This document provides an overview of thermodynamics presented by Ch.Sravanthi. It begins with defining thermodynamics as the branch of physics dealing with energy, equilibrium, and energy transformations governed by physical laws. Thermodynamics is concerned with the amount of heat transfer as a system changes between equilibrium states. Engineering thermodynamics applies basic thermodynamics to solve engineering problems. The main branches of thermodynamics are then outlined as equilibrium thermodynamics including classical and statistical thermodynamics, chemical thermodynamics, and non-equilibrium thermodynamics. Several key concepts are then defined, including system, surroundings, boundary, state, process, cycle, and properties. The document concludes by discussing temperature, the zeroth

1. THERMODYNAMICS
Presented
By
CH.SRAVANTHI
ASSISTANT PROFESSOR
MECHANICAL ENGINEERING DEPARTMENT
JBIET

2. References
1. Engineering Thermodynamics: PK Nag
/TMH, 5th Edition
2. Thermodynamics – An Engineering
Approach – Yunus Cengel & Boles, TMH

3. Definition of Thermodynamics
•Thermodynamics is the branch of physics
that deals with equilibrium, energy and it’s
transformation, and the laws governing
it’s transformation

4. •Thermodynamics is concerned with the
amount of heat transfer as a system
undergoes a process from one equilibrium
state to another.
•A thermodynamic analysis simply tells us
how much heat must be transferred to
realize a specified change of state to satisfy
the conservation of energy principle.

5. Definition of Engineering Thermodynamics
•The application of basic
thermodynamics for the solution of
engineering problems is called
engineering thermodynamics.

6. Branches of Thermodynamics
1.Equilibrium Thermodynamics
a) Classical Thermodynamics
b) Statistical Thermodynamics
2.Chemical Thermodynamics
3.Non Equilibrium Thermodynamics

7. UNIT 1
Lesson 1 - ( 3 Periods)
• Thermodynamic System
• Surrounding
• Boundary
• Universe
• Control Volume
• Types of System
• Concept of Continuum
• Thermodynamic Equilibrium
• Property, State, Process, Cycle, Reversibility
• Quasi Static Process

8. Difference between Classical Thermodynamics and Statistical Thermodynamics
Classical Thermodynamics
• It is also called as macroscopic
thermodynamics.
• In this approach certain quantity of matter
is considered, without taking into account
the events occurring at molecular level.
• This approach doesn’t require the
knowledge of the behaviour of individual
molecules to study thermodynamics.
• Macroscopic observations are completely
independent of the assumptions regarding
the nature of matter.
Statistical Thermodynamics
• It is also called as microscopical
Thermodynamics.
• From the microscopic point of view, matter
is composed of a large number of small
molecules and atoms.
• This approach requires the knowledge of
the behaviour of individual molecules to
study thermodynamics.
• Microscpic observations are completely
dependent on the assumptions regarding the
nature of the matter.

9. Classical
Thermodynamics
• In microscopic approach, the value of quantity changes
with time so advanced statistical and mathematical
methods are needed to explain the change in the system.
• Large number of variables are required to describe a
system.
• This approach is complicated.
• Changes in properties of molecules can not be sensed
• Examples are velocity, momentum, kinetic energy, impulse
etc.
• The analysis of macroscopic system
requires Simple mathematical formulae.
• Few properties are required to describe a
system.
• This approach is quite simple.
• The changes in properties can be felt by
our senses.
• Examples are Pressure , Temperature etc.
Statistical
Thermodynamics

10. Thermodynamic system
•A thermodynamic system is defined as a
quantity of matter or a region in space
upon which attention is concentrated in
the analysis of a problem.

11. Surroundings
•Everything external to the system
is called the surroundings or
environment.

12. Boundary
• The real or imaginary surface that separates the system from it’s
surroundings is called the boundary.
• Boundary is the contact surface shared by both the system and
surroundings.
• Boundary of system can be fixed or movable.
• The boundary has zero thickness. Thus it can neither contain any
mass nor occupy any volume in space.

13. Universe
•A system and its surroundings together
comprise a universe.
Universe = System + Surrounding

14. Types of Thermodynamic System
•Closed System
•Open System
•Isolated System

15. Open system
Closed system
Isolated system
Thermodynamic
system

16. Closed System
• It is also called as control mass
system.
• It consists of fixed amount of mass
and no mass can cross it’s
boundary.
• Energy in the form of heat or work
can cross it’s boundary.
• Volume of a closed system does
not have to be fixed.
Open System
• It is also called as countrol volume system.
• It consists of fixed volume calledas
control volume and mass can cross it’s
boundary. Boundaries of control volume
is called as control surface.
• Energy in the form heat or work can cross
it’s boundary.
• Mass flow rate may or may not be
constant.

