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ENGINEERING

THERMODYNAMICS
THIRD EDITION
SI Units Ve r s io n

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R. K. Rajput

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ENGINEERING THERMODYNAMICS


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Also  available  :

Edited  by
R.K. RAJPUT

Patiala

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STEAM TABLES
and
MOLLIER DIAGRAM
(S.I. UNITS)


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ENGINEERING
THERMODYNAMICS
[For Engineering Students of All Indian Universities
and Competitive Examinations]

By

R.K. RAJPUT
M.E. (Heat Power Engg.) Hons.–Gold Medallist ; Grad. (Mech. Engg. & Elect. Engg.) ;
M.I.E. (India) ; M.S.E.S.I. ; M.I.S.T.E. ; C.E. (India)
Principal (Formerly)


Punjab College of Information Technology
PATIALA, Punjab

LAXMI PUBLICATIONS (P) LTD
BANGALORE l CHENNAI
JALANDHAR

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KOLKATA

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COCHIN

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GUWAHATI

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HYDERABAD

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LUCKNOW

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MUMBAI


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RANCHI

NEW DELHI

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BOSTON, USA

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S.I. UNITS


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LAXMI PUBLICATIONS (P) LTD
113, Golden House, Daryaganj,
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Phone : 011-43 53 25 00
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© All rights reserved with the Publishers.
No part of this publication may be reproduced, stored in a retrieval system, or
transmitted in any form or by any means, electronic, mechanical, photocopying,
recording or otherwise without the prior written permission of the publisher.
ISBN: 978-0-7637-8272-6

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Price : Rs. 350.00 Only.

First Edition : 1996
Second Edition : 2003
Third Edition : 2007

Offices :
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Preface to The Third Edition
I am pleased to present the third edition of this book. The warm reception which the
previous editions and reprints of this book have enjoyed all over India and abroad has been
a matter of great satisfaction to me.
The entire book has been thoroughly revised ; a large number of solved examples (questions
having been selected from various universities and competitive examinations) and ample
additional text have been added.
Any suggestions for the improvement of the book will be thankfully acknowledged and
incorporated in the next edition.


Preface to The First Edition
Several books are available in the market on the subject of “Engineering Thermodynamics” but either they are too bulky or are miserly written and as such do not cover the
syllabii of various Indian Universities effectively. Hence a book is needed which should
assimilate subject matter that should primarily satisfy the requirements of the students from
syllabus/examination point of view ; these requirements are completely met by this book.
The book entails the following features :
— The presentation of the subject matter is very systematic and language of the text
is quite lucid and simple to understand.
— A number of figures have been added in each chapter to make the subject matter
self speaking to a great extent.
— A large number of properly graded examples have been added in various chapters
to enable the students to attempt different types of questions in the examination
without any difficulty.
— Highlights, objective type questions, theoretical questions, and unsolved examples
have been added at the end of each chapter to make the book a complete unit in
all respects.
The author’s thanks are due to his wife Ramesh Rajput for rendering all assistance
during preparation and proof reading of the book. The author is thankful to Mr. R.K. Syal
for drawing beautiful and well proportioned figures for the book.
The author is grateful to M/s Laxmi Publications for taking lot of pains in bringing out
the book in time and pricing it moderately inspite of heavy cost of the printing.
Constructive criticism is most welcome from the readers.
—Author

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Contents
Chapter

Pages

1. INTRODUCTION—OUTLINE OF SOME DESCRIPTIVE SYSTEMS
1.1.

1.2.
1.3.

1.4.

1.5.

Steam Power Plant
1.1.1. Layout
1.1.2. Components of a modern steam power plant
Nuclear Power Plant
Internal Combustion Engines
1.3.1. Heat engines
1.3.2. Development of I.C. engines

1.3.3. Different parts of I.C. engines
1.3.4. Spark ignition (S.I.) engines
1.3.5. Compression ignition (C.I.) engines
Gas Turbines
1.4.1. General aspects
1.4.2. Classification of gas turbines
1.4.3. Merits and demerits of gas turbines
1.4.4. A simple gas turbine plant
1.4.5. Energy cycle for a simple-cycle gas turbine
Refrigeration Systems
Highlights
Theoretical Questions

2. BASIC CONCEPTS OF THERMODYNAMICS
2.1.
2.2.
2.3.

2.4.
2.5.
2.6.
2.7.
2.8.

