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Heat and Mass Transfer • Hans Dieter Baehr  Karl Stephan

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Heat and Mass Transfer • Hans Dieter Baehr  Karl Stephan Heat and Mass Transfer • Hans Dieter Baehr Karl Stephan Heat and Mass Transfer Third, revised edition With 343 Figures, Many Worked Examples and Exercises 123 Dr.-Ing. E.h. Dr.-Ing. Hans Dieter Baehr Dr.-Ing. E.h. mult. Dr.-Ing. Karl Stephan Professor em. of Thermodynamics Professor em. Institute of Thermodynamics University of Hannover and Thermal Process Engineering Germany University of Stuttgart 70550 Stuttgart Germany [email protected] ISBN 978-3-642-20020-5 e-ISBN 978-3-642-20021-2 DOI 10.1007/978-3-642-20021-2 Springer Heidelberg Dordrecht London New York Library of Congress Control Number: 2011934036 c Springer-Verlag Berlin Heidelberg 2011 This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilm or in any other way, and storage in data banks. Duplication of this publication or parts thereof is permitted only under the provisions of the German Copyright Law of September 9, 1965, in its current version, and permission for use must always be obtained from Springer. Violations are liable to prosecution under the German Copyright Law. The use of general descriptive names, registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. Cover design: SPi Publisher Services Printed on acid-free paper Springer is part of Springer Science+Business Media (www.springer.com) Preface to the third edition In this edition of our book we still retained its concept: The main emphasis is placed on the fundamental principles of heat and mass transfer and their applica- tion to practical problems of process modelling and apparatus design. Like the previous editions, the third edition contains five chapters and several appendices, particularly a compilation of thermophysical property data needed for the solution of problems. In this third edition the text has been expanded to include recent develop- ments. In chapter 2 on “Numerical solution to heat conduction problems” we added now an introduction into the numerical solution of heat conduction problems with the method of Finite Elements. It shall familiarise the student with the principles of the method, so that he will be able to solve basic problems by himself. For the solution of more complicated problems it is advisable to make use of one of the many programs available either commercially or on the Internet. The acquired knowledge will help to do so. The chapter 3 on “Convective heat and mass transfer, Single phase flow” was thoroughly revised. It is now complemented by a chapter on heat and mass transfer in porous bodies. In chapter 4 the subchapter explaining the phenomena of the mechanism of boiling heat transfer was revised. It presents now the recent state of our knowledge in the field. As in the previous editions changes were made in those chapters presenting heat and mass transfer correlations based on theoretical results or experimental findings. They were adapted to the most recent state of our knowledge. Also the compilation of the thermophysical properties, needed to solve heat and mass transfer problems, was revised and adapted to our present knowledge. As a con- sequence many of the worked examples and exercises had to be updated with the new thermophysical properties. The list of references was updated as well, including recent publications in the field. The worked examples not only illustrate the application of the theory, but are also relevant for apparatus design. Solving the exercises is essential for a sound understanding and for relating principles to real engineering situations. Numerical answers and hints to the solution of the exercises are given in the final appendix. The new edition also presented an opportunity to correct printing errors and mistakes. vi Preface In preparing this edition we were assisted by Annika Zeitz and Sebastian Asenbeck, who helped us to submit a printable version of the manuscript to the publisher. We owe them sincere thanks. We also appreciate the efforts of friends and colleagues who provided their good advice with constructive suggestions. Par- ticular thanks are due to Dr. Arno Laesecke at the National Institute of Science and Technology (NIST), Boulder, Colorado, USA. Bochum and Stuttgart, H.D. Baehr April 2011 K. Stephan • Preface to the first edition This book is the English translation of our German publication, which appeared in 1994 with the title “W¨arme und Stoffubertragung”¨ (7th edition Berlin: Springer- Verlag 2010). The German version originated from lecture courses in heat and mass transfer which we have held for many years at the Universities of Hannover and Stuttgart, respectively. Our book is intended for students of mechanical and chemical engineering at universities and engineering schools, but will also be of use to students of other subjects such as electrical engineering, physics and chemistry. Firstly our book should be used as a textbook alongside