JNTUK syllubus, 1st unit of Thermodynamics

1. THERMODYNAMICS
Mr. I. SATISH
ASSISTANT PROFESSOR
MECHANICAL DEPARTEMENT

2. Introduction:
• Thermodynamics is the science of energy transfer and its effect on the physical
properties of substances.
• Thermo means Heat, dynamics means Motion.
• Applications: Steam and nuclear power plants, Internal combustion engines, gas
turbines etc.

7. Thermodynamic System:
• System is defined as a quantity of matter or a region in space upon which
attention is concentrated in the analysis of a problem.
• Everything external to the system is called surroundings by the system boundary.
• The boundary may be either fixed or moving.

8. Systems can be:
• Open: Mass and Energy can transfer between the System and the Surroundings
• Closed: Energy can transfer between the System and the Surroundings, but NOT
mass
• Isolated: Neither Mass nor Energy can transfer between the System and the
Surroundings

10. System :
• All engineering devices/Components are referred as Systems.
• A system is a finite quantity of matter or region upon which our attention is
focused.
Surrounding:
• Things that are external to the system are referred as Surrounding.
Boundary:
• It is an interface between system and surrounding.
• System and surrounding interact through boundary.
• Boundary can be real (or) imaginary.
Boundary can be fixed (or) moving.

11. Interaction Between System and Surrounding
Interaction
between
system and
surrounding
Mass Transfer
Energy Transfer
Heat
Work
Based on the type of interaction, the systems are
classified as
• CLOSED SYSTEM
• OPEN SYSTEM
• ISOLATED SYSTEM

12. • CLOSED SYSTEM
No mass transfer occurs but only energy transfer occurs
Eg: A certain amount of gas enclosed in a cylinder piston arrangement.

13. • OPEN SYSTEM
Both mass transfer and energy transfer occurs
eg: A certain amount of gas entering and leaving a cylinder pistonarrangement.

14. • ISOLATED SYSTEM
Neither mass transfer nor energy transfer occurs.
eg:If our entire universe is considered as a single system then it is an
isolated system.

15. Mass Transfer Energy Transfer Type of System
No Yes Closed System
Yes Yes Open System
No No Isolated System

16. Macroscopic and Microscopic Viewpoint:
• In the macroscopic approach, a certain quantity of matter is considered, without the
events occurring at molecule level being taken into account.
• From the microscopic point of view, matter is composed of myriads of molecules.

18. Thermodynamic Properties, Process and Cycle
• Every system has certain characteristics by which its physical condition may be
described, e.g., volume, temperature, pressure, etc.
• Such characteristics are called properties of the system.
• These all are macroscopic in nature.
• When all properties of a system have definite values, the system is said to exist at a
definite state.
• Any operation in which in which one or more of the properties of a system changes is
called a change of system.

23. PATH
• It is the succession of intermediate states passed during a change
of state.
(OR)
• It is the loci of intermediate states passed during a change of
state.

24. PROCESS
If the path followed by the system during change
of state is specified or defined completely, then it
is called a process.
eg: Constant pressure process
Constant temperature process
Constant volume process
Adiabatic process
Polytropic process

25. CYCLE
Series of processes executed by the system in such a way that the
initial and final states of the system are same.

26. Homogeneous and Heterogeneous:
• A quantity of matter homogeneous throughout in chemical composition and physical
structure is called a phase.
• Every substance can exist in any one of the three phases, viz. solid, liquid and gas.
• A system consisting of a single phase is called a homogeneous system.
• While the system consisting of more then one phase is known as a heterogeneous
system.

27. A system is said to be in thermodynamic
equilibrium if it is in the following equilibriums
Thermal Equilibrium
Mechanical Equilibrium
Chemical Equilibrium

28. Thermal Equilibrium:
The temperature at all points of the system remains the same
anddoesnot changewithtime.
Mechanical Equilibrium:
No unbalanced forces acts within the system or between system
andsurrounding.
Chemical Equilibrium:
Nochemicalreaction takes place within thesystem.

40. Zeroth law of Thermodynamics
• Base for all temperature measurement.
• Thermal equilibrium is the key word for zeroth law
Definition:
When a body A is in thermal equilibrium with a
body B, and also separately with a body C, then
B and C will be in thermal equilibrium with each
other.