Introduction to Kinetic Theory of Gases
Definition of Thermodynamics
Thermodynamic Systems
2.3.1. System, boundary and surroundings
2.3.2. Closed system
2.3.3. Open system

2.3.4. Isolated system
2.3.5. Adiabatic system
2.3.6. Homogeneous system
2.3.7. Heterogeneous system
Macroscopic and Microscopic Points of View
Pure Substance
Thermodynamic Equilibrium
Properties of Systems
State

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(xxi)—(xxii)

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Introduction to S.I. Units and Conversion Factors
Nomenclature


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2.9.
2.10.
2.11.
2.12.
2.13.
2.14.
2.15.

2.16.

2.17.
2.18.
2.19.

2.20.

Pages

Process
Cycle
Point Function
Path Function
Temperature
Zeroth Law of Thermodynamics
The Thermometer and Thermometric Property
2.15.1. Introduction
2.15.2. Measurement of temperature
2.15.3. The international practical temperature scale
2.15.4. Ideal gas
Pressure
2.16.1. Definition of pressure
2.16.2. Unit for pressure
2.16.3. Types of pressure measurement devices
2.16.4. Mechanical type instruments
Specific Volume
Reversible and Irreversible Processes
Energy, Work and Heat
2.19.1. Energy
2.19.2. Work and heat
Reversible Work
Highlights
Objective Type Questions
Theoretical Questions
Unsolved Examples

3. PROPERTIES OF PURE SUBSTANCES
3.1.
3.2.

3.3.
3.4.
3.5.
3.6.
3.7.
3.8.
3.9.
3.10.
3.11.
3.12.
3.13.
3.14.
3.15.
3.16.
3.17.

Definition of the Pure Substance
Phase Change of a Pure Substance
p-T (Pressure-temperature) Diagram for a Pure Substance
p-V-T (Pressure-Volume-Temperature) Surface
Phase Change Terminology and Definitions
Property Diagrams in Common Use
Formation of Steam
Important Terms Relating to Steam Formation
Thermodynamic Properties of Steam and Steam Tables
External Work Done During Evaporation
Internal Latent Heat
Internal Energy of Steam
Entropy of Water
Entropy of Evaporation

Entropy of Wet Steam
Entropy of Superheated Steam
Enthalpy-Entropy (h-s) Chart or Mollier Diagram

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Chapter
Determination of Dryness Fraction of Steam
3.18.1. Tank or bucket calorimeter
3.18.2. Throttling calorimeter
3.18.3. Separating and throttling calorimeter
Highlights
Objective Type Questions

Theoretical Questions
Unsolved Examples

4. FIRST LAW OF THERMODYNAMICS
4.1.
4.2.
4.3.
4.4.
4.5.
4.6.
4.7.
4.8.

4.9.
4.10.
4.11.
4.12.

4.13.
4.14.
4.15.

Internal Energy
Law of Conservation of Energy
First Law of Thermodynamics
Application of First Law to a Process
Energy—A Property of System
Perpetual Motion Machine of the First Kind-PMM1
Energy of an Isolated System
The Perfect Gas

4.8.1. The characteristic equation of state
4.8.2. Specific heats
4.8.3. Joule’s law
4.8.4. Relationship between two specific heats
4.8.5. Enthalpy
4.8.6. Ratio of specific heats
Application of First Law of Thermodynamics to Non-flow or Closed
System
Application of First Law to Steady Flow Process
Energy Relations for Flow Process
Engineering Applications of Steady Flow Energy Equation (S.F.E.E.)
4.12.1. Water turbine
4.12.2. Steam or gas turbine
4.12.3. Centrifugal water pump
4.12.4. Centrifugal compressor
4.12.5. Reciprocating compressor
4.12.6. Boiler
4.12.7. Condenser
4.12.8. Evaporator
4.12.9. Steam nozzle
Throttling Process and Joule-Thompson Porous Plug Experiment
Heating-Cooling and Expansion of Vapours
Unsteady Flow Processes
Highlights
Objective Type Questions
Theoretical Questions
Unsolved Examples

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96
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101
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103
103
104
105
105
105
106
107
107
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109

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Chapter

Pages

5.1.
5.2.
5.3.
5.4.

5.5.
5.6.
5.7.
5.8.
5.9.

5.10.
5.11.
5.12.

