xviii THERMODYNAMICS have largely been achieved.It is our philosophy that the best way to learn is by practice.Therefore,special effort is made throughout the book to reinforce material that was presented earlier. Yesterday's engineer spent a major portion of his or her time substituting values into the formulas and obtaining numerical results.However,formula manipulations and number crunching are now being left mainly to computers. Tomorrow's engineer will need a clear understanding and a firm grasp of the basic principles so that he or she can understand even the most complex prob- lems,formulate them,and interpret the results.A conscious effort is made to emphasize these basic principles while also providing students with a per- spective of how computational tools are used in engineering practice. The traditional classical,or macroscopic,approach is used throughout the text,with microscopic arguments serving in a supporting role as appropriate. This approach is more in line with students'intuition and makes learning the subject matter much easier. NEW IN THIS EDITION The primary change in this eighth edition of the text is the effective use of full color to enhance the learning experience of students and to make it more enjoyable.Another significant change is the addition of a new web chapter on Renewable Energy available via the Online Learning Center.The third important change is the update of the R-134a tables to make property values consistent with those from the latest version of EES.All the solved examples and end-of-chapter problems dealing with R-134a are modified to reflect this change.This edition includes numerous new problems with a variety of applications.Problems,whose solutions require parametric investigations and thus the use of a computer,are identified by a computer-EES icon,as before. Some existing problems from previous editions have been removed,and other updates and changes for clarity and readability have been made throughout the text. The eighth edition also includes McGraw-Hill's ConnectR Engineering. This online homework management tool allows assignment of algorithmic problems for homework,quizzes and tests.It connects students with the tools and resources they'll need to achieve success.To learn more,visit www.mcgrawhillconnect.com. McGraw-Hill LearnSmartTM is also available as an integrated feature of McGraw-Hill Connect@Engineering.It is an adaptive learning system designed to help students learn faster.study more efficiently,and retain more knowledge for greater success.LearnSmart assesses a student's knowledge of course content through a series of adaptive questions.It pinpoints concepts the student does not understand and maps out a personalized study plan for success.Visit the following site for a demonstration:www.mhlearnsmart.com. LEARNING TOOLS EARLY INTRODUCTION OF THE FIRST LAW OF THERMODYNAMICS The first law of thermodynamics is introduced early in Chapter 2,"Energy, Energy Transfer,and General Energy Analysis."This introductory chapter
xviii THERMODYNAMICS have largely been achieved. It is our philosophy that the best way to learn is by practice. Therefore, special effort is made throughout the book to reinforce material that was presented earlier. Yesterday’s engineer spent a major portion of his or her time substituting values into the formulas and obtaining numerical results. However, formula manipulations and number crunching are now being left mainly to computers. Tomorrow’s engineer will need a clear understanding and a firm grasp of the basic principles so that he or she can understand even the most complex problems, formulate them, and interpret the results. A conscious effort is made to emphasize these basic principles while also providing students with a perspective of how computational tools are used in engineering practice. The traditional classical, or macroscopic, approach is used throughout the text, with microscopic arguments serving in a supporting role as appropriate. This approach is more in line with students’ intuition and makes learning the subject matter much easier. NEW IN THIS EDITION The primary change in this eighth edition of the text is the effective use of full color to enhance the learning experience of students and to make it more enjoyable. Another significant change is the addition of a new web chapter on Renewable Energy available via the Online Learning Center. The third important change is the update of the R-134a tables to make property values consistent with those from the latest version of EES. All the solved examples and end-of-chapter problems dealing with R-134a are modified to reflect this change. This edition includes numerous new problems with a variety of applications. Problems, whose solutions require parametric investigations and thus the use of a computer, are identified by a computer-EES icon, as