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Nitesh Kumar, Assistant Professor, Dept. of
Mech & Mfg. Engg.1
MechanicalMechanicalMMEE
SS
EngineeringEngineering
ScienceScience
2
MMechanicalechanical EEngineeringngineering SSciencecience
1. Properties of steam
2. Steam boilers
3. Steam turbines
4. Refrigeration5. I. C. Engines
6. Lubrication
1. Transmission of power
2. Machine tools
3. Casting
4. Forging5. Welding
6. Milling machine
7. Shaper
8. Grinding machine
Part APart A Part BPart B
ThermalThermal ProductionProduction
Nitesh Kumar, Assistant Professor, Dept. of
Mech & Mfg. Engg.
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InstructionsInstructions
Mark distribution:Mark distribution:
Test = 40 marksTest = 40 marksAssignment / surprise test = 10 marksAssignment / surprise test = 10 marks
EndEnd SemSem Exam = 50 marksExam = 50 marks
Test: 40 marksTest: 40 marks
There will be 2 Tests.
Each test is of 20 marks
Assignment / surprise test:
There will be 2/3 assignments / surprise tests.
Each assignment / surprise test is of 10 marks.
To award 10 marks, all are considered.Nitesh Kumar, Assistant Professor, Dept. of
Mech & Mfg. Engg.
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Reference booksReference books
1. Mechanical Engineering Science: K.R.
Gopalakrishna, Subhas Publications
2. Elements of Mechanical Engineering:
Roy & Choudhury, Laxmi Publications Pvt. Ltd
3. Mechanical Engineering Science: B.K.
Mishra, Kumar & Kumar Publishers Pvt. Ltd
4. Mechanical Engineering Science: R.K
Rajput, Laxmi Publications Pvt. Ltd.
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Chapter 1:Chapter 1:
PROPERTIES OF STEAMPROPERTIES OF STEAMPROPERTIES OF STEAMPROPERTIES OF STEAMPROPERTIES OF STEAMPROPERTIES OF STEAMPROPERTIES OF STEAMPROPERTIES OF STEAM
Steam:
Vapour form of water is called STEAM.
Water in solid phase: We call it as ICEICE
Water in liquid phase: We call it as WATERWATER
Water in gaseous phase: We call it as STEAMSTEAM
Nitesh Kumar, Assistant Professor, Dept. of
Mech & Mfg. Engg.
Application of steam
Food processing industry
Cooking: hotels, restaurants etc
Used as working fluid in steam engines andsteam turbines
Used in industries for heating process
Petrochemical industries Washing, drying, sterilizing in hospitals
Health clinic and gym
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Mech& Mfg. Engg.6
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FORMATION OF STEAM EXPERIMENTFORMATION OF STEAM EXPERIMENTFORMATION OF STEAM EXPERIMENTFORMATION OF STEAM EXPERIMENTFORMATION OF STEAM EXPERIMENTFORMATION OF STEAM EXPERIMENTFORMATION OF STEAM EXPERIMENTFORMATION OF STEAM EXPERIMENT
(Constant Pressure)(Constant Pressure)
Consider 11 kgkg of water at 00ooCC
taken in a cylinder fitted
with a freely moving
frictionless piston as shown
in figure.
Cylinder
I kg of
water at
OoC
Pressure
P
Nitesh Kumar, Assistant Professor, Dept. of
Mech & Mfg. Engg.
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The initial condition of water at 0oC is represented by the point AAon
the Temperature Enthalpy graph
A
Temperature
Enthalpy
(h)
Temperature
(ToC)
Nitesh Kumar, Assistant Professor, Dept. of
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AA
Temperature
EnthalpyEnthalpy
(h)(h)
TemperatureTemperature
(T)(T)ooCC
TTSatSat BB
hhff
Sensible heatSensible heat
hhfgfg
Latent heatLatent heat
TTSupSup
AOSAOS
CC
DD
DOSDOS
Fig. 1
WW
WW
W
Fig. 2 Fig. 3 Fig. 4 Fig. 5
AA BB CC DD
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Mech & Mfg. Engg.10
DefinitionsDefinitions
Sensible heatSensible heat(hf):: (Enthalpy of water)
It is the amount of heat required to raise the temperature of 1
kg of water from 0 0C to the saturation temperature Tsat0C a t a
given constant pressure P.
hf= m x Cpx Tsat kJ/kgkJ/kg
Where, m = mass of water in kg.
Cp = specific heat of water
= 4.1868 kJ/kg0K
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SaturationSaturation temperaturetemperature ((TTsatsat))::
It is the temperature at which the water begins to boil at the
stated pressure.
LatentLatent heatheat ((hhfgfg)):: (Enthalpy(Enthalpy ofof evaporation)evaporation)
It is the amount of heat required to evaporate 1 kg of water at
saturation temperature to 1 kg of dry steam at the same
saturation temperature and at the given constant pressure P.
SuperheatedSuperheated temperaturetemperature ((TTsupsup))::
It is the temperature of the steam above the saturation
temperature at a given constant pressure.
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Mech & Mfg. Engg.12
AmountAmount ofof superheatsuperheat (AOS)(AOS):: (Enthalpy(Enthalpy ofof superheat)superheat)
It is the amount of heat required to raise the temperature of
dry steam from its saturation temperature to any desired
higher temperature at the given constant pressure P.
AOS = m x Csup (Tsup - Tsat) kJ/kgkJ/kg
DegreeDegree ofof superheatsuperheat (DOS)(DOS)::
It is the difference between the superheated temperature and
the saturation temperature.