5.13.
5.14.
5.15.
5.16.
5.17.

5.18.
5.19.

Limitations of First Law of Thermodynamics and Introduction to
Second Law
Performance of Heat Engines and Reversed Heat Engines
Reversible Processes
Statements of Second Law of Thermodynamics
5.4.1. Clausius statement
5.4.2. Kelvin-Planck statement
5.4.3. Equivalence of Clausius statement to the Kelvin-Planck
statement
Perpetual Motion Machine of the Second Kind
Thermodynamic Temperature
Clausius Inequality
Carnot Cycle
Carnot’s Theorem
Corollary of Carnot’s Theorem
Efficiency of the Reversible Heat Engine
Entropy

5.12.1. Introduction
5.12.2. Entropy—a property of a system
5.12.3. Change of entropy in a reversible process
Entropy and Irreversibility
Change in Entropy of the Universe
Temperature Entropy Diagram
Characteristics of Entropy
Entropy Changes for a Closed System
5.17.1. General case for change of entropy of a gas
5.17.2. Heating a gas at constant volume
5.17.3. Heating a gas at constant pressure
5.17.4. Isothermal process
5.17.5. Adiabatic process (reversible)
5.17.6. Polytropic process
5.17.7. Approximation for heat absorbed
Entropy Changes for an Open System
The Third Law of Thermodynamics
Highlights
Objective Type Questions
Theoretical Questions
Unsolved Examples

6. AVAILABILITY AND IRREVERSIBILITY
6.1.
6.2.
6.3.
6.4.

Available and Unavailable Energy
Available Energy Referred to a Cycle

Decrease in Available Energy When Heat is Transferred Through
a Finite Temperature Difference
Availability in Non-flow Systems

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233
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5. SECOND LAW OF THERMODYNAMICS AND ENTROPY


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Chapter
Availability in Steady-flow Systems
Helmholtz and Gibb’s Functions
Irreversibility
Effectiveness
Highlights
Objective Type Questions
Theoretical Questions
Unsolved Examples

7. THERMODYNAMIC RELATIONS

7.1.
7.2.
7.3.
7.4.
7.5.
7.6.

7.7.

General Aspects
Fundamentals of Partial Differentiation
Some General Thermodynamic Relations
Entropy Equations (Tds Equations)
Equations for Internal Energy and Enthalpy
Measurable Quantities
7.6.1. Equation of state
7.6.2. Co-efficient of expansion and compressibility
7.6.3. Specific heats
7.6.4. Joule-Thomson co-efficient
Clausius-Claperyon Equation
Highlights
Objective Type Questions
Exercises

8. IDEAL AND REAL GASES
8.1.
8.2.
8.3.
8.4.
8.5.

8.6.
8.7.
8.8.
8.9.
8.10.
8.11.
8.12.

Introduction
The Equation of State for a Perfect Gas
p-V-T Surface of an Ideal Gas
Internal Energy and Enthalpy of a Perfect Gas
Specific Heat Capacities of an Ideal Gas
Real Gases
Van der Waal’s Equation
Virial Equation of State
Beattie-Bridgeman Equation
Reduced Properties
Law of Corresponding States
Compressibility Chart
Highlights
Objective Type Questions
Theoretical Questions
Unsolved Examples

9. GASES AND VAPOUR MIXTURES
9.1.

Introduction


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311
312
313
336
337
338
338

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6.5.
6.6.
6.7.
6.8.

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Chapter
Dalton’s Law and Gibbs-Dalton Law
Volumetric Analysis of a Gas Mixture
The Apparent Molecular Weight and Gas Constant
Specific Heats of a Gas Mixture
Adiabatic Mixing of Perfect Gases
Gas and Vapour Mixtures
Highlights
Objective Type Questions
Theoretical Questions
Unsolved Examples


10. PSYCHROMETRICS
10.1.
10.2.
10.3.
10.4.
10.5.
10.6.

Concept of Psychrometry and Psychrometrics
Definitions
Psychrometric Relations
Psychrometers
Psychrometric Charts
Psychrometric Processes
10.6.1. Mixing of air streams
10.6.2. Sensible heating
10.6.3. Sensible cooling
10.6.4. Cooling and dehumidification
10.6.5. Cooling and humidification
10.6.6. Heating and dehumidification
10.6.7. Heating and humidification
Highlights
Objective Type Questions
Theoretical Questions
Unsolved Examples

11. CHEMICAL THERMODYNAMICS
11.1.
11.2.

11.3.
11.4.
11.5.
11.6.
11.7.
11.8.
11.9.
11.10.
11.11.
11.12.
11.13.
11.14.
11.15.

