2. • Prime movers,
• Sources of energy,
• Types of prime movers,
• Force and mass, Pressure, Work, Power, Energy, Heat,
• Temperature, Units of heat, Specific heat capacity,
• Interchange of heat, Change of state,
• Mechanical equivalent of heat, Internal energy, Enthalpy,
Entropy, efficiency,
• Statements of Zeroth Law,
• First law and Second Law of Thermodynamics
CONTENTS
3. • In engineering, a prime mover is an engine
that converts fuel to useful work.
• So anything that converts fuel energy into
useful work is a primemover.
PRIME MOVER
4. • Various energy sources.
1. Conventional energy sources
– Coil, oil, uranium
2. Non conventional energy
sources
– Energies like Solar, wind, biogas
and biomass, ocean thermal,
geothermal, fuel cells, hydrogen,
tidal etc.
SOURCES OF ENERGY
5. • There are a wide variety of different types of
prime movers. Each is designed to use a
different type of energy source.
1. Thermal prime movers
– Eg. Heat engines
2. Electric power prime movers
– Electric motors
3. Hydraulic power prime movers
– Turbines
TYPES OF PRIME MOVERS
6. • Force and Mass:
Something which changes or tends to change the
state of rest or of uniform motion of a body in a
straight line is called force.
Its defined by Newton’s second law of motion.
Unit is Newton (N)
• Mass is the amount of matter contained in a
body.
Unit is kg.
BASIC DEFINATIONS
7. • Pressure:
• Pressure is force per unit area.
P=F/A.
• Its units are atmosphere,bar,pascal.N/m2.
• A diagram for relation between relative
pressure and absolute pressure is shown here.
• Pabs=Patm+Pguage
1
8. • Units of pressure & its relation:
1 N/m2=1 pascal
But,1 bar=10^5 pascal
So, 1 bar=10^5 N/m2
• It can also measured by taking reference of
the pressure of Mercury(Hg).
• 1atm=1.01325 bar=760 mm of Hg.
9. • Work:
A force is said to do work when it acts on a
body, and there is a displacement of the point
of application in the direction of the force.
i.e, as the bowler throws the ball, he works
on ball by applying force.
• It is denoted by W=F*D
here F=force
D=distance covered by object
• Unit of work is Joule.
10. • Power:
It is known by work done in unit time.
or
Rate of doing work.
P=W/s
• The SI unit of power is watt.
• 1 watt=1 J/s
• Other units are KW, MW, etc.
11. • Energy:
energy is
a property of objects, transferable among
them via fundamental interactions, which can
be converted in form but not created or
destroyed.
• Unit of energy is joule(J).
12. • Heat:
Simply we can say about heat,
heating is transfer of energy, from a hotter
body to a colder one, other than by work or
transfer of matter.
It occurs spontaneously whenever a suitable
physical pathway exists between the bodies.
• SI unit of heat is also joule(J).
13. • Temperature:
A temperature is a numerical measure of hot
and cold.
or we can say
thermal state of body which distinguishes a
hot body from a cold body.
• Main units of temperature is centigrade,
Fahrenheit, Kelvin, etc.
14. • The specific heat is the amount of heat per
unit mass required to raise the temperature
by one degree Celsius.
• Q = m c dT
• Here the product of mass and heat is known
as HEAT CAPACITY of substance.
SPECIFIC HEAT
15. • It is the energy stored in the system.
• Joule’s law of internal energy states that internal
energy of perfect gas is only depends on
temperature.
• It is denoted by U.
• We can’t measure internal energy but we can find
change in it.
INTERNAL ENERGY
16. • Enthalpy is a defined thermodynamic
potential, designated by the letter "H", that
consists of the internal energy of the system
(U) plus the product of pressure (P)
and volume (V) of the system:
H=U+PV
ENTHALPY
17. • Entropy is a law of nature in which everything
slowly goes into disorder.
• The entropy of an object is a measure of the
amount of information it takes to know the
complete state of that object, atom by atom.
• The entropy is also a measure of the number
of possible arrangements the atoms in a
system can have. In this sense, entropy is a
measure of uncertainty.
ENTROPY
18. • It can be defined as the ratio of work output
to the given work.