before. Some existing problems from previous editions have been removed, and other updates and changes for clarity and readability have been made throughout the text. The eighth edition also includes McGraw-Hill’s Connect® Engineering. This online homework management tool allows assignment of algorithmic problems for homework, quizzes and tests. It connects students with the tools and resources they’ll need to achieve success. To learn more, visit www.mcgrawhillconnect.com. McGraw-Hill LearnSmart™ is also available as an integrated feature of McGraw-Hill Connect® Engineering. It is an adaptive learning system designed to help students learn faster, study more efficiently, and retain more knowledge for greater success. LearnSmart assesses a student’s knowledge of course content through a series of adaptive questions. It pinpoints concepts the student does not understand and maps out a personalized study plan for success. Visit the following site for a demonstration: www.mhlearnsmart.com. LEARNING TOOLS EARLY INTRODUCTION OF THE FIRST LAW OF THERMODYNAMICS The first law of thermodynamics is introduced early in Chapter 2, “Energy, Energy Transfer, and General Energy Analysis.” This introductory chapter cen98179_fm_i-xxvi.indd xviii 11/29/13 6:39 PM
xix PREFACE sets the framework of establishing a general understanding of various forms of energy,mechanisms of energy transfer,the concept of energy balance, thermo-economics,energy conversion,and conversion efficiency using familiar settings that involve mostly electrical and mechanical forms of energy.It also exposes students to some exciting real-world applications of thermodynamics early in the course,and helps them establish a sense of the monetary value of energy.There is special emphasis on the utilization of renewable energy such as wind power and hydraulic energy,and the efficient use of existing resources. EMPHASIS ON PHYSICS A distinctive feature of this book is its emphasis on the physical aspects of the subject matter in addition to mathematical representations and manipulations. The authors believe that the emphasis in undergraduate education should remain on developing a sense of underlying physical mechanisms and a mas- tery of solving practical problems that an engineer is likely to face in the real world.Developing an intuitive understanding should also make the course a more motivating and worthwhile experience for students. EFFECTIVE USE OF ASSOCIATION An observant mind should have no difficulty understanding engineering sciences.After all,the principles of engineering sciences are based on our everyday experiences and experimental observations.Therefore,a physi- cal,intuitive approach is used throughout this text.Frequently,parallels are drawn between the subject matter and students'everyday experiences so that they can relate the subject matter to what they already know.The process of cooking,for example,serves as an excellent vehicle to demonstrate the basic principles of thermodynamics. SELF-INSTRUCTING The material in the text is introduced at a level that an average student can follow comfortably.It speaks to students,not over students.In fact,it is self- instructive.The order of coverage is from simple to general.That is,it starts with the simplest case and adds complexities gradually.In this way,the basic principles are repeatedly applied to different systems,and students master how to apply the principles instead of how to simplify a general formula.Not- ing that the principles of sciences are based on experimental observations,all the derivations in this text are based on physical arguments,and thus they are easy to follow and understand. EXTENSIVE USE OF ARTWORK Figures are important learning tools that help students"get the picture,"and the text makes very effective use of graphics.This edition of Thermodynamics: An Engineering Approach,Eighth Edition features an enhanced art program done in four colors to provide more realism and pedagogical understand- ing.Further,a large number of figures have been upgraded to become three- dimensional and thus more real-life.Figures attract attention and stimulate curiosity and interest.Most of the figures in this text are intended to serve as a means of emphasizing some key concepts that would otherwise go unnoticed; some serve as page summaries