19. Isolated System
• Isolated system is one in which there is no interaction
between the system and surroundings.
• It is of fixed mass and energy.
• There is no mass or energy transfer across the system
boundary.

20. Concept of Continuum
Mean Free Path : The mean free path of a
particle, such as a molecule, is the average
distance the particle travels between collisions
with other moving particles.

21. Knudsen Number : If the Knudsen number is near or greater
than one, the mean free path of a molecule is comparable to a
length scale of the problem, and the continuum assumption
of fluid mechanics is no longer a good approximation. In such
cases, statistical methods should be used.
Continuum Flow
Mean free path
Representative physical scale

22. • As microscopic approach is time consuming and in most of the applications it
is not required to go to the details of individual molecule and then taking out
average.
• The analysis is possible when the size of the system is much larger than the
mean free path of the molecules. Under this situations matter is considered as
continuous. This is called continuum concept. That is matter is uniformly and
continuously distributed.
• In such situations what happens to the individual molecule is of no concern,
and the only interest to know the interaction between system and surroundings.
Such an approach is called macroscopic approach.
• We may follow any approach, but the results should be same, as the results do
not depend upon the method of analysis used.

23. Reason behind considering Continuum
Concept
• Know what happens before and after a certain amount of volume under
consideration.
• Is density constant or varying.
• If it constant, applicable to classical Thermodynamics.
• If it is varying go for statistical Thermodynamics.
• Every property is calculated in macroscopic approach because properties are
having constant values.

25. Thermodynamic Equilibrium
• A system is said to exist in a state of thermodynamic equilibrium when no change in
any macroscopic property is registered.
• An Isolated system always reaches in course of time a state of thermodynamic
equilibrium and can never depart from it spontaneously.
• A system will be in state of thermodynamic equilibrium, if the conditions for the
following three types of equilibrium are satisfied.
1. Mechanical Equilibrium
2. Thermal Equilibrium
3. Chemical Equilibrium
Note: Thermodynamic properties are the macroscopic coordinates
defined for, and significant to only thermodynamic equilibrium states.

26. Mechanical Equilibrium: In the absence of any unbalanced force
within the system itself and also between system and surroundings, the
system is said to be in a state of mechanical equilibrium. If not what
happens?
Chemical Equilibrium : If there is no chemical reaction or transfer
of matter from one part of the system to anotger, such as diffusion or
solution, tge system is said to exist in a state of equilibrium.
Thermal Equilibrium : When a system existing in mechanical and
chemical equilibrium is separated from it’s surroundings by diathermic
wall and if there is no spontaneous change in any property of the
system, the system is said to exist in a state of thermal equilibrium. If
not what happens?

27. Property : Every system has certain characteristics by which it’s physical
condition may be described. Such characteristics are called properties of tge
system. Properties are macroscopic in nature. Eg: Volume, temperature,
pressure etc.
State : When all the properties have definite values, the system is said to exist at
a definite state.
Note: Properties are the coordinates to describe the state of a system. They are
the state variables of the system.
Change of State : Any operation in which one or more properties of the
system changes is called a change of state.
Path : The succession of states passed through during a change of state is
called the path of change of state.

28. Process : When the path is completely specified, the change of state is called a
process. Eg: Constant volume process, constant pressure process.
Thermodynamic Cycle : A thermodynamic cycle is defined as a series of
state changes such that the final state is identical with the initial state.

29. Types of Properties
1. Extensive Properties : A system property that depend on the
system mass is called an intensive or extensive property. Eg:
Volume, Energy.
2. Intensive properties : A system property that does not depend
on the system mass is called an intensive or intensive property.
Eg: Temperature, Pressure. Specific extensive properties or
Extensive properties per unit mass are intensive properties. Eg :
Specific volume, specific energy.

30. Phase : A quantity of homogeneous throughout its
chemical composition and physical structure is called
a phase. Eg: Solid, Liquid, Gas
Homogeneous System : A system consists of a
single phase is called homogeneous system.
Heterogeneous System : A system consists of
more than one phase is called heterogeneous system.

31. Quasi Static Process
Let us consider a system of gas contained in a cylinder. The system
initially is in an equilibrium state, represented by the properties p1, v1, t1. The
weight on the piston just balances the upward force exerted by the gas. If the weight
is removed, there will be an unbalanced force between the system and the
surroundings, and under gas pressure, the piston will move up till it hits the stops.
The system again comes to an equilibrium state, being described by the properties
p2, v2, t2. But the intermediate states passed through by the system are
nonequilibrium states which cannot be described by thermodynamic coordinates.
Figure shows points 1 and 2 as the initial and final equilibrium states joined by
a dotted line, which has got no meaning otherwise.

