The document is a comprehensive overview of basic thermodynamics, covering its definitions, laws, types of systems, properties, and processes. It explains concepts such as internal energy, enthalpy, and various thermodynamic processes including isothermal and adiabatic changes. Additionally, it discusses the laws of thermodynamics, including the Zeroth, First, Second, and Third Laws, detailing their implications and applications.

1. DEPARTMENT OF MECHANICAL
ENGINEERING ,
LNCT,BHOPAL
BT-203, B.M.E
Unit-4
THERMODYNAMICS
Prepared By… Prof. Sachin Kumar Nikam
Assistant Professor

2. Basic Thermodynamics
Thermodynamics Laws
Internal energy, Enthalpy
Thermodynamics Process

3. BASIC THERMODYNAMICS
What is thermodynamics
System , Surrounding, System Boundary
Thermodynamic Properties
Thermodynamics State
Process
Path
Cycle

4. What is thermodynamics:-
The branch of physical science that deals with the relations between heat and other forms
of energy (such as mechanical, electrical, or chemical energy), and, by extension, of the
relationships between all forms of energy.
American biophysicist Donald Haynie claims that thermodynamics was coined in 1840
from the Greek root θέρμη therme, meaning “heat”, and δύναμις dynamis, meaning
“power”.
Example of Thermodynamics:-
Melting Ice Cube.
Sweating in a Crowded Room.
Taking a Bath.
Flipping a Light Switch.
Use of Thermodynamics:-
Properties can be combined to express internal energy and thermodynamic potentials,
which are useful for determining conditions for equilibrium and spontaneous processes.
With these tools, thermodynamics can be used to describe how systems respond to
changes in their environment.

5. A system in thermodynamics is nothing more than the collection of matter that is being
studied.
In a thermodynamic analysis, the system is the subject of the investigation.
System , Surrounding, System Boundary
There are three types of systems in thermodynamics:
Open,
Closed,
Isolated

6. •An open system can exchange both energy
and matter with its surroundings. The stovetop
example would be an open system, because
heat and water vapor can be lost to the air.
•A closed system, on the other hand, can
exchange only energy with its surroundings,
not matter. If we put a very tightly fitting lid
on the pot from the previous example, it would
approximate a closed system.
• An isolated system is one that cannot
exchange either matter or energy with its
surroundings. A perfect isolated system is hard
to come by, but an insulated drink cooler with
a lid is conceptually similar to a true isolated
system. The items inside can exchange energy
with each other, which is why the drinks get
cold and the ice melts a little, but they
exchange very little energy (heat) with the
outside environment.

7. A boundary is a closed surface surrounding a system through which energy and mass may
enter or leave the system.
Everything external to the system is the surroundings.
Thermodynamic Properties:
The characteristics which can be used to describe
the condition or state of a system is
called thermodynamics property. Examples :
temperature, pressure, volume, energy etc.
Thermodynamic properties can be divided into
two general classes,
Intensive
Extensive properties.
An intensive property is one that does not depend
on the mass of the substance or system.
Temperature (T), pressure (P) and density (r)
are examples of intensive properties.
An extensive property of a system depends on the
system size or the amount of matter in the system.
Volume, energy, and mass are examples of
extensive properties.

8. Thermodynamics State
Thermodynamics, a thermodynamic state of a system is its condition at a specific time, that
is fully identified by values of a suitable set of parameters know as state variables(Properties)
state parameters or thermodynamic variables.
Thermodynamics Process:- A thermodynamic process is defined as a change from one
equilibrium macro state to another macro state.
Or
A thermodynamic process is a passage of a thermodynamic system from an initial to a final
state of thermodynamic equilibrium. The initial and final states are the defining elements of
the process

9. Process f-i
Following are the various types of thermodynamic process.
Quasi-static Process
Cyclic Process
Free Expansion
Isothermal Process
Adiabatic Process
Isobaric Process
Isochoric Process
Reversible process
Irreversible process

10. Quasi-static Process:
The process in which change in any of the parameters take place at such a slow speed that
the values of P,V, and T can be taken to be, practically, constant, is called a quasi-static
process.
Cyclic Process
In a system in which the parameters acquire
the original values, the process is called a
cyclic process.