xix PREFACE sets the framework of establishing a general understanding of various forms of energy, mechanisms of energy transfer, the concept of energy balance, thermo-economics, energy conversion, and conversion efficiency using fa mil iar settings that involve mostly electrical and mechanical forms of energy. It also exposes students to some exciting real-world applications of thermodynamics early in the course, and helps them establish a sense of the monetary value of energy. There is special emphasis on the utilization of renewable energy such as wind power and hydraulic energy, and the efficient use of existing resources. EMPHASIS ON PHYSICS A distinctive feature of this book is its emphasis on the physical aspects of the subject matter in addition to mathematical representations and manipulations. The authors believe that the emphasis in undergraduate education should remain on developing a sense of underlying physical mechanisms and a mastery of solving practical problems that an engineer is likely to face in the real world. Developing an intuitive understanding should also make the course a more motivating and worthwhile experience for students. EFFECTIVE USE OF ASSOCIATION An observant mind should have no difficulty understanding engineering sciences. After all, the principles of engineering sciences are based on our everyday experiences and experimental observations. Therefore, a physical, intuitive approach is used throughout this text. Frequently, parallels are drawn between the subject matter and students’ everyday experiences so that they can relate the subject matter to what they already know. The process of cooking, for example, serves as an excellent vehicle to demonstrate the basic principles of thermodynamics. SELF-INSTRUCTING The material in the text is introduced at a level that an average student can follow comfortably. It speaks to students, not over students. In fact, it is selfinstructive. The order of coverage is from simple to general. That is, it starts with the simplest case and adds complexities gradually. In this way, the basic principles are repeatedly applied to different systems, and students master how to apply the principles instead of how to simplify a general formula. Noting that the principles of sciences are based on experimental observations, all the derivations in this text are based on physical arguments, and thus they are easy to follow and understand. EXTENSIVE USE OF ARTWORK Figures are important learning tools that help students “get the picture,” and the text makes very effective use of graphics. This edition of Thermodynamics: An Engineering Approach, Eighth Edition features an enhanced art program done in four colors to provide more realism and pedagogical understanding. Further, a large number of figures have been upgraded to become threedimensional and thus more real-life. Figures attract attention and stimulate curiosity and interest. Most of the figures in this text are intended to serve as a means of emphasizing some key concepts that would otherwise go unnoticed; some serve as page summaries. cen98179_fm_i-xxvi.indd xix 11/29/13 6:39 PM
THERMODYNAMICS LEARNING OBJECTIVES AND SUMMARIES Each chapter begins with an overview of the material to be covered and chapter-specific learning objectives.A summary is included at the end of each chapter,providing a quick review of basic concepts and important rela- tions,and pointing out the relevance of the material. NUMEROUS WORKED-OUT EXAMPLES WITH A SYSTEMATIC SOLUTIONS PROCEDURE Each chapter contains several worked-out examples that clarify the material and illustrate the use of the basic principles.An intuitive and systematic approach is used in the solution of the example problems,while maintaining an informal conversational style.The problem is first stated,and the objectives are identified. The assumptions are then stated,together with their justifications.The proper- ties needed to solve the problem are listed separately if appropriate.Numerical values are used together with their units to emphasize that numbers without units are meaningless,and that unit manipulations are as important as manipulating the numerical values with a calculator.The significance of the findings is dis- cussed following the solutions.This approach is also used consistently in the solutions presented in the instructor's solutions manual. A WEALTH OF REAL-WORLD END-OF-CHAPTER PROBLEMS The end-of-chapter problems are grouped under specific topics to make prob- lem selection easier for both instructors and students.Within each group of problems are Concept Ouestions,indicated by "C,"to check the students' level of understanding of basic concepts.The problems under Review Prob- lems are more comprehensive in nature and are not directly tied to any specific section of a chapter-in some cases they require review of material learned in previous chapters.Problems designated as Design and Essay are intended to encourage students to make engineering judgments,to conduct indepen- dent exploration of topics of interest,and to communicate their findings in a professional manner.Problems designated by an"E"are in English units, and SI users can ignore them.Problems with the are solved using EES, and complete solutions together with parametric studies are included on the textbook's website.Problems with the are comprehensive in nature and are intended to be