• The work we achieve from the system by
giving unit work is the Efficiency of system.
EFFICIENCY
19. • The zeroth law of thermodynamics states that
if two thermodynamic systems are each
in thermal equilibrium with a third, then all
three are in thermal equilibrium with each
other.
ZEROTH LAW OF
THERMODYNAMICS
2
20. • Energy is neither created nor destroyed, thus
the energy of the universe is a constant.
However, energy can certainly be transferred
from one part of the universe to another.
FIRST LAW OF
THERMODYNAMICS
21. • CLAUSIUS STATEMENT: It is impossible for a
self acting machine working in a cyclic process
unaided by any external agency, to convey
heat from a body at a lower temperature to a
body at a higher temperature.
SECOND LAW OF
THERMODYNAMICS
22. • KELVIN PLANK STATEMENT: It is impossible to
construct an engine, which while operating in
a cycle produces no other effect except to
extract heat from a single reservoir and do
equivalent amount of work.
24. The Nature of a Gas:
• have mass
• easy to compress
• have low densities
• fill containers completely
• diffuse quickly (move through each)
• exert pressure (depends on temperature)
25. Kinetic-Molecular Theory (KMT)
describes the behavior of gases
• A gas consists of very small particles
• The distances between gas particles are relatively
large.
• Gas particles are in constant, random motion.
• Collisions between gas particles are perfectly
elastic.
• Average KE of particles depends only on the
temperature of the gas.
• There is no attractive force between particles of a
gas.
26. Variables That Effect Gases
• Moles (n) – the amount of gas.
• Volume (V) – the size of the container that holds
the gas in liters (L).
• Temperature (T) – the speed or kinetic energy of
the particles in kelvin (oC +273)
• Pressure (P) – The outward push of gas particles on
their container in atmospheres (atm) or millimeters
of mercury (mm Hg) or pounds per square inch
(psi)
*Think of pressure as the number of collisions
between gas particles and their container.
27. • if P increases, V decreases
• If P decreases, V increases
• If T increases, V increases
• if T decreases, V decreases
• If P increases, T increases
• if P decreases, T decreases
28. STP – Standard Temperature Pressure
• The behavior of a gas depends on its
temperature and the pressure at which the
gas is held.
• So far we have only dealt with gases at STP.
Standard Temperature and Pressure.
• 273 kelvins and 1 atm.
29. The Gas Laws
• Boyle’s Law
• Charles’s Law
• Gay-Lussac’s Law
• The Combined Gas Law
• The Ideal Gas Law
30. Boyle’s Law
• The Pressure-Volume Relationship
• The pressure and volume of a sample of gas
at constant temperature are inversely
proportional to each other.
(As one goes up, the other goes down)
• P1V1 =P2V2
• If 3 of the variables are known, the fourth
can be calculated.
31. Boyle’s Law
• The gas in a 20.0mL container has a pressure
of 2.77atm. When the gas is transferred to a
34.0mL container at the same temperature,
what is the new pressure of the gas.
P1V1 =P2V2
2
11
2
V
VP
P
mL
atmmL
P
0.34
)77.2(0.20
2
atmP 63.12
32. Boyle’s Law
• If a set amount of gas is transferred into a
larger container, would the pressure go up
or down?
• Would there be more collisions, or fewer
collisions with the container holding the
gas?
• More volume (space) means fewer
collisions with the container, therefore
pressure goes down. (From 2.77 atm to
1.63 atm)
33. Charles’s Law
• The temperature-volume relationship
• At constant pressure, the volume of a fixed
amount of gas is directly proportional to its
absolute temperature.
•
2
2
1
1
T
V
T
V
If 3 of the variables are known, the
fourth can be calculated.
34. Charles’s Law
• What will be the volume of a gas sample at
355K if its volume at 273K is 8.57L?
2
2
1
1
T
V
T
V
1
21
2
T
TV
V
kelvin
kelvinL
V
273
)355(57.8
2
LV 1.112
35. Charles’s Law
• If the temperature of a given quantity of
gas is increased, what will happen to the
volume it occupies? (In an elastic
container?)
• Gas particles moving faster would have
more collisions with the container and
exert more force to enlarge the volume of
the elastic container.
