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Thermodynamics THERMODYNAMICS For MECHANICAL ENGINEERING THERMODYNAMICS SYLLABUS Thermodynamic systems and processes; properties of pure substances, behaviour of ideal and real gases; zeroth and first laws of thermodynamics, calculation of work and heat in various processes; second law of thermodynamics; thermodynamic property charts and tables, availability and irreversibility; thermodynamic relations. Power Engineering: Air and gas compressors; vapour and gas power cycles, concepts of regeneration and reheat. I.C. Engines: Air-standard Otto, Diesel and dual cycles. Refrigeration and air-conditioning: Vapour and gas refrigeration and heat pump cycles; properties of moist air, psychrometric chart, basic psychrometric processes. ANALYSIS OF GATE PAPERS Exam Year 1 Mark Ques. 2 Mark Ques. Total 2003 5 6 17 2004 3 6 15 2005 2 7 16 2006 - 7 14 2007 2 6 14 2008 2 9 20 2009 3 4 11 2010 2 4 10 2011 2 7 16 2012 1 2 5 2013 1 4 9 2014 Set-1 2 4 10 2014 Set-2 2 2 6 2014 Set-3 1 3 7 2014 Set-4 - 4 8 2015 Set-1 4 3 10 2015 Set-2 3 4 11 2015 Set-3 2 3 8 2016 Set-1 3 3 9 2016 Set-2 3 2 7 2016 Set-3 1 2 5 2017 Set-1 1 4 9 2017 Set-2 2 4 10 2018 Set-1 2 3 8 2018 Set-2 2 4 10 © Copyright Reserved by Gateflix.in No part of this material should be copied or reproduced without permission CONTENTS Topics Page No 1. BASIC CONCEPTS OF THERMODYNAMICS 1.1 Thermodynamic 01 1.2 Microscopic Approach and Macroscopic Approach 01 1.3 System 01 1.4 Property of System 02 1.5 State 03 1.6 Thermodynamic Equilibrium 04 1.7 Zeroth Law of Thermodynamics 04 1.8 Ideal gas Equation and Process 06 1.9 Work Transfer 08 1.10 Heat Transfer 10 1.11 Example 11 2. FIRST LAW OF THERMODYNAMICS 2.1 First Law of Thermodynamics for a Cycle 13 2.2 Application of First Law of Thermodynamics 13 2.3 Meyer’s Formula 14 2.4 Heat Transfer in Different Process 15 2.5 Free Expansion 15 2.6 First Law of Thermodynamics for Flow Process 16 2.7 First Law of Thermodynamics for Variable Flow Process 17 2.8 Examples 18 3. SECOND LAW OF THERMODYNAMICS - ENTROPY 3.1 Thermal Reservoir 23 3.2 Equivalence of Kelvin Plank and Clausius Statement 25 3.3 Carnot Cycle 25 3.4 Refrigeration & Heat Pump working on Reversed Carnot Cycle 26 3.5 Clausius Theorem 26 3.6 Entropy 28 3.7 Combined First Law and Second Law of Thermodynamics 28 3.8 Entropy change for an ideal gas 29 3.9 Entropy change for finite body 29 3.10 Slope of isobaric process & isochoric process on T-S Diagram 29 3.11 Example 29 4. AVAILABLE ENERGY & THERMODYNAMIC RELATIONS 4.1 Available Energy 34 © Copyright Reserved by Gateflix.in No part of this material should be copied or reproduced without permission 4.2 Unavailable Energy 35 4.3 Loss in Available Energy 35 4.4 Available Function 35 4.5 Irreversibility 36 4.6 Exact Differential Equations 36 4.7 Maxwell’s Equations 36 4.8 T – DS Equations 36 4.9 Energy Equation 38 4.10 Enthalpy Equation 38 4.11 Difference in Heat Capacities 38 4.12 Joule Kelvin Coefficient 39 4.13 Examples 39 5. PROPERTIES OF PURE SUBSTANCE & GAS MIXTURE 5.1 Pure substance 44 5.2 P – V diagram of Pure substance 44 5.3 Triple Point 45 5.4 Gibbs phase rule 45 5.5 Phase Change of Pure substance 45 5.6 T – S diagram of pure substance 46 5.7 Properties of Pure Substance 47 5.8 Specific volume, Enthalpy and Entropy of different Phases 48 5.9 Equation of State 49 5.10 Properties of Gas mixture 51 5.11 Examples 51 6. REFRIGERATION 6.1 Introduction 56 6.2 Air Standard Refrigeration Cycle 56 6.3 Refrigerator working on reversed brayton Cycle 58 6.4 Vapour Compression Refrigeration Cycle 60 6.5 Effect of Parameters on COP of Vapour Compression Refrigeration cycle 62 6.6 Vapour Absorption Refrigeration Systems 63 6.7 Refrigerant 65 6.8 Designation of refrigerants 66 6.9 Examples 66 7. PSYCHOMETRY 7.1 Properties of Moist Air 72 7.2 Psychometric Chart 73 7.3 Significance, Different Lines on Psychometric Chart 74 7.4 Different Process on Psychometric Chart 78 7.5 Examples 79 © Copyright Reserved by Gateflix.in No part of this material should be copied or reproduced without permission 8. POWER PLANT ENGINEERING 8.1 Stirling cycle 84 8.2 Ericson cycle 84 8.3 Gas Power Plant 84 8.4 Steam Power Plant 88 8.5 Nozzle and Diffuser 90 8.6 Compressor 92 8.7 Steam turbine 93 8.8 Examples 93 9. INTERNAL COMBUSTION ENGINE 9.1 Heat Engine 101 9.2 Applications of IC Engines 101 9.3 Classifications of IC Engines 101 9.4 Basic components of IC Engine 101 9.5 Terms used in internal combustion engine 102 9.6 Difference between four stroke and two stroke Engine 103 9.7 Performance