1. This document discusses key concepts in thermodynamics and heat transfer including definitions of heat, work, internal energy, enthalpy, and entropy. 2. It explains the first and second laws of thermodynamics, including the Kelvin-Planck and Clausius statements. The first law states that energy is conserved while the second law introduces the concept of entropy and the impossibility of perpetual motion machines. 3. Reversible and irreversible processes are defined, with reversible processes being those that can return a system and its surroundings to their initial state without changes to the universe.

1. Thermodynamics & Heat Transfer
Mr. S.S.Sajane
BE(Mech), ME (Heat & Power Engineering)
Department of Mechatronics Engineering,
Sharad Institute of Technology College of Engineering,
Yadrav-Ichalkaranji.

2. Thermodynamic definition of heat:
It is the energy in transition between the system and the
surroundings by virtue of its temperature difference.
SI unit : Joule
Heat & Work Relation Example:
Heat to work  Thermal power plant
Work to heat  Refrigeration

3. Sign Conventions:
Work done BY the system is +ve
work done ON the system is –ve
Heat given TO the system is +ve
Heat rejected by the system is -ve

4. Difference in Heat & Work :

5. Energy:

6. Definition:
“Energy is the ability to do work”.
• Types of energy:
1) Kinetic Energy.
Energy possessed by body due to its motion is called as Kinetic
Energy.
For example a running car, flowing water, etc.
Kinetic Energy=1/2xm×v2
Where,
m = Mass of the object
V = Velocity of the object

7. Example:

8. 2) Potential Energy:
Energy Possessed by a body due to its rest position is
called as potential energy.
For example, a pen on a table, water in a lake, dam, etc.
Potential Energy = m×g×h
Where,
m = Mass of the object (in kilograms)
g = Acceleration due to gravity (m/s2)
h = Height in meters

11. 3. Internal Energy (U):
• The internal energy for a system is the total energy for that system
(potential + kinetic).
• We are interested in tracking the internal energy as it allows us to
know if energy is coming into or out of a system.
• If there is a change in the internal energy of a system, then energy
must have been exchanged between the system and the
surroundings. This energy flow is in the form of either heat or
work. Therefore, we equate any change in the internal energy of a
system with the sum of the heat and the work.
• ΔU=q + w

12. Concept of Enthalpy (H):
• Enthalpy, the sum of the internal energy and the product of the
pressure and volume of a thermodynamic system.
H = U + PV
Or
• The total heat content of the system.
• Enthalpy is the measurement of energy in a thermodynamic
system.
• Enthalpy is not measured directly, however, the change in
enthalpy (ΔH) is measured, which is the heat added or lost by
the system.
ΔH=ΔU+ΔPV

13. Concept of Entropy (S):
• Entropy is the measure of a system’s thermal energy per unit
temperature that is unavailable for doing useful work. Because
work is obtained from ordered molecular motion, the amount of
entropy is also a measure of the molecular disorder, or randomness,
of a system.
• The change in entropy (ΔS) equals the change in heat (ΔQ)
divided by the absolute temperature (T):
• ΔS = ΔQ / T
• Unit : J/k

16. Previous Lecture:
Heat & Work.
Energy and its Types.
Concept of Enthalpy.
Concept of Entropy.

17. Flow Work :

18. Laws of Thermodynamics:
Zeroth law of thermodynamics.
Law of Conservation of Energy.
First law of thermodynamics.
Second law of thermodynamics.

19. Zeroth Law of Thermodynamics:
• The zeroth law of thermodynamics states that if two thermodynamic systems
are each in thermal equilibrium with a third one, then they are also in
thermal equilibrium with each other.
• Let A, B, and C be three systems. If A and C are in thermal equilibrium, and
A and B are in thermal equilibrium, then B and C are in thermal equilibrium.

20. For example:
An ice that has been dropped in a glass
of hot coffee. After some time, the ice (later
water) and the coffee will reach a certain
temperature that is in between that of the ice
and the coffee. Though the two objects were
not in thermal equilibrium at the beginning
but after sometime they will reach thermal
equilibrium and this temperature is in
between the hot and cold temperatures.
• Zeroth law gives us the idea that whether the
heat transfer will take place or not.

21. Law of Conservation of Energy:
• The law of conservation of energy states that energy can neither be
created nor be destroyed. Although, it may be transformed from one
form to another. The total amount of energy in the universe remains
constant.

22. • The amount of energy in any system is determined
by the following equation:
• UT is the total energy of a system
• Ui is the internal energy of a system
• Q is the heat added to, or removed from, the system
• W is the work done by or on the system
• The change in the internal energy of the system is determined
using the equation.

23. First Law of thermodynamics:
It can be stated in different ways as follows:
1) When a closed system undergoes a cyclic process then
the sum of heat interactions is equal to the sum of
work interactions. Mathematically,
ΣQ=Σ W
2) For a cyclic process heat and work are mutually
convertible. Ex: Engine.

24. 3) The change in internal energy is equal
to the difference of the heat transfer into
the system and work done by the system.
ΔU=Q – W
where ΔU denotes the change in
the internal energy of a closed system, Q
denotes the quantity of energy supplied to
the system as heat, and W denotes the
amount of thermodynamic work done by
the system on its surroundings.

25. Limitations of First Law of thermodynamics:
1. It does not give any information regarding the
direction of heat and work transfer.
2. It does not tell whether the system will undergo change
or not.
3. No clarity that how much percentage of one form of
energy converted into another form of energy.

26. Perpetual Motion Machine of First Kind (PMM-I):
• A device or machine that violates
first law of thermodynamics is
called as PMM-I.
• Such a machine will give continuous
work without receiving energy from
other system.
• It is impossible to construct such
machine.

27. Previous Lecture:
Flow Work
Zeroth law of Thermodynamics.
Law of conservation of energy
First Law of thermodynamics.
PMM-I.

28. Second Law of thermodynamics:
There are two statements of Second Law of Thermodynamics.
• The first regarding a heat engine-----Kelvin Planck
Statement.
• Second regarding a heat pump------Clausius Statement.

29. Kelvin Planck Statement:
• We know that Heat(Q) and Work(W) are the two
forms of energy. Both follow the S.I unit Joules
and both are interconvertible. However, work
can be fully converted into heat but heat cannot
be fully converted into work. Hence work is
called as high-grade energy and heat is called as
low-grade energy.
• Statement: It is impossible to construct a
device working on a cycle that would convert
the entire supplied heat energy into equivalent
amount of output work.

30. Example:

31. Clausius Statement:
Statement:
It is impossible to construct a device
that operates in a cycle which extracts heat
from a low temperature reservoir and
supplies to a high temperature reservoir
without any external energy.

32. Example :

33. Perpetual motion machine of Second kind
(PMM-II):
• A machine that violates second law of
thermodynamics is called as perpetual
motion machine of second kind (PMM-II).
• Such a machine will convert the entire heat
into equal amount of output work.
• 100 % Efficiency.
• It is impossible to construct such machine.

35. Reversible Process:
• The process in which the system
and surroundings can be restored
to the initial state from the final
state without producing any
changes in the thermodynamics
properties of the universe is called
a reversible process.

36. Irreversible Process:
• An irreversible process is a
process that cannot return both the
system and the surroundings to
their original conditions.
• Water flows from high level to low
level, current moves from high
potential to low potential, Heat
Flow etc.

37. Equivalence of Kelvin Planck and Clausius Statement :

38. Violation of Kelvin Planck Statement:

39. Violation of Clausius Statement: