AHMEDABAD INSTITUTE
OF TECHNOLOGY
SUBJECT : ENGINEERING THERMODYNAMICS
ENROLLMENTNO:120020119538
GUIDED BY : MR. ALPESH Parmar
 BASIC CONCEPTS

Thermodynamic can be defied as the
science
of ‘ENERGY’.
1) Thermo - meaning hot or heat
 2) Dynamics - meaning power or
powerful
 The word ‘THERMODYNAMICS’ means
study of heat related to matter in
motion.

 Thermodynamics
follows
 It
may be defined as
is science the deals with the interaction
between energy and material systems.
 It is law of science which deals with the
relations among heat, work and properties
of system which are in equilibrium.

In thermodynamics, there are four laws
as

Zeroth law : It represent the concept of
temperature, and deals with thermal
equilibrium.
“If two bodies are each in thermal
equilibrium with a third body, they are
also in thermal equilibrium with each
other”
Body
Body
B
A
Body
C

First law : It represent the concept of
internal energy.
“energy can be neither created nor be
destroyed, energy can changed from one
form to another form”

Second law : It indicates the limit of
converting heat into work and introduce
principle of increase of entropy.

kelvin-plank statement :
“It is impossible for any device as
heat engine that operates on a cycle to
receive heat from a single reservoir and
produce a net amount of work.”
 Third
law : It concerned with the level of
availability of energy and defined the
absolute zero of entropy.
“The entropy of all perfect crystalline
substance is zero at absolute zero
temperature.”
 MICROSCOPIC AND
MACROSCOPIC POINT OF VIEW
Microscopic approach:

This approach to thermodynamics is
concerned with individual behaviour of
molecule.

It is known as statistical
thermodynamics.

The description of system is so
complicated in which larger number of
variables are required.






Macroscopic approach:
This approach to thermodynamics is
concerned with overall or gross behaviour
of molecule.
It is known as classical
thermodynamics.
The description of system is simple
which only few properties are required.
The behaviour of the system is found
by using simple mathematical formula.
 THERMODYNAMIC SYSTEM
System
Boundar
y
Surroundings
system : It is defined as a quantity of
matter or a region in space chosen for
study.

surrounding : It is the matter of region
out side of system.

Boundary : The boundary is contact
surface shared by both system and the
surrounding.
 Universe : The combination of system
and the surroundings together is usually
refered to as the universe.


The system can be classified as
1) closed system
2) open system
3) isolated system
1)
Closed system : In this system no mass
transfer across the system boundary. but
energy, in form of heat or work , cross
the boundary as shown in fig.
Closed system
Open system
2) Open system : In this system the mass
as well as energy transfer across the
boundary of system as shown in fig.
3) Isolated system : In this system, fixed
mass and fixed energy, and there is no
mass or energy transfer across the system
boundary as shown fig.
Homogeneous and heterogeneous system
 Homogeneous system : A system which
consists of a single phase is termed as
homogeneous system.
 Heterogeneous system : A system which
consists of two or more phases is called
heterogeneous system.


Phase : It is quantity of matter which is
homogeneous through in chemical
composition and physical structure.
 THERMODYNAMIC
PROPERTIES
Intensive properties : These properties
do not depend on the mass of the system.
Ex. Tempreture,pressure,density
 Extensive properties : These properties
depend on the mass of the system.
Ex. Volume,mass,total energy

State : It is the condition of the system at
an instant of time as described by its
properties.
 Process : Any change that a system
undergoes from one state to another state
is called a process.
 Path : It is series of state through which a
system passes during a process.

P
2
Process
A
Process
B
1
V

Cycle : It is defined as a series of state
changes such that the final state is
identical with the initial state.
 THERMODYNAMIC
EQUILIBRIUM
Equilibrium: A state of balance
“A system is said to be in a state of thermodynamic
equilibrium if the value of properties is the same at
all points in the system.”
 Thermal equilibrium: If the temperature Is the same
throughout the entire system.
 Mechanical equilibrium: If there is no change in
pressure at any point of the system with time.


Chemical equilibrium: If the chemical composition of
a system does not change with time, that is no
chemical reactions occur.

QUASI-STATIC PROCESS

When process proceeds in such way that
the system remains close to an
thermodynamic equilibrium state at all
times,it is called a quasi-static process.

let consider system of gas contained in
cylinder. The system initially is in an
equilibrium state,and describe by properties
p1,v1,T1. the upward force exerted by gas on
the piston. If the weights is removed, there
will be unbalanced forced between the
system and the surroundings. Due to gas
pressure, the piston will move up the stops.

Then system again comes to the
equilibrium state which described by the
properties p2,v2,T2. but the intermediate
state through by the system are nonequilibrium and it will not be possible to
describe the path.
Non-quasi-static
process
Quasi-static
process
gas
(Fast expansion)
Non quasi-static
process
gas
(slow expansion)
Quasi-static
process


Thus process 1-2 is non-quasi-static
process. It represent in dotted line on p-v
diagram.
If above process 1-2 takes place slowly,
then each step, there is only an infinitesimal
(very small part) change in properties. it is
possible, if single weight on the piston is
replaced by number of many small pieces of
weights. These weight are removed one by
one very slowly from the top of the piston. If
piston moved slowly, the molecule will have
sufficient time to redistribute. As a result, the
pressure inside the cylinder will always be
uniform and will rise at the same rate at all
locations. so every state passed through all
the equilibrium point is called ‘QUASI-STATIC
PROCESS’


A quasi-static process is also called a
reversible process. The main characteristic
of this process is a succession of
equilibrium states and infinite slowness.
Example Of quasi-static process
1) iso-thermal process : Temperature
constant
2) iso-baric process : pressure constant
3) iso-choric process : volume constant
 Temperature and zeroth law of
thermodynamic
 The zeroth law of thermodynamics: If two
bodies are in thermal equilibrium with a third
body, they are also in thermal equilibrium
with each other.

By replacing the third body with a
thermometer, the zeroth law can be
restated as two bodies are in thermal
equilibrium if both have the same
temperature reading even if they are not
in contact.
Two bodies reaching thermal equilibrium after bein
brought into contact in an isolated enclosure.
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