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Noida Institute of Engineering and Technology, Greater Noida
2nd Law of thermodynamics & Entropy
Nisha Yadav
Assistant Professor
[Department of Mechanical
Engineering]
5/6/2020
1
Unit: 2
Nisha Yadav Thermodynamics[TD] Unit - 2
Subject Name
Thermodynamics
Course Details: B.Tech. (3rd Sem)
• Course Objectives
• Course Outcomes
• CO-PO Mapping
• CO-PSO Mapping
• Prerequisite and recap
• Limitations of first law of thermodynamics
• 2nd law of thermodynamics
• Direction of change
• Heat Engines
• Heat Pumps & Refrigerators
• Carnot Cycle
• 2nd law statements
• Equivalence of both statements
• Entropy of ideal gas
• The Carnot Principle
• P-V diagram
2
Content
Nisha Yadav Thermodynamics[TD] Unit : 25/6/2020
• To learn about work and heat interactions, and balance of energy
between system and its surroundings.
• To learn about application of First law to various energy conversion
devices.
• To evaluate the changes in properties of substances in various
processes.
• To understand the difference between high grade and low-grade
energies and second law limitations on energy conversion.
• To get conversant with pure substance , psychrometric charts , human
comfort conditions , vapour processes and thermodynamics vapour
cycles , Refrigeration cycles and performance estimation.
3
Course Objective
Nisha Yadav Thermodynamics[TD] Unit : 2
5/6/2020
• CO1- Identify and use units and notations in Thermodynamics, State
and illustrate Zeroth and First law of Thermodynamics.
• CO2- To understand the concepts of Second law of Thermodynamics
and Entropy, Apply the first and second laws to various gas process
and cycle.
• CO3- Understand the role of Thermodynamic cycles, Availability and
Irreversibility, second law of efficiency and different thermodynamic
relations.
• CO4- Ability to recognize and understand the different forms of pure
substances and to get conversant with properties of steam, dryness
fraction measurement. Also get conversant with Psychrometric Charts,
Psychrometric processes and human comfort conditions.
• CO5- Study and analyze different Refrigeration Cycles. Understand
the effect of Supercooling and sub-cooling and change in evaporator
and condenser pressure on performance of Refrigeration Cycle. 4
Course Outcome
Nisha Yadav Thermodynamics[TD] Unit : 25/6/2020
CO PO1 PO2 PO3 PO4 PO5 PO6 PO7 PO8 PO9 PO10 PO11 PO12
KME301.1 3 3 2 2 1 2 2 1 1 1 1 2
KME301.2 3 3 2 3 1 2 2 1 1 1 1 2
KME301.3 3 3 2 3 1 2 2 1 1 1 1 2
KME301.4 3 3 3 2 1 2 2 1 3 1 1 2
KME301.5 3 3 2 2 1 2 2 1 2 1 1 2
5
CO-PO Mapping
Nisha Yadav Thermodynamics[TD] Unit : 2
5/6/2020
6
CO-PSO Mapping
CO PSO1 PSO2 PSO3 PSO4
KME301.1 3 2 3 2
KME301.2 3 3 3 3
KME301.3 3 3 3 3
KME301.4 3 2 3 3
KME301.5 3 2 1 2
Nisha Yadav Thermodynamics[TD] Unit : 2
5/6/2020
• Student must aware with the basics of heat , temperature and
work etc.
• Student should have basic mathematical equations.
7
Prerequisite and Recap
Nisha Yadav Thermodynamics[TD] Unit : 2
5/6/2020
8
Why 2nd Law of thermodynamics?
Nisha Yadav Thermodynamics[TD] Unit : 2
• The 1st law of thermodynamics states that a certain energy flow
takes place when a system under goes a process or change of
state.
• But , it does not give any information on whether that process or
change of state is possible or not.
• This change of state is possible or not is find out with the help of
2nd law of thermodynamics.
5/6/2020
9
According to 1st Law of thermodynamics?
Nisha Yadav Thermodynamics[TD] Unit : 2
• Work is completely converted in to heat or heat is completely
converted into work.
(δW = δQ and δQ=δW)
• Potential energy can be transformed into kinetic energy or kinetic
energy can be transformed into Potential energy.
(PE→KE and KE→PE)
• Heat flows from hot to cold or from cold to hot.
(Th→ Tl and Tl → Th)
• Gas expands from high pressure to low pressure or from low
pressure to high pressure
5/6/2020
10
Limitation of 1st Law of termodynamics
Nisha Yadav Thermodynamics[TD] Unit : 2
• Heat is not completely converted into work.(Q ˃ W)
• kinetic energy can not be transformed into Potential energy.
(KE ≠> PE)
• Heat flow from cold to hot is not possible.
(Tl ≠> Th)
• Gas expands from low pressure to high pressure is not
possible.
5/6/2020
11
Limitation of 1st Law of termodynamics
Nisha Yadav Thermodynamics[TD] Unit : 2
• 1st law does not help to predict whether the certain process
is possible or not.
• A process can be proceed in particular direction only , but 1st
law does not gives information about direction.
• 1st law not provides sufficient condition for certain process to
take place.
5/7/2020
12
2nd Law of Thermodynamics
Nisha Yadav Thermodynamics[TD] Unit : 2
Heat can not flow itself from cold body to hot
body.
• It is a spontaneous process.
• The 2nd law of thermodynamics is also used to determine the
theoretical limits for the performance of mostly used in
engineering systems like heat engines and refrigerators.
5/7/2020
13
Direction of Change
Nisha Yadav Thermodynamics[TD] Unit : 2
• The second law of thermodynamics asserts that processes
occur in a certain direction and that the energy has quality as
well as quantity.
Hot
Container
Possible
Impossible
Cold
Surroundings
• In above example, two bodies are different temperature are
brought into contact, heat energy flows from the body at
high temperature to that at low temperature. Heat energy
never flow from lower temperature level to higher
temperature without applying external work.
5/7/2020
14
Heat Engines
Nisha Yadav Thermodynamics[TD] Unit : 2
• A heat engine cycle is a thermodynamic cycle in which there is
a net heat transfer to the system and a net work transfer from
the system.
• The system which executes a heat engine cycle is called a heat
engine.
• The function of the eat engine cycle is to produce the work
continuously at the expense of heat input to the system.
• So the efficiency of the heat engine and heat engine cycle is
defined as follows:
 𝑡ℎ
=
Net work output of the cycle
Total heat input to te cycle
5/7/2020
15
Heat Engines
Nisha Yadav Thermodynamics[TD] Unit : 2
The thermal efficiency is always less than 1 or less than
100percent.
 𝑡ℎ
=
𝑊𝑛𝑒𝑡 ,𝑜𝑢𝑡
𝑄𝑖𝑛
where
Wnet ,out = Wout − Win
Qin ≠ Qout
5/7/2020
16
Heat Engines
Nisha Yadav Thermodynamics[TD] Unit : 2
Applying the first law to the cyclic heat engine
Qnet , in Wnet , out  U
Wnet, out Qnet , in
Wnet, out  Qout
The cycle thermal efficiency may be written as

th 
Wnet , out
Q

Qin  Qout
Qin
 1
Qout
in
Qin
5/8/2020
17
Heat Engines
Nisha Yadav Thermodynamics[TD] Unit : 2
A thermodynamic temperature scale related to the heat transfers
between a reversible device and the high and low-temperature
reservoirsby
QL
QH
=
TL
TH
The heat engine that operates on the reversible Carnot cycle is
called the Carnot Heat Engine in which its efficiencyis
1
𝑇 𝐻
𝑇 𝐿
5/8/2020
18
Heat Engines
Nisha Yadav Thermodynamics[TD] Unit : 2
The work-producing device that
best fit into the definition of a
heat engine is the steam power
plant, which is an external
combustion engine.
5/7/2020
19
Heat Pumps and Refrigerators
Nisha Yadav Thermodynamics[TD] Unit : 2
• A device that transfers heat from a low temperature medium to a high
temperature one is the heat pump.