the lecture course. Its intention is to make the student familiar with the fundamentals of heat and mass transfer, and enable him to solve practical problems. On the other hand we placed special emphasis on a systematic development of the theory of heat and mass transfer and gave extensive discussions of the essential solution methods for heat and mass transfer problems. Therefore the book will also serve in the advanced training of practising engineers and scientists and as a reference work for the solution of their tasks. The material is explained with the assistance of a large number of calculated examples, and at the end of each chapter a series of exercises is given. This should also make self study easier. Many heat and mass transfer problems can be solved using the balance equa- tions and the heat and mass transfer coefficients, without requiring too deep a knowledge of the theory of heat and mass transfer. Such problems are dealt with in the first chapter, which contains the basic concepts and fundamental laws of heat and mass transfer. The student obtains an overview of the different modes of heat and mass transfer, and learns at an early stage how to solve practical problems and to design heat and mass transfer apparatus. This increases the mo- tivation to study the theory more closely, which is the object of the subsequent chapters. In the second chapter we consider steady-state and transient heat conduction and mass diffusion in quiescent media. The fundamental differential equations for the calculation of temperature fields are derived here. We show how analytical and numerical methods are used in the solution of practical cases. Alongside the Laplace transformation and the classical method of separating the variables, we have also presented an extensive discussion of finite difference methods which are very important in practice. Many of the results found for heat conduction can be transferred to the analogous process of mass diffusion. The mathematical solution formulations are the same for both fields. Preface ix The third chapter covers convective heat and mass transfer. The derivation of the mass, momentum and energy balance equations for pure fluids and multi- component mixtures are treated first, before the material laws are introduced and the partial differential equations for the velocity, temperature and concentration fields are derived. As typical applications we consider heat and mass transfer in flow over bodies and through channels, in packed and fluidised beds as well as free convection and the superposition of free and forced convection. Finally an introduction to heat transfer in compressible fluids is presented. In the fourth chapter the heat and mass transfer in condensation and boil- ing with free and forced flows is dealt with. The presentation follows the book, “Heat Transfer in Condensation and Boiling” (Berlin: Springer-Verlag 1992) by K. Stephan. Here, we consider not only pure substances; condensation and boiling in mixtures of substances are also explained to an adequate extent. Thermal radiation is the subject of the fifth chapter. It differs from many other presentations in so far as the physical quantities needed for the quantita- tive description of the directional and wavelength dependency of radiation are extensively presented first. Only after a strict formulation of Kirchhoff’s law, the ideal radiator, the black body, is introduced. After this follows a discussion of the material laws of real radiators. Solar radiation and heat transfer by radiation are considered as the main applications. An introduction to gas radiation, important technically for combustion chambers and furnaces, is the final part of this chapter. As heat and mass transfer is a subject taught at a level where students have already had courses in calculus, we have presumed a knowledge of this field. Those readers who only wish to understand the basic concepts and become familiar with simple technical applications of heat and mass transfer need only study the first chapter. More extensive knowledge of the subject is expected of graduate mechanical and chemical engineers. The mechanical engineer should be familiar with the fundamentals of heat conduction, convective heat transfer and radiative transfer, as well as having a basic knowledge of mass transfer. Chemical engineers also require, in addition to a sound knowledge of these areas, a good understanding of heat and mass transfer in multiphase flows. The time set aside for lectures is generally insufficient for the treatment of all the material in this book. However, it is important that the student acquires a broad understanding of the fundamentals and methods. Then it is sufficient to deepen this knowledge with selected examples and thereby improve problem solving skills. In the preparation of the manuscript we were assisted by a number of our colleagues, above all by Nicola Jane Park, MEng., University of London, Imperial College of Science, Technology and Medicine.
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