Heat and Mass Transfer: A Practical Approach, 3/e
Yunus A. Çengel, University of Nevada-Reno
ISBN: 0073129305
Copyright year: 2007
1 Introduction and Basic Concepts
2 Heat Conduction Equation
3 Steady Heat Conduction
4 Transient Heat Conduction
5 Numerical Methods in Heat Conduction
6 Fundamentals of Convection
7 External Forced Convection
8 Internal Forced Convection
9 Natural Convection
10 Boiling and Condensation
11 Heat Exchangers
12 Fundamentals of Radiation
13 Radiation Heat Transfer
14 Mass Transfer
*15 Cooling of Electronic Equipment (online only)
*16 Heating and Cooling of Buildings (online only)
*17 Refrigeration and Freezing of Foods (online only)
Appendices
1 Property Tables and Charts (SI Units)
2 Property Tables and Charts (English Units)
*3 Introduction to EES (online only)
Overview
With complete coverage of the basic principles of heat transfer and a broad range of applications in a flexible format, Heat and Mass Transfer: A Practical Approach provides the perfect blend of fundamentals and applications. The text provides a highly intuitive and practical understanding of the material by emphasizing the physics and the underlying physical phenomena involved.
The text covers the standard topics of heat transfer with an emphasis on physics and real-world every day applications, while de-emphasizing the intimidating heavy mathematical aspects. This approach is designed to take advantage of students' intuition, making the learning process easier and more engaging. Nearly half of the Homework Problems including design, computer, essay, lab-type, and FE problems are new or revised to this edition. Using a reader-friendly approach and a conversational writing style, the book is self-instructive and entertains while it teaches. It shows that highly technical matter can be communicated effectively in a simple yet precise language.
Preface
BACKGROUND
Heat and mass transfer is a basic science that deals with the rate of transfer of thermal energy. It has a broad application area ranging from biological systems to common household appliances, residential and commercial buildings, industrial processes, electronic devices, and food processing. Students are assumed to have an adequate background in calculus and physics. The completion of first courses in thermodynamics, fluid mechanics, and differential equations prior to taking heat transfer is desirable. However, relevant concepts from these topics are introduced and reviewed as needed.
OBJECTIVES
This book is intended for undergraduate engineering students in their sophomore or junior year, and as a reference book by practicing engineers. The objectives of this text are
• To cover the basic principles of heat transfer.
• To present a wealth of real-world engineering examples to give students a feel for how heat transfer is applied in engineering practice.
• To develop an intuitive understanding of heat transfer by emphasizing the physics and physical arguments.
It is our hope that this book, through its careful explanations of concepts and its use of numerous practical examples and figures, helps the students develop the necessary skills to bridge the gap between knowledge and the confidence for proper application of that knowledge.
In engineering practice, an understanding of the mechanisms of heat transfer is becoming increasingly important since heat transfer plays a crucial role in the design of vehicles, power plants, refrigerators, electronic devices, buildings, and bridges, among other things. Even a chef needs to have an intuitive understanding of the heat transfer mechanism in order to cook the food “right” by adjusting the rate of heat transfer. We may not be aware of it, but we already use the principles of heat transfer when seeking thermal comfort. We insulate our bodies by putting on heavy coats in winter, and we minimize heat gain by radiation by staying in shady places in summer. We speed up the cooling of hot food by blowing on it and keep warm in cold weather by cuddling up and thus minimizing the exposed surface area. That is, we already use heat transfer whether we realize it or not.
GENERAL APPROACH
This text is the outcome of an attempt to have a textbook for a practically oriented heat transfer course for engineering students. The text covers the standard topics of heat transfer with an emphasis on physics and real-world applications. This approach is more in line with students’ intuition, and makes learning the subject matter enjoyable.
The philosophy that contributed to the overwhelming popularity of the prior editions of this book has remained unchanged in this edition. Namely, our goal has been to offer an engineering textbook that
• Communicates directly to the minds of tomorrow’s engineers in a simple yet precise manner.
• Leads students toward a clear understanding and firm grasp of the basic principles of heat transfer.
• Encourages creative thinking and development of a deeper understanding and intuitive feel for heat transfer.
• Is read by students with interest and enthusiasm rather than being used as an aid to solve problems.