• Refrigerator operates exactly like heat pump except that the desired
output is the amount of heat removed out of the system
• The index of performance of a heat pumps or refrigerators are
expressed in terms of the coefficient of performance.
5/8/2020
20
Heat Pumps and Refrigerators
Nisha Yadav Thermodynamics[TD] Unit : 2
COPR =
TL
TH − TL
=
1
TH
TL
−1
COPHP =
TH
TH − TL
=
1
TL
TH
−1
5/8/2020
21
Heat Pumps and Refrigerators
Nisha Yadav Thermodynamics[TD] Unit : 2
COPHP =
QH
QH − QL
=
QH
W net,in
COPR =
QL
QH − QL
=
QL
W net,in
5/8/2020
12/19/2020 22
Carnot Cycle
Nisha Yadav Thermodynamics[TD] Unit : 2
23
Carnot Cycle
Execution of Carnot cycle in a piston cylinder device
Nisha Yadav Thermodynamics[TD] Unit : 25/8/2020
24
Carnot Cycle
Nisha Yadav Thermodynamics[TD] Unit : 2
Process Description
a-b (1-2)( Isothermal Expansion) Reversible isothermal heat addition at
high temperature
b-c (2-3)( Adiabatic Expansion) Reversible adiabatic expansion from
high temperature to low temperature
c-d(3-4)(Isothermal Compression) Reversible isothermal heat rejection at
low temperature
d-a(4-1)( Adiabatic Compression) Reversible adiabatic compression from
low temperature to high temperature
5/8/2020
12/19/2020 25
Carnot Cycle
Nisha Yadav Thermodynamics[TD] Unit : 2
26
Carnot Cycle
Nisha Yadav Thermodynamics[TD] Unit : 25/8/2020
12/19/2020 27

th

Wnet , out
in
Q
 Qin QoutWnet , out
 Qin Qout
Q
in

th = 1 -
Q
out
in
Q
Qout
Q
in
= m Cp L
T
= m Cp TH
Nisha Yadav Thermodynamics[TD] Unit : 2
Carnot Cycle
28
Carnot Cycle
Nisha Yadav Thermodynamics[TD] Unit : 2
The thermal efficiencies of actual and reversible heat engines
operating between the same temperature limits compare as follows:
The coefficients of performance of actual and reversible refrigerators
operating between the same temperature limits compare as follows
5/8/2020
12/19/2020 29
Carnot Cycle
Nisha Yadav Thermodynamics[TD] Unit : 2
12/19/2020 30
Carnot Cycle
Nisha Yadav Thermodynamics[TD] Unit : 2
12/19/2020 31
Carnot Cycle
Nisha Yadav Thermodynamics[TD] Unit : 2
12/19/2020 32
Carnot Cycle
Nisha Yadav Thermodynamics[TD] Unit : 2
12/19/2020 33
Carnot Cycle
Nisha Yadav Thermodynamics[TD] Unit : 2
12/19/2020 34
Carnot Cycle
Nisha Yadav Thermodynamics[TD] Unit : 2
12/19/2020 35
Carnot Cycle
Nisha Yadav Thermodynamics[TD] Unit : 2
12/19/2020 36
Carnot Cycle
Nisha Yadav Thermodynamics[TD] Unit : 2
12/19/2020 37
Class Test (Numericals)
Q.1 A Carnot engine operates between two reservoirs whose difference in
temperature is 200◦C. If the work output of the engine is 0.5 times the eat rejected ,
make calculations for the temperature of source and sink and the thermal efficiency of
the engine.
Q.2 An engine operation on a Carnot cycle works with in temperature limits of 600
K and 300 K . If the engine receives 2000 KJ of heat , evaluate the work done and
thermal efficiency of the engine.
Q.3 A perfect as flows through a nozzle where it expands in a reversible adiabatic
manner. The inlet conditions are 22 bar, 500 ◦C , 38 m/s. At exit the pressure is 2
bar. Determine the exit velocity and exit area if the flow rate is 4 Kg/s. Take R
190 J/Kg K . And ϒ = 1.35.
Nisha Yadav Thermodynamics[TD] Unit : 2
38
Carnot Cycle
Example1:
A steam power plant
produces 50 MW of net
work while burning fuel
to produce 150 MW of
heat energy at the high
temperature. Determine
the cycle thermal
efficiency and the heat
rejected by the cycle to
the surroundings.
Solution:

th 
Wnet , out
QH

50 MW
150 MW
 0.333 or 33.3%
Wnet , out  QH QL
QL  QH  Wnet, out
 150 MW  50 MW
 100 MW
5/8/2020 Nisha Yadav Thermodynamics[TD] Unit : 2
39
KELVIN PLANK STATEMENT
5/9/2020 Nisha Yadav Thermodynamics[TD] Unit : 2
• It is impossible to construct a heat engine that operates on cycle
to receive heat from single reservoir and produce equivalent
amount of work.
• It implies that it is impossible to build a heat engine that has
100%thermal efficiency.
TH
QH
Heat engine
Wnet
Impossible
40
CLAUSIUS STATEMENT
Nisha Yadav Thermodynamics[TD] Unit : 2
• It is impossible to construct a device as heat pump that
operates in a cycle and produces no effect other then the
transfer of heat from a lower temp body to higher temp body.
• Heat can not itself flow from colder body to hater body.
Heat pump
QL
TH
TL
Impossible
5/9/2020
41
EQUIVALENCE OF THE TWO
STATEMENTS
Nisha Yadav Thermodynamics[TD] Unit : 2
• It can be shown that the violation of one statement leads to a
violation of the other statement, i.e. they are equivalent.
1. Violation of Kelvin-plank statement leading to violation of
Clausius statement.
2. Violation of Clausius statement leading to violation of
Kelvin-plank statement .
5/9/2020
42
EQUIVALENCE OF THE TWO
STATEMENTS
Nisha Yadav Thermodynamics[TD] Unit : 2
Wnet =QH
TL
QL
QH+QL
TH
QH
Heat engine Heat pump
Heat pump
TH
QH
QL
TL
Heat transfer from low-temp body to high-
temp body without work; A violation of the
Clausius statement
A 100% efficient heat engine; violates K-P
Statement
5/9/2020
43
VIOLATION OF KELVIN-PLANK STATEMENT
LEADING TO VIOLATION OF CLAUSIUS
STATEMENT
Nisha Yadav Thermodynamics[TD] Unit : 25/9/2020
44
VIOLATION OF KELVIN-PLANK
STATEMENT LEADING TO VIOLATION
OF CLAUSIUS STATEMENT
5/3/2020 Nisha Yadav Thermodynamics[TD] Unit : 1
45
VIOLATION OF CLAUSIUS STATEMENT
LEADING TO VIOLATION OF KELVIN-PLANK
STATEMENT
5/3/2020 Nisha Yadav Thermodynamics[TD] Unit : 1
12/19/2020 46
PMM II
Nisha Yadav Thermodynamics[TD] Unit : 2
12/19/2020 47
Carnot Theorem and its Corollaries
Nisha Yadav Thermodynamics[TD] Unit : 2
12/19/2020 48
Carnot Theorem
Nisha Yadav Thermodynamics[TD] Unit : 2
12/19/2020 49
Efficiency of Reversible Engine
Nisha Yadav Thermodynamics[TD] Unit : 2
12/19/2020 50Nisha Yadav Thermodynamics[TD] Unit : 2
Numericals on Carnot Theorem
12/19/2020 51Nisha Yadav Thermodynamics[TD] Unit : 2
Numericals on Carnot Theorem
12/19/2020 52Nisha Yadav Thermodynamics[TD] Unit : 2
Numericals on Carnot Theorem
12/19/2020 53Nisha Yadav Thermodynamics[TD] Unit : 2
Numericals on Carnot Theorem
12/19/2020 54
Thermodynamic Temperature Scale
Nisha Yadav Thermodynamics[TD] Unit : 2
“A temperature scale which is independent of the property of
thermometric substance is defined as thermodynamic
temperature scale”.