11. Free Expansion
Such an expansion in which no external work is done and the total internal energy of the
system remains constant is called free expansion.
Isothermal Process
The process in which change in pressure
and volume takes place at a constant
temperature, is called a isothermal
change. It may be noted that in such a
change total amount of heat of the
system does not remain constant.

12. Adiabatic Process: The process in which change in pressure and volume and temperature
takes place without any heat entering or leaving the system is called adiabatic change.
Isobaric Process
The process in which change in
volume and temperature of a gas
take place at a constant pressure is
called an isobaric process.

13. Isochoric Process:-The process, during
which the volume of the system remains
constant, is an isochoric process. Heating of a
gas in a closed cylinder is an example of
the isochoric process.
Reversible process:-
In thermodynamics, a reversible process is
a process whose direction can be returned to
its original position by inducing infinitesimal
changes to some property of the system via its
surroundings. Throughout the entire reversible
process, the system is in thermodynamic
equilibrium with its surroundings.
Any reversible process is a quasi-static one.
However, quasi-static processes involving
entropy production are not reversible

14. Irreversible process:-An irreversible process is a process that cannot return both the
system and the surroundings to their original conditions. That is, the system and the
surroundings would not return to their original conditions if the process was reversed.
Some examples of irreversible processes are electric current flow through a conductor with
a resistance, magnetization or polarization with hysteresis, inelastic deformation, fluid flow
with shock wave, and mixing of fluid with different temperatures, pressures, and/or
compositions.
Path:-A thermodynamic process path is the path or series of states
through which a system passes from an initial equilibrium state to a
final equilibrium state and can be viewed graphically on a pressure-
volume (P-V), pressure-temperature (P-T), and temperature-entropy
(T-s) diagrams.
Thermodynamic cycle :-A thermodynamic cycle consists of a
linked sequence of thermodynamic processes that involve
transfer of heat and work into and out of the system, while
varying pressure, temperature, and other state variables within
the system, and that eventually returns the system to its initial
state.

15. Thermodynamics Laws:-
The laws of thermodynamics describe the relationships between thermal energy, or
heat, and other forms of energy, and how energy affects matter.
Following are the four law of thermodynamics:
Zeroth law
Ist Law of Thermodynamics
II Law of thermodynamics
III Law of thermodynamics

16. Zeroth law:- The Zeroth Law of Thermodynamics states that if two bodies are each in
thermal equilibrium with some third body, then they are also in equilibrium with each other.
This says in essence that the three bodies are all the same temperature. This property makes
it meaningful to use thermometers as the “third system” and to define a temperature scale.
The thermometer may be the most well-
known example of the zeroth law in action.
For example, say the thermostat in your
bedroom reads 35 degrees Celsius. This means
that the thermostat is in thermal equilibrium
with your bedroom.

17. Ist Law of Thermodynamics:-The first law of thermodynamics, or the law of
conservation of energy. The change in a system’s internal energy is equal to the difference
between heat added to the system from its surroundings and work done by the system on its
surroundings. Its consist two statement
a) Energy can neither be created nor destroyed (Law of conservation of energy).
b) Total energy of an isolated system is constant. Mathematically it can be stated that, the
change in internal energy of a system is equal to the heat added to the system plus the
amount of work done on the system by the surroundings.

18. II Law of thermodynamics:-The Second Law of Thermodynamics says that processes that
involve the transfer or conversion of heat energy are irreversible.
It also states that the state of entropy of the entire universe, as an isolated system, will always
increase over time. The second law also states that the changes in the entropy in the universe
can never be negative.
Mathematically, the second law of thermodynamics is represented as;
ΔSuniv > 0
where ΔSuniv is the change in the entropy of the universe.
Different Statements of The Law:-
There are two statements on the second law of thermodynamics which are;
Kelvin- Plank Statement
Clausius Statement
Limitations of First Law of Thermodynamics
The limitation of the first law of thermodynamics is that
1. It does not say anything about the direction of flow of heat.
2. It does not say anything whether the process is a spontaneous process or not. In actual
practice, the heat doesn't convert completely into work.
PMM1 (Perpetual motion machine of first kind):
A hypothetical machine which can produce useful energy(work) without any source or
which can produce more energy than consumed. It violates the first law of Thermodynamics.