solved with a computer,possibly using the EES software. Several economics-and safety-related problems are incorporated throughout to promote cost and safety awareness among engineering students.Answers to selected problems are listed immediately following the problem for conve- nience to students.In addition,to prepare students for the Fundamentals of Engineering Exam (that is becoming more important for the outcome-based ABET 2000 criteria)and to facilitate multiple-choice tests,over 200 multiple- choice problems are included in the end-of-chapter problem sets.They are placed under the title Fundamentals of Engineering (FE)Exam Problems for easy recognition.These problems are intended to check the understanding of fundamentals and to help readers avoid common pitfalls. RELAXED SIGN CONVENTION The use of a formal sign convention for heat and work is abandoned as it often becomes counterproductive.A physically meaningful and engag- ing approach is adopted for interactions instead of a mechanical approach
xx THERMODYNAMICS LEARNING OBJECTIVES AND SUMMARIES Each chapter begins with an overview of the material to be covered and chapter-specific learning objectives. A summary is included at the end of each chapter, providing a quick review of basic concepts and important relations, and pointing out the relevance of the material. NUMEROUS WORKED-OUT EXAMPLES WITH A SYSTEMATIC SOLUTIONS PROCEDURE Each chapter contains several worked-out examples that clarify the material and illustrate the use of the basic principles. An intuitive and systematic approach is used in the solution of the example problems, while maintaining an informal conversational style. The problem is first stated, and the objectives are identified. The assumptions are then stated, together with their justifications. The properties needed to solve the problem are listed separately if appropriate. Numerical values are used together with their units to emphasize that numbers without units are meaningless, and that unit manipulations are as important as manipulating the numerical values with a calculator. The significance of the findings is discussed following the solutions. This approach is also used consistently in the solutions presented in the instructor’s solutions manual. A WEALTH OF REAL-WORLD END-OF-CHAPTER PROBLEMS The end-of-chapter problems are grouped under specific topics to make problem selection easier for both instructors and students. Within each group of problems are Concept Questions, indicated by “C,” to check the students’ level of understanding of basic concepts. The problems under Review Problems are more comprehensive in nature and are not directly tied to any specific section of a chapter—in some cases they require review of material learned in previous chapters. Problems designated as Design and Essay are intended to encourage students to make engineering judgments, to conduct independent exploration of topics of interest, and to communicate their findings in a professional manner. Problems designated by an “E” are in English units, and SI users can ignore them. Problems with the are solved using EES, and complete solutions together with parametric studies are included on the textbook’s website. Problems with the are comprehensive in nature and are intended to be solved with a computer, possibly using the EES software. Several economics- and safety-related problems are incorporated throughout to promote cost and safety awareness among engineering students. Answers to selected problems are listed immediately following the problem for convenience to students. In addition, to prepare students for the Fundamentals of Engineering Exam (that is becoming more important for the outcome-based ABET 2000 criteria) and to facilitate multiple-choice tests, over 200 multiplechoice problems are included in the end-of-chapter problem sets. They are placed under the title Fundamentals of Engineering (FE) Exam Problems for easy recognition. These problems are intended to check the understanding of fundamentals and to help readers avoid common pitfalls. RELAXED SIGN CONVENTION The use of a formal sign convention for heat and work is abandoned as it often becomes counterproductive. A physically meaningful and engaging approach is adopted for interactions instead of a mechanical approach. cen98179_fm_i-xxvi.indd xx 11/29/13 6:39 PM