41. Zeroth law of Thermodynamics

42. Zeroth law of Thermodynamics

48. Electrical resistance thermometer:

49. Thermocouple:

56. Work:
The action of force on a moving body or through a distance.
In Mechanics the work is defined as:
the work is done by a force as it acts upon a body moving in the direction of
force
In Thermodynamics, Work transfer is considered as occurring between the system and
surrounding.
Work is said to be done by a system if the sole effect on the things external to the
system can be reduced to the rising of a weight.

57. WORK:

59. PdV-Work or Displacement Work:

60. Path function and Point function:

62. Mechanical Forms of Work Expressing Boundary
Work on a P-V Diagram
Since a gas can follow different paths as it expands from state 1 to state 2, each
path will have a different area underneath it.
The work associated with each path will be different because the area under
each curve will be different.
62

63. Mechanical Forms of Work
Some typical process
1. Boundary work at constant volume process.
If the volume is held constant, dv=0 and the boundary
work equation becomes
63

64. Mechanical Forms of Work
Some typical process
2. Boundary work at constant pressure
If the pressure is held constant the boundary work
equation becomes.
64

65. Mechanical Forms of Work
Some typical process
3. Boundary work at constant temperature
If the temperature of an ideal gas system is held
constant, then the equation of state provides the pressure
volume relation.
65

68. Problem 1. Consider as a system, the gas in the cylinder. The cylinder is fitted with a piston on
which number of small weights is placed. The initial pressure is 200kPa, and the initial volume
of the gas is 0.04 m3.
1.Let the gas in the cylinder be heated, and let the volume of the gas increase to 0.1 m3 while
the pressure remains constant. Calculate the work done by the system during this process.

69. 2. Consider the same system and initial condition, but at the same time the cylinder is being
heated and the piston is rising, let the weights be removed from the piston at such a rate that,
during the process the temperature of the gas remains constant.

70. 3. For the same system, let the weights be removed at such a rate that the expression
PV1.3 = const. Again the final volume is 0.1 m3. Calculate the work.

71. 4. Consider the system and initial state as before, but let the piston be held by a pin so that the
volume remains constant. In addition, let heat transfer take place from the cylinder so that the
pressure drops to 100kPa. Calculate the work.

72. Problem:- Consider a gas closed in a piston cylinder arrangement. The gas is initially at
150KPa and occupies a volume of 0.03 m3 The gas is now heated until the volume of
gas increases to 0.2m3 .Calculate the work done by the gas if volume of the gas is
inversely proportional to the pressure.

73. Problem:-A gas under goes a reversible non flow process according to the relation P=(-
3V+15) bar where V is the volume in m3 where P is the pressure in Bar. Determine the
work done when the volume changes from 3 to 6 m3 .

79. Other types of Work Transfer:
1. Electrical Work: 2. Shaft Work:

80. 3. Paddle-wheel Work or Stirring Work:

81. 4. Flow Work:

85. Free expansion with zero work transfer:

87. Heat is the form of energy that is transferred between two systems (or a
system and its surroundings) by virtue of temperature difference.
It is recognized only as it crosses the boundary of a system.
Heat transfer is not a property.
Heat transfer between two states is denoted by Q
A process during which there is no heat transfer is called an adiabatic
process.
Heat Transfer

88. Surrounding
System at higher temperature
looses energy as heat
System and surrounding at
same temperature, no energy
is transferred as heat
System at lower temperature
gains energy as heat
QAbsorbed = Positive (+)
Qreleased = Negative (-)
System System System
Surroundings
Surroundings
Heat Transfer

89. Rate of Heat Transfer:
The rate of heat transfer is the amount of heat transfer
per unit time
It is denoted by and it can be given by:
The unit of is kJ/s, which is equivalent to kW

108. An insulated rigid vessel is divided into two parts by a membrane. One part of the vessel contains air at
10 Mpa and other part is fully evacuated. The membrane ruptures and the air fills the entire vessel. Is
there any heat and / or work transfer during this process? Justify your answer.

109. A certain fluid expands from 10 bar, 0.05m3 to 2 bar, and 0.2m3
according to linear law. Find the work done in the process.

110. A spherical balloon of 0.5 m diameter contains air at a pressure of 500 kPa. The diameter increases to 0.55m in a
reversible process during which pressure is proportional to diameter. Determine the work done by the air in the
balloon during this process. Also calculate the final pressure.