Parameters 103 9.8 Air standard cycle and efficiency 103 9.9 Comparison of Otto, Diesel, dual Cycle 106 9.10 Examples 107 10. GATE QUESTIONS 112 © Copyright Reserved by Gateflix.in No part of this material should be copied or reproduced without permission 1 BASIC CONCEPTS OF THERMODYNAMICS 1.1 THERMODYNAMICS 1.3 SYSTEM Thermodynamics is the science of energy A quantity of matter or region in space transfer and its effect on the physical upon which attention is concentrated is properties of the substances. known as thermodynamic System. The Some students have difficulties with system and the boundary are specified by thermodynamics because of global nature the analyst, these are not specified in a of its applicability. Most students are used problem statement. to courses that focus on a few specific topics like statics, dynamics, fluid flows etc. 1.3.1 SURROUNDING all deals with the limited range of topics. Thermodynamics, on the other hands, deals Anything external to the system is called as with many issues that are inherent in every surrounding or Environment. The engineering system. A thermodynamic combination of the system and surrounding analysis can span from analyzing a makes universe. It means in the universe if complete power plant to analyzing the anything is specified by the analyst as a smallest component in power plant. system the things except that system are We begin by introducing some basic considered as the surrounding. thermodynamic terms and definitions. Some of these terms are already in our everyday vocabulary as a result of the broad result of thermodynamics concepts in non engineering concepts (for example cooling process of tea in the open environment is a thermodynamic process). 1.2 MICROSCOPIC APPROACH AND Fig.1.1system, surrounding and boundary MACROSCOPIC APPROACH 1.3.2 BOUNDARY In microscopic approach, a certain quantity of matter is considered with The separation line which separates the considering the event occurring at system from surrounding is called as molecular level. It is called as statistical Boundary. Thermodynamics. In Macroscopic Boundary may be fixed or rigid, may be approach, a certain quantity of matter is real or imaginary. considered without considering the event occurring at molecular level. In this, 1.3.3 UNIVERSE average behaviour of molecules is considered. It is called as Dynamic The combination of system and surrounding Thermodynamic. is called as Universe. At the higher altitude or where the density Universe = system + Surrounding of the system is low, the microscopic approach is used for checking the 1.3.4 TYPE OF SYSTEM behaviour of the system. There are three types of thermodynamic systems. © Copyright Reserved by Gateflix.in No part of this material should be copied or reproduced without permission 1) Closed System: fluid id transmitted from the outlet valve (for example the process of compression in The system in which only energy can compressor),the mass with energy leaves transfer without transferring the mass from the system it means in this system across the system boundary is called as mass and energy both crosses the closed system. An example of closed system boundary so this is considered as the Open is mass of gas in the piston cylinder System. without valve. Let us consider the piston cylinder 3) Isolated System: arrangement as shown in fig 1.2. When heat is supplied to system, gas inside the The system in which, neither energy nor cylinder expands and thermal energy is mass can transfer across the system converted into mechanical work. But mass boundary is called as isolated system. of the gas will be the same after the process Example: Universe, Insulated thermal flask. in cylinder it means there is no mass which Let consider a proper insulated thermal crosses the boundary of the system so it is flask and hot water is filled in the thermal considered as closed system. flask after passing of the time mass and temperature are same which shows neither energy nor mass crosses the thermal boundary of the flask, so it is considered as an isolated system. fig.:1.2 closed system 2) Open System: The system in which energy and the mass Fig. 1.4 isolated system can transfer across the system boundary is called as open system. Most of engineering 1.4 PROPERTY OF SYSTEM devices are open systems. Examples: Turbine, Pump, Boiler, condenser Etc. A property of the system is a characteristic of system that depends upon the state of the system .as long as state is fixed, property of system is fixed.
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