19. Kelvin–Planck statement :-The Kelvin–Planck statement (or the Heat Engine Statement)
of the second law of thermodynamics states that it is impossible to devise
a cyclically operating heat engine, the effect of which is to absorb energy in the form of
heat from a single thermal reservoir and to deliver an equivalent amount of work. This
implies that it is impossible to build a heat engine that has 100% thermal efficiency.
Clausius’s Statement:-
It is impossible to construct a device operating in a cycle that can transfer heat from colder
body to warmer without consuming any work.
In other words, unless the compressor is driven by an external source, the refrigeratowon’t
be able to operate.
Heat pump and Refrigerator works on Clausius’s statement.

20. Equivalence of Kelvin-Planck and Clausius Statements:-
The Clausius and Kelvin-Planck statements of the second law are entirely equivalent. This
equivalence can be demonstrated by showing that the violation of either statement can result
in violation of the other one.

21. A perpetual motion machine of the second
kind, or PMM2 is one which converts all the
heat input into work while working in a cycle.
A PMM2 has an ηth of 1.
III Law of thermodynamics
The third law of thermodynamics states that the entropy of a system approaches a constant
value as the temperature approaches absolute zero.
The third law of thermodynamics is also called as Nernst law. It provides the basis for
the calculation of absolute entropy of the substances.
The Importance of third law of thermodynamics
is given below:
It helps to calculate the thermodynamic properties.
It is helpful to measure the chemical affinity.
It explains the behavior of the solids at very low
temperature.
It also helps to analyze the chemical and phase
equilibrium.
PMM2

22. Internal Energy (U)
The internal energy is a property of the system and depends on temperature only.
Q = W + dU
If there is a case when heat is supplied to a fix volume of gas (thermodynamic system)
confined in fix boundary of the system i.e. there is no change in volume of gas during
supplying of heat, then there will not be any work. So
W = 0 and dU = Q
As Q is heat supplied to gas keeping it at constant volume, it can be calculated as mCvdt.
Thus change in internal energy is heat exchanged at constant volume and can be calculated
as: dU = Q= mCvdt
Enthalpy (H):
It is also a property of thermodynamic system which is calculated in terms of other
properties. It is defined as the sum of internal energy and product of pressure and volume of
a thermodynamic system. Thus it is a calculated property and loosely defined as total heat
content of the system. It is denoted by H.
H = U + PV
And dH = dU + d (PV)
dH = dU + P.dV + V. dP

23. A non-flow system is one that contains a fixed quantity of matter into which no matter is
allowed to flow in but energy may flow in or out. Such system can be made to undergo
a process by varying its properties and the path can take variety of forms that can affect the
amount of work done and heat absorbed or rejected.
If we consider a fixed mass m of a gas confined in closed boundaries and remaining at
constant pressure P, while absorbing heat Q. The temperature of gas will increase and
simultaneously it will expand from initial volume V1 to final volume V2. So, by first law of
thermodynamics
Q = W + ∆U
Or
mCp(T2 - T1) = (U2 - U1) + P(V2 -V1)
Also enthalpy change during this constant pressure process 1- 2
H2-H1 = (U2-U1) + (P2V2-P1V1)
= (U2 - U1) + P(V2 -V1)
∴ P1=P2 in constant pressure process
H2-H1 = mCp(T2 - T1)
Thus change in enthalpy is also dependent on temperature only and is always calculated
as Cp∆T.
NON-FLOW PROCESS

24. When infinitely small heat 𝛅Q is supplied to gas from outside through the wall of cylinder,
the gas tends to expand and forces the piston weight F to move up. Let piston moves by a
short distance, dl. Then the infinitesimal work done can be calculated as:
=
= F/A x dl x A
= P.dV
= Pressure x Change in volume
Total work during a non-flow process 1-2 i.e. compression or expansion of gases can be
calculated as taking integral of P.dV.

25. Different Non Flow thermodynamic processes:

39. The main difference between isentropic and polytrophic process 𝞬 is replace by n.

42. Throttling Process:
Sometimes a pressure drop occurs adiabatically when fluids flow through a restriction, such
as an orifice, a valve, or a porous medium. If the changes in kinetic and potential energy are
negligible, this flow process is called as throttling process, which causes no change
in enthalpy between the inlet and the outlet: ΔH = 0.
Some properties of throttling processes are:
•In an ideal gas, enthalpy is a function of
temperature only, and temperature remains
constant.
•Temperature decreases for most real gases.
•Liquids may evaporate.