12/19/2020 55
12/19/2020 56
Thermodynamic Temperature Scale
Nisha Yadav Thermodynamics[TD] Unit : 2
12/19/2020 57
Clausius Inequality
Nisha Yadav Thermodynamics[TD] Unit : 2
12/19/2020 58
Clausius Inequality
Nisha Yadav Thermodynamics[TD] Unit : 2
12/19/2020
Faculty Name Subject code and
abbreviation Unit Number
59
Clausius Inequality
12/19/2020 60
Clausius Inequality
Nisha Yadav Thermodynamics[TD] Unit : 2
12/19/2020 61Nisha Yadav Thermodynamics[TD] Unit : 2
Clausius Inequality
12/19/2020 62Nisha Yadav Thermodynamics[TD] Unit : 2
Numerical on Clausius Inequality
12/19/2020 63
Solution of Numerical on Clausius Inequality
Nisha Yadav Thermodynamics[TD] Unit : 2
12/19/2020 64
Numerical on Clausius Inequality
Nisha Yadav Thermodynamics[TD] Unit : 2
12/19/2020 65Nisha Yadav Thermodynamics[TD] Unit : 2
Solution of Numerical on Clausius Inequality
12/19/2020 66
Numerical on Clausius Inequality
Nisha Yadav Thermodynamics[TD] Unit : 2
12/19/2020 67
Solution of Numerical on Clausius Inequality
Nisha Yadav Thermodynamics[TD] Unit : 2
68
ENTROPY
Nisha Yadav Thermodynamics[TD] Unit : 2
• Entropy is a thermodynamic function of the state of the system can
be interpreted as the amount of order or disorder of a system
• Change in Entropy:-
The change in entropy  S of a system when an amount of thermal
energy Q is added to a system by a reversible process at constant
absolute temperature T is given by:
 S = dQ / T
5/9/2020
69
Example
Nisha Yadav Thermodynamics[TD] Unit : 2
A heat engine removes 100 J each cycle from a heat reservoir at
400 K and exhausts 85 J of thermal energy to a reservoir at 300 K.
Compute the change in entropy for each reservoir.
• Since the hot reservoir loses heat, we have that:
 S = Q / T = -100 J / 400 K = -0.25 JK-1
For the cold reservoir we have:
 S = Q / T = 85 J / 300 K = 0.283 JK-1
Therefore:
The increase in entropy of the cold reservoir is greater than the
decrease for the hot reservoir.
5/9/2020
70
ENTROPY OF IDEAL GAS
Nisha Yadav Thermodynamics[TD] Unit : 2
• An expression for the entropy change of an ideal gas can be
obtained from Eq.
ds =
𝑑𝑢 𝑃 𝑑𝑣
𝑇 + ----- Eq. 1
𝑇
Or
ds = 𝑑ℎ 𝑣 𝑑𝑃
𝑇 𝑇
- ----- Eq. 2
• By employing the property relations forideal gases. By
substituting du=𝑪 𝒗dTand P =
𝑹𝑻
𝑽
into
Eq. 1, the differential entropy change of an ideal gas becomes
ds = 𝐶𝑣
𝑑𝑇 𝑑𝑣
+ R
𝑇 𝑣
5/9/2020
71
ENTROPY OF IDEAL GAS
Nisha Yadav Thermodynamics[TD] Unit : 2
The entropy change for a process is obtained by integrating this
relation between the endstates.
∆𝑆 = 𝐶𝑣
𝑑𝑇
𝑇
+ 𝑅 ln
𝑣2
𝑣1
…………Eq.3
 A second relation for the entropy change of an ideal gas is
obtained in a similar manner by substitutingdh = 𝐶 𝑝dT and V =
𝑅𝑇
𝑇
in Eq. 2 and integrating. The result is
∆𝑆= 𝐶 𝑝
𝑑𝑇
𝑇
+ 𝑅 ln
𝑝1
𝑝2
………….Eq.4
5/9/2020
72
ENTROPY OF IDEAL GAS
Nisha Yadav Thermodynamics[TD] Unit : 2
From Eq.(3) and (4), we see that for constant volume process,
∆𝑆 = 𝐶𝑣
𝑑𝑇
𝑇
= 𝐶𝑣 ln
𝑇2
𝑇1
For constant pressure process, we have
∆𝑆 = 𝐶 𝑝
𝑑𝑇
𝑇
= 𝐶 𝑝 ln
𝑇2
𝑇1
For isothermal process,
∆𝑆 = 𝑅 ln
𝑣2
𝑣1
= 𝑅 ln
𝑝2
𝑝1
5/9/2020
73
THE CARNOT PRINCIPLE
Nisha Yadav Thermodynamics[TD] Unit : 2
The Carnot cycle is a thermodynamic process that describes how a
fluid is used to convert thermal energy into work.
• Characteristics:
• High Efficiency
• Multi-Source Engine
• Better reliability and easier maintenance
• Reversible
• Safe, discrete and oxygen-free
• Modularity and flexibility
5/9/2020
74
P-V DIAGRAM
Nisha Yadav Thermodynamics[TD] Unit : 2
• A pressure volume diagram is used to describe corresponding
changes in volume and pressure in a system.
• The PV diagram, called an indicator diagram, was developed
by James Watt and his employee John Southern (1758–1815)
to improve the efficiency of engines.
isothermal segments (AB and CD) occur when there is perfect
thermal contact between the working fluid and one of the
reservoirs, so that whatever heat is needed to maintain constant
temperature will flow into or out of the working fluid, from or
to the reservoir.
5/9/2020
75
P-V DIAGRAM
Nisha Yadav Thermodynamics[TD] Unit : 2
This is the PV diagram…..
5/9/2020
76
P-V DIAGRAM
Nisha Yadav Thermodynamics[TD] Unit : 2
 adiabatic segments (BC and DA)
occur when there is perfect thermal
insulation between the working
fluid and the rest of the universe,
including both reservoirs, thereby
preventing the flow of any heat into
or out of the working fluid.
5/9/2020
Youtube/other Video Links
https://www.youtube.com/watch?v=77EIce2Nu8Y
https://www.youtube.com/watch?v=zD2XDeBu8sI
https://www.youtube.com/watch?v=0Cn--CqXals
https://www.youtube.com/watch?v=tJAH_cgXc3Q
https://www.youtube.com/watch?v=KOEJ4UvlnAc
https://www.youtube.com/watch?v=XyQ9P4eKn6E
https://www.youtube.com/watch?v=ePTc1mtBmcM
77
Faculty Video Links, Youtube & NPTEL Video Links and Online
Courses Details
5/11/2020 Nisha Yadav Thermodynamics[TD] Unit : 2
78
Youtube & NPTEL Video Links and Online Courses Details
NPTEL/Swayam online course: Fundamental of thermodynamics
5/11/2020 Nisha Yadav Thermodynamics[TD] Unit : 2
https://www.youtube.com/watch?v=tyr6vNII3Bk
https://www.youtube.com/watch?v=uEErWdtkRUM
https://www.youtube.com/watch?v=kNNwrp7tHPU
https://www.youtube.com/watch?v=9GMBpZZtjXM&list=PLseVjnVx50AN97Kav4
UYk3JCuyRQDkL6T
79
Daily Quiz
5/11/2020 Nisha Yadav Thermodynamics[TD] Unit : 2
Q.1.Statement of II law of thermodynamics and equivalence of both the statement.
Q.2.Explain throttling process.
Q.3.What do you mean by “Perpetual motion machine of second kind-PMM 2”?
Q.4.Define principle of entropy increase.
Q.5.What are the limitation of first law of thermodynamics?
Q.6.Explain Carnot engine and Carnot theorem.
Q.7.Statement of third law of thermodynamics.
Q.8.Explain Clausius Inequality.
Q.9. What is the working of Heat engine?
Q.10. What is the difference between Heat pump and Refrigerator?