xxi PREFACE Subscripts "in"and "out,"rather than the plus and minus signs,are used to indicate the directions of interactions. PHYSICALLY MEANINGFUL FORMULAS The physically meaningful forms of the balance equations rather than formu- las are used to foster deeper understanding and to avoid a cookbook approach. The mass,energy,entropy,and exergy balances for any system undergoing any process are expressed as Mass balance: ma-mout=△my3iem Energy balance: Ein-Eout △E system Net energy transfer Change in intemal,kinetic. by heat.work,and mass potential.etc.,energies Entropy balance: Sin-Sou S en Net entropy transfer Entropy Change by heat and mass generation in entropy Exergy balance: Xin-Xout △X ystem Net exergy transfer Exergy Change by heat.work.and mass destruction in exergy These relations reinforce the fundamental principles that during an actual process mass and energy are conserved,entropy is generated,and exergy is destroyed.Students are encouraged to use these forms of balances in early chapters after they specify the system,and to simplify them for the particular problem.A more relaxed approach is used in later chapters as students gain mastery. A CHOICE OF SI ALONE OR SIENGLISH UNITS In recognition of the fact that English units are still widely used in some industries,both SI and English units are used in this text,with an emphasis on SI.The material in this text can be covered using combined SI/English units or SI units alone,depending on the preference of the instructor.The property tables and charts in the appendices are presented in both units,except the ones that involve dimensionless quantities.Problems,tables,and charts in English units are designated by"E"after the number for easy recognition,and they can be ignored by SI users. TOPICS OF SPECIAL INTEREST Most chapters contain a section called "Topic of Special Interest"where interesting aspects of thermodynamics are discussed.Examples include Ther- modynamic Aspects of Biological Systems in Chapter 4,Household Refrigera- tors in Chapter 6,Second-Law Aspects of Daily Life in Chapter 8,and Saving Fuel and Money by Driving Sensibly in Chapter 9.The topics selected for these sections provide intriguing extensions to thermodynamics,but they can be ignored if desired without a loss in continuity
xxi PREFACE Subscripts “in” and “out,” rather than the plus and minus signs, are used to indicate the directions of interactions. PHYSICALLY MEANINGFUL FORMULAS The physically meaningful forms of the balance equations rather than formulas are used to foster deeper understanding and to avoid a cookbook approach. The mass, energy, entropy, and exergy balances for any system undergoing any process are expressed as Mass balance: min 2 mout 5 Dmsystem Energy balance: Ein 2 Eout 5 DEsystem Net energy transfer Change in internal, kinetic, by heat, work, and mass potential, etc., energies Entropy balance: Sin 2 Sout 1 Sgen 5 DSsystem Net entropy transfer Entropy Change by heat and mass generation in entropy Exergy balance: Xin 2 Xout 2 Xdestroyed 5 DXsystem Net exergy transfer Exergy Change by heat, work, and mass destruction in exergy These relations reinforce the fundamental principles that during an actual process mass and energy are conserved, entropy is generated, and exergy is destroyed. Students are encouraged to use these forms of balances in early chapters after they specify the system, and to simplify them for the particular problem. A more relaxed approach is used in later chapters as students gain mastery. A CHOICE OF SI ALONE OR SI/ENGLISH UNITS In recognition of the fact that English units are still widely used in some industries, both SI and English units are used in this text, with an emphasis on SI. The material in this text can be covered using combined SI/English units or SI units alone, depending on the preference of the instructor. The property tables and charts in the appendices are presented in both units, except the ones that involve dimensionless quantities. Problems, tables, and charts in English units are designated by “E” after the number for easy recognition, and they can be ignored by SI users. TOPICS OF SPECIAL INTEREST Most chapters contain a section called “Topic of Special Interest” where interesting aspects of thermodynamics are discussed. Examples include Thermodynamic Aspects of Biological Systems in Chapter 4, Household Refrigerators in Chapter 6, Second-Law Aspects of Daily Life in Chapter 8, and Saving Fuel and Money by Driving Sensibly in Chapter 9. The topics selected for these sections provide intriguing extensions to thermodynamics, but they can be ignored if desired without a loss in continuity. cen98179_fm_i-xxvi.indd xxi 11/29/13 6:39 PM