Special effort has been made to appeal to students’ natural curiosity and to help them explore the various facets of the exciting subject area of heat transfer. The enthusiastic response we received from the users of prior editions— from small colleges to large universities all over the world—indicates that our objectives 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, now formula manipulations and number crunching are being left mainly to the computers. Tomorrow’s engineer will have to have 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 at how computational tools are used in engineering practice.
NEW IN THIS EDITION
All the popular features of the previous edition are retained while new ones are added. With the exception of the coverage of the theoretical foundations of transient heat conduction and moving the chapter “Cooling of Electronic Equipment” to the
A NEW TITLE
The title of the book is changed to Heat and Mass Transfer: A Practical Approach to attract attention to the coverage of mass transfer. All topics related to mass transfer, including mass convection and vapor migration through building materials, are introduced in one comprehensive chapter (Chapter 14).
EXPANDED COVERAGE OF TRANSIENT CONDUCTION
The coverage of Chapter 4, Transient Heat Conduction, is now expanded to include (1) the derivation of the dimensionless Biot and Fourier numbers by nondimensionalizing the heat conduction equation and the boundary and initial conditions, (2) the derivation of the analytical solutions of a one-dimensional transient conduction equation using the method of separation of variables, (3) the derivation of the solution of a transient conduction equation in the semiinfinite medium using a similarity variable, and (4) the solutions of transient heat conduction in semi-infinite mediums for different boundary conditions such as specified heat flux and energy pulse at the surface.
FUNDAMENTALS OF ENGINEERING (FE) EXAM PROBLEMS
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, about 250 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.
MICROSCALE HEAT TRANSFER
Recent inventions in micro and nano-scale systems and the development of micro and nano-scale devices continues to pose new challenges, and the understanding of the fluid flow and heat transfer at such scales is becoming more and more important. In Chapter 6, microscale heat transfer is presented as a Topic of Special Interest.
THREE ONLINE APPLICATION CHAPTERS
The application chapter “Cooling of Electronic Equipment” (Chapter 15) is now moved to the Online Learning Center together with two new chapters “Heating and Cooling of Buildings” (Chapter 16) and “Refrigeration and Freezing of Foods” (Chapter 17).
CONTENT CHANGES AND REORGANIZATION
With the exception of the changes already mentioned, minor changes are made in the main body of the text. Nearly 400 new problems are added, and many of the existing problems are revised. The noteworthy changes in various chapters are summarized here for those who are familiar with the previous edition.
• The title of Chapter 1 is changed to “Introduction and Basic Concepts.” Some artwork is replaced by photos, and several review problems on the first law of thermodynamics are deleted.
• Chapter 4 “Transient Heat Conduction” is revised greatly, as explained previously, by including the theoretical background and the mathematical details of the analytical solutions.
• Chapter 6 now has the Topic of Special Interest “Microscale Heat Transfer” contributed by Dr. Subrata Roy of
• Chapter 8 now has the Topic of Special Interest “Transitional Flow in Tubes” contributed by Dr. Afshin Ghajar of Oklahoma State University. • Chapter 13 “Heat Exchangers” is moved up as Chapter 11 to succeed “Boiling and Condensation” and to precede “Radiation.”
• In the appendices, the values of some physical constants are updated, and Appendix 3 “Introduction to EES” is moved to the enclosed CD and the
Ch-1: Introduction and Basic Concepts
OBJECTIVES
1. Understand how thermodynamics and heat transfer are related to each other,
2. Distinguish thermal energy from other forms of energy, and heat transfer from other forms of energy transfer,
3. Perform general energy balances as well as surface energy balances,
4. Understand the basic mechanisms of heat transfer, which are conduction, convection, and radiation, and Fourier's law of heat conduction,
5. Identify the mechanisms of heat transfer that occur simultaneously in practice,
6. Develop an awareness of the cost associated with heat losses, and
7. Solve various heat transfer problems encountered in practice.
Ch-2: Heat Conduction Equation
OBJECTIVES
1. Understand multidimensionality and time dependence of heat transfer, and the conditions under which a heat transfer problem can be approximated as being one-dimensional,
2. Obtain the differential equation of heat conduction in various coordinate systems, and simplify it for steady one-dimensional case,
3. Identify the thermal conditions on surfaces, and express them mathematically as boundary and initial conditions,
4. Solve one-dimensional heat conduction problems and obtain the temperature distributions within a medium and the heat flux,