80
Weekly Assignment
5/11/2020 Nisha Yadav Thermodynamics[TD] Unit : 2
Q.1. A Carnot refrigerator exhaust 250 KJ of heat from a reservoir at 150K and
rejects heat to a reservoir at 450 K this heat serves as the energy input to a
second Carnot refrigerator which separates between 450K and 1500 K.
Determine the COP of
(i) The cold refrigerator
(ii) The Hot refrigerator
(iii) The composite system
Check the answer of composite system with the relation established above.
Q.2. Find the entropy change of 5 Kg of a perfect gas whose temperature
varies from 150°C to 200°C. During the constant volume process the specific
heat varies linearly with absolute temperature and is presented by the relation
(V = 10.45+ 0.009T ) KJ/Kg K.
Q.3. Three Carnot Engines E1, E2, E3 operate between temperatures of 1000K
and 300K. Make calculations for the intermediate temperatures if the works
produced by the engines are in the ratio of 4:3:2.
Q.4. What are the statement of II law of thermodynamics and equivalence of
both the statement?
81
Weekly Assignment
5/11/2020 Nisha Yadav Thermodynamics[TD] Unit : 2
Q.5.Calculate the change in entropy at 368.3 g of ice at 32.0oF32.0oF melts.
The latent heat of fusion of water is 333000 J/kg
Q.6. What is the relationship between Entropy and The Second Law of
Thermodynamics?
N2(g) + 3H2(g) 2NH3(g)
So
298 (J/mol
K)
191.5 130.6 192.3
Q.7.What is the standard entropy change of the reaction below at 298 K with
each compound at the standard pressure?
Q.8.A heat pump is used to meet the heating requirements of a house and
maintain it at 20°C. On a day when the outdoor air temperature drops to 2°C,
the house is estimated to lose heat at a rate of 80,000 kJ/h. If the heat pump
under these conditions has a COP of 2.5, determine the rate at which heat is
absorbed from the cold
82
Q.9.During a cyclic process, a heat engine absorbs 500 J of heat from a hot
reservoir, does work and ejects an amount of heat 300 J into the
surroundings (cold reservoir). Calculate the efficiency of the heat engine?
Q.11.There are two Carnot engines A and B operating in two different
temperature regions. For Engine A the temperatures of the two reservoirs are
150°C and 100°C. For engine B the temperatures of the reservoirs are 350°C
and 300°C. Which engine has lesser efficiency?
Q.10.A cyclic machine, as shown below, receives 325 kJ from a 1000 K
energy reservoir. It rejects 125 kJ to a 400 K energy reservoir and the cycle
produces 200kJ of work as output. Is this cycle reversible, irreversible, or
impossible?
Weekly Assignment
5/11/2020 Nisha Yadav Thermodynamics[TD] Unit : 2
83
MCQ s
1. The entropy of an isolated system can never ____
a) increase
b) decrease
c) be zero
d) none of the mentioned
2. This set of Thermodynamics Multiple Choice Questions & Answers
(MCQs) focuses on “Entropy Principle and its Applications”.
Which of the following is true?
a) for an isolated system, dS>=0
b) for a reversible process, dS=0
c) for an irreversible process, dS>0
d) all of the mentioned
3. According to entropy principle, the entropy of an isolated system can never
decrease and remains constant only when the process is reversible.
a) true
b) false
Nisha Yadav Thermodynamics[TD] Unit : 25/11/2020
84
MCQ s
4. Entropy may decrease locally at some region within the isolated system.
How can this statement be justified?
a) this cannot be possible
b) this is possible because entropy of an isolated system can decrease.
c) it must be compensated by a greater increase of entropy somewhere
within the system.
d) none of the mentioned
5. Clausius summarized the first and second laws of thermodynamics as
a) the energy of the world is constant
b) the entropy of the world tends towards a maximum
c) both of the mentioned
d) none of the mentioned
6. The entropy of an isolated system always ____ and becomes a ____ at the
state of equilibrium.
a) decreases, minimum
b) increases, maximum
c) increases, minimum
d) decreases, maximum
5/11/2020
Nisha Yadav Thermodynamics[TD] Unit : 2
85
MCQ s
7. Entropy principle is the quantitative statement of the second law of
thermodynamics.
a) true
b) false
8. Which of the following can be considered as an application of entropy
principle?
a) transfer of heat through a finite temperature difference
b) mixing of two fluids
c) maximum temperature obtainable from two finite bodies
d) all of the mentioned
9. The final temperatures of two bodies, initially at T1 and T2 can range from
a) (T1-T2)/2 to sqrt(T1*T2)
b) (T1+T2)/2 to sqrt(T1*T2)
c) (T1+T2)/2 to (T1*T2)
d) (T1-T2)/2 to (T1*T2)
Nisha Yadav Thermodynamics[TD] Unit : 2
5/11/2020
86
MCQ s
10. Which of the following processes exhibit external mechanical
irreversibility?
a) isothermal dissipation of work
b) adiabatic dissipation of work
c) both of the mentioned
d) none of the mentioned
5/11/2020 Nisha Yadav Thermodynamics[TD] Unit : 2
87
Old Question Papers
Nisha Yadav Thermodynamics[TD] Unit : 2
5/11/2020
Q.1.A steam engine boiler is maintained at 250°C and water is converted into steam.
This steam is used to do work and heat is ejected to the surrounding air at
temperature 300K. Calculate the maximum efficiency it can have?
Q.2.Three Carnot Engines E1, E2, E3 operate between temperatures of 1000K and
300K. Make calculations for the intermediate temperatures if the works produced by
the engines are in the ratio of 4:3:2.
Q.3.Find the entropy change of 5 Kg of a perfect gas whose temperature varies from
150°C to 200°C. During the constant volume process the specific heat varies linearly
with absolute temperature and is presented by the relation (V = 10.45+ 0.009T )
KJ/Kg K.
Q.4.A Carnot refrigerator exhaust 250 KJ of heat from a reservoir at 150K and
rejects heat to a reservoir at 450 K this heat serves as the energy input to a second
Carnot refrigerator which separates between 450K and 1500 K. Determine the COP
of
(i) The cold refrigerator
(ii) The Hot refrigerator
(iii) The composite system
88
Expected Questions for University Exam
Nisha Yadav Thermodynamics[TD] Unit : 25/11/2020
89
Expected Questions for University Exam
Q.5.There are two Carnot engines A and B operating in two different
temperature regions. For Engine A the temperatures of the two reservoirs are
150°C and 100°C. For engine B the temperatures of the reservoirs are 350°C
and 300°C. Which engine has lesser efficiency?
Q.6.During a cyclic process, a heat engine absorbs 500 J of heat from a hot
reservoir, does work and ejects an amount of heat 300 J into the surroundings
(cold reservoir). Calculate the efficiency of the heat engine.
Q.7.A heat pump is used to meet the heating requirements of a house and
maintain it at 20°C. On a day when the outdoor air temperature drops to 2°C, the
house is estimated to lose heat at a rate of 80,000 kJ/h. If the heat pump under
these conditions has a COP of 2.5, determine the power consumed by the heat
pump.
Q.8.A car engine operates with a thermal efficiency of 35%. Assume the air-
conditioner has a coefficient of performance of 3 working as a refrigerator
cooling the inside using engine shaft work to drive it. How much fuel energy
should be spend extra to remove 1 kJ from the inside?
5/11/2020 Nisha Yadav Thermodynamics[TD] Unit : 2
90
Expected Questions for University Exam
Q.9.A cyclic machine, as shown below, receives 325 kJ from a 1000 K
energy reservoir. It rejects 125 kJ to a 400 K energy reservoir and the cycle
produces 200kJ of work as output. Is this cycle reversible, irreversible, or
impossible?