XXii THERMODYNAMICS GLOSSARY OF THERMODYNAMIC TERMS Throughout the chapters,when an important key term or concept is intro- duced and defined,it appears in boldface type.Fundamental thermodynamic terms and concepts also appear in a glossary located on our accompanying website (www.mhhe.com/cengel).This unique glossary helps to reinforce key terminology and is an excellent learning and review tool for students as they move forward in their study of thermodynamics.In addition,students can test their knowledge of these fundamental terms by using the flash cards and other interactive resources. CONVERSION FACTORS Frequently used conversion factors and physical constants are listed on the inner cover pages of the text for easy reference. SUPPLEMENTS The following supplements are available to users of the book. ENGINEERING EQUATION SOLVER (EES) Developed by Sanford Klein and William Beckman from the University of Wisconsin-Madison,this software combines equation-solving capability and engineering property data.EES can do optimization,parametric analysis, and linear and nonlinear regression,and provides publication-quality plot- ting capabilities.Thermodynamics and transport properties for air,water,and many other fluids are built in,and EES allows the user to enter property data or functional relationships. EES is a powerful equation solver with built-in functions and property tables for thermodynamic and transport properties as well as automatic unit checking capability.It requires less time than a calculator for data entry and allows more time for thinking critically about modeling and solving engineer- ing problems.Look for the EES icons in the homework problems sections of the text. The Limited Academic Version of EES is available for departmental license upon adoption of the Eighth Edition of Thermodynamics:An Engineering Approach (meaning that the text is required for students in the course).You may load this software onto your institution's computer system,for use by students and faculty related to the course,as long as the arrangement between McGraw-Hill Education and F-Chart is in effect.There are minimum order requirements stipulated by F-Chart to qualify. PROPERTIES TABLE BOOKLET (1SBN0-07-762477-7) This booklet provides students with an easy reference to the most important property tables and charts,many of which are found at the back of the text- book in both the SI and English units. COSMOS McGraw-Hill's COSMOS (Complete Online Solutions Manual Organization System)allows instructors to streamline the creation of assignments,quizzes, and tests by using problems and solutions from the textbook,as well as their own custom material.COSMOS is now available online at http://cosmos.mhhe.com/
xxii THERMODYNAMICS GLOSSARY OF THERMODYNAMIC TERMS Throughout the chapters, when an important key term or concept is introduced and defined, it appears in boldface type. Fundamental thermo dynamic terms and concepts also appear in a glossary located on our accompanying website (www.mhhe.com/cengel). This unique glossary helps to reinforce key terminology and is an excellent learning and review tool for students as they move forward in their study of thermodynamics. In addition, students can test their knowledge of these fundamental terms by using the flash cards and other interactive resources. CONVERSION FACTORS Frequently used conversion factors and physical constants are listed on the inner cover pages of the text for easy reference. SUPPLEMENTS The following supplements are available to users of the book. ENGINEERING EQUATION SOLVER (EES) Developed by Sanford Klein and William Beckman from the University of Wisconsin—Madison, this software combines equation-solving capability and engineering property data. EES can do optimization, parametric analysis, and linear and nonlinear regression, and provides publication-quality plotting capabilities. Thermodynamics and transport properties for air, water, and many other fluids are built in, and EES allows the user to enter property data or functional relationships. EES is a powerful equation solver with built-in functions and property tables for thermodynamic and transport properties as well as automatic unit checking capability. It requires less time than a calculator for data entry and allows more time for thinking critically about modeling and solving engineering problems. Look for the EES icons in the homework problems sections of the text. The Limited Academic Version of EES is available for departmental license upon adoption of the Eighth Edition of Thermodynamics: An Engineering Approach (meaning that the text is required for students in the course). You may load this software onto your institution’s computer system, for use by students and faculty related to the course, as long as the arrangement between McGraw-Hill Education and F-Chart is in effect. There are minimum order requirements stipulated by F-Chart to qualify. PROPERTIES TABLE BOOKLET (ISBN 0-07-762477-7) This booklet provides students with an easy reference to the most important property tables and charts, many of which are found at the back of the textbook in both the SI and English units. COSMOS McGraw-Hill’s COSMOS (Complete Online Solutions Manual Organization System) allows instructors to streamline the creation of assignments, quizzes, and tests by using problems and solutions from the textbook, as well as their own custom material. COSMOS is now available online at http://cosmos.mhhe.com/ cen98179_fm_i-xxvi.indd xxii 11/29/13 6:39 PM