Preface
My goal with this book is to provide the undergraduate student in chemical engineering with the solid background to perform thermodynamic calculations with confidence, and the course instructor with a resource to help students achieve this goal. The intended audience is sophomore/junior students in chemical engineering. The book is divided into two parts. Part I covers the laws of thermodynamics, with applications to pure fluids; Part II extends thermodynamics to mixtures, with emphasis on phase and chemical equilibrium. The selection of topics was guided by the realities of the undergraduate curriculum, which gives us about 15 weeks per semester to develop the material and meet the learning objectives. Given that thermodynamics requires some minimum “sink-in” time, the deliberate choice was made to prioritize topics and cover them at a comfortable pace. Each part consists of seven chapters, corresponding to an average of about two weeks (six lectures) per chapter. Under such restrictions certain topics had to be left out and for others their coverage had to be limited. Highest priority is given to material that feeds directly to other key courses of the curriculum: separations, reactions, and capstone design. A deliberate effort was made to stay away from specialty topics such as electrochemical or biochemical systems on the premise that these are more appropriately dealt with (and at a depth that a book such as this could do no justice) in physical chemistry, biochemistry, and other dedicated courses. Students are made aware of the amazing generality of thermodynamics and are directed to other fields for such details as needed. A theme that permeates the book is the molecular basis of thermodynamics. Discussions of molecular phenomena remain at a qualitative level (except for very brief excursions to statistical concepts in the chapter on entropy), consistent with the background of the typical sophomore/junior. But the molecular picture is consistently brought up to reinforce the idea that the quantities we measure in the lab and the equations that describe them are manifestations of microscopic effects at the molecular level.
The two parts of the book essentially mirror the material of a two-course sequence in thermodynamics that is typically required in chemical engineering. The focus of Part I is on pure fluids exclusively. The PVT behavior is introduced early on (Chapter 2) so that when it comes to the first and second law (Chapters 3 and 4), students have the tools to perform basic calculations of enthalpy and entropy using steam tables (a surrogate for tabulated properties in general) and equations of state. Chapter 5 discusses fundamental relationships and the calculation of properties from equations of state. It is mathematically the densest chapter of Part I. Chapter 6 goes into applications of thermodynamics to chemical processes. The range of applications is limited to systems involving pure fluids, namely power plants and refrigeration/liquefaction systems. This is the part of the course that most directly relates to processes discussed in capstone design and justifies the “Chemical Engineering” in the title of the book. It is one of the longer chapters, with several examples and end-of-chapter problems. The last chapter in this part covers phase equilibrium for a single fluid and serves as the connector between the two parts, as fugacity is the main actor in Part II.
The second part begins with a survey of phase diagrams of binary and simple ternary systems. It introduces the variety of phase behaviors of mixtures and establishes the notion that each phase at equilibrium has its own composition, and introduces the lever rule as a basic material balance tool. Many programs probably cover some of that material in the Materials and Energy Balances course but the topics are central to subsequent discussions so that a separate chapter is justified. Chapter 9 extends the fundamental relationships, which in Part I were applied to pure fluids, to mixtures. This chapter also introduces the equation of state for mixtures and the calculation of mixture properties from the equation of state. Chapter 10 is a short chapter that establishes the phase equilibrium criterion for mixtures and applies the equation of state to calculate the phase diagram of a binary mixture. Chapters 11 and 12 deal with ideal and nonideal solutions, respectively. Chapter 13 goes over several topics of phase equilibrium that are too small to be in separate chapters. These include partial miscibility, solubility of gases and solids, and osmotic processes. The last chapter in this part, 14, covers reaction equilibrium. The focus of the chapter is to establish the fundamental relationships, which are then applied to single and multiphase reactions. Standard states are discussed in quite some detail, since this is a topic that seems to confuse students.
Overall, a great effort has been made to balance theory with examples and applications. Examples cover a wide range, from direct application of formulas and methodologies, to larger processes that require synthesis of several smaller problems. It has been my experience that students are more willing to accept what they perceive as abstract theory if they can see how this theory is tied to practical industrial situations. Realistic problems are rarely of the paper-and-pencil type, and this brings up the need for mathematical/computational tools. The choices today are many, from sophisticated hand calculators to spreadsheets and numerical packages. The textbook takes an agnostic approach when it comes to the type of software and leaves it up to the instructor to make that choice. Typically, the problems that require numerical tools are those involving calculations with equations of state. Some problems lend themselves to the use of process simulators but, by deliberate decision, there is no specific mention of these simulators in the book. As with the other computational tools, the choice is left to the instructor. In my experience, the best approach with problems that require a significant number of computations is to assign them as projects. Picking problems with industrial flavor not only motivates students in engineering, it also offers convincing justification for the practical need for theory and numerical methodologies.