Introduction
Classification of Fuels
Solid Fuels
Liquid Fuels
Gaseous Fuels
Basic Chemistry
Combustion Equations
Theoretical Air and Excess Air
Stoichiometric Air Fuel (A/F) Ratio
Air-Fuel Ratio from Analysis of Products
How to Convert Volumetric Analysis to Weight Analysis
How to Convert Weight Analysis to Volumetric Analysis
Weight of Carbon in Flue Gases
Weight of Flue Gases per kg of Fuel Burnt
Analysis of Exhaust and Flue Gas


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485

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9.2.
9.3.
9.4.
9.5.
9.6.
9.7.

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Pages

11.16.
11.17.
11.18.
11.19.


Internal Energy and Enthalpy of Reaction
Enthalpy of Formation (∆Hf)
Calorific or Heating Values of Fuels
Determination of Calorific or Heating Values
11.19.1. Solid and Liquid Fuels
11.19.2. Gaseous Fuels
11.20. Adiabatic Flame Temperature
11.21. Chemical Equilibrium
11.22. Actual Combustion Analysis
Highlights
Objective Type Questions
Theoretical Questions
Unsolved Examples

12. VAPOUR POWER CYCLES
12.1.
12.2.
12.3.
12.4.
12.5.
12.6.

Carnot Cycle
Rankine Cycle
Modified Rankine Cycle
Regenerative Cycle
Reheat Cycle
Binary Vapour Cycle
Highlights

Objective Type Questions
Theoretical Questions
Unsolved Examples

13. GAS POWER CYCLES
13.1.
13.2.
13.3.
13.4.
13.5.
13.6.
13.7.

Definition of a Cycle
Air Standard Efficiency
The Carnot Cycle
Constant Volume or Otto Cycle
Constant Pressure or Diesel Cycle
Dual Combustion Cycle
Comparison of Otto, Diesel and Dual Combustion Cycles
13.7.1. Efficiency versus compression ratio
13.7.2. For the same compression ratio and the same heat input
13.7.3. For constant maximum pressure and heat supplied
13.8. Atkinson Cycle
13.9. Ericsson Cycle
13.10. Gas Turbine Cycle-Brayton Cycle
13.10.1. Ideal Brayton cycle
13.10.2. Pressure ratio for maximum work
13.10.3. Work ratio
13.10.4. Open cycle gas turbine-actual brayton cycle

13.10.5. Methods for improvement of thermal efficiency of open cycle
gas turbine plant

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( xiii )

Chapter

Pages

14. REFRIGERATION CYCLES
14.1.

14.2.

14.3.


14.4.

14.5.

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... 713—777

Fundamentals of Refrigeration
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14.1.1. Introduction
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14.1.2. Elements of refrigeration systems
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14.1.3. Refrigeration systems
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14.1.4. Co-efficient of performance (C.O.P.)
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14.1.5. Standard rating of a refrigeration machine
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Air Refrigeration System
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14.2.1. Introduction

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14.2.2. Reversed Carnot cycle
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14.2.3. Reversed Brayton cycle
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14.2.4. Merits and demerits of air refrigeration system
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Simple Vapour Compression System
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14.3.1. Introduction
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14.3.2. Simple vapour compression cycle
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14.3.3. Functions of parts of a simple vapour compression system
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14.3.4. Vapour compression cycle on temperature-entropy (T-s) diagram ...
14.3.5. Pressure-enthalpy (p-h) chart
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14.3.6. Simple vapour compression cycle on p-h chart
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14.3.7. Factors affecting the performance of a vapour compression
system
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14.3.8. Actual vapour compression cycle
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14.3.9. Volumetric efficiency
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14.3.10. Mathematical analysis of vapour compression refrigeration
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Vapour Absorption System

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14.4.1. Introduction
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14.4.2. Simple vapour absorption system
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14.4.3. Practical vapour absorption system
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14.4.4. Comparison between vapour compression and vapour
absorption systems
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Refrigerants
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14.5.1. Classification of refrigerants
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14.5.2. Desirable properties of an ideal refrigerant
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14.5.3. Properties and uses of commonly used refrigerants
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Theoretical Questions
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Unsolved Examples
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671
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679
706
707
707
709

713
713
714
714
714
715
715
715
716
722
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730
730
730
731
732
734
735
736

737
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740
741
741
742
743
744
764
764
766
768
771
772
773
774

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13.10.6. Effect of operating variables on thermal efficiency
13.10.7. Closed cycle gas turbine
13.10.8. Gas turbine fuels
Highlights
Theoretical Questions
Objective Type Questions
Unsolved Examples


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Chapter

Pages

15.1.
15.2.