Q.10.A heat pump is used to meet the heating requirements of a house and
maintain it at 20°C. On a day when the outdoor air temperature drops to
2°C, the house is estimated to lose heat at a rate of 80,000 kJ/h. If the heat
pump under these conditions has a COP of 2.5, determine the rate at
which heat is absorbed from the cold
Nisha Yadav Thermodynamics[TD] Unit : 25/11/2020
915/5/2020 Nisha Yadav Thermodynamics[TD] Unit : 1

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SECOND LAW OF THERMODYNAMICS

  • 1. Noida Institute of Engineering and Technology, Greater Noida 2nd Law of thermodynamics & Entropy Nisha Yadav Assistant Professor [Department of Mechanical Engineering] 5/6/2020 1 Unit: 2 Nisha Yadav Thermodynamics[TD] Unit - 2 Subject Name Thermodynamics Course Details: B.Tech. (3rd Sem)
  • 2. • Course Objectives • Course Outcomes • CO-PO Mapping • CO-PSO Mapping • Prerequisite and recap • Limitations of first law of thermodynamics • 2nd law of thermodynamics • Direction of change • Heat Engines • Heat Pumps & Refrigerators • Carnot Cycle • 2nd law statements • Equivalence of both statements • Entropy of ideal gas • The Carnot Principle • P-V diagram 2 Content Nisha Yadav Thermodynamics[TD] Unit : 25/6/2020
  • 3. • To learn about work and heat interactions, and balance of energy between system and its surroundings. • To learn about application of First law to various energy conversion devices. • To evaluate the changes in properties of substances in various processes. • To understand the difference between high grade and low-grade energies and second law limitations on energy conversion. • To get conversant with pure substance , psychrometric charts , human comfort conditions , vapour processes and thermodynamics vapour cycles , Refrigeration cycles and performance estimation. 3 Course Objective Nisha Yadav Thermodynamics[TD] Unit : 2 5/6/2020
  • 4. • CO1- Identify and use units and notations in Thermodynamics, State and illustrate Zeroth and First law of Thermodynamics. • CO2- To understand the concepts of Second law of Thermodynamics and Entropy, Apply the first and second laws to various gas process and cycle. • CO3- Understand the role of Thermodynamic cycles, Availability and Irreversibility, second law of efficiency and different thermodynamic relations. • CO4- Ability to recognize and understand the different forms of pure substances and to get conversant with properties of steam, dryness fraction measurement. Also get conversant with Psychrometric Charts, Psychrometric processes and human comfort conditions. • CO5- Study and analyze different Refrigeration Cycles. Understand the effect of Supercooling and sub-cooling and change in evaporator and condenser pressure on performance of Refrigeration Cycle. 4 Course Outcome Nisha Yadav Thermodynamics[TD] Unit : 25/6/2020
  • 5. CO PO1 PO2 PO3 PO4 PO5 PO6 PO7 PO8 PO9 PO10 PO11 PO12 KME301.1 3 3 2 2 1 2 2 1 1 1 1 2 KME301.2 3 3 2 3 1 2 2 1 1 1 1 2 KME301.3 3 3 2 3 1 2 2 1 1 1 1 2 KME301.4 3 3 3 2 1 2 2 1 3 1 1 2 KME301.5 3 3 2 2 1 2 2 1 2 1 1 2 5 CO-PO Mapping Nisha Yadav Thermodynamics[TD] Unit : 2 5/6/2020
  • 6. 6 CO-PSO Mapping CO PSO1 PSO2 PSO3 PSO4 KME301.1 3 2 3 2 KME301.2 3 3 3 3 KME301.3 3 3 3 3 KME301.4 3 2 3 3 KME301.5 3 2 1 2 Nisha Yadav Thermodynamics[TD] Unit : 2 5/6/2020
  • 7. • Student must aware with the basics of heat , temperature and work etc. • Student should have basic mathematical equations. 7 Prerequisite and Recap Nisha Yadav Thermodynamics[TD] Unit : 2 5/6/2020
  • 8. 8 Why 2nd Law of thermodynamics? Nisha Yadav Thermodynamics[TD] Unit : 2 • The 1st law of thermodynamics states that a certain energy flow takes place when a system under goes a process or change of state. • But , it does not give any information on whether that process or change of state is possible or not. • This change of state is possible or not is find out with the help of 2nd law of thermodynamics. 5/6/2020
  • 9. 9 According to 1st Law of thermodynamics? Nisha Yadav Thermodynamics[TD] Unit : 2 • Work is completely converted in to heat or heat is completely converted into work. (δW = δQ and δQ=δW) • Potential energy can be transformed into kinetic energy or kinetic energy can be transformed into Potential energy. (PE→KE and KE→PE) • Heat flows from hot to cold or from cold to hot. (Th→ Tl and Tl → Th) • Gas expands from high pressure to low pressure or from low pressure to high pressure 5/6/2020
  • 10. 10 Limitation of 1st Law of termodynamics Nisha Yadav Thermodynamics[TD] Unit : 2 • Heat is not completely converted into work.(Q ˃ W) • kinetic energy can not be transformed into Potential energy. (KE ≠> PE) • Heat flow from cold to hot is not possible. (Tl ≠> Th) • Gas expands from low pressure to high pressure is not possible. 5/6/2020
  • 11. 11 Limitation of 1st Law of termodynamics Nisha Yadav Thermodynamics[TD] Unit : 2 • 1st law does not help to predict whether the certain process is possible or not. • A process can be proceed in particular direction only , but 1st law does not gives information about direction. • 1st law not provides sufficient condition for certain process to take place. 5/7/2020
  • 12. 12 2nd Law of Thermodynamics Nisha Yadav Thermodynamics[TD] Unit : 2 Heat can not flow itself from cold body to hot body. • It is a spontaneous process. • The 2nd law of thermodynamics is also used to determine the theoretical limits for the performance of mostly used in engineering systems like heat engines and refrigerators. 5/7/2020
  • 13. 13 Direction of Change Nisha Yadav Thermodynamics[TD] Unit : 2 • The second law of thermodynamics asserts that processes occur in a certain direction and that the energy has quality as well as quantity. Hot Container Possible Impossible Cold Surroundings • In above example, two bodies are different temperature are brought into contact, heat energy flows from the body at high temperature to that at low temperature. Heat energy never flow from lower temperature level to higher temperature without applying external work. 5/7/2020
  • 14. 14 Heat Engines Nisha Yadav Thermodynamics[TD] Unit : 2 • A heat engine cycle is a thermodynamic cycle in which there is a net heat transfer to the system and a net work transfer from the system. • The system which executes a heat engine cycle is called a heat engine. • The function of the eat engine cycle is to produce the work continuously at the expense of heat input to the system. • So the efficiency of the heat engine and heat engine cycle is defined as follows:  𝑡ℎ = Net work output of the cycle Total heat input to te cycle 5/7/2020
  • 15. 15 Heat Engines Nisha Yadav Thermodynamics[TD] Unit : 2 The thermal efficiency is always less than 1 or less than 100percent.  𝑡ℎ = 𝑊𝑛𝑒𝑡 ,𝑜𝑢𝑡 𝑄𝑖𝑛 where Wnet ,out = Wout − Win Qin ≠ Qout 5/7/2020
  • 16. 16 Heat Engines Nisha Yadav Thermodynamics[TD] Unit : 2 Applying the first law to the cyclic heat engine Qnet , in Wnet , out  U Wnet, out Qnet , in Wnet, out  Qout The cycle thermal efficiency may be written as  th  Wnet , out Q  Qin  Qout Qin  1 Qout in Qin 5/8/2020
