Chemical, Biochemical, and Engineering Thermodynamics 5th Edition
PREFACE FOR INSTRUCTORS
This book is intended as the text for a course in thermodynamics for undergraduate and graduate students in chemical engineering and also for practicing engineers. Its previous four editions have served this purpose at the University of Delaware for almost forty years. In writing the first edition of this book I had two objectives that have been retained in the succeeding editions. The first was to develop a modern applied thermodynamics text, especially for chemical engineers, relevant to other parts of the curriculum–specifically to courses in separation sprocesses, chemical reactor analysis, and process design. The other objective was to develop, organize and present material in sufficient detail for students to obtain a good understanding of the basic principles of thermodynamics and a proficiency in applying these principles to the solution of a large variety of energy flow and equilibrium problems.
Since the earlier editions largely met these goals, and since the principles of thermodynamics have not changed over the past decade, this edition is similar in structure to the earlier ones. During this time, however, important changes in engineering education have taken place. The first is the increasing availability of powerful desktop computers and computational software, along with well-developed and easy-to-use process simulation software. Another is the increasing application of chemical engineering thermodynamics principles and models to new areas of technology such as polymers, biotechnology, solid-state processing, and the environment. The current edition of this text includes applications that address each of these changes.
The availability of desktop computers and equation-solving software has now made it possible to closely align engineering science, industrial practice, and undergraduate education. In their dormitory rooms or at home, students can now perform sophisticated thermodynamics and phase equilibrium calculations similar to those they will encounter in industry. In this fifth edition, I provide several different methods for making such calculations. The first is to utilize the set of programs I have developed for making specific types of calculations included in the fourth edition. These programs enable (1) the calculation of thermodynamic properties and vapor-liquid equilibrium of a pure fluid described by a cubic equation of state; (2) the calculation of the thermodynamic properties and phase equilibria for a multicomponent mixture described by a cubic equation of state; and (3) the prediction of activity coefficients in a mixture using the UNIFAC group-contribution activity coefficient model. These programs are available on the website for this book as both program-code and stand-alone executable modules; they are unchanged from the previous edition of this book. However, I suggest instead the use of the thermodynamics
package in Aspen Plus(R), which is continually updated and has an easy-to-use interface.
The second is to employ the computer algebra/calculus programs for MATHCAD on the website that provides solutions to many illustrations and homework problems in this edition. Alternatively, students and instructors could use similar programs such as MATHEMATICA, MAPLE, and MATLAB. Students who develop their own codes for such computer programs can achieve a thorough understanding of the methods required (and the computational difficulties involved) in solving complex problems without having to become experts in computer programming and numerical analysis. Students who use my prepared codes will be able to solve interesting problems and concentrate on the subject matter at hand, namely, thermodynamics, without being distracted by computational methods, algorithms, and programming languages. These equation-solving programs are, in my view, valuable educational tools; but there is no material in this textbook that requires their use. Whether to implement them or not is left to the discretion of the instructor.
More recently in engineering practice, these one-off thermodynamics programs written by textbook authors have been replaced by suites of programs, process simulators, that make it possible to quickly model a whole chemical plant using current unit operations and thermodynamics models, as well as to access enormous databanks of pure fluid and mixture thermodynamic data. A number of such simulators are available, such as ASPEN, HYSIS, PROSIM, and CAPE-OPEN. In this fifth edition, I have incorporated the ASPEN process simulator by adding thermodynamics illustrations and homework problems that use ASPEN. I recognize, however, that there is no universal agreement on the use of a process simulator in, especially, an undergraduate thermodynamics course. Indeed, there are those in my own department who argue against it. The argument against the use of prepared computer programs in general, and process simulators in particular, is that students will treat them as “black boxes” without understanding the fundamentals of thermodynamics or the methods for choosing the thermodynamic models most appropriate to the problem at hand. My argument for using process simulators in undergraduate instructional courses is two-fold. First, it allows students to solve with great efficiency more interesting and practical problems than they could, within a reasonable time-frame, solve by hand; and it provides them an opportunity to ask and answer “what-if” questions. For example, what happens to the vapor-liquid split and the compositions of each of the co-existing phases in a multi-component Joule-Thomson expansion if the inlet temperature or pressure is changed? Answering such what-if questions allows students to quickly develop an intuitive sense of the way processes behave, an understanding that otherwise might only be attained by repeated, tedious hand calculations. Second, using a process simulator introduces students to a tool they are likely to employ in their professional career.Moreover, modern process-simulation software is generally bug-free, providing an easy-to-use interface that is the same for all problems.