15.3.
15.4.

15.5.

Modes of Heat Transfer
Heat Transmission by Conduction
15.2.1. Fourier’s law of conduction
15.2.2. Thermal conductivity of materials
15.2.3. Thermal resistance (Rth)
15.2.4. General heat conduction equation in cartesian coordinates
15.2.5. Heat conduction through plane and composite walls
15.2.6. The overall heat transfer coefficient
15.2.7. Heat conduction through hollow and composite cylinders
15.2.8. Heat conduction through hollow and composite spheres
15.2.9. Critical thickness of insulation
Heat Transfer by Convection
Heat Exchangers
15.4.1. Introduction
15.4.2. Types of heat exchangers
15.4.3. Heat exchanger analysis

15.4.4. Logarithmic temperature difference (LMTD)
Heat Transfer by Radiation
15.5.1. Introduction
15.5.2. Surface emission properties
15.5.3. Absorptivity, reflectivity and transmittivity
15.5.4. Concept of a black body
15.5.5. The Stefan-Boltzmann law
15.5.6. Kirchhoff ’s law
15.5.7. Planck’s law
15.5.8. Wien’s displacement law
15.5.9. Intensity of radiation and Lambert’s cosine law
15.5.10. Radiation exchange between black bodies separated by a
non-absorbing medium
Highlights
Objective Type Questions
Theoretical Questions
Unsolved Examples

16. COMPRESSIBLE FLOW
16.1.
16.2.

16.3.

Introduction
Basic Equations of Compressible Fluid Flow
16.2.1. Continuity equation
16.2.2. Momentum equation
16.2.3. Bernoulli’s or energy equation
Propagation of Disturbances in Fluid and Velocity of Sound

16.3.1. Derivation of sonic velocity (velocity of sound)
16.3.2. Sonic velocity in terms of bulk modulus
16.3.3. Sonic velocity for isothermal process
16.3.4. Sonic velocity for adiabatic process

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... 778—856
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...
...
...
...
...
...
...
...
...
...
...
...
...
...
...
...
...

...
...
...
...
...
...
...
...
...

778
778
778
780
782
783
787
790
799
805
808
812
815
815
815
820
821
832
832
833

834
836
836
837
837
839
840

...
...
...
...
...

843
851
852
854
854

... 857—903
...
...
...
...
...
...
...
...
...

...

857
857
857
858
858
862
862
864
864
865

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15. HEAT TRANSFER


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( xv )

Pages

16.4.
16.5.
16.6.

Mach Number
Propagation of Disturbance in Compressible Fluid

Stagnation Properties
16.6.1. Expression for stagnation pressure (ps) in compressible flow
16.6.2. Expression for stagnation density (ρs)
16.6.3. Expression for stagnation temperature (Ts)
16.7. Area—Velocity Relationship and Effect of Variation of Area for
Subsonic, Sonic and Supersonic Flows
16.8. Flow of Compressible Fluid Through a Convergent Nozzle
16.9. Variables of Flow in Terms of Mach Number
16.10. Flow Through Laval Nozzle (Convergent-divergent Nozzle)
16.11. Shock Waves
16.11.1. Normal shock wave
16.11.2. Oblique shock wave
16.11.3. Shock Strength
Highlights
Objective Type Questions
Theoretical Questions
Unsolved Examples
l

l

...
...
...
...
...
...

865
866

869
869
872
872

...
...
...
...
...
...
...
...
...
...
...
...

876
878
883
886
892
892
895
895
896
899
901
902


Competitive Examinations Questions with Answers

...

904—919

Index

...

920—922

Steam Tables and Mollier Diagram

...