  • 17. 17 Heat Engines Nisha Yadav Thermodynamics[TD] Unit : 2 A thermodynamic temperature scale related to the heat transfers between a reversible device and the high and low-temperature reservoirsby QL QH = TL TH The heat engine that operates on the reversible Carnot cycle is called the Carnot Heat Engine in which its efficiencyis 1 𝑇 𝐻 𝑇 𝐿 5/8/2020
  • 18. 18 Heat Engines Nisha Yadav Thermodynamics[TD] Unit : 2 The work-producing device that best fit into the definition of a heat engine is the steam power plant, which is an external combustion engine. 5/7/2020
  • 19. 19 Heat Pumps and Refrigerators Nisha Yadav Thermodynamics[TD] Unit : 2 • A device that transfers heat from a low temperature medium to a high temperature one is the heat pump. • Refrigerator operates exactly like heat pump except that the desired output is the amount of heat removed out of the system • The index of performance of a heat pumps or refrigerators are expressed in terms of the coefficient of performance. 5/8/2020
  • 20. 20 Heat Pumps and Refrigerators Nisha Yadav Thermodynamics[TD] Unit : 2 COPR = TL TH − TL = 1 TH TL −1 COPHP = TH TH − TL = 1 TL TH −1 5/8/2020
  • 21. 21 Heat Pumps and Refrigerators Nisha Yadav Thermodynamics[TD] Unit : 2 COPHP = QH QH − QL = QH W net,in COPR = QL QH − QL = QL W net,in 5/8/2020
  • 22. 12/19/2020 22 Carnot Cycle Nisha Yadav Thermodynamics[TD] Unit : 2
  • 23. 23 Carnot Cycle Execution of Carnot cycle in a piston cylinder device Nisha Yadav Thermodynamics[TD] Unit : 25/8/2020
  • 24. 24 Carnot Cycle Nisha Yadav Thermodynamics[TD] Unit : 2 Process Description a-b (1-2)( Isothermal Expansion) Reversible isothermal heat addition at high temperature b-c (2-3)( Adiabatic Expansion) Reversible adiabatic expansion from high temperature to low temperature c-d(3-4)(Isothermal Compression) Reversible isothermal heat rejection at low temperature d-a(4-1)( Adiabatic Compression) Reversible adiabatic compression from low temperature to high temperature 5/8/2020
  • 25. 12/19/2020 25 Carnot Cycle Nisha Yadav Thermodynamics[TD] Unit : 2
  • 26. 26 Carnot Cycle Nisha Yadav Thermodynamics[TD] Unit : 25/8/2020
  • 27. 12/19/2020 27  th  Wnet , out in Q  Qin QoutWnet , out  Qin Qout Q in  th = 1 - Q out in Q Qout Q in = m Cp L T = m Cp TH Nisha Yadav Thermodynamics[TD] Unit : 2 Carnot Cycle
  • 28. 28 Carnot Cycle Nisha Yadav Thermodynamics[TD] Unit : 2 The thermal efficiencies of actual and reversible heat engines operating between the same temperature limits compare as follows: The coefficients of performance of actual and reversible refrigerators operating between the same temperature limits compare as follows 5/8/2020
  • 29. 12/19/2020 29 Carnot Cycle Nisha Yadav Thermodynamics[TD] Unit : 2
  • 30. 12/19/2020 30 Carnot Cycle Nisha Yadav Thermodynamics[TD] Unit : 2
  • 31. 12/19/2020 31 Carnot Cycle Nisha Yadav Thermodynamics[TD] Unit : 2
  • 32. 12/19/2020 32 Carnot Cycle Nisha Yadav Thermodynamics[TD] Unit : 2
  • 33. 12/19/2020 33 Carnot Cycle Nisha Yadav Thermodynamics[TD] Unit : 2
  • 34. 12/19/2020 34 Carnot Cycle Nisha Yadav Thermodynamics[TD] Unit : 2
  • 35. 12/19/2020 35 Carnot Cycle Nisha Yadav Thermodynamics[TD] Unit : 2
  • 36. 12/19/2020 36 Carnot Cycle Nisha Yadav Thermodynamics[TD] Unit : 2
  • 37. 12/19/2020 37 Class Test (Numericals) Q.1 A Carnot engine operates between two reservoirs whose difference in temperature is 200◦C. If the work output of the engine is 0.5 times the eat rejected , make calculations for the temperature of source and sink and the thermal efficiency of the engine. Q.2 An engine operation on a Carnot cycle works with in temperature limits of 600 K and 300 K . If the engine receives 2000 KJ of heat , evaluate the work done and thermal efficiency of the engine. Q.3 A perfect as flows through a nozzle where it expands in a reversible adiabatic manner. The inlet conditions are 22 bar, 500 ◦C , 38 m/s. At exit the pressure is 2 bar. Determine the exit velocity and exit area if the flow rate is 4 Kg/s. Take R 190 J/Kg K . And ϒ = 1.35. Nisha Yadav Thermodynamics[TD] Unit : 2
  • 38. 38 Carnot Cycle Example1: A steam power plant produces 50 MW of net work while burning fuel to produce 150 MW of heat energy at the high temperature. Determine the cycle thermal efficiency and the heat rejected by the cycle to the surroundings. Solution:  th  Wnet , out QH  50 MW 150 MW  0.333 or 33.3% Wnet , out  QH QL QL  QH  Wnet, out  150 MW  50 MW  100 MW 5/8/2020 Nisha Yadav Thermodynamics[TD] Unit : 2
  • 39. 39 KELVIN PLANK STATEMENT 5/9/2020 Nisha Yadav Thermodynamics[TD] Unit : 2 • It is impossible to construct a heat engine that operates on cycle to receive heat from single reservoir and produce equivalent amount of work. • It implies that it is impossible to build a heat engine that has 100%thermal efficiency. TH QH Heat engine Wnet Impossible
  • 40. 40 CLAUSIUS STATEMENT Nisha Yadav Thermodynamics[TD] Unit : 2 • It is impossible to construct a device as heat pump that operates in a cycle and produces no effect other then the transfer of heat from a lower temp body to higher temp body. • Heat can not itself flow from colder body to hater body. Heat pump QL TH TL Impossible 5/9/2020
  • 41. 41 EQUIVALENCE OF THE TWO STATEMENTS Nisha Yadav Thermodynamics[TD] Unit : 2 • It can be shown that the violation of one statement leads to a violation of the other statement, i.e. they are equivalent. 1. Violation of Kelvin-plank statement leading to violation of Clausius statement. 2. Violation of Clausius statement leading to violation of Kelvin-plank statement . 5/9/2020
  • 42. 42 EQUIVALENCE OF THE TWO STATEMENTS Nisha Yadav Thermodynamics[TD] Unit : 2 Wnet =QH TL QL QH+QL TH QH Heat engine Heat pump Heat pump TH QH QL TL Heat transfer from low-temp body to high- temp body without work; A violation of the Clausius statement A 100% efficient heat engine; violates K-P Statement 5/9/2020
  • 43. 43 VIOLATION OF KELVIN-PLANK STATEMENT LEADING TO VIOLATION OF CLAUSIUS STATEMENT Nisha Yadav Thermodynamics[TD] Unit : 25/9/2020
  • 44. 44 VIOLATION OF KELVIN-PLANK STATEMENT LEADING TO VIOLATION OF CLAUSIUS STATEMENT 5/3/2020 Nisha Yadav Thermodynamics[TD] Unit : 1
  • 45. 45 VIOLATION OF CLAUSIUS STATEMENT LEADING TO VIOLATION OF KELVIN-PLANK STATEMENT 5/3/2020 Nisha Yadav Thermodynamics[TD] Unit : 1
  • 46. 12/19/2020 46 PMM II Nisha Yadav Thermodynamics[TD] Unit : 2
  • 47. 12/19/2020 47 Carnot Theorem and its Corollaries Nisha Yadav Thermodynamics[TD] Unit : 2
  • 48. 12/19/2020 48 Carnot Theorem Nisha Yadav Thermodynamics[TD] Unit : 2
  • 49. 12/19/2020 49 Efficiency of Reversible Engine Nisha Yadav Thermodynamics[TD] Unit : 2
  • 50. 12/19/2020 50Nisha Yadav Thermodynamics[TD] Unit : 2 Numericals on Carnot Theorem
  • 51. 12/19/2020 51Nisha Yadav Thermodynamics[TD] Unit : 2 Numericals on Carnot Theorem
  • 52. 12/19/2020 52Nisha Yadav Thermodynamics[TD] Unit : 2 Numericals on Carnot Theorem
  • 53. 12/19/2020 53Nisha Yadav Thermodynamics[TD] Unit : 2 Numericals on Carnot Theorem
  • 54. 12/19/2020 54 Thermodynamic Temperature Scale Nisha Yadav Thermodynamics[TD] Unit : 2 “A temperature scale which is independent of the property of thermometric substance is defined as thermodynamic temperature scale”.
