Define One Ton.
One ton of refrigeration is equal to the amount of refrigeration produced by melting 1 ton of
ice in 24 hours.
16. What are the main parts in vapour compression refrigeration system?
Receiver, Refrigeration control device, Evaporator, Compressor, Condenser
17. What are the main components in vapour absorption refrigeration system?
Generator, Condenser, Refrigeration control device, Evaporator, Absorber
18. The type of heat that is absorbed by a liquid to convert to gas is called .
Ans; Latent heat of vaporization.
19. Define Air conditioning.
Air conditioning is the process of conditioning the air according to the human comfort
irrespective of external conditions.
20. What is the purpose of air conditioner?
Air conditioner controls the temperature, moisture, cleanliness and movement of indoor air.
It cools the air when the weather is hot. It warms the air when weather is cold. By controlling air
movement, air conditioning brings fresh air in to a room and pushes out still air. This makes the air
inside the room fresh and pure.
21. Define relative humidity.
It is the ratio of water vapour in a given volume of air at a given temperature to the mass of
water vapour present in the same volume under same temperature of air when it is fully saturated.
22. Define DBT.
The temperature of air measured by the ordinary thermometer is called Dry Bulb
temperature.
23. Define WBT.
The temperature of air measured by the thermometer when it is covered by a wet cloth is
known as Wet Bulb Temperature.

24. Mention the types of air conditioning.
1. Comforting air conditioning 2. Industrial air conditioning.
25. is the refrigerant commonly used in ice plants. Ans: Ammonia
26. List out the types of air conditioners
1. Room air conditioner 2. Window air conditioner 3. Central air conditioner
27. List out the function air conditioner
1. Cleaning air. 2. Controlling the temperature of air
3. Controlling the moisture content. 4. Circulating the air.
28. What is the dry air?
The atmospheric air which contains no water vapour is called dry air.
29. What is psychometric?
It is the study of the properties of atmospheric air.
30. What is moist air?
The atmospheric air which contains water vapour is called moist air.
31. What is moisture?
Moisture is the water vapour present in the air.
32. Define the humidity?
The amount of water vapour present in the air is called the humidity.
33. Define the relative humidity?
It is the ratio of the water vapour in a given volume of air at a given temperature to the mass
of water vapour present in the same volume under the same temperature of air when it is fully
saturated.
34. Define the Dew point temperature?
The temperature at which the water vapour starts condensing is called Dew point
temperature.
35. What is the water vapour?
It is the moisture present in dry air. The moisture content in air in an important factor in all
air conditioning system.
36. Mention 4 industrial application of the air conditioning?
1. Food industry. 2. Photographic industry. 3. Textile industry. 4. Printing industry.
37. How is air conditioning system classified?
1. Comfort air conditioning a) summer air conditioning
b) Winter air conditioning
c) Year round air conditioning.
2. Industrial air conditioning

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