(i)—(xx)

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Chapter



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Introduction to SI Units and Conversion Factors
A. INTRODUCTION TO SI UNITS
SI, the international system of units are divided into three classes :
1. Base units
2. Derived units
From the scientific point of view division of SI units into these classes is to a certain extent
arbitrary, because it is not essential to the physics of the subject. Nevertheless the General Conference, considering the advantages of a single, practical, world-wide system for international relations, for teaching and for scientific work, decided to base the international system on a choice of
six well-defined units given in Table 1 below :
Table 1. SI Base Units
Quantity

Name

Symbol

length

metre

m

mass

kilogram

kg

time


second

s

electric current

ampere

A

thermodynamic temperature

kelvin

K

luminous intensity

candela

cd

amount of substance

mole

mol

The second class of SI units contains derived units, i.e., units which can be formed by combining base units according to the algebraic relations linking the corresponding quantities. Several

of these algebraic expressions in terms of base units can be replaced by special names and symbols
can themselves be used to form other derived units.
Derived units may, therefore, be classified under three headings. Some of them are given in
Tables 2, 3 and 4.

(xvi)

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3. Supplementary units.


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(xvii)

INTRODUCTION TO SI UNITS AND CONVERSION FACTORS

Table 2. Examples of SI Derived Units Expressed in terms of Base Units
SI Units

Quantity

Symbol

area

square metre

m2


volume

cubic metre

m3

speed, velocity

metre per second

m/s

acceleration

metre per second squared

m/s2

wave number

1 per metre

m–1

density, mass density

kilogram per cubic metre

kg/m3


concentration (of amount of substance)

mole per cubic metre

mol/m3

activity (radioactive)

1 per second

s–1

specific volume

cubic metre per kilogram

m3/kg

luminance

candela per square metre

cd/m2

Table 3. SI Derived Units with Special Names
SI Units

Quantity


Name

Symbol

Expression
in terms of
other
units

Expression
in terms of
SI base
units

frequency

hertz

Hz

—

s–1

force

newton

N


—

m.kg.s–2

pressure

pascal

Pa

N/m2

m–1.kg.s–2

energy, work, quantity of heat power

joule

J

N.m

m2.kg.s–2

radiant flux quantity of electricity

watt

W


J/S

m2.kg.s–3

electric charge

coloumb

C

A.s

s.A

electric tension, electric potential

volt

V

W/A

m2.kg.s–3.A–1

capacitance

farad

F


C/V

m–2.kg–1.s4

electric resistance

ohm

Ω

V/A

m2.kg.s–3.A–2

conductance

siemens

S

A/V

m–2.kg–1.s3.A2

magnetic flux

weber

Wb


V.S.

m2.kg.s–2.A–1

magnetic flux density

tesla

T

Wb/m2

kg.s–2.A–1

inductance

henry

H

Wb/A

m2.kg.s–2.A–2

luminous flux

lumen

lm


—

cd.sr

illuminance

lux

lx

—

m–2.cd.sr

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Name


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(xviii)

ENGINEERING THERMODYNAMICS

Table 4. Examples of SI Derived Units Expressed by means of Special Names
SI Units

Name

Symbol

Expression
in terms of
SI base
units

dynamic viscosity

pascal second

Pa-s

m–1.kg.s–1

moment of force

metre newton

N.m

m2.kg.s–2

surface tension

newton per metre

N/m


kg.s–2

heat flux density, irradiance

watt per square metre

W/m2

kg.s–2

heat capacity, entropy

joule per kelvin

J/K

m2.kg.s–2.K–1

specific heat capacity, specific
entropy

joule per kilogram kelvin

J/(kg.K)

m2.s–2.K–1

specific energy


joule per kilogram

J/kg

m2.s–2

thermal conductivity

watt per metre kelvin

W/(m.K)

m.kg.s–3.K–1

energy density

joule per cubic metre

J/m 3

m–1.kg.s–2

electric field strength

volt per metre

V/m

m.kg.s–3.A–1


electric charge density

coloumb per cubic metre

C/m 3

m–3.s.A

electric flux density

coloumb per square metre

C/m 2

m–2.s.A

permitivity

farad per metre

F/m

m–3.kg–1.s4.A4

current density

ampere per square metre

A/m 2


—

magnetic field strength

ampere per metre

A/m

—

permeability

henry per metre

H/m

m.kg.s–2.A–2

molar energy

joule per mole

J/mol

m2.kg.s–2mol–1

molar heat capacity

joule per mole kelvin


J/(mol.K)

m2.kg.s–2.K–1.mol–1

The SI units assigned to third class called “Supplementary units” may be regarded either as
base units or as derived units. Refer Table 5 and Table 6.
Table 5. SI Supplementary Units
SI Units