• In this case, from 8.57L to 11.1L.
36. Gay-Lussac’s Law
• The Temperature-Pressure Relationship
• If a volume of a sample of gas remains
constant, the temperature of a fixed
amount of gas is directly proportional to its
pressure.
•
2
2
1
1
T
P
T
P
If you know 3 of the variables, you can
calculate the 4th.
37. Gay-Lussac’s Law
• The gas left in a used aerosol can is at a pressure of
2.03atm at 25oC. If this can is thrown onto a fire,
what is the pressure of the gas when its temperature
reaches 928oC?
•
•
2
2
1
1
T
P
T
P
1
21
2
T
TP
P
K
Katm
P
298
)1201(03.2
2
atmP 18.82
38. Gay-Lussac’s Law
• If the temperature of a fixed amount of gas
goes up, the particles will have more
collisions. More collisions means the pressure
will increase.
• In this case, when the temp went up the
pressure increased from 2.03atm to 8.18atm.
39. The Combined Gas Law
• If more than one variable changes, a different
equation is needed to analyze the behavior of
the gas.
•
2
22
1
11
T
VP
T
VP
5 of the variables must be known to
calculate the 6th.
40. The Combined Gas Law
• The volume of a gas-filled balloon is 30.0L at
40oC and 1.75atm of pressure. What volume
will the balloon have at standard temperature
and pressure?
2
22
1
11
T
VP
T
VP
12
211
2
TP
TPVV
)313(00.1
)273)(75.1(0.30
2
Katm
KatmL
V
LV 8.452
41. The Combined Gas Law
• You have a fixed volume of gas. The
temperature decreases which would cause
fewer collisions and the pressure decreases
which causes fewer collisions as well. What
can you do to volume to make the pressure
decrease???
• Increase it. More space means fewer
collisions.
42. The Ideal Gas Law
• Describes the physical behavior of an ideal
gas in terms of the pressure, volume,
temperature and the number of moles of
gas.
• Ideal – a gas as it is described by the
kinetic-molecular theory postulates.
• All gases are REAL gases… which behave like
ideal gases only under most ordinary
conditions.
43. The Ideal Gas Law
• Only at very low temperatures and very high
pressures do real gases show significant non-
ideal behavior.
• We will assume that gases are close to ideal
and that the ideal gas equation applies.
44. Ideal Gas Equation
PV=nRT
• P-pressure
• V-volume
• n-number of moles of gas
• R-ideal gas constant (universal gas constant) 0.0821
atm.L/mol.K
or 62.396 torr.L/mol.K
• T-temperature
45. Ideal Gas Equation
• What is the volume occupied by 9.45g of C2H2
at STP?
nRTPV
P
nRT
V
First, calculate amount
of gas in moles.
22
22
22
03788.26
1
45.9
HgC
HmolC
HgCn
223629328.0 HmolCn
46. Ideal Gas Law
LV 1345217.8
LV 13.8
P
nRT
V
atm
kKmolLatmmol
V
00.1
273)/0821.0(3629328.0
47. Ideal Gas Law
• How many moles of a gas at 100oC does it take
to fill a 1.00L flask to a pressure of 1.5atm?
RT
PV
n
nRTPV
)373(/0821.0
)00.1(5.1
kKmolLatm
Latm
n
moln 0490.0
48. • Internal energy is defined as
the energy associated with the random,
disordered motion of molecules.
INTERNAL ENERGY
49. • Cv = du/dT......(1)
Cp = dh/dT......(2)
h = u+Pv
dh = d(u+Pv) = du+Pdv+ vdp...(3)
(3)-->(2)
Cp = du+Pdv+ vdp / dT = du / dT+Pdv / dT+ vdp
/ dT = Cv+(Pdv + vdp) / dT....(4)
For gas ideal, Pv=RT
RELATION BETWEEN Cp & Cv.
50. • Pdv+vdp = RdT...(5)
(5)-->(4)
Cp = Cv +RdT/dT = Cv+R
Cp-Cv = R
So, as temperature change, Cp-Cv will be the
same as gas constant, R.
