THERMAL ENGINEERING. (Including : Thermodynamics, Heat Engines and Non-Conventional Power Generation)

Transcription

1 THERMAL ENGINEERING

2 By the Same Author Engineering Thermodynamics Applied Thermodynamics Manufacturing Technology (Manufacturing Processes) Automobile Engineering Internal Combustion Engines Power Plant Engineering and Steam Tables & Mollier Diagram (SI Units)

3 THERMAL ENGINEERING (Including : Thermodynamics, Heat Engines and Non-Conventional Power Generation) For Engineering Students preparing for B.E./B. Tech. ; AMIE-Section B (India) ; GATE and UPSC (Engg. Services) Examinations. SI UNITS By Er. 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) Recipient of : Best Teacher (Academic) Award Distinguished Author Award Jawahar Lal Nehru Memorial Gold Medal for an outstanding research paper (Institution of Engineers India) Principal (Formerly): Thapar Polytechnic College; Punjab College of Information Technology, PATIALA LAXMI PUBLICATIONS (P) LTD BANGALORE CHENNAI COCHIN GUWAHATI HYDERABAD JALANDHAR KOLKATA LUCKNOW MUMBAI RANCHI NEW DELHI BOSTON, USA

4 All rights reserved with the Author and the Publisher. 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. Published by : LAXMI PUBLICATIONS (P) LTD 113, Golden House, Daryaganj, New Delhi Phone : Fax : info@laxmipublications.com Price : ` Only. First Edition : 1993 ; Second Edition : 1999 ; Third Edition : 2001 Fourth Edition : 2004 ; Fifth Edition : 2005 ; Sixth Edition : 2006 Seventh Edition : 2009 ; Eighth Edition : 2010 Reprint : 2011, 2012 ; Ninth Edition : 2013 OFFICES Bangalore Kolkata Chennai Lucknow Cochin , Mumbai , Guwahati , Hyderabad Ranchi Jalandhar ETE THERMAL ENGG-RAJ Typeset at : GOSWAMI ASSOCIATES, Delhi C 5166/012/04 Printed at : PRINT MAN (INDIA)

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7 Preface to The Ninth Edition I am pleased to present the Ninth Edition (Two Colours) of this standard treatise on large size paper to enable the reader to handle the book comfortably. 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 ; besides adding a large number of Additional/Typical Worked Examples in various chapters. It is hoped that the book in this comprehensive and complete form will prove to be of immense use for the students preparing various Universities and Competitive Examinations (e.g., UPSC, GATE etc.). The author s thanks are due to his wife Ramesh Rajput for extending all cooperation during preparation and proof reading of this revised manuscript. Any suggestions for the improvement of this book will be thankfully acknowledged and incorporated in the next edition. R.K. Rajput (Author) ( vii )

8 Preface to The First Edition On the subject of Thermal Engineering several books are available in the market but most of them either lack in proper subject treatment or the solved examples are small in number and their solutions are too difficult to understand. The purpose of writing this book is to bridge these gaps and to present such a book to the students which should be easy to understand and assimilate comprehensive treatment of the subject matter in simple, lucid and direct language. The book comprises of 26 Chapters, dealing with Thermodynamics, Heat Engines and Non- Conventional Power Generation. Each chapter contains adequate text supported by simple and self explanatory figures, large number of Worked Examples both in SI and MKS units,, and several. The book will prove to be of great help to the students preparing for engineering degree, A.M.I.E. (India), diploma and other competitive examinations. The author s grateful thanks are due to Smt. Ramesh Rajput (wife) for extending full co-operation during the preparation of the manuscript. The author is also thankful to Mr. Rakesh Syal for drawing neat diagrams for this book. In the end, the author wishes to express his grateful thanks to M/s Laxmi Publications for taking extra pains in printing the book at a rapid pace and very systematically. Although every care has been taken to make the book free of errors both in text as well as in solved examples, yet the author shall feel obliged if errors present are brought to his notice. Constructive criticism of the book will be warmly received. R.K. Rajput (Author) ( viii )

9 Contents Chapters INTRODUCTION TO SI UNITS AND CONVERSION FACTORS Pages (i) (v) 1. KINETIC THEORY OF GASES AND BASIC CONCEPTS OF THERMODYNAMICS Introduction to Kinetic Theory of Gases Definition of Thermodynamics Thermodynamic Systems Macroscopic and Microscopic Points of View Pure Substance Thermodynamic Equilibrium Properties of Systems State Process Cycle Point Function Path Function Temperature Zeroth Law of Thermodynamics The Thermometer and Thermometric Property Pressure Specific Volume Reversible and Irreversible Processes Energy, Work and Heat Reversible Work Objective Type Questions PROPERTIES OF PURE SUBSTANCES 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 ( ix )

10 ( x ) Chapters Pages 2.9. 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 Determination of Dryness Fraction of Steam Objective Type Questions FIRST LAW OF THERMODYNAMICS 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 PMM Energy of an Isolated System The Perfect Gas 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.) Throttling Process and Joule-Thompson Porous Plug Experiment Heating-Cooling and Expansion of Vapours Unsteady Flow Processes Additional/Typical Worked Examples Objective Type Questions SECOND LAW OF THERMODYNAMICS AND ENTROPY 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 Perpetual Motion Machine of the Second Kind PMM Thermodynamic Temperature Clausius Inequality Carnot Cycle Carnot s Theorem Corollary of Carnot s Theorem Efficiency of the Reversible Heat Engine Entropy Entropy and Irreversibility