  • 56. 12/19/2020 56 Thermodynamic Temperature Scale Nisha Yadav Thermodynamics[TD] Unit : 2
  • 57. 12/19/2020 57 Clausius Inequality Nisha Yadav Thermodynamics[TD] Unit : 2
  • 58. 12/19/2020 58 Clausius Inequality Nisha Yadav Thermodynamics[TD] Unit : 2
  • 59. 12/19/2020 Faculty Name Subject code and abbreviation Unit Number 59 Clausius Inequality
  • 60. 12/19/2020 60 Clausius Inequality Nisha Yadav Thermodynamics[TD] Unit : 2
  • 61. 12/19/2020 61Nisha Yadav Thermodynamics[TD] Unit : 2 Clausius Inequality
  • 62. 12/19/2020 62Nisha Yadav Thermodynamics[TD] Unit : 2 Numerical on Clausius Inequality
  • 63. 12/19/2020 63 Solution of Numerical on Clausius Inequality Nisha Yadav Thermodynamics[TD] Unit : 2
  • 64. 12/19/2020 64 Numerical on Clausius Inequality Nisha Yadav Thermodynamics[TD] Unit : 2
  • 65. 12/19/2020 65Nisha Yadav Thermodynamics[TD] Unit : 2 Solution of Numerical on Clausius Inequality
  • 66. 12/19/2020 66 Numerical on Clausius Inequality Nisha Yadav Thermodynamics[TD] Unit : 2
  • 67. 12/19/2020 67 Solution of Numerical on Clausius Inequality Nisha Yadav Thermodynamics[TD] Unit : 2
  • 68. 68 ENTROPY Nisha Yadav Thermodynamics[TD] Unit : 2 • Entropy is a thermodynamic function of the state of the system can be interpreted as the amount of order or disorder of a system • Change in Entropy:- The change in entropy  S of a system when an amount of thermal energy Q is added to a system by a reversible process at constant absolute temperature T is given by:  S = dQ / T 5/9/2020
  • 69. 69 Example Nisha Yadav Thermodynamics[TD] Unit : 2 A heat engine removes 100 J each cycle from a heat reservoir at 400 K and exhausts 85 J of thermal energy to a reservoir at 300 K. Compute the change in entropy for each reservoir. • Since the hot reservoir loses heat, we have that:  S = Q / T = -100 J / 400 K = -0.25 JK-1 For the cold reservoir we have:  S = Q / T = 85 J / 300 K = 0.283 JK-1 Therefore: The increase in entropy of the cold reservoir is greater than the decrease for the hot reservoir. 5/9/2020
  • 70. 70 ENTROPY OF IDEAL GAS Nisha Yadav Thermodynamics[TD] Unit : 2 • An expression for the entropy change of an ideal gas can be obtained from Eq. ds = 𝑑𝑢 𝑃 𝑑𝑣 𝑇 + ----- Eq. 1 𝑇 Or ds = 𝑑ℎ 𝑣 𝑑𝑃 𝑇 𝑇 - ----- Eq. 2 • By employing the property relations forideal gases. By substituting du=𝑪 𝒗dTand P = 𝑹𝑻 𝑽 into Eq. 1, the differential entropy change of an ideal gas becomes ds = 𝐶𝑣 𝑑𝑇 𝑑𝑣 + R 𝑇 𝑣 5/9/2020
  • 71. 71 ENTROPY OF IDEAL GAS Nisha Yadav Thermodynamics[TD] Unit : 2 The entropy change for a process is obtained by integrating this relation between the endstates. ∆𝑆 = 𝐶𝑣 𝑑𝑇 𝑇 + 𝑅 ln 𝑣2 𝑣1 …………Eq.3  A second relation for the entropy change of an ideal gas is obtained in a similar manner by substitutingdh = 𝐶 𝑝dT and V = 𝑅𝑇 𝑇 in Eq. 2 and integrating. The result is ∆𝑆= 𝐶 𝑝 𝑑𝑇 𝑇 + 𝑅 ln 𝑝1 𝑝2 ………….Eq.4 5/9/2020
  • 72. 72 ENTROPY OF IDEAL GAS Nisha Yadav Thermodynamics[TD] Unit : 2 From Eq.(3) and (4), we see that for constant volume process, ∆𝑆 = 𝐶𝑣 𝑑𝑇 𝑇 = 𝐶𝑣 ln 𝑇2 𝑇1 For constant pressure process, we have ∆𝑆 = 𝐶 𝑝 𝑑𝑇 𝑇 = 𝐶 𝑝 ln 𝑇2 𝑇1 For isothermal process, ∆𝑆 = 𝑅 ln 𝑣2 𝑣1 = 𝑅 ln 𝑝2 𝑝1 5/9/2020
  • 73. 73 THE CARNOT PRINCIPLE Nisha Yadav Thermodynamics[TD] Unit : 2 The Carnot cycle is a thermodynamic process that describes how a fluid is used to convert thermal energy into work. • Characteristics: • High Efficiency • Multi-Source Engine • Better reliability and easier maintenance • Reversible • Safe, discrete and oxygen-free • Modularity and flexibility 5/9/2020
  • 74. 74 P-V DIAGRAM Nisha Yadav Thermodynamics[TD] Unit : 2 • A pressure volume diagram is used to describe corresponding changes in volume and pressure in a system. • The PV diagram, called an indicator diagram, was developed by James Watt and his employee John Southern (1758–1815) to improve the efficiency of engines. isothermal segments (AB and CD) occur when there is perfect thermal contact between the working fluid and one of the reservoirs, so that whatever heat is needed to maintain constant temperature will flow into or out of the working fluid, from or to the reservoir. 5/9/2020
  • 75. 75 P-V DIAGRAM Nisha Yadav Thermodynamics[TD] Unit : 2 This is the PV diagram….. 5/9/2020
  • 76. 76 P-V DIAGRAM Nisha Yadav Thermodynamics[TD] Unit : 2  adiabatic segments (BC and DA) occur when there is perfect thermal insulation between the working fluid and the rest of the universe, including both reservoirs, thereby preventing the flow of any heat into or out of the working fluid. 5/9/2020
  • 78. 78 Youtube & NPTEL Video Links and Online Courses Details NPTEL/Swayam online course: Fundamental of thermodynamics 5/11/2020 Nisha Yadav Thermodynamics[TD] Unit : 2 https://www.youtube.com/watch?v=tyr6vNII3Bk https://www.youtube.com/watch?v=uEErWdtkRUM https://www.youtube.com/watch?v=kNNwrp7tHPU https://www.youtube.com/watch?v=9GMBpZZtjXM&list=PLseVjnVx50AN97Kav4 UYk3JCuyRQDkL6T
  • 79. 79 Daily Quiz 5/11/2020 Nisha Yadav Thermodynamics[TD] Unit : 2 Q.1.Statement of II law of thermodynamics and equivalence of both the statement. Q.2.Explain throttling process. Q.3.What do you mean by “Perpetual motion machine of second kind-PMM 2”? Q.4.Define principle of entropy increase. Q.5.What are the limitation of first law of thermodynamics? Q.6.Explain Carnot engine and Carnot theorem. Q.7.Statement of third law of thermodynamics. Q.8.Explain Clausius Inequality. Q.9. What is the working of Heat engine? Q.10. What is the difference between Heat pump and Refrigerator?