DOSDOS == ((TTsupsup TTsatsat))
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Different states of steamDifferent states of steam
The steam as it is being generated can exist in threethree different
states,
1. Wet steam
2. Dry saturated steam (dry steam)
3. Superheated steam
Nitesh Kumar, Assistant Professor, Dept. of
Mech & Mfg. Engg.14
Wet Steam:Wet Steam:
A wet steam is defined as a twotwo--phasephase mixturemixture of finely
divided waterwater particlesparticles and steamsteam at the saturation
temperature corresponding to a given stated pressure.
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EnthalpyA
B C
Sensible
Heat
Latent Heat
hfg
Tsup
Temperature
Amount of
Superheat
Degree of Superheat
Ts
hf
D
Temperature
hg
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Mech & Mfg. Engg.16
The quality of wet steam is specified by the drynessdryness fractionfraction
which indicates the amount of dry steam present in the given
quantity of wet steam and is denoted as xx.
The dryness fraction of a steam is defined as the ratio of mass of
the actual dry steam present in a known quantity of wet steam to
the total mass of the wet steam.
SteamWetofMassTotal
Steamin WetpresentSteamDryofMassxfraction,Dryness =
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Let,
mg = Mass of dry steam present in the sample quantity of wet
steam
mf= Mass of suspended water molecules in the sample quantity
of wet steam
The dryness fraction of wet steam is always lessless thanthan 11.
The dryness fraction of dry steam is equalequal toto 11.
g
f g
mx
m m=
+
Nitesh Kumar, Assistant Professor, Dept. of
Mech & Mfg. Engg.18
Dry Saturated Steam:Dry Saturated Steam:
(dry steam)(dry steam)
Dry saturated steam is the steam at saturation temperature
and at a given pressure having nono waterwater moleculesmolecules entrained
in it.
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SuperheatedSuperheated SteamSteam::
A superheated steam is defined as the steam at a temperature
higher than the saturation temperature at the given stated
pressure.
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Mech & Mfg. Engg.20
Advantages of Superheated Steam:Advantages of Superheated Steam:
Superheated steam possess very high energy compared to dry
saturated steam or wet steam at the same pressure, hence its
capacity to do the work will be higher.
It doesnt create any problems like rusting or corrosion of
blades of turbine / engine cylinder.
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Disadvantages of Superheated Steam:Disadvantages of Superheated Steam:
The high superheated temperatures poses problems in thelubrication.
Higher initial cost.
EnergyEnergy contentcontent ofof steamsteam::
Superheated
steam
Dry saturated
steam
Wet
steam> >
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Mech & Mfg. Engg.22
Enthalpy equations for different states of steamEnthalpy equations for different states of steam
a) Enthalpy of Dry saturated Steam (ha) Enthalpy of Dry saturated Steam (hgg):):
hg = hf+ hfg kJ/kg
EnthalpyA
B C
Sensible
Heat
Latent Heat
hfg
Tsup
Temperature
Amount of
Superheat
Degree of Superheat
Ts
hf
D
Temperature
hg
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b) Enthalpy of Wet Steam (h):b) Enthalpy of Wet Steam (h):
A
B C
Sensible
Heat
Latent Heat
hfg
Tsup
Temperature
Enthalpy
Amount of
Superheat
Degree of Superheat
Tsat
hf
D
Temperature
h = hf+ x .hfgkJ/kg
Nitesh Kumar, Assistant Professor, Dept. of
Mech & Mfg. Engg.24
c) Amount of superheat (AOS):c) Amount of superheat (AOS): (Enthalpy of superheat)(Enthalpy of superheat)
A
B C
Sensible
Heat
Latent Heat
hfg
Tsup
Temperature
Enthalpy
Amount of
Superheat
Degree of Superheat
Ts
hf
D
Temperature
AOS = Csup (Tsup - Tsat) kJ/kg
where, Csup = Specific heat of the superheated steam
= 2.25 kJ/kg0K
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d) Enthalpy of Superheatedd) Enthalpy of Superheated Steam (hSteam (hsupsup):):
A
B C
Sensible
Heat
Latent
Heat
hfg
Tsup
Temperature
Enthalpy
Amount ofSuperheat
Degree of Superheat
Tsat
hf
D
Temperature
hg
hsup
= hf
+ hfg
+ Csup
(Tsup
- Tsat
) kJ/kg
Nitesh Kumar, Assistant Professor, Dept. of
Mech & Mfg. Engg.26
e)e) Degree of superheat (DOS):Degree of superheat (DOS):
A
B C
Sensible
Heat
Latent
Heat
hfg
Tsup
Temperatur
Enthalpy
Amount of
Superheat
Degree of Superheat
Tsat
hf
D
Temperature
DOS = (Tsup - Tsat)0C
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a) Enthalpy of Dry saturated Steam:
hg = hf+ hfg kJ/kg
b) Enthalpy of Wet Steam:
h = hf+ x .hfg kJ/kg
c) Enthalpy of Superheated Steam:
hsup = hf+ hfg + Csup (Tsup - Tsat) kJ/kg
d) Degree of superheat (DOS):
DOS = (Tsup - Tsat)0C
e) Amount of superheat (AOS):AOS = Csup (Tsup - Tsat) kJ/kg
Nitesh Kumar, Assistant Professor, Dept. of
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Critical Temperature &Critical Temperature &Pressure.Pressure.
PPcc == 221.2 bar221.2 bar
TTcc == 374.15374.1500CC
At a particular pressure waterwater
is directly converted into drydry
steamsteam without going through
the phase of evaporation. i.e.,
hhfgfg == 00 . This point is called
criticalcritical pointpoint..
Temperature
Enthalpy
Tc
Pc
Pi
P3
P2
P1
hf hfghf
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CriticalCritical pressurepressure::
It is the pressure at which the water is directly converted into
dry steam without undergoing the state of evaporation.
CriticalCritical temperaturetemperature::
It is the corresponding temperature at the critical point.