Basics of mechanical engineering

BASICS OF THERMODYNAMICS
WORKING SUBSTANCE:
The working substance is mostly gas or vapors and liquid in
equilibrium. It is very important to know the behavior of the substance and its
properties
Pure substances are those which have homogeneous chemical
structure. Water is the example of pure substance. Air is also considered as a pure
substance in gaseous form.
Thermodynamics System:
It is defined as the space on which attention is concentrated to analyze it.
Thermodynamics Surrounding :
It is defined as the remaining space of the universe except system
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Boundary:
An envelop enclosing the system is known as boundary.
Universe:
When the system and surrounding are put together, is called universe.
Types of Systems:
1. Open System
2. Closed System
3. Isolated System
1. Open system: A system is called open when there is transfer of mass as well
as heat between the system and surrounding.
2. closed system: A system is called closed when there is transfer of heat
between the system and surrounding and there is no transfer of mass
between system and surrounding.
3. Isolated system: A system is called isolated when there is transfer no
transfer of mass as well as heat between the system and surrounding
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Property or Parameters of substance:
Property or Parameters are those quantities which specify the state of the
substance. So we can say that the properties of a substance dependent on the state
of substance e.g. Mass, Physical Composition, Vol., Pressure, Temp, Surface Area,
Velocity, Thermal Conductivity, Entropy, Enthalpy ect.
Types of Properties :
1. Intensive Properties
2. Extensive Properties
1. Intensive Properties: Are those properties which does not depend on the
mass of system. E.g. pressure, temp., density, velocity , height, viscosity
2. Extensive Properties: Are those properties which depend on the mass of
system. E.g. vol., Surface area, internal energy, potential energy
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Pressure:
Pressure is defined as the force per unit area. Its unit is Pascal, Bar,
N/M2.
Atm. Pressure :
It is the pressure exerted by the weight of air column on the surface
of earth is called atm. Pressure.
Atm. Pressure = hρg Where h is the height of air column, ρ is
the density of air, g is acc. due to gravity
Gauge. Pressure :
Pressure measured by the pressure gauge is called gauge pressure
and it is one atm. less pressure than the absolute pressure. It is the
pressure above the atm. Pressure.
Absolute Pressure :
Absolute pressure is the total pressure.
Absolute Pressure= Atm. Pressure+ Gauge Pressure
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Thermodynamic Equilibrium:
A system is said to be in thermal equilibrium if the value of property is same
at all the points of the system. For thermodynamic equilibrium following
condition must be satisfied.
1. Mechanical Equilibrium
2. Chemical Equilibrium
3. Thermal Equilibrium
1. Mechanical Equilibrium:
A system is said to be in mechanical equilibrium if Algebraic sum of
all the forces and moments are zero
2. Chemical Equilibrium:
A system is said to be in chemical equilibrium if there is no chemical
reaction with in the system.
3. Thermal Equilibrium:
A system is said to be in thermal equilibrium if there is no temp.
difference between the parts of system.
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State:
Instantaneous condition on of a thermodynamic system is called state. It the
condition of the system at any time. The state of the system is define by the
temp. pressure vol. density.
Path :
It is the locus of points of states at different time.
Process:
A process is defined as when a system changes its state from one state to
another state.
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Cyclic Process :
When a process or processes are performed on the system in such
away that the final state is same with the initial state.
Reversible Process:
If the process in the reverse, follow the same path from one state to
another state as the path traced during forward path called reversible path.
Irreversible Process:
If the process in the reverse, do not follow the same path from one
state to another state as the path traced during forward path called irreversible
path. Dinesh Panchal

Energy :
It is the capacity to do work.
1. Mechanical Energy
(a) Potential Energy: It is the energy possessed by virtue of its
position .e.g. Potential energy due to height
P.E. =mgh
(b) Kinetic Energy : It is the energy possessed by virtue of its
motion .
K.E. =1/2mv2
2. Internal Energy:
It is the energy possessed by the body due to its molecular
arrangement and motion of the molecules.
3. Total Energy:
It is the sum of K.E., P.E. and I.E.
E=P.E.+K.E.+U
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Law of conservation of Energy :
It state that energy can neither be created nor be destroyed, but can be
changed from one form to another form. It means electrical energy can be
converted in to mech. Energy and vice versa. Similarly thermal energy can be
converted in to mechanical or electrical energy.
Law of conservation of Mass:
It state that mass can neither be created nor be destroyed, but can be
changed from one form to another form. A solid can be changed from solid
to liquid, liquid to gas or vice versa.
Heat:
Heat is defined as the energy that is transferred across the boundary of a
system due to temp. difference. Heat flow from high temp. to low temp.
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Specific Heat :
Specific Heat is defined as the amount of heat required to raise the temp.
of the unit mass through one degree centigrade.
It has two type
(a) Specific heat at constant volume :
It is defined as the amount of heat
required to raise the temp. of the
unit mass through one degree
centigrade at constant volume. It is
denoted by
(b) Specific heat at constant pressure:
It is defined as the amount of heat
required to raise the temp. of the
unit mass through one degree
centigrade at constant Pressure.
It is denoted by
vC
pC
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Sign Convention for Heat and Work :
# Work done by the System is +ve
# Work done on the System is -ve
# Heat Transferred to the system is +ve
# Heat Transferred from the system is –ve
Gas Law :
It is the relation between Temperature, Volume, Pressure and mass of a gas
at any particular state.
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Boyle’s Law : (Isothermal Process)
The absolute pressure of a given mass of perfect gas varies inversely
proportional to its volume at constant temp.
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Boyle’s Law : (Isobaric Process)
The absolute volume of a given mass of perfect gas varies directly
proportional to its volume.
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Dinesh Panchal

Gay – Lussac Law : (Isochoric Process)
It state that the absolute pressure of a given mass of a perfect gas
varies directly as its temperature.
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Temperature :
Temp. is defined as the hotness and coldness of the system or body. Its unit of
measurement are Celsius or Centigrade, Fahrenheit and Kelvin. Relation
between these temp. measuring scale is given below .
Absolute Zero Temp. :
It is defined as the temp below which temp. does not fall. Its value is
Zeroth Law of Temperature :
It state that if body A is in thermal equilibrium
with body B and body B is in thermal
equilibrium with body C then body A is also
thermal equilibrium with body C.
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First Law of Thermodynamics :
It state that heat and mechanical work are mutually convertible. In others
words cyclic integral of heat transfer equal to the cyclic integral of work.
Another statement is that Energy can neither be created nor be destroyed,
but can be changed from one form to another.
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Application of first law to non flow processes:
1. Constant Volume Process:
If the volume remains constant during the process , then the process is
called Isochoric or constant volume process.
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2. Constant Temperature (Isothermal Process) :
In this process temperature remains constant throughout the
process. This process is called Isothermal Process.
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Dinesh Panchal

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2. Constant Pressure (Isobaric Process) :
In this process pressure remains constant throughout the process.
This process is called Isobaric Process.
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3. Adiabatic Process (Isentropic Process) :
In this process there is no heat addition or removal from the syatem
to surrounding.
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Dinesh Panchal

QUESTION NO. 1 (A) A dry saturated steam at a pressure of 600KPa is contained in a
thermally insulated cylinder fitted with a frictional piston. As the piston moves outwards, the
steam expands to a pressure 60KPa.Calculatye the work done by the gas.
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Free Expansion :
The free expansion process is an irreversible process. Free expansion
is a process in which the fluid expands suddenly in to the vacuum
chamber.
In this process no external heat is supplied and no external work
is done. In this process enthalpy of the system remains constant.
Limitations of 1st Law of Thermodynamics:
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Heat Engine :
Heat engine is a device which convert heat energy in to mechanical
work in cyclic process. In heat engine high pressure and temp steam is generated in
the boiler and supplied to the steam turbine. Turbine convert the heat energy of
steam in to mechanical work.
Suppose a heat engine is working between two heat reservoir one at high temp
and one at low temp. Heat is supplied by the reservoir at high temp. and heat is
rejected to the reservoir at low temp.
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Dinesh Panchal

Heat Pump :
Heat engine is a device which transfer heat energy from low temp to
high temp. this can be done by doing the external work on the system.
Suppose a heat pump is working between two heat reservoir one at high temp and
one at low temp. Heat is transferred from low temp to high temp.
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Second Law of Thermodynamics:
1. Kelvin – Planks Statement : It is impossible to construct a heat engine
which operate in a cycle, will produce no effect other than the exchange of
heat from a single reservoir and produce work . Or no actual engine operating
in a cycle can convert whole of heat energy supplied to it in to work.
2. Clausius Statement : It is impossible to construct a heat pump, which is
operating in a cycle, will produce no effect other than the transfer of heat
from lower temp. body to higher temp. body. Or heat can not flow from
lower temp. to higher temp. without help of external work
Third Law of Thermodynamics:
This law state that absolute value of entropy can not be achieved. The
entropy of perfect crystal is zero at absolute zero temp.
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Enthalpy:
Enthalpy is the sum of internal energy and the product of pressure and
volume or work done
Enthalpy = U + p V
Where U is the internal energy
P is the pressure
V is the volume
Internal Energy:
Internal energy is defined as the sum of all the microscopic forms of energy of
the system. It is the energy associated with the molecular activity of the
constituent partials of the system. It is the sum of kinetic energy and potential
energy of the partials. It is denoted by U.
Entropy :
It is the function of quantity of heat which shows the possibility of conversion
of that heat in to useful work. It is an important thermodynamic property of a
working substance, which increases with the addition of heat and decreases with
its removal.
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THERMODYNAMICS PROPERTIES OF STEAM
1. Vaporization: It is the process of change of liquid to vapor phase. Water vapor
are obtained by vaporization and steam from boiling.
2. Evaporation: is the process of vapor generation only from the surface of the
liquid.
3. Boiling :- is the process of vapor formation that take place in the whole mass
of the liquid.
4. Saturated Temperature:- The boiling of liquid take place at a definite temp.
and this temp dependent on the pressure called saturate temp. It is denoted
by
5. Saturated Pressure:- The boiling of liquid take place at a definite Pressure at
given temp. called Saturate Pressure . It is denoted by .
st
sp
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THERMODYNAMICS PROPERTIES OF STEAM
1. WET STEAM:- When the steam contain moist or water partial called wet steam.
2. DRY SATURATED STEAM:- When the wet steam is further heated and it does not
contain any suspended partials of water it is known as dry saturated steam.
Dry saturated steam absorbed its full latent heat.
3. SUPERHEATED STEAM:- When the dry stem is further heated at constant
pressure for raising its temp then it is to be said superheated steam.
4. DRYNESS FRACTION:- It is the ratio of mass of actual dry steam to mass of total
mass of wet steam denoted by x
5. Latent Heat of Vaporization:- It is the amount of heat absorbed to evaporate 1
kg of water at its boiling point or saturation temp without change in temp.
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1. Sensible heat of Water:- :- It is the amount of heat absorbed by 1 kg of water, when
heated at a constant pressure from to the temp of formation of steam
2. Latent Heat of vaporization: It is the quantity of heat required to convert 1 kg. of water
at saturation temp. at a given pressure in to dry saturated steam at
that temp. and pressure. It is denoted by
3. Enthalpy or Total Heat of steam:- It is the amount of heat absorbed by the water from
freezing point to saturation temp plus heat absorbed during
evaporation Enthalpy= Sensible Heat + Latent Heat•
(1) Wet Steam
(2) Dry Steam
(3) Superheated steam
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Entropy of Steam: Heating and vaporization of water during the steam formation
take place at constant pressure. Even superheating is done at constant
pressure.
Entropy of water :
Suppose 1 Kg. of water is heated from temp. T1 to T2 . Then Entropy change is given
by
(1) Wet Steam
(2) Dry Steam
(3) Superheated steam
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Dinesh Panchal

FORMATION OF STEAM UNDER DIFFERENT PRESSURE
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Q .No. 2(b) Determine the enthalpy , entropy and volume of steam at 1.4 MPa and
380 C
Ans:
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• Degree of superheat
The Degree of Superheat can be defined as the amount by which the
temperature of a superheated vapor/steam exceeds the temperature of
the saturated vapor/steam at the same pressure. Superheated steam is a
steam at a temperature higher than its vaporization (boiling) point at the
absolute pressure where the temperature is measured. The difference
between the superheated temperature and saturation vapor temperature
is called the degree of superheat. It applied to vapors only. It is carried out
at constant pressure. It is expressed as degree of superheat. Degree of
superheat is the difference between actual temperature and the boiling (
saturation) temperature at a CERTAIN pressure.

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Example : (i) Pressure 1 bar For water vapor
Actual temperature is 1070C.
Boiling (saturation) temperature is 1000C.
Degree of superheat is 107 –100 = 7 0C
(ii) Pressure is 2 bars
For water vapor
Say actual temperature of vapor is 1350C.
Boiling (saturation) is 1200C.
Degree of superheat is 135 – 120 =150C
(iii) Pressure is 1 bar.
For refrigerant R-22.
Say actual temperature is -350C.
Boiling (saturation temperature at 1 bar is –410C.
Degree of superheat is -35 –(-41) = 60C

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Degree of sub cooling.
• The opposite of this is sub-cooling, the amount of additional heat removed from a
fluid below its condensing point. An example would be refrigerant liquid coming off
a condenser at its saturation point and then being cooled another ten or so
degrees F., which is common. This too allows the fluid (refrigerant) more available
capacity for work. It applied to LIQUID PHASE only. It is carried out at constant
pressure. It is expressed as degree of sub-cooling. Degree of sub-cooling is the
difference between the boiling (saturation) temperature and actual temperature of
a liquid at a CERTAIN pressure. Actual temperature will be less than the
condensation (saturation) temperature.