11 ( xi ) Chapters Pages Change in Entropy of the Universe Temperature Entropy Diagram Characteristics of Entropy Entropy Changes for a Closed System Entropy Changes for an Open System The Third Law of Thermodynamics Additional/Typical Worked Examples Objective Type Questions AVAILABILITY AND IRREVERSIBILITY 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 Availability in Steady Flow Systems Helmholtz and Gibbs Functions Irreversibility Effectiveness Objective Type Questions THERMODYNAMIC RELATIONS General Aspects Fundamentals of Partial Differentiation Some General Thermodynamic Relations Entropy Equations (Tds Equations) Equations for Internal Energy and Enthalpy Measurable Quantities Clausius-Claperyon Equation Objective Type Questions Exercises IDEAL AND REAL GASES 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 Waals Equation Virial Equation of State Beattie-Bridgeman Equation Reduced Properties Law of Corresponding States

12 ( xii ) Chapters Pages Compressibility Chart Objective Type Questions GASES AND VAPOUR MIXTURES Introduction 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 Objective Type Questions PSYCHROMETRICS Concept of Psychrometry and Psychrometrics Definitions Psychrometric Relations Psychrometers Psychrometric Charts Psychrometric Processes Objective Type Questions FUELS AND COMBUSTION (Including Chemical Thermodynamics) 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 Internal Energy and Enthalpy of Formation Enthalpy of Formation ( H f ) Calorific or Heating Values of Fuels

13 ( xiii ) Chapters Pages Determination of Calorific or Heating Values Adiabatic Flame Temperature Chemical Equilibrium Actual Combustion Analysis Objective Type Questions STEAM GENERATORS Introduction Classification of Boilers Comparison Between Fire-Tube and Water-Tube Boilers Selection of a Boiler Essentials of a Good Steam Boiler Boiler Terms Fire Tube Boilers Water Tube Boilers High Pressure Boilers Combustion Equipment for Steam Boilers Objective Type Questions BOILER MOUNTINGS AND ACCESSORIES Introduction Boiler Mountings Accessories Objective Type Questions DRAUGHT Definition and Classification of Draught Natural Draught Chimney Chimney Height and Diameter Condition for Maximum Discharge Through a Chimney Efficiency of a Chimney Draught Losses Artificial Draught Objective Type Questions PERFORMANCE OF STEAM GENERATORS Evaporative Capacity Equivalent Evaporation Factor of Evaporation

14 ( xiv ) Chapters Pages Boiler Efficiency Heat Losses in a Boiler Plant Objective Type Questions BASIC STEAM POWER CYCLES Carnot Cycle Rankine Cycle Modified Rankine Cycle Regenerative Cycle Reheat Cycle Binary Vapour Cycle Additional/Typical Worked Examples Objective Types Questions RECIPROCATING STEAM ENGINE General Aspects of Heat Engines Definition and Classification of a Reciprocating Steam Engine Steam Engine Parts and their Description Working of a Steam Engine Steam Engine Terminology Hypothetical or Theoretical Indicator Diagram Actual Indicator Diagram and Diagram Factor Methods of Reducing Condensation Mean Effective Pressure (m.e.p. or p m ) Engine Indicators Indicated Power (I.P.) Brake Power (B.P.) Efficiencies of Steam Engine Mass of Steam in Cylinder Saturation Curve and Missing Quantity Governing of Steam Engines Valves Heat Balance Sheet Performance Curves Worked Examples Additional/Typical Examples Objective Type Questions COMPOUND STEAM ENGINES Introduction Advantages of Compound Steam Engines Classification of Compound Steam Engines

15 ( xv ) Chapters Pages Multi-cylinder Engines Estimation of Cylinder Dimensions (Compound Steam Engines) Causes of Loss of Thermal Efficiency in Compound Steam Engines The Governing of Compound Steam Engines Uniflow Steam Engine Worked Examples Additional/Typical Examples Objective Type Questions STEAM NOZZLES Introduction Steam Flow Through Nozzles Nozzle Efficiency Supersaturated or Metastable Expansion of Steam in a Nozzle General Relationship Between Area, Velocity and Pressure in Nozzle Flow Steam Injector Worked Examples Objective Type Questions STEAM TURBINES Introduction Classification of Steam Turbines Advantages of Steam Turbine Over Steam Engines Description of Common Types of Turbines Methods of Reducing Wheel or Rotor Speed Difference Between Impulse and Reaction Turbines Impulse Turbines Reaction Turbines Turbines Efficiencies Types of Power in Steam Turbine Practice State Point Locus and Reheat Factor Reheating Steam Bleeding Energy Losses in Steam Turbines Steam Turbine Governing and Control Special Forms of Steam Turbines Objective Type Questions STEAM CONDENSERS Introduction Vacuum

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