5. Analyze one-dimensional heat conduction in solids that involve heat generation, and
6. Evaluate heat conduction in solids with temperature-dependent thermal conductivity.
Ch-3: Steady Heat Conduction
OBJECTIVES
1. Understand the concept of thermal resistance and its limitations, and develop thermal resistance networks for practical heat conduction problems,
2. Solve steady conduction problems that involve multilayer rectangular, cylindrical, or spherical geometries,
3. Develop an intuitive understanding of thermal contact resistance, and circumstances under which it may be significant,
4. Identify applications in which insulation may actually increase heat transfer,
5. Analyze finned surfaces, and assess how efficiently and effectively fins enhance heat transfer, and
6. Solve multidimensional practical heat conduction problems using conduction shape factors.
Ch-4: Transient Heat Conduction
OBJECTIVES
1. Assess when the spatial variation of temperature is negligible, and temperature varies nearly uniformly with time, making the simplified lumped system analysis applicable,
2. Obtain analytical solutions for transient one-dimensional conduction problems in rectangular, cylindrical, and spherical geometries using the method of separation of variables, and understand why a one-term solution is usually a reasonable approximation,
3. Solve the transient conduction problem in large mediums using the similarity variable, and predict the variation of temperature with time and distance from the exposed surface, and
4. Construct solutions for multi-dimensional transient conduction problems using the product solution approach.
Ch-5: Numerical Methods in Heat Conduction
OBJECTIVES
1. Understand the limitations of analytical solutions of conduction problems, and the need for computation-intensive numerical methods,
2. Express derivates as differences, and obtain finite difference formulations,
3. Solve steady one- or two-dimensional conduction problems numerically using the finite difference method, and
4. Solve transient one- or two-dimensional conduction problems using the finite difference method.
Ch-6: Fundamentals of Convection
OBJECTIVES
1. Understand the physical mechanism of convection, and its classification,
2. Visualize the development of velocity and thermal boundary layers during flow over surfaces,
3. Gain a working knowledge of the dimensionless Reynolds, Prandtl, and Nusselt numbers,
4. Distinguish between laminar and turbulent flows, and gain an understanding of the mechanisms of momentum and heat transfer in turbulent flow,
5. Derive the differential equations that govern convection on the basis of mass, momentum, and energy balances, and solve these equations for some simple cases such as laminar flow over a flat plate,
6. Nondimensionalize the convection equations and obtain the functional forms of friction and heat transfer coefficients, and
7. Use analogies between momentum and heat transfer, and determine heat transfer coefficient from knowledge of friction coefficient.
Ch-7: External Forced Convection
OBJECTIVES
1. Distinguish between internal and external flow,
2. Develop an intuitive understanding of friction drag and pressure drag, and evaluate the average drag and convection coefficients in external flow,
3. Evaluate the drag and heat transfer associated with flow over a flat plate for both laminar and turbulent flow,
4. Calculate the drag force exerted on cylinders during cross flow, and the average heat transfer coefficient, and
5. Determine the pressure drop and the average heat transfer coefficient associated with flow across a tube bank for both in-line and staggered configurations.
Ch-8: Internal Forced Convection
OBJECTIVES
1. Obtain average velocity from a knowledge of velocity profile, and average temperature from a knowledge of temperature profile in internal flow,
2. Have a visual understanding of different flow regions in internal flow, such as the entry and the fully developed flow regions, and calculate hydrodynamic and thermal entry lengths,
3. Analyze heating and cooling of a fluid flowing in a tube under constant surface temperature and constant surface heat flux conditions, and work with the logarithmic mean temperature difference,
4. Obtain analytic relations for the velocity profile, pressure drop, friction factor, and Nusselt number in fully developed laminar flow, and
5. Determine the friction factor and Nusselt number in fully developed turbulent flow using empirical relations, and calculate the pressure drop and heat transfer rate.