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Degree of sub cooling.
Example : (i) Pressure 1 bar
For water vapor
Actual temperature is 400C.
Condensation (saturation) temperature is
1000C.
Degree of sub-cooling is 100 –40 = 60 0C
(ii) Pressure is 2 bars
For water vapor
Say actual temperature of vapor is 1050C.
Condensation (saturation) is 1200C.
Degree of sub-cooling is 120 – 105 =150C
(iii) Pressure is 1 bar.
For refrigerant R-22.
Say actual temperature is -450C.
Condensation (saturation temperature at 1 bar
is –410C.
Degree of sub-cooling is -41 –(-45) = 40C

STEAM TABLE
The properties of steam such as pressure temp. specific vol. enthalpy, entropy
ect. have been experimentally determined and tabulated and are available in
form of tables called steam table.
Steam table gives value of specific vol. , enthalpy, entropy, for saturated
liquid and dry saturated vapor tabulated against pressure or corresponding
saturation temp.
The properties of superheated steam are tabulated separately.
STEAM TABLE
P (Bar)
(Ts)
t
( centigrade)
200 250 300 350 400
5.0
(151.8)
v 0.425 0.474 0.523 0.570 0.617
h 2855.4 2960.7 3064 3167.7 3271.9
s 7.059 7.271 7.46 7.633 7.794
15.0
(198.3)
v 0.132 0.172 0.169 0.187 0.203
h 2796.8 2923.3 3037.6 3147.5 3255.8
s 6.455 6.709 6.918 7.102 7.269Dinesh Panchal

PROPERTIES OF DRY SATURATED STEAM
PROPERTIES OF SUPERHEATED STEAM
Absolute
Pressure
(Bar)
Saturation
temperature
Specific
Volume
Specific Enthalpy
(KJ/Kg)
Specific Entropy
(KJ/Kg K)
10 179.9 0.001127 0.194 762.6 2013.6 2776.2 2.138 4.4446 6.5825
20 233.8 0.001216 0.0666 1008.4 1793.9 2802.2.3 3.5382 3.5382 6.1837
Kgm /3
C0
p st fv gv fh fgh gh fs fgs fgs
Absolute
Temperature
(Bar)
Saturation
Pressure
Specific
Volume
Specific Enthalpy
(KJ/Kg)
Specific Entropy
(KJ/Kg K)
10 0.0123 0.001000 106.4 42.0 2477.7 2519.7 0.151 8.750 8.901
50 0.1235 0.001012 12.03 209.3 2382.7 2582.7 0.704 7.372 8.076
st p fv gv fh
fgh gh fs fgs gs
Dinesh Panchal

INTERPOLATION
This method is used to find the intermediate values of steam properties
 12
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Dinesh Panchal

Temp. and Entropy Diagram
It is a graph between the Temp. And Entropy of steam where Entropy on x- axis and
Temp on the Y – Axis
# The liquid boundary line originates at the axis of ordinate at temp. 273.16 k
# The boundary curve (ABCD) and saturated vapor line (EFGHI) divide the diagram in
two three parts
# To the left of AE is the liquid region. Between AE and EI wet vapor region. To the
right of EI Iies the region of superheated steam.
# The boundary curve meet at point E which is critical point of water. With pressure
221.2 bar and temp. 647.31 K .
# The constant pressure lines are parallel to the constant temp. lines in the wet
region.
# The wet region has plots of constant dryness fraction and constant vol. lines.
# The const. vol. lines are steeper than const. pressure lines in the superheated
region.
Dinesh Panchal

Mollier Diagram
It is a graphical representation of steam table in which enthalpy is plotted along
Ordinate and entropy along Abscissa
Dinesh Panchal

CARNOT CYCLE
Fig shows the P-V and T-S Diagram of Carnot Cycle.
This cycle consist of two isentropic and two isothermal processes.
1. Process 1-2 : (Isothermal Expansion Process) : In This process the cylinder
piston arrangement put on the source maintained at constant temp. and gas is
allowed to expand isothermally. During this process heat is added to the system
isothermally and heat addition is given by the equitation
1
2
11 logQSuppliedHeat
v
v
mRT
Dinesh Panchal

Process 2-3 Adiabatic Expansion:
In this process the gas in the cylinder piston is allowed to
expand adiabatically at the cost of the heat of the system. So the temp. of the
system drops up to temp. T2 . In this process there is no heat addition.
Process 3-4 Adiabatic Compression:
In This process the cylinder piston arrangement put on the
sink maintained at constant temp. T2 and gas is compressed isothermally. During
this process heat is rejected by the system to the sink isothermally and heat
addition is given by the equitation.
3
4
22 logQRejectedHeat
v
v
mRT
Dinesh Panchal

Efficiency of the Cycle:
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logTR
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Dinesh Panchal

Efficiency of Rankine Cycle:-
Dinesh Panchal
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Reasons for Considering Rankine Cycle as an Ideal Cycle For Steam Power Plants:
1) It is very difficult to build a pump that will handle a mixture of liquid and
vapor at state 1’ (refer T-s diagram) and deliver saturated liquid at
state 2’. It is much easier to completely condense the vapor and handle
only liquid in the pump.
2) In the Rankine cycle, the vapor may be superheated at constant pressure
from 3 to 3” without difficulty. In a Carnot cycle using superheated steam,
the superheating will have to be done at constant temperature along
path 3-5. During this process, the pressure has to be dropped. This means
that heat is transferred to the vapor as it undergoes expansion doing
work. This is difficult to achieve in practice.
Dinesh Panchal

Question : Discuss the effect of dryness fraction of steam on the performance of the steam
power plant. Steam at 15 bar and 300 c is throttled to 10 bar before supplying the steam
turbine. It is then undergoes isentropic expansion to 1 bar in the turbine. Determine isentropic
heat drop and condition of steam at exit from the turbine. Use enthalpy-entropy chart
Ans: With increase in dryness fraction the amount of liquid water decrease. As the liquid
particle have lesser velocity than that of vapor particles hence liquid particles obstruct the flow
of vapor particle therefore loss in the kinetic energy. Also the steam having high dryness fraction
carry high amount of heat. So efficiency of the steam turbine will increase with increase in
dryness fraction.
Dinesh Panchal

Dinesh Panchal
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BOILER
It is a closed vessel which generate steam at desired pressure and temp. by
transferring the heat from the burning fuel to water to change in to steam.
Applications of Steam:
# Power generation
# Industrial Process Work
# Heating Installations
# Hot water supplies
FACTOR AFFECTING THE BOILER SELECTION
• # Working pressure of steam
• # Quality of stem Required
• # Steam generation Rate
• # Fuel and water available
• #Type of fuel used
• # Facilities available for erection
• # Operation and Maintenance cost
• # Load Factor
• # Initial Cost
Dinesh Panchal

REQUIREMENTS OF GOOD BOILER
# It should produce max. quantity of steam with min. fuel
consumption
# It should be light in weight
# It should occupies small space
# Capable of quick start
# Meet Large variation of load
# Easy Maintenance
# Mud should not deposits on heated plates
# Installation should be simple
# It should as per safety regulation laid down by boiler act.Dinesh Panchal

CLASSIFICATION OF BOILERS
# According to the Content in the tube
1. Fire Tube Boiler :
fire tube boiler hot gases passes through the tubes and water surrounds them.
Heat conducted through the wall of the tube from the hot gases to the
surrounding water
Examples: Cochran Boiler, Lancashire Boiler, Cornish Boiler and Locomotive
Boiler
. :
2. Water Tube Boiler :-
In water tube boiler water flows through the tubes and flue gases flows around
the tubes. Heat conducted through the wall of the tube from the hot gases to
the water inside the tube.
Examples: Babcock and Wilcox Boiler, Strirling Boiler, La mont Boiler and
Benson Boiler
Dinesh Panchal

# According to the Method of Firing
1. Internally Fired Boiler :
Are those boilers in which furnace is located inside the
boiler shell or drum. Most of boiler are internally fired boilers. Examples: Cochran
Boiler, Lancashire Boiler, and Locomotive Boiler
.2. Externally Fired Boiler :
Are those boilers in which furnace is located outside the
boiler shell or drum. Most of boiler are internally fired boilers.
Examples: Babcock and Wilcox Boiler
# According to the Pressure of Steam
1. Low Pressure Boilers:
Are those boilers which generates the steam at a pressure
below 80 bar is called Low Pressure Boilers
Examples: Cochran Boiler, Lancashire Boiler, and Locomotive Boiler
2. High Pressure Boilers:
Are those boilers which generates the steam at a pressure
More than 80 bar is called Low Pressure Boilers.
Examples: Babcock and Wilcox Boiler, Lamont, Benson Boiler
Dinesh Panchal

# According to Method of Circulation Of Water
1. Natural Circulation:::
In natural circulation boilers, Circulation of water is due to gravity.
Examples: Babcock and Wilcox Boiler, Lancashire Boiler, and Locomotive Boiler
2. Forced Circulation::
In forced circulation boilers Circulation of water by the pump driven
by external power. Examples: Lamount , Benson Boiler
# According to Axis of Shell or Drum
1. Vertical Boiler::-If the axis of the shell of the boiler is vertical so called vertical
boilers. Examples: Cochran Boiler
2. Horizontal Boiler:
If the axis of the shell of the boiler is horizontal so called horizontal
boilers. Examples: Laocomotive Boiler , Lancashire Boiler
Dinesh Panchal

# According to No. of Tubes
1. Single Tube Boiler :
In single tube boiler there is only one water tube or fire tube.
Examples: Cornish Boiler
2. Multi Tube Boiler :
In multi tube boiler there are two or more than two water tubes or
fire tubes. Examples: Cochran Boiler , Lancashire Boiler and Locomotive boiler
# According to Nature of Draught
1. Natural draught boiler:-
in natural draught boilers , draught is produced by natural circulation
of air and gas
2. Forced draught Boilers:
in Forced draught boilers , draught is produced by means of
mechanical fans
Dinesh Panchal

COMPARISON FIRE TUBE AND WATER TUBE BOILER
FIRE TUBE BOILER
1. Hot gases flow through the tubes
2. Generate steam pressure up to 25 bar
3. Rate of steam generation is up to 9 tons per
hour
4. Floor area required is more
5. Overall efficiency is 75%
6. Transportation and erection is difficult
7. Water does not circulate in definite direction
8. Operating cost is less
9. Bursting chances are less
10. used in large power plant
11. Greater risk in case of bursting
WATER TUBE BOILER
1. Water circulate inside the tubes
2. Generate steam pressure up to 250 bar
3. Rate of steam generation is up to 450
tons per hour
4. Floor area required is less
5. Overall efficiency is 90%
6. Transportation and erection is easy
7. Water circulate in definite direction
8. Operating cost is high
9. Bursting chances are more
10. used in process industries
11. lesser risk in case of bursting
Dinesh Panchal

COCHRAN BOILER
It is vertical ,multi tubular, fire tube ,
internally fired natural circulation Boiler.
It consist of a vertical cylindrical shell
having a hemispherical top and furnace is
also hemispherical . The fire grate is
arranged in the furnace and ash pit is
provided below the grate . A fire door is
attached to the fire box . The boiler has a
combustion chamber which is lined with
fire bricks. the end of the smoke tube are
fitted in the smoke box. The chimney is
provided on the top of the smoke box to
discharge of gas to the atmosphere. The
furnace is surrounded by water on all
sides except at opening of the fire door
and combustion chamber.
Dinesh Panchal

BABCOCK AND WILCOX BOILER
It is a horizontal drum, multi tubular,
water tube, externally fired , natural
circulation boiler. The water tube
boiler are used when pressure above
10 bar and steam capacity more than
7000 kg per hr. is required.
It consist of a drum mounted at the top
and connected by upper header and
down take header. A large no. of.
Water tubes connects the uptake and
down take header. the water tubes
are inclined 5 to 15 degrees to
promote water circulation. The
heating surface of the tubes. And half
of the cylinder surface of the water
drum which is exposed to the flue
gases. Below the uptake header the
furnace of the boiler is arranged.
There is a bridge wall deflector which
deflect the combustion gases upward.
Dinesh Panchal

Baffles are arranged across the tubes to act as a deflectors for the flue gases and to
provide them with gas passes. A chimney is provided for the exit of gases. A damper is
placed at the inlet of the chimney to regulate the draught.
Working:
The hot combustion gases caused by burning of the fuel on the grate
rises and are deflected upward by the bridge walls deflectors and passers over to the
front portion water tubes and drum. By this way they complete the first pass. With the
provision of baffles they deflect downward and complete the second pass .During their
travel they give heat to the water and steam is formed. The circulation of the water in the
boiler is natural. The hottest water and stem rise from the tube to the uptake header and
then through the rise enter the boiler drum.
Specification –
Dia of Drum – 1.22 to 1.83 m
LENGTH – 6.096 To 9.144 M
SIZE OF SUPERHEATER TUBE – 3.84 TO 5.71
SIZE OF WATER TUBE – 7.62 To 10.16
WORKING PRESSURE – 40 BAR
STEAM CAPICITY- 40000 KG PER HR
EFFICIENCY – 60 To 80%
Dinesh Panchal

Boiler Mountings:
The boiler mountings are the part of the boiler and are required for proper
functioning. In accordance with the Indian Boiler regulations, of the boiler
mountings is essential fitting for safe working of a boiler. These mounting are the
integral part of the Boiler.
Some of the important mountings are:
Dinesh Panchal

1.WATER LEVEL INDICATOR Water level
indicator is a device to show the
level of water in boiler. It located in
front of boiler in such a position that
the level of water can easily be seen
by attendant. Two water level
indicators are used on all boilers. . It
consist three valve and a glass tube .
Steam valve D connects the glass
tube with steam space and valve E
connect the glass tube with water
.Drain Valve K is used at frequent
intervals. If glass is broken two balls
after B and C close the end of the
glass tube and protects the water
and steam from escaping.
Dinesh Panchal

Fusible Plug :-
It is very important safety device, which
protects the fire tube boiler against
overheating. It is located just above
the furnace in the boiler. It consists of
gun metal plug fixed in a gun metal
body with fusible molten metal.
During the normal boiler operation,
the fusible plug is covered by water
and its temperature does not rise to
its melting state. But when the water
level falls too low in the boiler, it
uncovers the fusible plug. The furnace
gases heat up the plug and fusible
metal of plug melts, the inner plug
falls down The water and steam then
rush through the hole and extinguish
the fire before any major damage
occurs to the boiler due to
overheating.
Dinesh Panchal

Pressure Gauge :-
The function of the pressure gauge is to
indicate the steam pressure of boiler in
bar gauge. A pressure gauge is fitted in
front of boiler in such a position that the
operator can conveniently read it. It reads
the pressure of steam in the boiler and is
connected to steam space by a siphon
tube. The most commonly, the Bourdon
pressure gauges used. I A burden tube
pressure gauge consist of a elliptical elastic
tube ABC bent in to an arc of a circle. One
end of the tube is fixed and connected to
the steam space in the boiler and other
end is connected to a sector link. When
pressure increases the tube tends to
straighten and pinion and sector
arrangement rotate a pointer. The pointer
moves over a calibrated scale.
Dinesh Panchal

Blow-Off Cock:-
The function of blow-off cock is to
discharge mud and other sediments
deposited in the bottom most part
of the water space in the boiler,
while boiler is in operation. It can
also be used to drain-off boiler
water. Hence it is mounted at the
lowest part of the boiler. When it is
open, water under the pressure
rushes out, thus carrying sediments
and mud. The cock is fitted to the
bottom of the boiler drum and
consist of a conical plug fitted to the
body.
Dinesh Panchal

SAFETY VALVES:
Safety valves are located on the top
of the boiler. They guard the boiler
against the excessive high pressure
of steam inside the drum. If the
pressure of steam in the boiler
drum exceeds the working
pressure then the safety valve
allows blow-off the excess quantity
of steam to atmosphere. Thus the
pressure of steam in the drum falls.
The escape of steam makes a audio
noise to warm the boiler
attendant.
There are four types of safety valve.
• 1. Dead weight safety valve.
• 2. Spring loaded safety valve
• 3. Lever loaded safety valve
• 4. High steam and low water safety
valve.
Dinesh Panchal

FEED CHECK VALVE :-
The feed check valve is fitted
to the boiler, slightly below
the working level in the
boiler. It is used to supply
high pressure feed water to
boiler. It also prevents the
returning of feed water from
the boiler if feed pump fails
to work.
Dinesh Panchal

Boiler Accessories
The accessories are mounted on the boiler to increase its efficiency. These units
are optional on an efficient boiler. With addition of accessories on the boiler,
the plant efficiency also increases.
The following accessories are normally used on a modern boiler:
(i) Economizer
(ii) Super heater
(iii) Air pre heater
(iv) Feed water pump
(v) Steam injector.
Dinesh Panchal

ECONOMIZER :-
An economizer is a heat
exchanger, used for heating
the feed water before it
enters the boiler. The
economizer recovers some of
waste heat of hot flue gases
going to chimney. It helps in
improving the boiler
efficiency. It is placed in the
path of flue gases at the rear
end of the boiler just before
air pre-heater.
Dinesh Panchal

SUPERHEATER:-
It is a heat exchanger in which
heat of combustion products
is used to dry the wet steam,
pressure remains constant,
its volume and temperature
increase. Basically, a super
heater consists of a set of
small diameter U tubes in
which steam flows and takes
up the heat from hot flue
gases.
Dinesh Panchal

AIR PRE- HEATER:-
The function of an air pre-heater is similar to that of an economizer. It
recovers some portion of the waste heat of hot flue gases going to chimney, and
transfers same to the fresh air before it enters the combustion chamber. Due to
preheating of air, the furnace temperature increases. It results in rapid combustion
of fuel with less soot, smoke and ash. The high furnace temperature can permit low
grade fuel with less atmospheric pollution. The air pre-heater is placed between
economizer and chimney.
FEED WATER PUMP:-
It is used to feed the water at a high pressure against the high pressure of
steam already existing inside the boiler.
STEAM INJECTOR:-
A steam injector lifts and forces the feed water into the boiler. It is usually
used for vertical and locomotive boilers and can be accommodated in small space.
It is less costly. It does not have any moving parts thus operation is salient.
Dinesh Panchal

STEAM TURBINE
FLOW
DIRECTION
AXIAL
RADIAL
WAY OF ENERGY
CONVERSION
IMPULSE
REACTION
TYPE OF
COMPOUNDING
PRESSURE
COMPOUNDING
VELOCITY
COMPOUNDING
PRESSURE
VELOCITY
COMPOUNDING
EXHAUSTING
CONDITION
CONDENSING
EXTRACTION
BACK PRESSURE
REHEAT
NO. OF STAGES
SINGLE
MULTI
INLET PRESSURE
LOW
MEDIUM
HIGH
STEAM TURBINE CLASSIFICATION
Dinesh Panchal

Stem Turbine :
In steam turbine enthalpy of the steam is first converted in to kinetic energy in the
nozzle or blade passage. The high velocity steam impinges on the curved blade
which change the direction of the steam. The chjange in the flow of direction
causes a force to be exerted on the blade fixed on the rotor and power is
developed.
Advantages of steam turbine over reciprocation steam engine:
1. Highly simplified in construction and operation
2. 2. Condensate can be used directly in the boiler without pretreatment.
3. The vibration and noise in minimum.
4. Much higher speed is possible.
5. Steam turbine can take considerable over load.
6. Steam turbines can be designed ranging from 1KW to 1000MW.
Dinesh Panchal

Classification of Steam turbine:
Steam turbine mainly classified in to two group.
1. Impulse Turbine
2. Reaction Turbine
1. Impulse Turbine:
The steam coming with very high velocity through the fixed nozzle and the high
velocity steam impinges on the blades fixed on the periphery of the rotor. The
blade changes the direction
of the steam flow without changing
its pressure. Due to change in the
direction of flow of steam , there
is change in the momentum of the
steam which exert the force on the
blades and hence there rotor moves. Example of impluse turbine
are De-Laval, Curties and Rateau.
Dinesh Panchal

Reaction Turbine :
The high pressure steam from the boiler is passed through the nozzle . As
shown in fig. When the steam comes out from the nozzle they produces the
reaction force on the rotation disk and the disk rotate opposite to the direction of
the steam flow.
Dinesh Panchal

Impulse Vs Reaction Turbine :
1. In impulse turbine, steam completely expands in the nozzle and its
pressure remain constant.
In Reaction turbine, steam partially expands in the nozzle and expansion also
takes place on the blades.
2. In impulse turbine, relative velocity of the steam passing over the blades
remain constant if there is no friction.
In impulse turbine, relative velocity of the steam passing over the blades
increases as its passes over the blades.
3. In impulse turbine, Blades shape are symmetrical.
But reaction turbine have aerofoil section . The area of flow changes along
the blade passage similar to the nozzle.
Dinesh Panchal

CONDENSERS
• Condenser is a device in which steam is condensed at a pressure lower than
atmospheric pressure
• Condensation can be done by removing the heat from exhaust steam by using
circulating cooling water.
• A condenser is basically stem to water exchanger in which heat from the exhaust
steam is transferred to the circulating water.
• Function of condensers is to reduce the turbine exhaust presure so as to increase
the specific output and hence increase the plant efficiency and to reduce the
specific steam consumption.
• It also condense the exhaust steam from the turbine and reuse it as a pure feed
water in the boiler.
Dinesh Panchal

Advantages of Condensers:
# High pressure ratio provide the larger enthalpy drop
# work output per kg of steam increases and hence specific steam consumption is
reduced.
# condensate can be reused as a hot feed water to the boiler. This reduces the fuel
consumption.
# No feed water treatment is required. Hence reduce the cost of plant.
# Formation of deposit in the boiler surface can be prevented with the use of
condensate instead of feed water from out sources.
Elements of condensers:
1. Condensers
2. Air extraction Pump
3. Condensate extraction Pump
4. Circulating cooling water pump
5. Hot well
6. Cooling Tower
7. Make up water pump
8. Boiler feed water pump
Dinesh Panchal

Classification of condensers :
Dinesh Panchal

CLASSIFICATION OF CONDENSER
condenser
JET
CONDENSER
PARALLEL
FLOW
LOW LEVEL
TYPE
HIGH LEVEL
TYPE
COUNTER
FLOW
EJECTOR FLOW
SURFACE
CONDENSER
DOWN FLOW
TYPE
CENTRAL
FLOW TYPE
INVERTED
FLOW TYPE
REGENERATIVE
TYPE
EVAPORATIVE
TYPE
Dinesh Panchal

Jet Condensers:
They are used in small capacity units where fresh clean water is available in
plenty. In jet condenser water is in direct contact with exhaust steam. Hence they
are called direct type or mixed type condensers
Advantages of jet Condensers:
1. As result of effective mixing, it require less circulating cooling water
2. Equipments are simple and occupy less space
3. Maintenance is cheap
Disadvantages :
1. Not suitable for higher capacity
2. Condensate can not be used as feed water to boiler
3. Air leakage are more
4. Require larger air pump
5. Less vacuum is maintained.
Dinesh Panchal

Surface condenser
are used in large capacity plants. In surface condenser, exhaust steam and water
do not mix together. Hence they are called Indirect contact type or non mixed type.
Advantages:
1. Can be used for large capacity plants.
2. High Vacuum is created.
3. Condensate is free from impurities and can be reused as feed water to the boiler.
4. Air leakage is completely less, hence less power is required to operate air pump.
Disadvantages :
1. Design is complicated and costly
2. High maintenance cost
3. Occupies more space
4. Require more circulating water.
Dinesh Panchal

I.C.ENGINES
ENGINE:- An Engine is a device which transforms the chemical energy of a fuel into
thermal energy and uses this thermal energy to produce mechanical work. Engines
normally convert thermal energy into mechanical work and therefore they are
called heat engines.
TYPES OF ENGINES:-
Heat engines can be broadly classified into :
i) External combustion engines ( E C Engines)
ii) Internal combustion engines ( I C Engines )
Dinesh Panchal

External combustion engines:-
are those in which combustion takes
place outside the engine. For example,
In steam engine or steam turbine the
heat generated due to combustion of
fuel and it is employed to generate high
pressure steam, which is used as
working fluid in a reciprocating engine
or turbine. See Figure 1.
Internal combustion engines:-
are those in which combustion takes place
inside the engine or cylinder . For
example, Diesel engine, petrol engine ,
gasoline engine the heat generated
due to combustion of fuel and it is
employed to give the motion to
cylinder
Dinesh Panchal

ADVANTAGES OF INTERNAL COMBUSTION ENGINES
1. Greater mechanical simplicity.
2. Higher power output per unit weight because of absence of auxiliary units like boiler
, condenser and feed pump
3. Low initial cost
4. Higher brake thermal efficiency as only a small fraction of heat energy of the fuel is
dissipated to cooling system
5. These units are compact and requires less space
6. Easy starting from cold conditions
DISADVANTAGES OF INTERNAL COMBUSTION ENGINES
1. I C engines cannot use solid fuels which are cheaper. Only liquid or gaseous fuel of
given specification can be efficiently used. These fuels are relatively more
expensive.
2. I C engines have reciprocating parts and hence balancing of them is problem and
they are also susceptible to mechanical vibrations.
Dinesh Panchal

CLASSIFICATION OF INTERNAL COMBUSTION ENGINES.
1. According to thermodynamic cycle
i) Otto cycle engine or Constant volume heat supplied cycle.
ii) Diesel cycle engine or Constant pressure heat supplied cycle
iii) Dual-combustion cycle engine
2. According to the fuel used:
i) Petrol engine
ii) Diesel engine
iii) Gas engine
3. According to the cycle of operation:
i) Two stroke cycle engine
ii) Four stroke cycle engine
4. According to the method of ignition:
i) Spark ignition (S.I) engine
ii) Compression ignition (C I ) engine
5. According to the number of cylinders.
i) Single cylinder engine
ii) Multi cylinder engine
Dinesh Panchal

6. According to the arrangement of cylinder:
I) Horizontal engine
ii) Vertical engine
iii) V-engine
v) In-line engine
vi) Radial engine, etc.
7. According to the method of cooling the cylinder:
I) Air cooled engine
ii) Water cooled engine
8. According to their applications:
i) Stationary engine
ii) Automobile engine
iii) Aero engine
iv) Locomotive engine
v) Marine engine, etc.
Dinesh Panchal

INTERNAL COMBUSTION ENGINE PARTS AND THEIR
FUNCTION
1. Cylinder :- It is a container fitted with piston,
where the fuel is burnt and power is
produced.
2. Cylinder Head/Cylinder Cover:-
One end of the cylinder is closed by
means of cylinder head. This consists of
inlet valve for admitting air fuel mixture and
exhaust valve for removing the products of
combustion.
• 3. Piston:- Piston is used to reciprocate inside
the cylinder. It transmits the energy to
crankshaft through connecting rod.
4. Piston Rings:- These are used to maintain a
pressure tight seal between the piston and
cylinder walls and also it transfer the heat
from the piston head to cylinder walls.
Dinesh Panchal

5. Connecting Rod:- One end of the
connecting rod is connected to
piston through piston pin while the
other is connected to crank through
crank pin. It transmits the
reciprocatory motion of piston to
rotary crank.
6. Crank:- It is a lever between
connecting rod and crank shaft.
7. Crank Shaft:- The function of crank
shaft is to transform reciprocating
motion in to a rotary motion.
8. Fly wheel:- Fly wheel is a rotating
mass used as an energy storing
device.
9. Crank Case:- It supports and covers
the cylinder and the crank shaft. It is
used to store the lubricating oil.
Dinesh Panchal

IC ENGINE – TERMINOLOGY
1. Bore: The inside diameter of the cylinder is called the bore.
2. Stroke: The linear distance along the cylinder axis between the two limiting
positions of the piston is called stroke.
3.Top Dead Centre (T.D.C) The top most position of the piston towards cover end side
of the cylinder” is called top dead centre. In case of horizontal engine, it is called as
inner dead centre
Dinesh Panchal

Working of a Four-Stroke Petrol Engine
1. Suction Stroke : During suction stroke, the piston
is moved from the top dead centre to the bottom
dead centre by the crank shaft. The crank shaft is
revolved either by the momentum of the
flywheel or by the electric starting motor. The
inlet valve remains open and the exhaust valve is
closed during this stroke. The proportionate air-
petrol mixture is sucked into the cylinder due to
the downward movement of the piston. This
operation is represented by the line AB on the P-
V diagram.
2. Compression Stroke:
During compression stroke, the piston moves from
bottom dead centre to the top dead centre, thus
compressing air petrol mixture. Due to
compression, the pressure and temperature are
increased and is shown by the line BC on the P- V
diagram. Just before the end of this stroke the
spark - plug initiates a spark, which ignites the
mixture and combustion takes place at constant
volume as shown by the line CD. Both the inlet and
exhaust valves remain closed during this stroke.Dinesh Panchal

3. Working Stroke:
The expansion of hot gases exerts a pressure on
the piston. Due to this pressure, the piston
moves from top dead centre to bottom dead
centre and thus the work is obtained in this
stroke. Both the inlet and exhaust valves remain
closed during this stroke. The expansion of the
gas is shown by the curve DE.
4. Exhaust Stroke:
During this stroke, the inlet valve remains
closed and the exhaust valve opens. The greater
part of the burnt gases escapes because of their
own expansion. The drop in pressure at
constant volume is represented by the line EB.
The piston moves from bottom dead centre to
top dead centre and pushes the remaining
gases to the atmosphere. When the piston
reaches the top dead centre the exhaust valve
closes and cycle is completed. This stroke is
represented by the line BA on the P- V diagram.
The operations are repeated over and over
again in running the engine. Thus a four stroke
engine completes one working cycle, during this
the crank rotate by two revolutions.Dinesh Panchal