51. • There are various types of non flow processes
just like
1. Reversible constant volume process
2. Reversible constant pressure process
3. Isothermal process
4. Adiabatic process
5. Polytropic process
TYPES OF NON FLOW
PROCESSES
52. TYPES OF NON FLOW
PROCESSES
• There are various types of non flow processes
just like
1. Reversible constant volume process
2. Reversible constant pressure process
3. Isothermal process
4. Adiabatic process
5. Polytropic process
62. PROPERTIES OF STEAM
• Steam is the vapour or gaseous phase of water
• It is produced by heating of water and carries
large quantities of heat within itself.
• Hence, it could be used as a working
substance for heat engines and steam
turbines.
• It does not obey ideal gas laws but in
superheated state it behaves like an ideal gas.
62
63. • Steam exists in following states or types or
conditions.
• (i) Wet steam (mixture of dry steam and some
water particles) – evaporation of water into
steam is not complete.
• (ii) Dry steam (dry saturated steam) – all water
is completely converted into dry saturated
steam.
• (iii) Superheated steam – obtained by further
heating of dry saturated steam with increase in
dry steam temperature.
63
65. • ENTHALPY OF STEAM
• Enthalpy of liquid or Sensible heat (hf)
It is the amount of heat required to raise the temperature of one kg of water
from 0°C to its saturation temperature (boiling point) at constant pressure.
(Line R-S)
hf = cpw (tsat – 0) kJ/kg
cpw = 4.187 kJ/kgK = specific heat of water
• Enthalpy of Evaporation or Latent heat (hfg)
• It is the amount of heat required to change the phase of one kg of water from
saturated liquid state to saturated vapour state at constant saturation
temperature and pressure. (Line S-T)
• Enthalpy of dry saturated steam (hg)
• It is the total amount of heat required to generate one kg of dry saturated
steam from water at
• 0°C. (Line R-S-T)
• hg = hf + hfg
65
66. Enthalpy of wet steam (h)
It is the total amount of heat required to generate one kg of wet steam having
dryness fraction x from water at 0°C. It is the sum of sensible heat and latent heat
taken by the dry part (x) of the wet steam.
h = hf + x(hfg)
Enthalpy of superheated steam (hsup)
It is the total amount of heat required to generate one kg of superheated steam
at required superheat temperature from water at 0°C. Superheated steam
behaves like an ideal gas and obeys gas laws. (Line R-S-T-U)
hsup = hf + hfg + cps (Tsup – Tsat)
hsup = hg + cps (Tsup – Tsat)
cps = 2.1 kJ/KgK = specific heat of superheated steam
Heat of superheat
Amount of heat required to get superheated steam from dry saturated steam is
called heat of superheat. (Line T-U)
Heat of superheat = cps (Tsup – Tsat) kJ/Kg
66
67. Degree of superheat
It is the temperature difference between superheated steam and dry
saturated steam.
Degree of superheat = (Tsup – Tsat)
Dryness Fraction of Saturated Steam (x )
It is a measure of quality of wet steam. It is the ratio of the mass of dry steam
(ms) to the mass of total wet steam (ms+mw), where mw is the mass of water
particles in suspension.
x = ms/( ms+mw)
Quality of Steam
It is the representation of dryness fraction in percentage: Quality of Steam =
100(x)
Wetness Fraction
It is the ratio of the mass of water vapor (mw) to the mass of total wet steam (ms
+mw)
Wetness fraction = mw/( ms+mw) = (1-x)
Priming
It is the wetness fraction expressed in percentage.
Priming = (1 - x) 100 67
68. SPECIFIC VOLUME OF STEAM
It is the volume occupied by steam per kg of its mass.
Specific volume of dry steam (vg) : Its value can be obtained directly from the
steam tables
Specific volume of wet steam (v) : v = x (vg)
Specific volume of superheated steam (vsup): vsup = vg (Tsup/Tsat)
INTERNAL ENERGY OF STEAM:
h = u + Pv
u = h – Pv
P = Pressure of steam
v = Specific volume of steam
ug = hg – P(vg) for dry saturated steam
u = h – P (v) for wet steam
usup = hsup – P(vsup) for superheated steam
68
69. Calorimeters
Calorimeters are used for measurement of
dryness fraction of steam.
