In this topic (Thermodynamics)the students will be able to analyze and evaluate Zeroth law and First law of thermodynamic cycles used for energy production - work and heat, within the natural limits of conversion.

1. 12/31/2016 Ravi Vishwakarma
UNIT-4

2. Contents
1. Thermodynamics
2. Macroscopic & Microscopic point of view
3. Concept of Continuum
4. Thermodynamic Equilibrium
5. Thermodynamic Properties
6. Quasi Static Process
7. Energy & Its Form
8. Zeroth Law of Thermodynamics
9. First Law of Thermodynamics
12/31/2016 Ravi Vishwakarma

3. Thermodynamics
Thermodynamics is a branch of science which deals with energy.
Engineering thermodynamics is modified name of this science
when applied to design and analysis of various energy conversion
system. Thermodynamics is core to engineering and allows
understanding of the mechanism of energy conversion.
12/31/2016 Ravi Vishwakarma

4. Macroscopic view point of thermodynamics
• In this approach, a certain quantity of matter is considered, without
taking into account the events occurring at the molecular level.
• This macroscopic approach to the study of thermodynamics that
does not require knowledge of the behavior of individuals particles.
• Macroscopic thermodynamics is only concerned with the effect of
the action of many molecules ,and these effect can be perceived by
human senses.
• The macroscopic observations are completely independent of the
assumptions regarding the nature of matter.
12/31/2016 Ravi Vishwakarma

5. Microscopic view point of thermodynamics
• From the microscopic view point ,matter is composed of a large
number of small molecules and atoms.
• This microscopic approach to the study of thermodynamics that
require knowledge of the behavior of individuals particles.
• Microscopic thermodynamics is concerned with the effect of the
action of many molecules, and these effect cannot be perceived by
human senses.
• The microscopic observations are completely dependent on the
assumptions regarding the nature of matter.
12/31/2016 Ravi Vishwakarma

6. Concept of continuum
In engineering thermodynamics where focus lies upon the gross
behavior of the system and substances in it, the statistical approach is to
be kept aside and classical thermodynamics approach be followed.in
classical thermodynamics ,for analysis the atomic structure of
substance is considered to be continuous. For facilitating the analysis
this concept of continuum is used in which the substance is treated free
from any kind of discontinuity.
12/31/2016 Ravi Vishwakarma

7. Thermodynamic Equilibrium
A system is considered to be in a thermodynamic equilibrium when it is
in thermal equilibrium ,mechanical equilibrium and chemical
equilibrium. A system is said to be in thermal equilibrium when the
temperature of the system is uniform. A system is said to be in
mechanical equilibrium having uniform pressure as well as the effect of
gravity is not significant. A system is said to be in chemical equilibrium
,there is no chemical reactions take place or no chemical changes occur.
12/31/2016 Ravi Vishwakarma

8. Thermodynamic Properties
Thermodynamic properties are the observable characteristics of the
Thermodynamic system. Pressure ,temperature volume, viscosity
,modulus of elasticity etc. are the examples of property.
Intensive Properties –the intensive properties are those properties
which have same value for any part of the system or the properties that
are independent of the mass of system are called intensive properties.
Example-Pressure ,temperature
Extensive Properties-Extensive Properties on the other hand are those
which depend upon the mass of system and do not maintain the same
value for any part of the system. Example-Mass, volume, energy,
enthalpy etc.
12/31/2016 Ravi Vishwakarma

9. Quasi Static Process
Basically the thermodynamics systems are concerned with the system
of equilibrium state. Whenever a system undergoes a change from one
state to another state is called process.
Consider a piston cylinder assembly with a gas enclosed within the
cylinder .piston carries many small weights on the piston. The system
is initially in equilibrium with pressure P1,tempertaure T1 and volume
V1.when these small weights are removed one by one very slowly. The
unbalanced potential is infinitesimally small. the piston will move
upward very slowly so that each state will consider as an equilibrium
state. The path followed by these equilibrium state on removal of each
masses called a quasi-static or quasi-equilibrium process. It may
represent as a continuous line or graph.
12/31/2016 Ravi Vishwakarma

10. 12/31/2016 Ravi Vishwakarma
1
2
Equilibrium State
P
V
Reversible & Quasi static
Process

11. Energy & Its Form
“Energy is usually defined as the ability to do mechanical work”.
It is indeed quite difficult to precisely define the energy. Energy can be
classified in the following general categories:
Potential energy: this type of energy is based an relative position of bodies in
a system i.e. elevation in a gravitational field.
Potential energy=mgz
Here g is the gravitational acceleration and elevation z is measured from some
reference point.
Kinetic energy: It is based on the relative movement of bodies. For a mass m
moving with certain velocity c the kinetic energy could be mathematically
expressed as:
12/31/2016 Ravi Vishwakarma
2
.
2
1
cmKE 







12. Internal Energy: Internal energy of a system is the energy associated with the
molecular structure at the molecular level. Internal energy is sum of energy
associated with molecules which may have translational ,vibrational and
rotational motion etc. and respective energies causing these motions.
Total Energy=KE+PE+IE
Where
KE=Kinetic energy
PE=Potential energy
IE=Internal energy
12/31/2016 Ravi Vishwakarma

13. Zeroth Law of thermodynamics
Zeroth law of thermodynamics states that if the bodies A and B are in thermal
equilibrium with a third body C separately then the two bodies A and B shall
also be in thermal equilibrium with each other. This is the principle of
temperature measurement.
12/31/2016 Ravi Vishwakarma
A B
C
Thermal EquilibriumThermal Equilibrium
Thermal Equilibrium

14. First Law of Thermodynamics
First law of thermodynamics states that “in closed system undergoing a cyclic
process the net work done is proportional to the net heat taken from the
surrounding’’ or “ for any cycle of a closed system the net heat transfer equals
the net work”
Mathematically expression for the first law of thermodynamics can be
rearranged and it shall be ,
Which shows that the quantity is a thermodynamics property.
12/31/2016 Ravi Vishwakarma
  0 Wq 
  0 Wq 