Working of 2-S Engine
Diagram 1: The piston moves up,
compressing the fuel-air mixture in
the cylinder. Simultaneously, the
bottom of the piston uncovers a port
(the inlet port), and sucks a fuel-air
charge into the bottom of the engine
.It can do this because as the piston
moves up, it creates a low pressure
zone in the enclosed space behind it,
and so the charge rushes in.
When the piston gets to the top of its
stroke, either the spark plug fires (in
a petrol engine), or diesel-fuel is
sprayed into the engine and ignites
because of the extreme heat
produced by the compression of air
in the cylinder.
Dinesh Panchal

• Diagram 2: The spark plug fires (or diesel-fuel is
injected into the cylinder), the piston is driven
down, and the bottom of the piston compresses
the charge below it. As the piston moves further
down, it uncovers the exhaust port, and the
burnt gasses begin to flow out of the cylinder.
Near the bottom of its stroke, the piston then
uncovers the inlet port, and the compressed
charge flows into the top of the cylinder helping
to drive the burnt gasses out of the cylinder.
Dinesh Panchal

Diagram 3-4: The spark plug fires (or diesel-
fuel is injected into the cylinder), the
piston is driven down, and the bottom of
the piston compresses the charge below
it. As the piston moves further down, it
uncovers the exhaust port, and the burnt
gasses begin to flow out of the cylinder.
Near the bottom of its stroke, the piston
then uncovers the inlet port, and the
compressed charge flows into the top of
the cylinder helping to drive the burnt
gasses out of the cylinder
Dinesh Panchal

COMPARISON OF SI AND CI ENGINES
1. Works on otto cycle
2. Petrol is used as a fuel
3. It has lass compression ratio
4. Ignition takes place with the help of
electric spark
5. Thermal efficiency is less
6. Initial cost is less
7. Starting is easy
8. Maintenance cost is less
9. It has carburetor to mix air and fuel
10. They are light in weight
1. Works on diesel cycle
2. Diesel is used as a fuel
3. It has more compression ratio
4. Ignition takes place due to
compression
5. Thermal efficiency is more
6. Initial cost is higher
7. Starting is difficult
8. Maintenance cost is high
9. It has injector to inject fuel.
10. They are heavy in weight
Dinesh Panchal

Comparison Between 2-S and 4- S Engines
2-Stroke
1. Crank complete one revolution in in
one power stroke
2. Turning effort on crank is much
uniform. So lighter flywheel is
required
3. It has three ports
4. It is compact and light in weight
5. It produce more noise and has more
wear and tear
7. Thermal efficiency is less
8. More lubricating oil is consumed
9. Crank case is made gas tight
4-Stroke
1. Crank complete two revolution in in
one power stroke
2. Turning effort on crank is not
uniform. So heavier flywheel is
required
3. It has two valves
4. It is heavier and complicated in
design
5. It produces less noise
6. Maintenance cost is high
7. Thermal efficiency is high
8. Less lubricating oil is consumed
9. Crank case ins not made gas tight
Dinesh Panchal

Otto Cycle
Fig. Shows the P-V and T-S Diagram of Otto Cycle
Diesel cycle consist four processes::
1. Process 1-2 (Isentropic Compression): In this Process piston moves from BDC to
TDC and compression of air will take place adiabatically. It means there is no heat
addition and removal from the gas.
2. Process 2-3 (heat addition at const. vol.): In this Process heat addition will take
place at constant vol. Fuel is continuously added to air up to point 3.Dinesh Panchal

3. Process 3-4 (Isentropic Expansion): In this Process piston moves from TDC to BDC
and expansion of air will take place adiabatically. It means there is no heat
4. Process 4-1 (heat rejection at const. vol.): In this Process heat rejection will take
place at constant vol.
Dinesh Panchal

EFFICIENCY OF OTTO CYCLE
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Dinesh Panchal

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Dinesh Panchal

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Dinesh Panchal

Diesel Cycle
Fig. Shows the P-V and T-S Diagram of Diesel Cycle
Diesel cycle consist four processes::
1. Process 1-2 (Isentropic Compression): In this Process piston moves from BDC to
TDC and compression of air will take place adiabatically. It means there is no heat
2. 1. Process 2-3 (heat addition at const. pressure): In this Process heat addition will
take place at constant pressure . Fuel is continuously added to air up to point 3.Dinesh Panchal

 
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Dinesh Panchal

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Dinesh Panchal

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Dinesh Panchal

QUESTION NO. 3(B) The following data pertains to C.I. Engine working on air standard diesel cycle.
Cylinder bore=15cm, stroke length =-25 cm. ,clearance volume= 400 cc. Calculate air standard efficiency if
fuel injection take place 5% of the stroke.
Dinesh Panchal
   
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Q. NO.2 An investor claims to have developed an engine that taken 105 MJ at a temp. of 400
K, rejects 42 MJ at temp of 200 K and deliver 15 KWH of mechanical work. Would you advise
investing money to this engine in the market.
Dinesh Panchal

project.in thatmadebenotshouldinvestmentHence
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Dinesh Panchal

Same Compression Ratio and Heat Addition:
Dinesh Panchal

Same Compression Ratio and Heat Addition:
The Otto cycle 1-2-3-4-1, the Diesel cycle 1-2-3'-4'-1 and t he Dual cycle 1-2-2”-
3”-4”-1 are shown in p-V and T-θ diagram in Fig.4.7.1 (a) and (b) respectively for
the same compression ratio and heat input. From the T -s diagram, it can be seen
that Area 5-2-3-6 = Area 5-2-3'-6’ = Area 5-2-2"- 3"-6" as this area represents the
heat input which is the same for all cycles. All the cycles start from the same
initial state point 1 and the air is compressed from state 1 to 2 as the
compression ratio is same. It is seen from the T-s diagram for the same heat
input, the heat rejection in Otto cycle (area 5-1-4-6) is minimum and heat
rejection in
Diesel cycle (5-1-4'-6') is maximum.. Consequently, Otto cycle has the highest
work output and efficiency. Diesel cycle has the least efficiency and Dual cycle
having the efficiency between the two. One more observation can be made i.e.,
Otto cycle allows the working medium to expand more whereas Diesel cycle is
least in this respect. The reason is heat is added before expansion in the case of
Otto cycle and the last portion of heat supplied to the fluid has a relatively short
Dinesh Panchal

Problem 1 :
The compression ratio of an I.C. Petrol Engine is 4 .Find the air standard efficiency.
Problem 2:
The efficiency of Otto cycle is 505 .What will be the compression ratio if ϒ=1.4
Problem 3:
An engine working on Otto cycle has a cylinder dia. Of 18 cm and a stroke of 25
cm. The clearance volume is 1400 cub. Cm. .Find the air standard efficiency of the
engine.
Problem 4:
In an engine working on Otto cycle , the pressure and temp. at the beginning of the
adiabatic compression are 1 bar and 30 0C Respectively. Calculate the compression
ratio and also calculate the pressure and temperature at the end of the
compression if air standard efficiency is 45% and ϒ=1.4
Problem 5 :
An engine working on Otto cycle has pressure and temperature at the beginning of
the adiabatic compression as 1 bar and 500 respectively. The pressure at the end of
the compression is 12 times that at the beginning,. If the temperature of the air at
the end of the heat supplied during constant vol. is 20000C . Calculate 1.
Compression Ratio 2. Efficiency 3. Heat Supplied/Kg OF Air 4. Work done/Kg of Air
5. Pressure at the end of the adiabatic Compression.
Dinesh Panchal

Problem 6. :
Calculate the efficiency of diesel cycle whose compression ratio is 18 and cut off
ratio is 2.133. Assume ϒ=1.4
Problem 7. :
Calculate the air standard efficiency of a diesel cycle whose compression ratio is 14.
The cut off takes place at 65 of stroke. Assume ϒ=1.4
Problem8 :
Following data relates to the diesel engine.
Stroke Length = 30 cm, Diameter of the cylinder = 20 cm, Clearance Volume = 800
Cubic cm, Cut off ratio take place at 55 of the stroke . Calculate the Compression
Ratio, Cut off Ratio and Air Standard Efficiency.
Dinesh Panchal

GAS TURBINE
It is a machine which produces power by utilizing the K.E. Obtained by burnt gases
under pressure and undergoes a pressure drop in a nozzle.
Dinesh Panchal

GAS TURBINE
It is a machine which produces power by
utilizing the K.E. Obtained by burnt
gases under pressure and undergoes a
pressure drop in a nozzle
The basic component of Gas Turbine are
shown in fig.
1. Air compressor
2. Combustion chamber
3. turbine
Dinesh Panchal

WORKING OF GAS TURBINE
In gas turbine air is obtained from
the atmosphere and compressed
in the compressor. Compression
may by 4 to 6 .The compressed air
then passed in to the combustion
chamber . , where it is heated.
The hot air is then made to flow
over the moving blade of gas
turbine. Which gives the
rotational motion. During this
process air gets expanded and
finally exhausted to the
atmosphere. Thermal efficiency
of gas turbine varies from 25 to
35%. Fuel used in gas turbine are
oil, natural gas, coal ect.
Dinesh Panchal

Types of Gas Turbines
1. Open Cycle gas Turbine
2. Closed Cycle Gas Turbine
Open cycle gas turbine:-
it is the simplest form and
consist compressor ,
combustion chamber and a gas
turbine which drives the
generator and compressor. In
this turbine air is sucked from
the atmosphere and then
compressed isentropic ally .This
compressed air is heated in the
combustion chamber and finally
made to flow over the blade of
the turbine and this hot air
gives the drive to the blades.
Dinesh Panchal

CLOSED CYCLE GAS TURBINE
A closed-cycle gas turbine is a turbine that uses a gas (e.g. air, nitrogen helium, argon
etc.) for the working as part of a closed thermodynamic system. Heat is supplied
from an external source. Such recalculating turbines follow the Brayton Cycle. The
diagram shows the closed cycle gas turbine. In this turbine air is compressed
isentropic ally in the compressor and then passed in to the heating chamber. The
compressed air is heated with the help of some external source and ten made to
flow over the turbine blade . The gas while flowing over the turbine blade ,gets
expanded. From the turbine , the gas is passed over to the cooling chamber where
it get cooled at constant pressure with the help of circulating water to original
water. Now the air is made to flow in to the compressor again .
Applications :
1. Aviation
2.Central Electric Generation Station
3.Used in Combined Cycle Power Station
Dinesh Panchal

Comparison Between Gas turbine and I.C. Engines
1. Balancing is perfect
2. Pressure used is low
3. Installation and running cost is less
4. Running speed is high
6. Lubrication and ignition system is
simple
7. Efficiency is higher.
8. Cooling system is simple.
9. Torque produced is uniform.
10. Starting is not simple.
11. Suitable for air craft.
12. Exhaust is free from smoke and less
polluting.
1. Balancing is not perfect
2. Pressure used is high
3. Installation and running cost is more
4. Running speed is low
5. Maintenance cost is more
6. Lubrication and ignition system is
complicated.
7. Efficiency is lower.
8. Cooling system is not simple.
9. Torque produced is not uniform.
10. Starting is simple.
11. Less Suitable for air craft.
12. Exhaust is more polluting.
Dinesh Panchal

SIMPLE
LIFTING
MACHINESDinesh Panchal

Machine:- it is a device that is capable of doing
useful work. It receive energy in some available
form and uses that energy in to useful work. The
energy may be electrical, mechanical, thermal,
chemical. The machine may be simple or
compound.
Simple machine:- simple machine has only one
point of application of effort and one point for
load
Examples:-
• Lever
• Pulley and pulley system
• Wheel and axle
• Inclined plane
• Screw jack
2. Compound Machines:- are those machines which
has more than one point of application of effort
and more than one point of applying the load.Dinesh Panchal

Lifting Machine:-
it is a device with the help of which we are
able to lift the heavy loads by applying the
less effort.
Examples :-
• Lever
• Pulley and pulley system
• Wheel and axle
• Inclined plane
• Screw jack
Dinesh Panchal

Some Definitions
Load: - a machine is used to lift the load or overcome to some resistance. The weight is
to be lifted by the machine is called Load. It is denoted by W
Effort: - The force required to lift the load or to overcome the resistance is called Effort
. It is denoted by P
Input :- input of a machine is the work done on machine. It is the product of effort and
distance moved by effort
Input=Effort x Distance moved by Effort
= P X y
Output :- output of a machine is the work done by the machine. It is the product of
Load and distance moved by Load
Output=Load x Distance moved by Load
=W X x
Mechanical Advantage:- It is defined as the ratio of the load to the effort applied
denoted by M.A.
Velocity Ratio :- It is defined as the ratio of the distance moved by effort to the
distance moved by load denoted by V.R.
P
W
AppliedEffort
LiftedLoad
M.A.AdvantageMechanical 
x
y

LoadbyMovedDistance
EffortbyMovedDistance
RatioVelocityDinesh Panchal

Efficiency of Machine:- it is defined as the ratio of output of a machine to input of a
machine. It is denoted by η
η = Output of Machine/ Input of Machine
= W X x / P X y
= M.A. / V.R.
So efficiency of a machine is the ratio of Mechanical Advantage to Velocity Ratio.
Ideal Machine:- A machine whose efficiency is 100% is called an ideal machine. It has
equal input and output
Ideal effort :- is the effort required to lift the load by the machine, assuming the
machine to be ideal.
Dinesh Panchal

LAW OF MACHINE
The law of machine may be defined as by an
equitation which gives the relationship
between the load lifted (W) and the effort
applied (P)
This is generally a straight line which does not
pass through the origin. The law of machine is
given below
P=mW+C
C – intercept OA , m- Slop of AB
P- Effort Applied, W – Load Lifted
For an ideal machine the line passes through the
origin
Max. M.A.=1/m
Max. Efficiency=Max. M.A./V.R.
m=(P2-P1)/ (W2-W1)
Y intercept P1=Mw1+C
Fig.
A
O
B
C
Effort
DLoad
E
F
m
1
For Actual Machine
ForIdealMACHINE
Dinesh Panchal