Ch-9: Natural Convection
OBJECTIVES
1. Understand the physical mechanism of natural convection,
2. Derive the governing equations of natural convection, and obtain the dimensionless Grashof number by nondimensionalizing them,
3. Evaluate the Nusselt number for natural convection associated with vertical, horizontal, and inclined plates as well as cylinders and spheres,
4. Examine natural convection from finned surfaces, and determine the optimum fin spacing,
5. Analyze natural convection inside enclosures such as double-pane windows, and
6. Consider combined natural and forced convection, and assess the relative importance of each mode.
Ch-10: Boiling and Condensation
OBJECTIVES
1. Differentiate between evaporation and boiling, and gain familiarity with different types of boiling,
2. Develop a good understanding of the boiling curve, and the different boiling regimes corresponding to different regions of the boiling curve,
3. Calculate the heat flux and its critical value associated with nucleate boiling, and examine the methods of boiling heat transfer enhancement,
4. Derive a relation for the heat transfer coefficient in laminar film condensation over a vertical plate,
5. Calculate the heat flux associated with condensation on inclined and horizontal plates, vertical and horizontal cylinders or spheres, and tube bundles,
6. Examine dropwise condensation and understand the uncertainties associated with them.
Ch-11: Heat Exchangers
OBJECTIVES
1. Recognize numerous types of heat exchangers, and classify them,
2. Develop an awareness of fouling on surfaces, and determine the overall heat transfer coefficient for a heat exchanger,
3. Perform a general energy analysis on heat exchangers,
4. Obtain a relation for the logarithmic mean temperature difference for use in the LMTD method, and modify it for different types of heat exchangers using the correction factor,
5. Develop relations for effectiveness, and analyze heat exchangers when outlet temperatures are not known using the effectiveness-NTU method,
6. Know the primary considerations in the selection of heat exchangers.
Ch-12: Fundamentals of Thermal Radiation
OBJECTIVES
1. Classify electromagnetic radiation, and identify thermal radiation,
2. Understand the idealized blackbody, and calculate the total and spectral blackbody emissive power,
3. Calculate the fraction of radiation emitted in a specified wavelength band using the blackbody radiation functions,
4. Understand the concept of radiation intensity, and define spectral directional quantities using intensity,
5. Develop a clear understanding of the properties emissivity, absorptivity, relflectivity, and transmissivity on spectral, directional, and total basis,
6. Apply Kirchhoff law’s law to determine the absorptivity of a surface when its emissivity is known,
7. Model the atmospheric radiation by the use of an effective sky temperature, and appreciate the importance of greenhouse effect.NTENTS
Ch-13: Radiation Heat Transfer
OBJECTIVES
1. Define view factor, and understand its importance in radiation heat transfer calculations,
2. Develop view factor relations, and calculate the unknown view factors in an enclosure by using these relations,
3. Calculate radiation heat transfer between black surfaces,
4. Determine radiation heat transfer between diffuse and gray surfaces in an enclosure using the concept of radiosity,
5. Obtain relations for net rate of radiation heat transfer between the surfaces of a two-zone enclosure, including two large parallel plates, two long concentric cylinders, and two concentric spheres,
6. Quantify the effect of radiation shields on the reduction of radiation heat transfer between two surfaces, and become aware of the importance of radiation effect in temperature measurements.
Ch-14: Mass Transfer
OBJECTIVES
1. Understand the concenration gradient and the physical mechanism of mass transfer,
2. Recognize the analogy between heat and mass transfer,
3. Describe the concenration at a location on mass or mole basis, and relate the rate of diffusion to the concentration gradient by Fick’s law,
4. Calculate the rate of mass diffusion through a plain layer under steady conditions,
5. Predict the migration of water vapor in buildings,
6. Perform a transient mass diffusion analysis in large mediums,
7. Calculate mass transfer by convection, and
8. Analyze simultaneous heat and mass transfer.
Ch-15: OBJECTIVES
Not available for this chapter.
Ch-16: OBJECTIVES
Not available for this chapter.
Ch-17: OBJECTIVES
Not available for this chapter.
SUPPLEMENTS
The following supplements are available to the adopters of the book.
ENGINEERING EQUATION SOLVER (EES) CD-ROM
(Limited Academic Version packaged free with every new copy of the text) Developed by Sanford Klein and William Beckman from the
ONLINE
Web support is provided for the text on our
COSMOS CD-ROM
(Available to instructors only)
The instructor CD provides electronic solutions delivered via our database management tool. 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