Quantity

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Name

Symbol

plane angle

radian

rad

solid angle

steradian

sr


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Quantity


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(xix)

INTRODUCTION TO SI UNITS AND CONVERSION FACTORS

Table 6. Examples of SI Derived Units Formed by Using Supplementary Units
SI Units

Quantity
Name

Symbol

angular velocity

radian per second

rad/s

angular acceleration

radian per second squared

rad/s2


radiant intensity

watt per steradian

W/sr

radiance

watt per square metre steradian

W-m–2.sr–1

Factor
1012
109
106
103

Prefix

Symbol

Factor

Prefix

Symbol

tera


T

10–1

deci

d

G

10–2

centi

c

M

10–3

milli

m

k

10–6

micro


µ

giga
mega
kilo

102

hecto

h

10–9

nano

n

101

deca

da

10–12

pico

p


10–15

fasnto

f

10–18

atto

a

B. CONVERSION FACTORS
1. Force :
1 newton = kg-m/sec2 = 0.012 kgf
1 kgf = 9.81 N
2. Pressure :
1 bar = 750.06 mm Hg = 0.9869 atm = 105 N/m2 = 103 kg/m-sec2
1 N/m2 = 1 pascal = 10–5 bar = 10–2 kg/m-sec2
1 atm = 760 mm Hg = 1.03 kgf/cm2 = 1.01325 bar
= 1.01325 × 105 N/m2
3. Work, Energy or Heat :
1 joule = 1 newton metre = 1 watt-sec
= 2.7778 × 10–7 kWh = 0.239 cal
= 0.239 × 10–3 kcal
1 cal = 4.184 joule = 1.1622 × 10–6 kWh
1 kcal = 4.184 × 103 joule = 427 kgf-m
= 1.1622 × 10–3 kWh
1 kWh = 8.6042 × 105 cal = 860 kcal = 3.6 × 106 joule

1 kgf-m =

dharm
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FG 1 IJ kcal = 9.81 joules
H 427 K

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Table 7. SI Prefixes


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(xx)

ENGINEERING THERMODYNAMICS

4. Power :
1 watt = 1 joule/sec = 0.860 kcal/h
1 h.p. = 75 m kgf/sec = 0.1757 kcal/sec = 735.3 watt
1 kW = 1000 watts = 860 kcal/h
5. Specific heat :
1 kcal/kg-°K = 0.4184 joules/kg-K
6. Thermal conductivity :
1 watt/m-K = 0.8598 kcal/h-m-°C
1 kcal/h-m-°C = 1.16123 watt/m-K = 1.16123 joules/s-m-K.
7. Heat transfer co-efficient :
1 watt/m2-K = 0.86 kcal/m2-h-°C

1 kcal/m2-h-°C = 1.163 watt/m2-K.

Engineering constants
and expressions

M.K.S. system

SI Units

1. Value of g0

9.81 kg-m/kgf-sec2

1 kg-m/N-sec2

2. Universal gas constant

848 kgf-m/kg mole-°K

848 × 9.81 = 8314 J/kg-mole-°K
(3 1 kgf-m = 9.81 joules)

3. Gas constant (R)

29.27 kgf-m/kg-°K
for air

4. Specific heats (for air)

cv = 0.17 kcal/kg-°K

cp = 0.24 kcal/kg-°K

8314
= 287 joules/kg-K
29
for air

cv = 0.17 × 4.184
= 0.71128 kJ/kg-K
cp = 0.24 × 4.184
= 1 kJ/kg-K

5. Flow through nozzle-Exit
velocity (C2)

91.5 U , where U is in kcal

44.7 U , where U is in kJ

6. Refrigeration 1 ton

= 50 kcal/min

= 210 kJ/min

Q = σT4 kcal/m2-h
when σ = 4.9 × 10–8
kcal/h-m2 -°K4

Q = σT4 watts/m2-h

when σ = 5.67 × 10–8
W/m2 K4

7. Heat transfer
The Stefan Boltzman
Law is given by :

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C. IMPORTANT ENGINEERING CONSTANTS AND EXPRESSIONS


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INTRODUCTION TO SI UNITS AND CONVERSION FACTORS

(xxi)