REVERSIBILITY OF A MACHINE
If a machine is capable of doing work in the reverse direction after the removal of
the Effort called reversible machine.
Let P be the effort required to lift the load W . Now if P is removed W may fall. It is
called reversible machine. Reversibility of a machine dependent on its efficiency,
if the efficiency is less than 50% it will be self locking and if it is greater than 50%
it is reversible.
CONDITION FOR REVERSIBILITY : -
W- Load Lifted by Machine
P- Effort Applied to Lift the Load
y- Distance moved by Effort
X- Distance moved by Load
Input = output + Work done by Friction
= Output + Work done to overcome to Friction
Work done Lost in Friction = Input -Output
= P . y - W . xDinesh Panchal

When effort is removed , the load can start moving down if it can overcome the
friction resistance(i.e. Input-Output) Hence the condition for the reversibility is the
output of the machine is more than that the work lost in friction when effort is
removed i.e. P=0
Output > Work Lost in Friction
Output > Input-Output
W . x > P . y - W . x
2W . x > P . y
W/P . x/y >1/2
M.A./V.R. >1/2
η > ½
η > 50%
Dinesh Panchal

• QUESTION NO. 7 In a lifting machine an effort of 16N is required to lift the load of 800 N at an
efficiency of 60% . The same machine require an effort 25 N to lift the load of 1500 N. Determine the
Law of Machine and calculate max. M.A. and efficiency.
• Ans:
%9393.
33.83
7.77
R.V.
M.A.Max.
Max.
7.77
9
700
m
1
M.A.Max.
:AdvantageMechanicalMax.
5.710.0128wP
:MachineofLaw
71.5
7
40
C;0128.0
700
9
m
(ii)and(i)equatationtheSolve
......(ii)..........C1500m25
....(i)..........C800m16
2and1CasefromWPandofvaluePut the
CmWP
:MachineofLaw
N800WLiftedLoad
16PappliedEffort:2Case
33.83
6.0
16/800M.A.
V.R.
V.R.
M.A.
N800WLiftedLoad
16PappliedEffort:1Case
60%
:
2
2
1
1

















N
N
Given
Dinesh Panchal

• QUESTION NO. 7 In case of lifting machine, effort required to lift the load 50N and 80N were 12N
and 18 N.If the velocity ratio of the machine was 6 . Determine (i) Law of machine (ii) Efficiency of the
machine and the effort lost in friction at 50 n load (iii) Max. efficiency expected from the machine
• Ans:
%8383.
6
5
R.V.
M.A.Max.
Max.
5
2.0
1
m
1
M.A.Max.
:AdvantageMechanicalMax.
%707.0
6
2.4
V.R.
M.A.
(Given)6R.V.And2.4
12
50
M.A.
1220.250P
50WloadAt
2W2.0P
:MachineofLaw
2C;20.0
30
6
m
(ii)and(i)equatationtheSolve
......(ii)..........Cm0818
....(i)..........Cm0512
2and1CasefromWPandofvaluePut the
CmWP
:MachineofLaw
N80WLiftedLoad18PappliedEffort
N05WLiftedLoad12PappliedEffort
60%
:
3
11
11

















N
N
N
Given
Dinesh Panchal

WHEEL AND AXLE
It consist of two cylinders A and B of different diameters rotating on the same axis.
The bigger cylinder A is called wheel and the smaller one B is called axle. Wheel
had diameter D and axle diameter is D. a string is wound round the axle. The one
end of the string is fixed to the axle and attached to the load W. Another string is
wound round on the wheel. One end of the string is fixed to wheel and effort is
applied on the other end. These two strings are wound in opposite directions, so
that one rope wrap and other unwrap on rotation.
Dinesh Panchal

D – Dia of wheel
d – Dia of Axle
W – Load Lifted
P – Effort Applied
Distance moved by Effort in one revolution = ΠD
Distance moved by Load in one revolution = πd
PD
Wd
RV
AM
Efficiency
d
D





d
D
P
W
..
..
P
W
AppliedEffort
edWeightLift
M.A.
d
D
LoadbymovedDistance
effortbymovedDistance
V.R.



Dinesh Panchal

Differential Wheel and Axle
It has one wheel and two axle.
It consist of wheel A of Diameter D
, Axle B of Diameter of d1 and axle
C of Diameter d2 . All three are
keyed to the same shaft.
One string is wound round the
wheel A . Another end of this string
is for applying effort.
Second string is wound round
the axle B, which after passing
rounds to the pulley is wound
round on axle C in the opposite
direction. So that when the string
on wheel A unwound, The string on
axle C should also unwind but
wound on axle B.
Dinesh Panchal

W – Load Lifted
D – Diameter of Wheel
d1 – Diameter of Axle B
D2 – Diameter of Axle C
Distance moved by Effort in one revolution = Πd
Length of string unwound from cylinder C= πd2
Length of string wounds from cylinder B= πd1
Length of string wound in one revolution = πd1- πd2
Displacement of Load = (πd1- πd2)/2
   
   2121
2121
D
d-d
P
W
..
..
P
W
M.A.
D
d-dd
LoadbymovedDistance
V.R.
ddP
WD
RV
AM
Efficiency
D
d











Dinesh Panchal

Differential Pulley Block
It consist of three pulleys
A, B and C. Pulleys A and B
having Diameters D, d
respectively which rotates
about a common axis through
O. Pulley C is a movable pulley
and load is attached to this
pulley.
A single string passes
around the pulleys as shown in
fig. The string first passes
round the pulley A then round
pulley C and then finally round
the pulley B. Effort is applied at
the end of the string passing
round the pulley A .
Dinesh Panchal

W – Load Lifted
D – Diameter of Pulley A
d1– Diameter of Pulley B
When pulley makes one revolution, it
moves downwards by an amount of .Then
string passes over the pulley B and moves
downwards by an amount
`So string passes over the pulley C is
=
Displacement of Effort P in one Revolution
of Pulley A =
Length of string released by pulley B =
Dinesh Panchal

   
 
 
DP
dDW
dD
D
RV
AM
Efficiency
dD
D
dD
D
22
P
W
..
..
P
W
AppliedEffort
LiftedWeight
M.A.
2
2
LoadbymovedDistance
V.R.


















Dinesh Panchal

Worm and Worm Wheel
It consist of a square
threaded screw B called worm and
a toothed wheel C known as worm
wheel. The worm B is in mesh with
worm wheel; C and their axis are at
right angle the each other.
On the axis of worm B , effort
wheel A of Diameter D is attached
, over which a rope is wounded.
The effort is applied at one end of
rope.
On the axis of the wheel c, a
small pulley or a load drum having
diameter d provided over which a
rope is wounded and one end of
the rope is used to attach load.
B
C
A
d
Dinesh Panchal

W – Load Lifted
D – Diameter of Effort Wheel A
r=d/2Diameter of load Drum
T – Number of teeth on worm wheel C
Single Start:
Distance moved by effort in one
revolution of effort wheel = π D
Load Drum will turn in one revolution
of worm B = 1/T Revolution
Distance moved by Load = 2π r X 1/T
A
B
C
D
P
W
M.A.
d
DT
d
DT
1
LoadbymovedDistance
V.R.







T
d
D
Dinesh Panchal

PDT
Wd
o
PDT
Wd
o
PDT
Wd
r
RV
AM
3
startdoublefEfficiencyHence
Bwormofrevolutioncompleteoneinrevolution3/TcompletewillDrumLoad
StartTripple:iiCase
2
startdoublefEfficiencyHence
Bwormofrevolutioncompleteoneinrevolution2/TcompletewillDrumLoad
StartDouble:iiCase
2
DT
P
W
..
..
Efficiency




Dinesh Panchal

Single Purchase Winch Crab
It consist of an effort axle having
a small toothed wheel known
as pinion with teeth T1 on it.
The pinion gear is the driving
gear and it is in mesh with
the larger toothed gear
known as spur gear having
teeth T2 .It is a driven gear.
This spur gear is connected
to the load drum. When
effort is applied to the effort
axle, the effort wheel and the
pinion wheel attached to it
start to move. As the pinion
wheel is coupled with spur
gear, later also rotates in
reverse direction
Dinesh Panchal

L – Length of Arm Lever
W - Load Lifted
d – Dia . Of Load Drum
T1 – No. of teeth on pinion
T2 – No. of teeth on Spur Gear
In one revolution of lever, pinion will
complete one revolution.
So distance moved by Effort in one
revolution of lever = 2π L
In one revolution of lever spur wheel will
complete T1/T2 revolution.
So distance moved by Load in one
revolution of lever =T1/T2 X πD
L
P
W
M.A.
DT
2LT
D
LT22
LoadbymovedDistance
V.R.
1
2
1
2
2
1



T
T
T
D
L




Dinesh Panchal

2
1
1
2 22LT
..
..
Efficiency
PLT
WDT
DT
P
W
RV
AM


Dinesh Panchal

Double Purchase Crab Winch
It is the extended version of single
purchase crab winch. Velocity ratio of
a crab winch is increased by providing
another axle with pair of pinion and
spur wheel. As shown in Fig.
L – Length of Arm Lever
W - Load Lifted
d – Dia . Of Load Drum
T1 – No. of teeth on pinion of effort
wheel
T2 – No. of teeth on Spur wheel of
intermediate wheel
T3– No. of teeth on pinion of
intermediate axle
T4 – No. of teeth on Spur wheel of load
axle
In one revolution of lever pinion will
complete one revolution. Dinesh Panchal

So distance moved by Effort in one revolution of lever
= 2π L
In one revolution of effort wheel intermediate axle
will complete T1/T2
No of revolutions made by spur wheel attached to
load axle = T1/T2 X T3/T4
42
31
31
42
31
42
31
42
4
3
2
1
T2LPT
TWDT
2..
..
P
W
M.A.
D
LT2
D
LT22
LoadbymovedDistance
V.R.





TDT
TLT
P
W
RV
AM
Efficiency
TT
T
TT
T
T
T
X
T
T
D
L





Dinesh Panchal

Simple Screw Jack
In screw jack , a square threaded
screw is used to raise the heavy
loads by applying smaller effort. It
consist of a nut, which form the
body. Screw with square thread
and handle attached to screw
thread. The load lifted is placed on
the screw head. The effort P is
applied at end of the handle
attached to the screw.
Pitch of screw = p
revolution of handle = 2π L
Distance moved by the Load = p
Dinesh Panchal

LP2
Wp
2..
..
P
W
M.A.
2
LoadbymovedDistance
V.R.









p
L
P
W
RV
AM
Efficiency
p
L
Dinesh Panchal

Differential Screw Jack
Fig shows the differential screw jack.
It gives more velocity ratio . So it
require less effort to lift the load. It
consist of two screws B and C
threaded on both inner and outer
side passes through a nut, while
small screw C threaded only on the
outer side meshes through the inner
side of screw B.
p1 – Pitch of thread of spindle B
p2 – Pitch of thread of spindle C
revolution of screw C = 2π L
Distance moved by load in one
revolution of screw C = p1-p2 Dinesh Panchal

 
 
 
LP2
pW
2..
..
P
W
M.A.
2
LoadbymovedDistance
V.R.
21
21
21




p
pp
L
P
W
RV
AM
Efficiency
pp
L








Dinesh Panchal

• QUESTION NO. 5 In a simple screw jack the pitch of the screw is 10 mm and the length of
the handle is 450mm . Find the velocity ratio. If an effort of 25 N applied on the handle can
lift a load of 3KN . Find efficiency of the jack. Also calculate the amount of effort wasted in
friction.
• Ans:
J40.79.58x70.65
)-(1supplikedEnergyfrictionintedEnergy was
70.65
1000
45025xx2π
effortbymovedDistanceEffort xmachinetheSuppliedEnergy
%5.42
2.282
120
..
..
120
25
3000
..
2.282
10
2x3.14x450
2
tan
tan
..
3LiftedLoad
25NappliedEffort
450mmhandletheofLength
10mmScrewtheofPitch
:Given
















RV
AM
P
W
AM
p
L
oadcemovedbyLDis
heEffortcemovedbytDis
RV
KNW
P
L
p
Dinesh Panchal

Problem 1:
In a simple machine, whose velocity ratio is 30, a load of 2400 N is to be lifted
by an effort of 150 N and a load of 3000N is lifted by an effort of 180 N . Find the
law of machine and calculate the load that could be lifted by a force of 200 N.
Calculate
(i) Amount of Effort wasted in overcoming the friction (ii) M.A. (III) Efficiency
Problem 2. :
In a differential wheel and axle the diameter of axles are 150mm and 70mm and
load 250N is raised by an effort of 10N at an efficiency of 80% . Find the diameter
of the wheel.
Problem 3:
In an differential wheel axle assembly, the diameter of the wheel is 150mm and
that of axles are 50mm and 30 mm respectively. If the machine has an efficiency of
65% find the effort required to lift the load of 2500 N .Calculate the no. of
revolution made by the machine in lifting the load by a distance of 150mm.
Dinesh Panchal

Problem 4 :
The western differential pulley consist of a lower block and upper block. The upper
block has two pulleys of diameter 230mm and 210 mm. If the efficiency of the
machine is 505 .Calculate the effort required to Raise the load of 160 N.
Problem 5 :
In a double threaded worm and worm wheel the no. of teeth on the worm wheel
is 25. The diameter of the effort wheel and the load drum are 500mm and 150mm
RESPECTIVELY. Calculate the velocity ratio and efficiency of the machine if it require
an effort of 300N to lift a load of 3200 N.
Problem 6.:
Following are the specifications of single purchase winch crab.
Dia. Of Load Drum=200mm, Length of Lever Arm=L= 1.2m, No. of Teeth on Pinion
= T1=10 , No. of Teeth on Pinion = T2=100. Find the velocity ratio of the . On this
machine effort of 100N and 160 N are require to lift the load of 3KN and 9 KN
respectively .Find the law of machine and efficiency.
Dinesh Panchal

Problem 7 :
In a double purchase crab winch , the pinions have 15 and 20 teeth, while the spur
wheels have 45 and 40 teeth. The effort handle is 400 mm long while the effective
diameter of the drum is 150mm .If the efficiency of the winch is 40% , what load
will be lifted by an effort of 250 N applied at the end of the handle.
Problem 8:
A screw Jack has a square threaded screw of 5cm did and 1cm pitch. The coefficient
of friction at the screw thread is 0.15. Find the force required at the end of the 70
cm long handle to raise a load of 2000N . What is the force required if screw jack is
considered to be an idle machine.
Problem 9:
A screw jack has square threads 50mm mean dia. And 10mm pitch. The load on the
jack revolve with the screw . The coefficient of friction at the screw thread is 0.05 .
Find the tangential force at the end of 300mm lever to lift load of 6000N. State
whether the jack is self locking. If not find the torque must be applied to keep the
load from descending.
Dinesh Panchal