33. Now if the single weight on the
piston is made up of many very small pieces of weights , and these
weights are removed one by one very slowly from the top of the piston, at any
instant of the upward travel of the piston, if the gas system is isolated, the departure
of the state of the system from the thermodynamic equilibrium state will be
infinitesimally small. So every state passed through by the system will be an
equilibrium state. Such a process, which is but a locus of all the equilibrium points
passed through by the system, is known as a quasi-static process quasi
Meaning almost. Infinite slowness is the characteristic feature of a quasi-static
process. A quasi-static process is thus a succession of equilibrium states. A quasi-
static process is also called a reversible process.

35. Pure Substance
• A pure substance is defined as one that is homogeneous and
invariable in chemical composition throughout its mass.
• The relative amounts of the chemical elements constituting the
substance ae also constant.
• Eg: Gaseous air, steam water mixture, combustion products of a
fuel.

36. • Mixture of air and liquid air is not a pure substance.
• Atmospheric air is not a pure substance.
• Two Property Rule : The state of a pure substance of a
given mass can be fixed by specifying two independent
intensive properties provided the system is in equilibrium.
This is known as two property rule. The state can thus be
represented as a point on thermodynamic property
diagrams.

37. Thermodynamics or Thermostatics?
Is Thermodynamics Misnomer?
• The science of thermodynamics deals with systems existing in
thermodynamics equilibrium states which are specified by properties.
• However most of the real processes are dynamic and non – quasi static,
although the initial and final states of the system might be in
equilibrium.
• The name thermodynamics is said to be a misnomer, since it does not
deal with the dynamics of heat. The term ‘thermostatics’ then seems to
be more appropriate.

38. • A change from one equilibrium state of a system to
another is called a thermodynami processs.
• Thermodynamics does not determine how much time
such a process will take, and the final state is independent
of the amount of time it takes to reach the equilibrium
state.
• To describe a state the system must be in thermodynamic
equilibrium.

39. • However, for any process to occur, the system
cannot be exactly in thermodynamic equilibriu
becausee at least one thermodynamic variable must
change.
• To attain equilibrium of every state in a process,
the process should be Quasi-static process.
• Hence, the term thermodynamics is not
inappropriate.

40. Assignment 1
(Chapter 1 + Chapter 2)
Chapter 1
1. Lesson 1 – (1-1)
2. Lesson 2 – (1-2)
3. Lesson 3 – (1-3)
4. Lesson 4 – (1-4)
Chapter 2
1. Lesson 1 – (2-1)
2. Lesson 2 – (2-2)
3. Lesson 3 – (2-3)
4. Lesson 4 – (2-4)
5. Lesson 5 – (2-5)

41. Assignment Questions from Lesson 1 of Unit 1
Q1. Write an essay about what you have learnt in lesson 1 in 100
words?
Q2. Give practical examples for Open System, Closed System and
Isolated System? Draw the diagrams?
Q3. Give 4 examples for each Intensive Properties and Extensive
Properties?

42. Lesson 2 - ( 4 Periods)
• Various Non- flow Processes, Properties, End States
• Heat and Work Transfer
• Irreversible Process
• Causes of Irreversibility
• Energy in Transition – Types, Displacement and Other Forms of Work, Heat
• Point Function and Path Function
• Exact and inexact differentials

43. Work Transfer
Work is said to be done by a system if the sole effect on
things external to the system can be reduced to the raising
of a weight
• Work done by the system
• Work done on the system

46. Free Expansion

47. pdV work or Displacement work

48. Quasi-static pdV work

49. Path function
or
dW is an
inexact and
imperfect
differential

50. Point function
dV is Exact or
Perfect Differential

51. • For a cyclic process initial and final states of the system are same and hence
change in any property is zero.
• Cyclic integral of a property is always zero.
Cyclic Integral for the Closed Path

52. pdV work in various Quasi-static Processes or
Nonflow Processes
• Constant pressure process
• Constant volume process
• Constant temperature process
• Polytropic process
• Adiabatic process

53. Constant pressure process or Isobaric Process
or Isopiestic Process

54. Constant volume process or Isochoric Process
or Isometric Process

55. Constant temperature process or Isothermal
process

56. Polytropic process

58. Adiabatic process
W 1-2 = (p1V1 – p2V2) / ( - 1)

60. Reversible and Irreversible Process
Reversible Process : Revrssible process is one which is
performed in such a way that at the conclusion of the
process, both the system and surroundings may be restored
to their initial states, without producing any changes in the
rest of universe.
Irreversible Process : Any natural process carried out with a
finite gradient is an irreversible process.