In this argument I have taken the middle road. By means of some of the illustrations and problems provided in this text, students will initially develop an understanding of the basic applications and methods of thermodynamics by doing hand calculations. Then, once they understand the basic principles and methods, I encourage them to use process simulators (rather than my previous programs) to explore many additional, and more complicated, applications of thermodynamic principles. Whereas nothing in this new edition requires students or the instructor to use a process simulator, the illustrations do contain examples of the results of using a process simulator. In addition, many opportunities for using process simulator software are provided in the numerous end-of-chapter problems. Furthermore, by using a process simulator the instructor can easily change the input parameters of a homework problem and obtain the solution, thereby providing unlimited opportunities for creating new problems. On the designated website for this new edition, I have, therefore, provided the ASPEN 8.6 input files for numerous illustrations and problems presented in the textbook. I have chosen ASPEN because it appears to be the process simulator most widely used in industry and at colleges and universities, in the United States at least. Clearly, any other process simulation software could be employed, but in these cases users will need to develop their own input files. Since I am introducing ASPEN in this fifth edition, I have not updated the thermodynamics programs included in previous editions of this textbook, and they remain available on the website. Still, I encourage the use of Aspen or other process-simulation software rather than these more primitive programs. (For assistance in employing the thermodynamics packages in Aspen, I suggest consulting my recent book, Using Aspen Plus in Thermodynamics Instruction, published by Wiley/AIChE in 2015.)
In an effort to make the subject of thermodynamics more accessible to students, the format of this book provides space for marginal notes. The notes I have added are meant to emphasize important ideas and concepts, as well as to make it easier for students to locate these concepts at a later time. Since I frequently write notes in the margins of books I own, I wanted to provide a place for students to add notes of their own. Also, I continue to enclose important equations in boxes, so that readers can easily identify the equations that are the end results of often detailed analysis. I hope this will enable students to quickly identify the central tree in what seems like a forest of equations. I have also provided a short title or description for each illustration to indicate the primary concept that is to be learned or grasped.
Readers familiar with earlier editions of this book will notice that while the basic structure remains the same, it contains many internal changes. For example, there are many new illustrative and homework problems. Illustrations have been added not only to demonstrate new concepts, but also to provide breaks among pages o mathematical derivations or thermodynamic philosophy. These should make thermodynamics and phase vi Preface equilibria more relevant to the interests of students. There are additional sections on chemical reactions in biochemical systems and I have included additional material on energy and energy-related processes. Furthermore, the biochemical applications now appear throughout the second half of the book rather than being relegated to the final chapter, as was the case in the previous edition.
Some of the idiosyncrasies present in earlier editions remain here. For example, I prefer to use the term energy balance rather than the first law, and to show that the Carnot efficiency easily follows once entropy is defined. Here I depart from the more common procedure of introducing entropy (and the second law) in terms of the Carnot cycle. My experience with the latter method is that students then have difficulty making the necessary generalization if the concept of entropy and the second law are introduced in terms of a specific device. Also, I continue to prefer the partial molar Gibbs energy, which describes the function precisely, to the term chemical potential. In most other areas, I employ traditional thermodynamic notation.
It has been a decade since the appearance of the fourth edition of this book. During this time many people have encouraged me to prepare a new edition and have graciously contributed their views, ideas, and advice. The most important contributors have been the undergraduate and graduate students I have taught at the University of Delaware. I have benefited greatly from their inquisitive minds and penetrating questions. I have also benefited from the helpful comments of colleagues at the University of Delaware and elsewhere who have used earlier editions of this book, and from the questions and comments of students around the world who have corresponded with me by email. I do refuse, however, to provide these students with solutions to homework problems assigned by their instructors, a not infrequent request.
I wish to thank the administration and my colleagues at the University of Delaware, who have provided the unencumbered time of a sabbatical leave necessary for the completion of this new edition. And I am grateful, as always, to my family for their support.
Stanley I. Sandler
January 25, 2016
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