A

area

b

steady-flow availability function

C


velocity

°C

temperature on the celsius (or centigrade) scale

c

specific heat

cp

specific heat at constant pressure

cv

specific heat at constant volume

Cp

molar heat at constant pressure

Cv

molar heat at constant volume

D, d

bore ; diameter


E

emissive power ; total energy

e

base of natural logarithms

g

gravitational acceleration

H

enthalpy

h

specific enthalpy ; heat transfer co-efficient

hf

specific enthalpy of saturated liquid (fluid)

hfg

latent heat

hg


specific enthalpy of saturated vapour ; gases

K

temperature on kelvin scale (i.e., celsius absolute, compressibility)

k

thermal conductivity, blade velocity co-efficient

L

stroke

M

molecular weight

m

mass


m

N

rate of mass flow
rotational speed


n

polytropic index, number of moles ; number of cylinders

P

power

p

absolute pressure

pm

mean effective pressure

pi

indicated mean effective pressure

pb

brake mean effective pressure, back pressure

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Nomenclature


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(xxii)

ENGINEERING THERMODYNAMICS

Q

heat, rate of heat transfer

q

rate of heat transfer per unit area

R

gas constant ; thermal resistance ; radius ; total expansion ratio in compound

R0

universal gas constant

r

radius, expansion ratio, compression ratio

S


entropy

s

specific entropy

T

absolute temperature ; torque

t

temperature

U

internal energy ; overall heat transfer co-efficient

u

specific internal energy

V

volume

v

specific volume


W

work ; rate of work transfer ; brake load ; weight

w

specific weight ; velocity of whirl

x

dryness fraction ; length

Greek Symbols
α

absorptivity

γ

ratio of specific heats, cp/cv

∈

emissivity ; effectiveness

η

efficiency


θ

temperature difference, angle

ρ

density

σ

Stefan-Boltzmann constant

φ

relative humidity, angle.

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steam engines


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1
Introduction—Outline of Some Descriptive Systems

1.1. STEAM POWER PLANT

1.1.1. Layout
Refer to Fig. 1.1. The layout of a modern steam power plant comprises of the following four
circuits :
1. Coal and ash circuit.
2. Air and gas circuit.
3. Feed water and steam flow circuit.
4. Cooling water circuit.
Coal and Ash Circuit. Coal arrives at the storage yard and after necessary handling,
passes on to the furnaces through the fuel feeding device. Ash resulting from combustion of coal
collects at the back of the boiler and is removed to the ash storage yard through ash handling
equipment.
Air and Gas Circuit. Air is taken in from atmosphere through the action of a forced or
induced draught fan and passes on to the furnace through the air preheater, where it has been
heated by the heat of flue gases which pass to the chimney via the preheater. The flue gases after
passing around boiler tubes and superheater tubes in the furnace pass through a dust catching
device or precipitator, then through the economiser, and finally through the air preheater before
being exhausted to the atmosphere.
Feed Water and Steam
ing the condenser is first heated
lowest pressure extraction point
more water heaters before going

Flow Circuit. In the water and steam circuit condensate leavin a closed feed water heater through extracted steam from the
of the turbine. It then passes through the deaerator and a few
into the boiler through economiser.

In the boiler drum and tubes, water circulates due to the difference between the density of
water in the lower temperature and the higher temperature sections of the boiler. Wet steam from
the drum is further heated up in the superheater for being supplied to the primemover. After
expanding in high pressure turbine steam is taken to the reheat boiler and brought to its original

dryness or superheat before being passed on to the low pressure turbine. From there it is exhausted
through the condenser into the hot well. The condensate is heated in the feed heaters using the
steam trapped (blow steam) from different points of turbine.

1

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1.1. Steam power plant : Layout—components of a modern steam power plant. 1.2. Nuclear
power plant. 1.3. Internal combustion engines : Heat engines—development of I.C. engines—
different parts of I.C. engines—spark ignition engines—compression ignition engines.
1.4. Gas turbines : General aspects—classification of gas turbines—merits and demerits of
gas turbines—a simple gas turbine plant—energy cycle for a simple-cycle gas turbine.
1.5. Refrigeration systems—Highlights—Theoretical questions.