61. Causes of Irreversibility
1) Lack of equilibrium during the process.
a) Heat Transfer through a Finite Temperature Difference
b) Lack of Pressure Equilibrium within the Interior of the
System or between the System and the Surroundings
c) Free Expansion

62. 2) Involvement of dissipative effects.
a) Friction
b)Paddle-Wheel Work Transfer
c) Transfer of Electricity through a Resistor

64. Polytropic Index or Adiabatic Index
Calculation

65. Relations Deduced from pVn = C

67. Heat Transfer
• Heat transfer is defined as the transmission of energy from region
to another as a result of temperature gradient.
• Q>0 : Heat Transfer to the system
• Q<0 : Heat Transfer from the system

68. Specific Heat at Constant Pressure and Specific
Heat at Constant Volume
• Specific heat of a substance is defined as the amount of heat
required to raise a unit mass of the substance through a unit rise
in temperature.

69. Types of Walls
• Adiabatic Wall : It is an insulating wall which doesn’t
allow heat to flow from one system to another. This
means temperature of both the systems won’t change
with time.
• Diathermic Wall : It is a conducting wall which allows the
flow of heat between any 2 systems.

71. Types of Work

72. Assignment Questions from Lesson 2 of Unit 1

73. Assignment Questions from Lesson 2 of Unit 1

74. Lesson 3 - ( 3 Periods)
• Zeroth Law of Thermodynamics
• Concept of Temperature
• Principles of Thermometry
• Reference Points
• Constant Volume Gas Thermometer
• Scales of Temperature
• Ideal Gas Scale

75. Zeroth Law of Thermodynamics
•When a body C is in thermal equilibrium
with a body A, and also separately with a
body B, then A and B will be in thermal
equilibrium with each other.

77. Concept of Temperature
• Temperature : Temperature is the degree of hotness or coldness of an object.
• Thermometer : Any object with one measurable property that changes as it’s
temperature changes is called as a thermometer.
• Thermometric Property : Property of an object that changes as it’s temperature
changes is called as a thermometric property.
• Thermometric Substance : The particular substance that exhibits in the change in
thermometric property is known as a thermometric substance.
• Thermometry : It is a process of measuring temperature.

78. Principles of Thermometry

79. Types of Thermometers

80. Reference Points
Methods Used before 1954 Methods Used after 1954

81. Reference Points
Before 1954
• Ice point : The temperature at which pure ice coexisted in equilibrium with
air saturated water at one atmosphere pressure.
• Steam point : The temperature of equilibrium between pure water and pure
steam at one atmosphere pressure.
After 1954
• Triple point of water : The state at which ice, liquid water and water vapour
coexist in equilibrium.

82. Constant Volume
Gas Thermometer
• Bulb B
• Capillaruly tube C
• Mercury Manometer M
• Lip L

84. Scales of
Temperature
• Celsius Scale – SI – Ordinary
Temperature
• Kelvin Scale ( Thermodynamic
temperature scale ) – SI –
Absolute Scale of Celsius scale
• Farenheit Scale – English
system – Ordinary Temperature
Scale
• Rankine Scale – English System
– Absolute scale of Farenheit
scale

86. Assignment Questions from Lesson 3 of Unit 1

88. Lesson 4 - ( 3 Periods)
• Joule’s Experiment
• Energy in State
• First Law of Thermodynamics, Corollaries
• First Law Applied to a Process
• First Law Applied to a Flow System
• Steady Flow Energy Equation
• Throttling and Free Expansion Processes
• Flow Processes

89. Joule’s Experiment

90. First Law Applied for a Closed System
Undergoing a Cycle

91. Energy in State

92. Energy – A Property of The System

95. First Law of Thermodynamics applied to a
process in a Open System

96. First Law of Thermodynamics applied to a
process in a Closed System

97. Perpetual Motion Machine of The First Kind
• PMM 1: There can be no machine which would continuously supply mechanical work without some
other form of energy disappearing simultaneously.
• Converse of PMM 1: There can be no machine which would continuously consume work without
some other form of energy appearing simultaneously.

101. Steady Flow Energy Equation

109. Unsteady Flow Energy Equation

112. Mixing of Fluids

114. Nozzle

115. Diffuser

116. Turbine

117. Compressor and Pump

118. Heat Exchanger

119. Throttling Device

120. Assignment Questions from Lesson 4 of Unit 1