Preface to 6th edition

Heat transfer is the process by which energy moves from high temperature regions to low temperature regions. Mass transfer is the similar process by which molecules naturally migrate. This textbook describes those physical phenomena. The book’s objective is to teach the analysis, modeling, and design of engineered systems that apply heat and mass transfer. Readers should have a background in elementary thermodynamics and fluid mechanics, as is typical for junior and senior-level engineering students. The book is suitable for a one-semester course in heat and mass transfer, with some of the more advanced material excluded. The text is also well suited for self-study of some or all the material.

Organization of the book

This textbook consists of eleven chapters, divided into five parts. Part 1, The General Problem of Heat Exchange, contains three chapters that provide a broad introduction to heat transfer. The first chapter introduces the modes heat transfer, and the second develops the basic theory of heat conduction and the essential ideas of thermal resistance and the overall heat transfer coefficient. The third chapter uses the first law of thermodynamics and the overall heat transfer coefficient to derive the relationships for heat exchange between two fluids streams. Together, these three chapters form a “minicourse” in heat transfer. We use all this material in later chapters. Readers should understand these topics before they venture farther into the text.

Part 2, Analysis of Heat Conduction, contains two chapters. We begin Chapter 4 with further discussion of the heat conduction equation, including well-posed boundary and initial conditions and some general solutions. We then develop a simplified approach to dimensional analysis, which we use throughout all chapters that follow. Chapter 4 closes with a discussion of heat conducting fins. Such fins arise frequently, in forms both obvious and subtle, throughout the practice of heat transfer.

Chapter 5 explores unsteady heat conduction and heat conduction in more than one dimension. One-dimensional unsteady conduction is at the foundation of heat transfer, with wide-ranging applications. In fact, unsteady conduction in semi-infinite media provides a conceptual framework for our study of convective boundary layers in Chapter 6. The last two sections of this chapter discuss steady and unsteady multidimensional conduction.

Part 3 addresses Convective Heat Transfer. These four chapters make up the largest section of the book. Chapter 6 introduces laminar and turbulent boundary layers. We discuss the physical behavior of boundary layers in detail. We also derive formulae for the heat transfer coefficient in various configurations. However, since few real flows meet the idealized conditions of the formulae, readers should not skip over the physical behavior. Similarly, turbulent flow is present more often than laminar flow. The last three sections dig into this essential topic. Chapters 7 and 8 require the material in Chapter 6, but they do not require one another.

Chapter 7 shifts focus to convection in conduits and some more complex external flows. The first three sections—on pipe flows—are of vital importance throughout heat transfer engineering. The next two sections generalize this material to other configurations. Flow across the outside of tubes is the final topic.

Chapter 8 covers convection in which fluid flow is driven by buoyancy, called natural convection. This chapter also treats condensation from pure vapors, which bears a substantial physical and analytical similarity to natural convection.

Chapter 9 is an introduction to the physics and modeling of boiling processes. This chapter should offer little difficulty at any point beyond Chapter 6.

Part 4 of the book consists of Chapter 10, Radiative Heat Transfer. This stand-alone chapter is accessible at any point after Chapter 2. Radiation heat transfer is present at any temperature, but it becomes increasingly important as the temperature rises. Some processes involve both high and low temperature radiation, as when the sun’s heat is absorbed by the Earth. And radiative transfer through gases ultimately determines the temperature and climate on our planet.

Part 5, Mass Transfer, is the single Chapter 11. Many important phase-change processes occur in mixtures, rather than pure vapors, as for example when water condenses out of or evaporates into air. Mass transfer processes usually involve both diffusive and convective transport, and we discuss distinction in detail. When one species in a mixture is dilute (as for water vapor in room-temperature air), we can form a simple analogy between heat and mass transfer. This analogy enables us to adapt many formulae from Chapters 6, 7, and 8. In more concentrated or multicomponent mixtures, however, the analogy breaks down. We discuss alternate formulations in the final sections of this book. Many of the homework problems in this chapter build out ideas mentioned only briefly in the text. Readers who wish to master the material should attempt all the problems. This chapter does not require Chapter 9 and 10, nor any prior study of chemical thermodynamics.

Finally, Appendix A includes the physical property data needed for solving the end-of-chapter problems and the examples in text.

Changes in this edition

This edition differs from the fifth edition as follows. We have substantially edited Chapters 1, 2, 3, and 6 for content and clarity. We have entirely reworked the material on heat transfer in turbulent boundary layers in Chapter 6. We have heavily revised and rearranged Chapter 11, on mass transfer: we give greater attention to distinguishing between convection and diffusion, especially as the mass transfer rate rises; we treat concentrated mixtures in more detail; we have added a new section on multicomponent diffusion, for which Fick’s law is inadequate; we have added many new figures and examples; and we have reviewed, edited, and changed all of the end-of-chapter problems.

In total, we have redrawn or added more than 40 figures. We have also added, revised, or replaced dozens of end-of-chapter problems throughout the book. In parallel, we have greatly edited and added-to the solutions manual, which now includes more than 520 solved problems. We have updated the properties of many fluids in Appendix~A to accommodate new data. We have done a vast amount of editing of the entire text to gain greater clarity and to eliminate typos or errors. And, we have reviewed the references cited, providing links for online access where available.

A Heat Transfer Textbook has now existed for almost half a century. JHL IV wrote the first edition (1981) in the 1970s at the University of Kentucky. He based it on many years of teaching heat transfer to junior and senior level students in mechanical and chemical engineering. We added the material on mass transfer, by JHL V, to the second edition (1987). JHL V has led the third edition and all later editions. The third edition (2001) was primarily distributed as an e-book, and it was one of the very first engineering textbooks to be distributed in this format. Hundreds of thousands of readers from seven continents accessed that e-book. The fourth (2011) and fifth (2019) editions incorporated many more updates, changes, and corrections within the existing framework of the text. We published those editions both as e-books and as low-cost paperbacks distributed by Dover Publications.

The present sixth edition continues the evolution of A Heat Transfer Textbook. We hope that readers will find the material to have lasting value.

JHL IV, University of Houston
JHL V, Massachusetts Institute of Technology
April 2024

Prefaces of previous editions of AHTT

Preface to the 5th edition
Preface to the 4th edition
Preface to the 3rd edition
Preface to 2nd edition
Preface to 1st edtion