REFRIGERATION
AND
AIR CONDITIONING
Dinesh Panchal

REFRIGERATION AND AIR CONDITIONING
Refrigeration
may be defined as the process of
achieving and maintaining a
temperature below that of the
surroundings, the aim being to cool
some product or space to the required
temperature.
Important application:
1.preservation of food and products
Refrigeration systems are
2. Water cooler
3. Refrigerator
4. Cold storage
5. Ice cream manufacturer.
Dinesh Panchal

Air Conditioning
refers to the treatment of air so as to
simultaneously control its temperature,
moisture content, cleanliness, odor and
circulation, as required by occupants, a
process, or products in the space.
Applications:
1. Buildings
2. Homes
3. Offices
4. Automobiles
5. railways
Dinesh Panchal

Rating of Refrigeration Machine:
Means the cooling effect produced by the machine. Unit for measurement of cooling
is Ton of known as ton of refrigeration
One ton of refrigeration is defined as the amount of refrigeration effect
produced by uniform melting of one ton of ice from and at 0 degree in 24 hours.
1TR=1000X335KJ in 24 Hours
= 232.6KJ/min
But in actual practice one ton of refrigeration is 210 KJ/Min or 3.5 KJ/Sec
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Coefficient of Performance:
It is defined as the ratio between refrigeration
effect and work done on the refrigerant
12
1
1
e
e
Workdone
ExtractedHeat
...
C.O.P.lTheoretica
C.O.P.Actual
C.O.P.Relative
unity.thanmorealwaysisC.O.P.
re.temperatulowatthebodyfrom
extractedheatooamounttheisEffectingRefrigerat
KJ/Secinworkdonetheis-W
KJ/SecinEffectingRefrigerattheisRWhere
W
R
Workdone
EffectingRefrigerat
...
QQ
Q
W
Q
POC
POC






Dinesh Panchal

Question no. 1(c) A household refrigerator maintain the refrigerated space at 3 C by
removing the heat from it at a rate of 4KW. The power required to run the
refrigerator is 1.5KW. Determine the C..O.P. of refrigerator.
Ans:
Dinesh Panchal
666.2
5.1
4
Workdone
RemovedHeat
C.O.P
KW5.51.54gSurroundinthetosuppliedHeat
4QRemovedHeat
5.1
3TempoLower
2
0





KW
KWWorkdone
C

SIMPLE VAPOUR COMPRESSION
CYCLE:
It is the most commonly used
refrigeration cycle. In this cycle
there are four fundamental
processes are required to complete
one cycle
1. Compression
2. Condensation
3. Expansion
4. Vaporization
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1. Compression
The low pressure and temp
vapor in dry state enters in the
compressor during the suction
stroke of the compressor. During
compression stroke, it
compresses the vapors
isentropic ally, hence temp. and
pressure increases.
2. Condensation:
After compression the high
pressure and temp refrigerant
vapors enters in the condenser ,
heat is removed from the
refrigerant and refrigerant temp.
decreases in the condenser and
refrigerant returned to the liquid
state.
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3. Expansion :
After condensation, the liquid
refrigerant is stored in a receiver
tank. From the receiver tank ,it
passes through an expansion valve
where it get throttled down and
allow to expand at low pressure .
Here the high pressure liquid
converts into the low temp vapors.
4. Vaporization:
The low pressure refrigerant
vapor after expansion in the
expansion valve enters in to the
evaporator or refrigerated space ,
where heat is absorbed by it from
the refrigerated space .After that
these vapors enters in the
compressor for compressor .the
same process repeats again and
again
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Fundamentals of Air Conditioning :
1. Dry Bulb Temp :
It is the temp. of moist air as measured by stranded thermometer.
2. Wet Bulb Temp. :
If the unsaturated air flows over a thermometer with a wet cloth over the
bulb of the thermometer. And the temp. recorded will be less than the DBT .This
temp. is known as WBT.
3. Relative Humidity :
it is defined as the ratio of actual mass of water vapor in a given vol. of moist
air to mass of water vapour in the same vol. of saturated air at the same temp and
pressure. It is denoted by φ
PressureandTemp.sameatAirSaturatedofvol.samein theVapourWaterofMass
AirMoistofgiven vol.inourwater vapofMassActual

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4. Humidity Ratio (W):
It is the ratio of mass of water to the mass of dry air in a given vol.
5. Absolute Humidity:
Water vapor in the air is called Humidity. The absolute Humidity of the air at
any given condition is the mass of water vapors per unit vol. of air at that condition.
6. Due Point Temp :
If an unsaturated moist air is cooled at constant pressure , then the temp. at
which the moister in the air begin to condense is known as dew point temp. of air
(DPT)
vt
v
a
a
a
v
pp
p
TR
Vp
T
m
m
w



622.0R
p
AirDryofMass
VapourwaterofMass
V
v
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Degree of Saturation:
The degree of saturation is the ratio of the Humidity Ratio W to the Humidity
Ratio of a saturated mixture Ws at the same temp and Pressure.
W= Humidity Ratio
Ws= Water vapour in the same mass and pressure of dry air when it is saturated at
the same temp.
ptSW
W
,1

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Refrigerant:
it is a heat carrying medium , which during the cycle absorb the heat at low temp
and release the heat at high temp. Ammonia and sulphur di-oxide are used as are
refrigerant in past. Most common refrigerants are
1. Freon 12 – dichloro difloro methane-CCl2F - R-12 OR F-12 . It is harmful gas for
ozone layer.
2. Ammonia is used for large industrial plants.
1.Halocarbon Compounds
(A) R-11 Trichloromonofloromethane CCl3F4
(b) R-12 dichlorodifloro methane CCl2F
( c) R-13 Monochlorodtrifloro methane CClF3
(d) R-22 Monochloroddifloro methane CHClF2
2. Inorganic Compounds:
(a) R-717 Ammonia NH3
(b) R-718 Water H2O
( c) R-729 Air
(d) R-744 Carbon dioxide CO2
3. Hydrocarbon :
(a) R-50 Methane CH4
(b) R-170 Ethane C2H6 Dinesh Panchal

Refrigerant Classification
1.Halocarbon Compounds
(A) R-11 Trichloromonofloromethane CCl3F4
(b) R-12 dichlorodifloro methane CCl2F
( c) R-13 Monochlorodtrifloro methane CClF3
(d) R-22 Monochloroddifloro methane CHClF2
2. Inorganic Compounds:
(a) R-717 Ammonia NH3
(b) R-718 Water H2O
( c) R-729 Air
(d) R-744 Carbon dioxide CO2
3. Hydrocarbon :
(a) R-50 Methane CH4
(b) R-170 Ethane C2H6
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Psychometric Chart
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Psychometric Chart
1. Dry Bulb Temp. Lines :
The dry bulb temp lines are
vertical to the ordinate and
uniformly spaced . The
Temperature range of these lines
is from -60C To 450C.
2. Specific Humidity :
The specific humidity are
horizontal lines and uniformly
spaced. The moister content
range is 0 to o.030 Kg/Kg of dry
air.
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3. Dew point temperature:
The due point temp. lines are
horizontal and non uniformly
spaced. At any point on the
saturation curve, the dry bulb
and dew point temp. are equal
4. Wet bulb temp. lines:
The wet bulb temp lines are
inclined straight lines and non
uniformly spaced . At any point
on the saturation curve, the dry
and wet bulb temp are equal.
5. Enthalpy lines:
Enthalpy or total heat lines
inclined straight lines and
uniformly spaced. These lines are
parallel to the wet bulb temp
lines .
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6. Specific Vol. Lines:
The specific vol. lines are obliquely
inclined straight lines and uniformly
spaced.
7. Relative Humidity Lines :
The relative humidity lines are
curved lines and follow the
saturation curve and drawn with
10%, 20%, 30% and up to 100%
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POWER TRANSMISION
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Introduction
# Power is transmitted from one shaft to another shaft by means of
1. belt
2. Ropes
3. chains
4. Gears
# For large distance between the shaft belt rope and chains are used.
# But gears are used for small distance.
# To decide the type of drive the following factors are considered
1. Angular position of the shaft
2. Distance between the shaft
3. Direction of motion
4. Requirement of sped
5. Type of maintenance required.
6. Power to be transmitted
7. Positive drive requirement
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Belt and Rope Drive :
The flexible wrapping connectors are used for
transmitting the power from one shaft to
another shaft. When the thickness of the
connector is small as compared to its width
then it is called belt . If the cress section is
approximately circular then it is called rope
drive. The rope and belt kept in tension so
that there is no slip between the pulley and
the connector. In case of rope grooved
pulleys are used.
Types of belts :
1. flat belt : A belt having the
rectangular cross section is known as
flat belt. It is used mostly in factories for
moderate power transmission. The
distance between the pully not more
than 8 meter
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2. V- belt : The belt having the trapezoidal cross section is known as V belt. It is
used in factories and workshops. It is used to transmit great power when the
distance between the pulleys is small. The belt does not touch the
bottom of the groove.
3. Rope belt : The belt having the circular cross section is known as rope or circular
belt. It is must have high coefficient of friction. They can be classified
according to the belt material
# Leather Belt
# Cotton Belt
# Rubber Belt
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Types of Flat Belt :
1. Open Belt Drive 2. Crossed Belt Drive
3. Quarter Turn Belt Drive 4. Belt Drive with idle pulley
5. Compound Belt Drive 6. stepped pulley drive
7. Fast and loose pulley drive
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Rope belt : The belt having the circular cross section is known as rope or circular
belt. It is must have high coefficient of friction. When the large amount of
power are to be transmitted over a considerable distance then rope are used.
The flat belt drive is limited to a distance of 8 m and for large power
transmission. The frictional grip of the rope drive is more as compared to the
V belt. The are used in well drawing, spinning mills . They are of two types
# Fiber Rope
# Wire Rope
Advantages of Rope Drive :
# They have low cost
# They have high mechanical efficiency
# The outdoor condition affect them very little.
# The shaft may be out of strict alignment.
#The have smooth ,steady and quite operation.
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Chain Drive :
A chain drive consist of endless chain running over two sprockets driver and
driven. These are used where positive action is required. The velocity ratio is
constant. These drives are use when the distance between the shafts are very
short. The are used in bicycles, motorcycles, agricultures machinery.
Advantages :
# It is positive drive.
# It can be employed between short
and long centre distance.
# Less load on shaft.
# Give constant velocity ratio.
# They are compact in size.
Disadvantages :
# High wear and tear
# Cost is high
# Drive needs lubrication.
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Types of Chain Drive :
1. Hoisting Chains
2. Conveyor Chains
3. Power transmission Chains
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Gear Drive :
Gear are toothed wheels used to transmit motion between two shafts, when
the centre between the shaft is very small. Gear is positive drive which give exact
velocity ratio. Intermediate link or connector .Two bodies have either rolling or
sliding contact. They do not use When the teeth are provided on the internal
surface called internal gears and if they are provided on the outer surface called
external gears. They are used in watches , cutting machine tools, automobiles,
rolling mills.
Diagrams
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Advantages :
# They are compact in size.
# They Give positive drive
# They have high efficiency
# They can be used for precise timing.
# They can transmit large power.
# Maintenance cost is less.
# They can drive loads without shock at speed up to 20 m/sec
Disadvantages :
# They are not suitable for large distance.
# Manufacturing is complex
# If there is error in manufacturing they gives undesirable noise
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Classification of Gears :
1. According to position of axis
(i) Parallel shafts
(a) Spur Gear (b) Spur Rack and Pinion
(c) Helical Gear (d) Double Helical Gear
(e) Herring Bone Gear
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(ii) Intersecting Shafts
(a) Straight bevel gear (b) Spiral bevel gear
(iii) Non Intersecting Shafts and non Parallel shafts
(a) Hypoid gear (b) Spiral bevel gear
(c) Worm Gear
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2. According to peripheral velocity of gears
(i) Low velocity (ii) Medium velocity
(iii) High velocity
3. According to type of gearing
(i) Internal Gearing (ii) External Gearing
4. According to shape of teeth of gears
(i) Straight teeth gear (ii) Inclined teeth gear
(iii) Curved teeth gear
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Gear Nomenclature :
1. Pitch Circle : It is the imaginary circle by which pure rolling action , would give the
same motion as the actual gear
2. Pitch Circle Diameter : It is the diameter of pitch circle
3. Pitch Point : It is the common point of contact Between two pitch circles
4. Pressure Angle : It is the angle between the common normal to the two teeth at the
point of contact and the common tangent at the pitch circle. It is usually denoted
by Ф. Pressure angle are 14.50 and 200.
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5. Addendum: It is the radial distance of a tooth from the pitch circle to the top of
tooth.
6. Dedendum: It is the radial distance of a tooth from the pitch circle to the bottom of
the tooth.
7. Addendum Circle: It is the circle drawn through the top of the and concentric with
the pitch circle.
8. Dedendum Circle: It is the circle drawn through the bottom of the teeth. It is also
called root circle.
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9. Circular Pitch : It the distance measured on the circumference of the pitch circle
from a point of one tooth to the corresponding point on the next tooth. It is
denoted by pc .
pc=∏D/T Where D is the pitch circle and T is the no. of teeth
10. Diametrical Pitch : It is the ratio of no. of teeth to the pitch circle diameter in mm
.It is denoted by pd.
pd.=T/D
11. Module : It is the ratio of pitch circle diameter in mm to the no. of teeth. It is
denoted by m.
m=D/T
12. Clearance : It is the radial distance from the top of the tooth to the bottom of the
tooth in meshing gear.
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13. Total Depth: It is equal to the sum of addendum and dedendum.
14. Working Depth: It the radial distance from the addendum circle to the clearance
circle. It is equal to the sum of the addendum of two meshing gears.
15. Tooth Thickness: It is the width of tooth measured along the pitch circle.
16. Tooth Space: It is the width of space between the two adjacent teeth measured
along the pitch circle.
17. Backlash : It is the difference between the tooth space and tooth thickness, as
measured along the pitch circle.
18. Face of tooth : It is the surface of the gear above the pitch circle.
19. Flank of Tooth : It is the surface of gear below the pitch circle.
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Gear trains :
It is the combination of two or more than two gears to transmit the motion
fro driving shaft to the driven shaft.
Types of gears trains:
(i) Simple Gear Train (ii) Compound Gear Train
(iii) Reverted Gear Train (iv) Epicyclical Gear Train
(i) Simple Gear Train : It is a series of gears capable of receiving and transmitting
the motion from one to another gear. Speed Ration is the ratio of speed of driver
to the speed of driven. Train value is the ratio of speed of driven to the speed of
driver
2
1
1
2
1
2
2
1
N
N
ValueTrain
N
N
RatioVelocityRatioSpeed
T
T
T
T