Types:
Barrel Calorimeter
Separating Calorimeter
Throttling Calorimeter
Combined Calorimeter
69
71. • Let
• mb =mass of the barrel (kg)
• mw =mass of the water before the steam goes in (kg)
• ms= mass of stem condensed (kg)
• T1= temperature of the water before the steam goes in
(oc)
• T2 =temperature of the water after the steam goes in (oc)
• Cb= relative heat capacity of the metal of the barrel (no
units)
• hf =specific enthalpy of the saturated liquid (steam) (kJ/kg)
• hfg =specific enthalpy of the evaporar of steam(kJ/kg)
• x =dryness fraction (no units)
• hf1= specific enthalpy of the water at temperature T1
(kJ/kg)
• Hf2= specific enthalpy of the water at temperature T2
(kJ/kg)
71
72. • Here known amount of water is filled in the
calorimeter. Then certain quantity of steam from
the main pipe is taken into the calorimeter.
• Steam and water mixes together and so
condensation of steam takes place and mass of
water in the calorimeter increases.
• Latent and sensible heat of steam is given to water
and its temperature will increase.
72
73. • Amount of heat lost by steam = Heat gain by water
and calorimeter
• ms(hf1+xhfg-hf2)=mb.cb(t2-t1)+mw.cpw(t2-t1)
• =(mb.cb+mwcpw)(t2-t1)
• =((mb × cb)/cpw +mw)(t2-t1)cPW
• (mb × cb)/cpw = water equi. Calorimeter
• Limitation
• 1)method is not accurate
• 2)losses are more at higher temp. diff.
73
75. •In this type of calorimeter water particles from the steam are
separated first in the inner chamber and its mass mw can be
measured.
•The dry steam is then condensed in the barrel calorimeter and its
mass ms can be calculated from the difference in mass of water of
barrel
calorimeter.
•So dryness fraction x = ms/(ms + mw)
•Limitation: It gives approximate value of x as total separation of
water particles from the steam is not possible by mechanical means.
75
76. Throttling Calorimeter
• Throttling
• A throttling process is one in which the fluid is
made to flow through a restriction,
• e.g. a partially opened valve or an orifice
plate, causing a considerable loss in the
pressure of the fluid.
76
79. •In this calorimeter a throttling valve is used to throttle the steam.
•The pressure of steam reduces after throttling. Pressure and
temperature of steam before and after throttling is measured.
•Enthalpy of steam before and after throttling remains constant.
•of water particles.
79
80. •To measure dryness fraction condition of steam after throttling must
be superheated steam.
•Enthalpy of stem before throttling = Enthalpy of stem after throttling
Limitation: Steam must become superheated after throttling. That
means it is not very useful for steam containing more amount of water
particles.
80
82. •The limitations of separating and throttling calorimeters can be
overcome if they are
used in series as in this type of calorimeter.
•It gives accurate estimation of dryness fraction.
x = x1. x2
x1 = dryness fraction of steam measured from separating
calorimeter.
x2 = dryness fraction of steam measured from throttling
calorimeter.
82
83. Reference-Sources
• Image References
• 1 – http://docs.engineeringtoolbox.com/documents/587/absolute_gauge_pressure.png
• 2 - https://sp.yimg.com/ib/th?id=HN.608050323071501280&pid=15.1&P=0
• 3 -
http://upload.wikimedia.org/wikipedia/commons/thumb/9/9d/Isochoric_process_SVG.svg/250px-
Isochoric_process_SVG.svg.png
• 4- http://voer.edu.vn/file/55477
• 5- http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/imgheat/isoth.gif
• 6 - http://mechanical-engineering.in/forum/uploads/blog-0248615001384049799.gif
• 7- http://static.zymergi.com/blog-steam-formation.gif
• 8,9,10,11Elements of Mechanical Engineering by H.G. Katariya, J.P Hadiya, S.M.Bhatt , Books India
Publication.
• Content References
• – Elements of Mechanical Engineering by H.G. Katariya, J.P Hadiya, S.M.Bhatt , Books India
Publication.
• -Elements of Mechanical Engineering by V.K.Manglik, PHI
• -Elements of Mechanical Engineering by R.K Rajput.
• -Elements of Mechanical Engineering by P.S.Desai & S.B.Soni