  • 80. 80 Weekly Assignment 5/11/2020 Nisha Yadav Thermodynamics[TD] Unit : 2 Q.1. A Carnot refrigerator exhaust 250 KJ of heat from a reservoir at 150K and rejects heat to a reservoir at 450 K this heat serves as the energy input to a second Carnot refrigerator which separates between 450K and 1500 K. Determine the COP of (i) The cold refrigerator (ii) The Hot refrigerator (iii) The composite system Check the answer of composite system with the relation established above. Q.2. Find the entropy change of 5 Kg of a perfect gas whose temperature varies from 150°C to 200°C. During the constant volume process the specific heat varies linearly with absolute temperature and is presented by the relation (V = 10.45+ 0.009T ) KJ/Kg K. Q.3. Three Carnot Engines E1, E2, E3 operate between temperatures of 1000K and 300K. Make calculations for the intermediate temperatures if the works produced by the engines are in the ratio of 4:3:2. Q.4. What are the statement of II law of thermodynamics and equivalence of both the statement?
  • 81. 81 Weekly Assignment 5/11/2020 Nisha Yadav Thermodynamics[TD] Unit : 2 Q.5.Calculate the change in entropy at 368.3 g of ice at 32.0oF32.0oF melts. The latent heat of fusion of water is 333000 J/kg Q.6. What is the relationship between Entropy and The Second Law of Thermodynamics? N2(g) + 3H2(g) 2NH3(g) So 298 (J/mol K) 191.5 130.6 192.3 Q.7.What is the standard entropy change of the reaction below at 298 K with each compound at the standard pressure? Q.8.A heat pump is used to meet the heating requirements of a house and maintain it at 20°C. On a day when the outdoor air temperature drops to 2°C, the house is estimated to lose heat at a rate of 80,000 kJ/h. If the heat pump under these conditions has a COP of 2.5, determine the rate at which heat is absorbed from the cold
  • 82. 82 Q.9.During a cyclic process, a heat engine absorbs 500 J of heat from a hot reservoir, does work and ejects an amount of heat 300 J into the surroundings (cold reservoir). Calculate the efficiency of the heat engine? Q.11.There are two Carnot engines A and B operating in two different temperature regions. For Engine A the temperatures of the two reservoirs are 150°C and 100°C. For engine B the temperatures of the reservoirs are 350°C and 300°C. Which engine has lesser efficiency? Q.10.A cyclic machine, as shown below, receives 325 kJ from a 1000 K energy reservoir. It rejects 125 kJ to a 400 K energy reservoir and the cycle produces 200kJ of work as output. Is this cycle reversible, irreversible, or impossible? Weekly Assignment 5/11/2020 Nisha Yadav Thermodynamics[TD] Unit : 2
  • 83. 83 MCQ s 1. The entropy of an isolated system can never ____ a) increase b) decrease c) be zero d) none of the mentioned 2. This set of Thermodynamics Multiple Choice Questions & Answers (MCQs) focuses on “Entropy Principle and its Applications”. Which of the following is true? a) for an isolated system, dS>=0 b) for a reversible process, dS=0 c) for an irreversible process, dS>0 d) all of the mentioned 3. According to entropy principle, the entropy of an isolated system can never decrease and remains constant only when the process is reversible. a) true b) false Nisha Yadav Thermodynamics[TD] Unit : 25/11/2020
  • 84. 84 MCQ s 4. Entropy may decrease locally at some region within the isolated system. How can this statement be justified? a) this cannot be possible b) this is possible because entropy of an isolated system can decrease. c) it must be compensated by a greater increase of entropy somewhere within the system. d) none of the mentioned 5. Clausius summarized the first and second laws of thermodynamics as a) the energy of the world is constant b) the entropy of the world tends towards a maximum c) both of the mentioned d) none of the mentioned 6. The entropy of an isolated system always ____ and becomes a ____ at the state of equilibrium. a) decreases, minimum b) increases, maximum c) increases, minimum d) decreases, maximum 5/11/2020 Nisha Yadav Thermodynamics[TD] Unit : 2
  • 85. 85 MCQ s 7. Entropy principle is the quantitative statement of the second law of thermodynamics. a) true b) false 8. Which of the following can be considered as an application of entropy principle? a) transfer of heat through a finite temperature difference b) mixing of two fluids c) maximum temperature obtainable from two finite bodies d) all of the mentioned 9. The final temperatures of two bodies, initially at T1 and T2 can range from a) (T1-T2)/2 to sqrt(T1*T2) b) (T1+T2)/2 to sqrt(T1*T2) c) (T1+T2)/2 to (T1*T2) d) (T1-T2)/2 to (T1*T2) Nisha Yadav Thermodynamics[TD] Unit : 2 5/11/2020
  • 86. 86 MCQ s 10. Which of the following processes exhibit external mechanical irreversibility? a) isothermal dissipation of work b) adiabatic dissipation of work c) both of the mentioned d) none of the mentioned 5/11/2020 Nisha Yadav Thermodynamics[TD] Unit : 2
  • 87. 87 Old Question Papers Nisha Yadav Thermodynamics[TD] Unit : 2 5/11/2020
  • 88. Q.1.A steam engine boiler is maintained at 250°C and water is converted into steam. This steam is used to do work and heat is ejected to the surrounding air at temperature 300K. Calculate the maximum efficiency it can have? Q.2.Three Carnot Engines E1, E2, E3 operate between temperatures of 1000K and 300K. Make calculations for the intermediate temperatures if the works produced by the engines are in the ratio of 4:3:2. Q.3.Find the entropy change of 5 Kg of a perfect gas whose temperature varies from 150°C to 200°C. During the constant volume process the specific heat varies linearly with absolute temperature and is presented by the relation (V = 10.45+ 0.009T ) KJ/Kg K. Q.4.A Carnot refrigerator exhaust 250 KJ of heat from a reservoir at 150K and rejects heat to a reservoir at 450 K this heat serves as the energy input to a second Carnot refrigerator which separates between 450K and 1500 K. Determine the COP of (i) The cold refrigerator (ii) The Hot refrigerator (iii) The composite system 88 Expected Questions for University Exam Nisha Yadav Thermodynamics[TD] Unit : 25/11/2020
  • 89. 89 Expected Questions for University Exam Q.5.There are two Carnot engines A and B operating in two different temperature regions. For Engine A the temperatures of the two reservoirs are 150°C and 100°C. For engine B the temperatures of the reservoirs are 350°C and 300°C. Which engine has lesser efficiency? Q.6.During a cyclic process, a heat engine absorbs 500 J of heat from a hot reservoir, does work and ejects an amount of heat 300 J into the surroundings (cold reservoir). Calculate the efficiency of the heat engine. Q.7.A heat pump is used to meet the heating requirements of a house and maintain it at 20°C. On a day when the outdoor air temperature drops to 2°C, the house is estimated to lose heat at a rate of 80,000 kJ/h. If the heat pump under these conditions has a COP of 2.5, determine the power consumed by the heat pump. Q.8.A car engine operates with a thermal efficiency of 35%. Assume the air- conditioner has a coefficient of performance of 3 working as a refrigerator cooling the inside using engine shaft work to drive it. How much fuel energy should be spend extra to remove 1 kJ from the inside? 5/11/2020 Nisha Yadav Thermodynamics[TD] Unit : 2
  • 90. 90 Expected Questions for University Exam Q.9.A cyclic machine, as shown below, receives 325 kJ from a 1000 K energy reservoir. It rejects 125 kJ to a 400 K energy reservoir and the cycle produces 200kJ of work as output. Is this cycle reversible, irreversible, or impossible? Q.10.A heat pump is used to meet the heating requirements of a house and maintain it at 20°C. On a day when the outdoor air temperature drops to 2°C, the house is estimated to lose heat at a rate of 80,000 kJ/h. If the heat pump under these conditions has a COP of 2.5, determine the rate at which heat is absorbed from the cold Nisha Yadav Thermodynamics[TD] Unit : 25/11/2020
  • 91. 915/5/2020 Nisha Yadav Thermodynamics[TD] Unit : 1

Editor's Notes

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