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(ii) Compound Gear Train : Compound gear train consist of series of gears connected
in such a way that two or more gears rotate around an axis with same angular
velocity.
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(iii) Reverted Gear Train : If the axis of driver shaft and the driven shaft is co axial then
it is known as reverted gear train.
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(iii) Epicyclical Gear Train: if one of the gear is rotating over other gear . Epic means
over and cyclic means around. There is an arm connecting these two gears.
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• CLUTCH
A Clutch is a machine member used to connect the driving shaft to a
driven shaft, so that the driven shaft may be started or stopped at will,
without stopping the driving shaft. A clutch thus provides an interruptible
connection between two rotating shafts Clutches allow a high inertia load to
be stated with a small power. A popularly known application of clutch is in
automotive vehicles where it is used to connect the engine and the gear box.
Here the clutch enables to crank and start the engine disengaging the
transmission Disengage the transmission and change the gear to alter the
torque on the wheels. Clutches are also used extensively in production
machinery of all types
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Clutch :
A Clutch is a machine member used to connect the driving shaft to a driven shaft,
so that the driven shaft may be started or stopped at will, without stopping the
driving shaft. A clutch thus provides an interruptible connection between two
rotating shafts. Clutches allow a high inertia load to be stated with a small power.
A popularly known application of clutch is in automotive vehicles where it is used
to connect the engine and the gear box. Here the clutch enables to crank and start
the engine disengaging the transmission Disengage the transmission and change
the gear to alter the torque on the wheels. Clutches are also used extensively in
production machinery of all types
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Requirement of clutch :
# For Transmission of torque under different conditions
# For transmitting the power gradually.
# Clutch should dissipate the large amount of heat.
# Clutch should be dynamically balanced.
# There should be suitable mechanism with in the clutch to reduce the noise.
# Size of clutch should be as small as possible.
# The rotating parts of clutch should have minimum inertia.
# Clutch design should be such that it is easy to operate.
Function of clutch :
# To engage the engine power to the gear box.
# To disengage the engine power to the gear box.
# To provide the smooth and gradual operation to take up the load without jerk.
# To help in shifting the gear in the gear box.
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Principle of clutch :
Suppose there are two discs as shown ion fig. Initially the disc A is rotating at
a speed N rpm and disc B is stationary. It means clutch is not engaged. Now load W
is applied on Disc B to engage it with disc A then the force of friction comes in to
play between the dices and the disc B will start rotate. If the load is increased, the
speed of B will increase and at last will attain the speed equal to the speed of A.
This is the principle of clutch.
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Types of clutches
Clutch
Dog Clutch Friction Clutch
Cone Clutch Disc Clutch
Single Plate
Cutch
Multi Plate
Clutch
Diaphragm
Clutch
Centrifugal
Clutch
Semi
Centrifugal
Clutch
Fluid Clutch
Electromagnetic
Clutch
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Single Plate Clutch :
It consist of only one clutch plate. Mounted on the splines of the clutch shaft. The
flywheel is mounted on the engine shaft and rotates with it. The Pressure plate is
bolted to the flywheel through clutch springs, and free to slide on the clutch shaft
when the clutch pedal is operated . When the clutch is engaged, the clutch plate is
gripped between the flywheel and the pressure plate. Friction lining are on the
both sides of the clutch plate . Due to friction between the flywheel, clutch plate
and pressure plate, the clutch plate revolve with flywheel. As the clutch plate
revolve the clutch shaft is also rotate. The clutch shaft is connected to the
transmission. Thus the engine power is transmitted to the transmission through
clutch.
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Brake:
Brake is the mechanical system which is used to reduce the speed or
to stop the motion. Brake convert the K.E. In to heat energy. Force of friction is
used in the braking system. As the force of friction oppose the motion.
There are two main functions of brakes :
(a) To slow down or stop the vehicle in the shortest possible time at the time of need.
(b) To control the speed of vehicle at turns and also at the time of driving down on a
hill slope.
PRINCIPLE OF VEHICLE BRAKING :
Braking of a vehicle depends upon the static function that acts between tyres and road
surface. Brakes work on the following principle to stop the vehicle :
“The kinetic energy due to motion of the vehicle is dissipated in the form of heat
energy due to friction between moving parts (wheel or wheel drum) and
stationary parts of vehicle (brake shoes)”.The heat energy so enerate4d due to
application of brakes is dissipated into air.
Brakes operate most effectively when they are applied in a manner so that wheels
do not lock completely but continue to roll without slipping on the surface of road.
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CLASSIFICATION OF BRAKES
On the Basis of Method of Actuation
(a) Foot brake (also called service brake) operated by foot pedal.
(b) Hand brake –it is also called parking brake operated by hand. On
the Basis of
Mode of Operation
(a) Mechanical brakes
(b) Hydraulic brakes
(c) Air brakes
(d) Vacuum brakes
(e) Electric brakes.
On the Basis of Action on Front or Rear Wheels
(a) Front-wheel brakes
(b) Rear-wheel brakes.
On the Basis of Method of Application of Braking Contact
(a) Internally –expanding brakes
(b) Externally –contracting brakes.
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Air Brakes :
Air brakes are applied by the pressure of compressed air. Air pressure applies force
on brakes shoes through suitable linkages to operate brakes. An air compressor is
used to compress air. This compressor is run by engine power.
Vacuum Brakes
Vacuum brakes are a piston or a diaphragm operating in a cylinder. For application
of brakes one side of piston is subjected to atmospheric pressure while the other is
applied vacuum by exhausting air from this side. A force acts on the piston due to
difference of pressure. This force is used to operate brake through suitable
linkages.
Electric Brakes
In electrical brakes an electromagnet is used to actuate a cam to expand the brake
shoes. The electromagnet is energized by the current flowing from the battery.
When flow of current is stopped the cam and brake shoes return to their original
position and brakes are disengaged. Electric brakes are not used in automobiles as
service brakes.
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Shear Force
and
Bending Moments
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Shear Force and Bending Moments
Beam: A structural member which carries lateral or transverse force is termed as
beam.
1. Cantilever Beam:
A beam which is fixed at one end and free from other end is called cantilever
beam.
Beam
Cantilever
Beam
Simply
Supported
Beam
Overhanging
Beam
Fixed Beam
Continuous
Beam
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2. Simply Supported Beam :
A beam supported or freely resting on the supported at its both ends, is
known as simply supported beam.
The whole length of the beam is known as its total span. The clear horizontal
distance between the walls is called the clear span of the beam. The horizontal
distance between the centers of the ends bearings is called effective span of the
beam.
3. Overhanging Beam:
A beam in which its end portion is extended beyond the support is known as
overhanging beam
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4. Fixed Beam ;
Abeam whose end points are fixed in wall is known as fixed beam.
5. Continuous Beam :
A beam supported on two or more supports is known as continuous beam.
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Types of End Supports Load :
1. Simply Supported Load :
A beam which rests freely on supports at its both ends is called simply
supported beam.
Supports
Simply
Supported
Load
Roller
Supported
beams
Hinged Beam
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2. Roller Supported Beam :
In this case one end of the beam is supported on roller in order to permit free
movement in horizontal direction. Roller reaction is vertical to the surface.
3. Hinged Beam:
In this case , the end of a beam is hinged to the support.
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Load :
Load is the force acting on the beam is called load.
1. Concentrated Load : A concentrated load or point load is the load acting on a pont
on the beam
Load
Concentrated
or Pont Load
Uniformly
Distributed
Load
Uniformly
Varying Load
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2. Uniformly Distributed Load :
A load which is spread uniformly over the entire span or small portion of the
beam is known as uniformly Distributed Load.
2. Uniformly Varying Load :
A load which is spread over the entire span or small portion of the beam in
such a manner that the rate of loading varies from one point to another point
uniformly is known as uniformly Distributed Load.
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Shear Force in Loaded Beam:
Shearing force at any section of a beam carrying load is the algebraic sum of
the forces on either side of the section.
Bending Moment :
The moment causing the bending in the beam is called bending moment.
Sign Convention :
Shear Force :
1. Shear force will be taken as positive if the total force on the right
side of the section is in the upward direction
2. Shear force will be taken as negative if the total force on the right
side of the section is in the downward direction.
Bending Moment :
1. Bending Moment will be taken as positive if the bending on the
right side of the section is in the upward direction
2. Shear force will be taken as negative if the total force on the right
side of the section is in the downward direction
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STRESSES AND STRAINS
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Load:
It is the external force on a body is called load.
Load
According to manor
of application of load
Dead Load or
Static Load
Live of Fluctuating
Loads
According to effect
Produced
Tensile
Load
Compressi
ve Load
Shearing
Load
Twisting or
torsion Load
Bending
Load
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(A) According to manor of application of load:
1. Dead Load : These are the loads which are applied very gradually increasing
from zero to max.
2. Live or Fluctuating Loads :
(i) These loads are always the same kind but vary in magnitude. E.g. weight of
vehicle crossing the bridge
(ii) Those load which are applied with velocity e.g. a hammer below
(iii) Those loads which changes from max. of one kind to the max. of opposite
kind e.g. alternate push and pull or piston force
(A) According to effect of load on the member :
1. Tensile Load : The load which tends to pull the member in the direction of its
application called tensile load
2. Compressive Load: The loads which tends to push together the opposite ends
of the member is called compressive load.
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3. Shearing Load :
The load which when applied at the opposite face of a body tends to cause
the sliding of one of these faces are called shearing force. This consist of equal ,
parallel and opposite force.
4. Twisting or Torsion Loads :
The load produced by two couple at opposite ends of the members, tending
to cause one end to rotate about its longitudinal axis relative to the other end
called torsion loads
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5. Bending Load :
The loads which tends to cause a certain degree of curvature or bending in
the member called bending load.
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Stress :
When a body is subjected to the external force or load , it tends to undergoes
the deformation i.e. change in dimension.
The force of resistance per unit area offered by the body against the
formation is called stress.
σ=P/A
Where σ is the stress, P is the Load and A is the cross sectional area.
Unity of Stress are N/m2 , N/mm2 ,
1MN/m2=1MPa=1X 106 N/m2 =1N/mm2
1GPa=1000MPa=1KN/mm2 =1000N/mm2
Stress
Tensile
Stress
Compressive
Stress
Shear Stress
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(i) Tensile Stress :
When two equal and opposite pulls are applied on the member, the stress
induced in the member is called tensile stress.
σt=P/A
(ii) Compressive Stress :
When two equal and opposite pushes are applied on the member, the
stress induced in the member is called compressive stress.
σc=P/A
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(iii) Shear Stress :
When two equal and opposite forces are acting tangentially to the cross-
section , the stress induced is called shear stress.
Dinesh Panchal

Strain :
It is the measurement of deformation or change in the shape of the loaded
body. It is the ratio of change in dimension to the original dimension.
(i) Tensile Strain :
If tensile load P is applied to a member of original length l and after
applying the load, increase in length is δl. So tensile strain is given as
DimensionOriginal
dimensioninChange
eStrain 
l
δ l

LengthOriginal
LengthinIncrease
eStrainTensile t
Dinesh Panchal

(ii) Compressive Strain :
If tensile load P is applied to a member of original length l and after
applying the load, decrease in length is δl. So tensile strain is
(iii) Shear Strain :
It is the measure of angle through which a body is distorted under action
of shear force.
(iv) Volumetric Strain:
It is the ratio of Change in volume to the ratio of original volume.
l
δ l

LengthOriginal
LengthinDecrease
eStrainTensile c
  taneStrainShear s
BC
CCI
V
V

VolumeOriginal
VolumeinChange
StrainVolumetric
Dinesh Panchal

Elasticity :
This is the property of material by virtue of it the material regain its original
shape after the removal of external force called elasticity. A material remain elastic
up to a certain limit called elastic limit.
Hooke’s Law:
This law state that when a material is loaded within the elastic limit, the
stress is directly proportional to the strain.
Young’s Modulus of Elasticity:
It is the ratio of tensile stress to the tensile strain or ratio of compressive
stress to compressive strain.It is denoted by E.
elasticityofmodulusasknownisContant
Strain
Stress
Constant
StrainConstant xStress
StrainStress



c
c
t
t
ee
E
orE



StraineCompressiv
StresseCompressiv
StrainTensile
StressTensile
Dinesh Panchal

Modulus of rigidity or shear modulus :
It is the ratio of shear stress to the shear strain. It is denoted by C or G
Bulk Modulus of Elasticity:
It is the ratio of normal stress to the volumetric strain, called Bulk Modulus of
Elasticity. It is denoted by K.
Longitudinal Strain :
When a body is subjected to tensile load there is a axial deformation in the
length of the body. The ratio of axial deformation to its original length is known as
longitudinal strain
strainsheartheisandstressshearistheWhere
StrainShear
StressShear



C
ve
K


StrainVolumetric
StressNormal
l
l

LengthOriginal
nDeformatioAxial
StainalLongitudin
Dinesh Panchal

Lateral Strain :
When a body is subjected to axial tensile or compressive load , there is an
axial deformation in its length of the body but at the same time there is
change in the other dimension of the body at right angle to the line of action
of force. Thus body have deformation in axial as well in right angle direction.
So lateral strain is given by
Poission’s Ratio :
It is the ratio of lateral strain to the longitudinal strain. It is denoted by γ or
1/m
LoadApplied-P
elongatioafterdiameterReduced-d
rodofdiameterOriginal
D
d-D
StrainLateral


D
diameterreducedtheisdandDiameterorigionaltheisD
LengthorigionaltheisLandlengthinchjangetheisLWhere
StrainalLongitudin
StrainLateral


L
L
D
dD
v


Dinesh Panchal

QUESTION NO. 8(B) A tensile load of 56 KN was applied to a bar 30 mm diameter with 300
mm gauge length. Measurement showed 0.12mm increase in length and the corresponding
.0036mm contraction in dia. Make tha calculation for Poisson Ratio and value of three elastic
constants.
Ans:
Dinesh Panchal
9
300
12.0
30
0036.0
StrainalLongitudin
StrainLateral
RatioPoission
0.0036LengthnContractio
0.12mmLlengthinIncrease
300mmbarofLength
300mmDbartheofDiameter
56KNWappliedLoad
:








L
L
D
dD
v
dD
L
Given



Relation between three elastic Constants (K,E, C):
Relation between E and C :
 
 
(ii)eq.withcompareand(i)eq.inBCandCCofvaluethePutting
2
AC
BC45cos
AC
BC
ABCtriangleanglerightIn
2
45cos
CCor45cos
CECtriangleanglerightIn
....................................
C
StrainShearAlso
................................StrainShear
45astakenbemayCACangle
,smallisndeformatioAsFig.inshownasACtoCElarprependicutheDraw
DABC
tochangedisABCDshapetheand,stressshearbydistortedisABCDcubeA
0
0
I0
I
0I
I
I




EC
EC
CC
EC
ii
i
BC
CC
I
I
I
I
I
I



Dinesh Panchal

 
   
   
     vvv
EC
ivv
EE
v
E
iii
AC
EC
CAC
EC
AC
EC
C
III
......................................12CE1
2
iiiandiveq.From
....................1
AC
EC
BDinstresscompessivetodueStrain-
ACinstresstensiletodueStrainbygivenisACdiagonalinstrainThe
ncompressiotosubjectedisBDdiagonaland
stresstensiletosubjectedisitthatindicateswhichelongates,ACdiagonal
AC
EC
ACdiagonalinstrainalLongitudin
ACdiagonaloflengthin theincreasetheisCE
AEACBut
.................................
2
222
I
I
I
















Dinesh Panchal

Relation between E and K :
Consider a cubical element is subjected to the volumetric stress σ which act
simultaneously along the mutually perpendicular x, y, z direction.
The resultant strain along the three direction can be worked out by taking
thee effect of individual stresses.
Strain in x direction
ex = strain in x direction due to σx - strain in x direction due to σy - strain in x
direction due to σz
 
 
 v
E
e
v
E
e
v
EE
v
E
v
E
e
E
v
E
v
E
e
z
y
x
zyx
x
21
and21
Similarly
21
But zyx










Dinesh Panchal

 
   
   
   
   
   
6K
3
2
2
So
6K
3
2
2
2
3K
-121
3K
1
2
1
2
21312
viandveq.From
KC,betweenE,Relation
vi.............................2-13KE
21321
3
StrainVolumetric
StressNormal
KModulusBulk
21
3
StrainVolumetric
EK
C
CE
v
EK
v
C
CE
v
E
v
E
v
C
E
v
C
E
vKEvCE
v
v
E
v
E
v
E
eeee zyxv




















Dinesh Panchal

   
CK
CK
E
CKCEKE
CKCEKE
CECKCKKE
EKCCEK
EK
C
CE









3
9
923
1826
26126
3226
MultiplyCross
6K
3
2
2
Dinesh Panchal

Stress strain diagram:
When a ductile material is subjected to the tensile loading under increasing
load . The following stress strain diagram is obtained.
1. Proportional Limit :
Pont A is the limit of proportionality.
From the origin O to point A, Stress
diagram is a straight line i.e. stress is
directly proportional to the strain.
Beyond this point stress is no longer
proportional to strain.
2. Elastic Limit :
Point B is the elastic limit stage.
Between A and B although the strain
increases slightly more than stress, yet
the material is elastic i.e. on removal of
load the material will regain its original
shape and size. If the material is
stressed beyond the point B plastic
deformation will take place. Dinesh Panchal

3. Yield Point :
Point C is the yield point, between B
and c, the strain increases more quickly
than the stress.
4. Maximum Stress Point :
Beyond point C, the load again start
increasing but the elongation now
increases at a much faster rate than
the load . As the test is continued, a
point of max. stress is reached at D .
The stress at this point is called ultimate
stress.
5. Breaking Point :
The reduction in area at the neck lead to
drop in the load. After point D extension
remains continuous even with lesser load and ultimately fracture occur at
point E. The stress corresponding to Pont E is called Breaking Stress.
Dinesh Panchal

Maximum or Ultimate Stress :
It is the ratio of maximum load to the original cross – sectional area
Working Stress:
The stress used in practical design is called working stress. Iot is called safe
stress or allowable stress.
Factor of Safety :
It is the ratio of ultimate stress to the working stress.
SectionCrossOriginal
LoadMaximum
ressUltimateSt


SafetyofFactor
StressUltimate
essWorkingStr 
essWorkingStr
StressUltimate
SafetyofFactor 
Dinesh Panchal

Breaking Stress :
It is determined by dividing the load at the time of fracture or breaking by the
original cress – section area.
Proof Stress :
It is stress necessary to cause the a non proportional or permanent extension
equal to a defined % of gauge length. If the specified % is 0.15 of the gauge length
the corresponding proof stress is designed as 0.1% of proof stress
AreaSectionalCrossOriginal
PointStressBreakingat theLoad
StressBreaking


Dinesh Panchal

QUESTION NO. 8(A) The bending moment and shear force diagram for simply supported beam as shown
in fig.
Dinesh Panchal

0)825.7()64()46()25(APointatMomentBending
5.14)625.7()44()26(CPointatMomentBending
21)425.7()24(DPointatMomentBending
5.1425.72EPointatMomentBending
0BPointatMomentBending
:MomentBending
KN75.756425.7A&CbetweenforceShear
KN75.26425.7C&DbetweenforceShear
KN25.3425.7D&EbetweenforceShear
KN25.7E&BbetweenforceShear
:ForceShear
75.725.715R
25.7
8
644625
8R644625
ApontaboutmomentTaking
15R
equilbriummechanicalperAs
A
B
A















KN
R
KNR
B
B
Dinesh Panchal

Dinesh Panchal
2
3
2
3
/8.31
4040
4
1040
BCin
/127
2020
4
1040
ABin
mmN
Area
Forcc
Stress
mmN
Area
Forcc
Stress













Problem 1 :
A rod of 20 mm in diameter and 2m long is subjected to an axial pull of 35 KN . If
the modulus of elasticity of material of the rod is 219GN/m2. Determine
(i) Stress (ii) Strain (iii) Elongation in Rod
Problem 2 :
A steel rod of 30 mm in diameter and 3oomm long is subjected to an axial force
alternating between a max. compression of 20 KN and max. tension of 8 KN. Find
the difference between the greatest and least length of rod. Take W=210KN/mm2
Problem 3 :
The ultimate stress , for a hollow steel column which carries an axial load of 2.2MN
is 500N/mm2 . If the external diameter of the column is 250mm, Determine the the
difference between the greatest and least length of rod. Take W=210KN/mm2
Problem 4 :
A metallic bar 25o mm x 100 mm x 50 mm is loaded as shown in fig. Find change in
volume . Take E=2 x 105 N/mm2 and Poisson Ratio=0.25
Dinesh Panchal

Problem 5:
Fig. shows a steel bar consisting three lengths. Find the stresses in the three parts
and the total elongation of the bar for axial pull of 40 KN. Take E = 2.1N/mm2.
Problem 6:
A round bar as shown in fig. subjcted to an axial tensile load of 100 KN . What must
be the diameter d if the stress there is to be 100MN/m2? Find Total elongation.
Take E=200 Gpa.
Dinesh Panchal

Problem 7 :
A bar is subjected to axial force as shown in fig. Find the total change in length of
bar . Take E =1 x 105 N/mm2.
Problem 8:
Two copper bars and a steel bar together support a load of 350 KN as shown
in fig. Find the Stress in the rods Young's Modulus for steel is twice as that of
copper.
Dinesh Panchal

Problem 9 :
A load of 30 KN is jointly supported by three equidistance vertical loads in the same
vertical plane. The rods are so adjusted that they share load equally. All the rods
are of 25 mm diameter. Calculate the final tresses if an additional load of 20 KN is
added. Take ES =2EC =210 GPa
Dinesh Panchal

Q. NO. Abrass rod in static equilibrium is subjected to axial load as shown in fig find load P and change in
the length of the bar if its diameter is 10 cm. Take E= 90 GN/mm2
Dinesh Panchal

Dinesh Panchal
 
 
  mm
lFlFlF
AE
AE
lF
AE
lF
AE
lF
EEAA
EA
lF
EA
lF
EA
lF
D
mmN
cmD
Given
8
8
14
6
333
94
332211
332211
321321
11
11
11
11
11
11
321
24
2
29
1035.7
65.7
1056
45101
1065.7
101
5001090100010105001020
109010785.0
1
1
EEandAAWhere
lengthinincreasenetSo
s.elongationhavesectiontheallfigtheFrom
mm10785.0
4
10010014.3
4
ABarBrassofArea
/1090E
mm10001BarBrassofDia.
:




































TURBINES
 A hydraulic machine is a device in which mechanical energy is transferred from the
liquid flowing through the machine to its operating member (runner, piston and
others) or from the operating member of the machine to the liquid flowing through
it.
 Hydraulic machines in which, the operating member receives energy from the
liquid flowing through it and the inlet energy of the liquid is greater than the outlet
energy of the liquid are referred as hydraulic turbines.
 Hydraulic machines in which energy is transmitted from the working member to
the flowing liquid and the energy of the liquid at the outlet of the hydraulic
machine is less than the outlet energy are referred to as pumps.
 It is well known from Newton’s Law that to change momentum of fluid, a force Is
required. Similarly, when momentum of fluid is changed, a force is generated. This
principle is made use in hydraulic turbine.Dinesh Panchal

 In a turbine, blades or buckets are provided on a wheel and directed against water
to alter the momentum of water. As the momentum is changed with the water
passing through the wheel, the resulting force turns the shaft of the wheel
performing work and generating power.
 A hydraulic turbine uses potential energy and kinetic energy of water and converts
it into usable mechanical energy . The mechanical energy made available at the
turbine shaft is used to run an electric power generator which is directly coupled to
the turbine shaft
 The electric power which is obtained from the hydraulic energy is known as Hydro
electric energy. Hydraulic turbines belong to the category of roto-dynamic
machinery
 The hydraulic turbines are classified according to type of energy available at
the inlet of turbine, direction of flow through vanes, head at the inlet of the
turbines and specific speed of the turbinesDinesh Panchal

FRANCIS TURBINE
The Francis turbine is an inward flow reaction turbine which was designed and
developed by the American engineer James B. Francis. Francis turbine has a purely
radial flow runner; the flow passing through the runner had velocity component only
in a plane of the normal to the axis of the runner. Reaction hydraulic turbines of
relatively medium speed with radial flow of water in the component of turbine are
runner.
Dinesh Panchal

CONSTRUCTION DETAILS OF FRANCIS TURBINE:
Components of the Francis turbine:-
Pen stoke: – It is a large sized shaped; where the water is provided to the turbine
runner from the dam.
Scroll casing: – Penstocks connected to and feeds water directly into an annular
channel surrounding the turbine runner. The channel is spiral in its layout.
Guide vanes: – A series of airfoil shaped vanes called the guide vanes are arranged
inside the casing to form a number of flow passages between the casing and the
runner blades. Guide vanes are fixed in position (they do not rotate with rotating
runner).
Guide wheel and governing mechanism: – It changes the position of guide blades to a
ffect variation in the water flow rate in the wake of changing load conditions on the
turbine. When the load changes, the governing mechanism rotates all the guide
blades about their axis through the same angle so that the water flow rate to the
runner.
Runner and runner blades: – Runner of the Francis turbine is a rotor which has
passages formed between the drat tube and scroll casing.
Draft tube: – After passing through the runner, the water is discharged to the tail race
through a gradually expanding tube.
Dinesh Panchal

• WORKING OF FRANCIS TURBINE: The amount of water falls on the vanes (buckets) of
the runner. The turbine rotor is called runner. Runner revolves at constant with the help
of governing mechanism. The runner shaft is connected with the generator; thus the
electricity is produce with the help of generator. And the water is discharge from the tail
race.
• APPLICATION: Francis Inlet Scroll, Grand Coulee Dam Large Francis turbines are
individually designed for each site to operate at the highest possible efficiency, typically
over 90%. They are best suited for sites with high flows and low to medium head.
Francis Turbines are very expensive to design, manufacture and install, but operate for
decades.
• In addition to electrical production, they may also be used for pumped storage; where a
reservoir is filled by the turbine (acting as a pump) during low power demand, and then
reversed and used to generate power during peak demand.
• Francis turbines may be designed for a wide range of heads and flows. This, along with
their high efficiency, has made them the most widely used turbine in the world.
Dinesh Panchal

: Classification of Hydraulic Turbines:
1.According to the type of energy at inlet:
i) Impulse turbine
ii) Reaction Turbine
2. According to the direction of flow through runner:
i) Tangential flow turbines
ii) Radial flow turbines
Inward flow turbine:
Outward flow turbine
iii) Axial flow turbine
iv) Mixed flow turbine:
3. According to the head at inlet of turbine:
i) High head turbine
ii) Medium head turbine
iii) Low head turbine:
4. According to the specific speed of the turbine
i) Low specific speed turbine
ii) Medium specific turbine
iii) High specific turbine
Dinesh Panchal

Radial flow turbines
# Radical flow turbines are those turbines in which the water flows in
radial direction. The water may flow radically from outwards to
inwards or from inwards to outwards.
# If the water flows from outwards to inwards through the runner, the
turbine is known as inward radial flow turbine. If the water flows from
inwards to outwards, the turbine is known as outward radial flow
turbine.
# Reaction turbine means that the water at inlet of turbine possesses
kinetic energy as well as pressure energy.
The main parts of a radial flow reaction turbine are:
1. Casing: The water from penstocks enters the casing which is of spiral
shape in which area of cross section of casing goes on decreasing
gradually. The casing completely surrounds the runner of the turbine.
2. Guide mechanism:- It consists of stationary circular wheel all round
the runner of the turbine. The stationary guide vanes are fixed on
guide mechanism. The guide vanes allow the water to strike the
vanes fixed on the runner without shock at inlet.
3. Runner:-It is a circular wheel on which a series of radial curved
vanes are fixed. The surfaces of the vanes are made very smooth.
The radial curved are so shaped that the water enters and leaves
without shock.
Dinesh Panchal

4. Draft tube: The pressure at the exit of the runner of reaction turbine is generally
less than atmospheric pressure. The water exit cannot be directly discharged to the tail
race. A tube or pipe of gradually increasing area is used for discharging water from the
exit of turbine to the tailrace.This tube of increasing area is called draft tube.
Dinesh Panchal

Basics of mechanical engineering

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