HEAT TRANSFER IN INDUSTRIAL COMBUSTION Charles E. Baukal, Jr. CRC Press Boca Raton New York © 2000 by CRC Press LLC Library of Congress Cataloging-in-Publication Data Baukal, Charles E. Heat transfer in industrial combustion / Charles E. Baukal, Jr. p. cm. Includes bibliographical references and index. ISBN 0-8493-1699-5 (alk. paper) 1. Heat--Transmission. 2. Combustion engineering. I. Title TJ260.B359 2000 621.402′2--dc21 99-088045 This book contains information obtained from authentic and highly regarded sources. Reprinted material is quoted with permission, and sources are indicated. A wide variety of references are listed. Reasonable efforts have been made to publish reliable data and information, but the author and the publisher cannot assume responsibility for the validity of all materials or for the consequences of their use. 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Specific permission must be obtained in writing from CRC Press LLC for such copying. Direct all inquiries to CRC Press LLC, 2000 N.W. Corporate Blvd., Boca Raton, Florida 33431. Trademark Notice: Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation, without intent to infringe. © 2000 by CRC Press LLC No claim to original U.S. Government works International Standard Book Number 0-8493-1699-5 Library of Congress Card Number 99-088045 Printed in the United States of America 1 2 3 4 5 6 7 8 9 0 Printed on acid-free paper © 2000 by CRC Press LLC Preface This book is intended to fill a gap in the literature for books on heat transfer in industrial combustion, written primarily for the practicing engineer. Many textbooks have been written on both heat transfer and combustion, but both types of book generally have only a limited amount of information concerning the combination of heat transfer and industrial combustion. One of the purposes of this book is to codify the many relevant books, papers, and reports that have been written on this subject into a single, coherent reference source. The key difference for this book compared to others is that it looks at each topic from a somewhat narrow scope to see how that topic affects heat transfer in industrial combustion. For example, in Chapter 2, the basics of combustion are considered, but from the limited perspective as to how combustion influences the heat transfer. There is very little discussion of combustion kinetics because in the overall combustion system, the kinetics of the chemical reactions in the flame only significantly impact the heat transfer in somewhat limited circumstances. Therefore, this book does not attempt to go over subjects that have been more than adequately covered in other books, but rather attempts to look at those subjects through the narrow lens of how they influence the heat transfer in the system. The book is basically organized in three parts. The first part deals with the basics of heat transfer in combustion and includes chapters on the modes of heat transfer, computer modeling, and experimental techniques. The middle part of the book deals with general concepts of heat transfer in industrial combustion systems and includes chapters on heat transfer from flame impinge- ment, from burners, and in furnaces. The last part of the book deals with specific applications of heat transfer in industrial combustion and includes chapters on lower and higher temperature applications and some advanced applications. The book has discussions on the use of oxygen to enhance combustion and on flame impingement, both of particular interest to the author. These subjects have received very little, if any, coverage in previous books on heat transfer in industrial combustion. As with any book of this type, there are many topics that are not covered. The book does not address other aspects of heat transfer in combustion such as power generation (stationary turbines or boilers) and propulsion (internal combustion, gas turbine or rocket engines), which are not normally considered to be industrial applications. It also does not treat packed bed combustion, material synthesis in flames, or flare applications, which are all fairly narrow in scope. Because the vast majority of industrial applications use gaseous fuels, that is the focus of this book, with only a cursory discussion of solid and liquid fuels. This book basically concerns atmospheric combustion, which is the predominant type used in industry. There are also many topics that are discussed in the book, but with a very limited treatment. One example is optical diagnostics. The reason for the limited discussion is that there has been very little application of such techniques to industrial combustors because of the difficulties in making them work on a large scale in sometimes hostile environments. This book attempts to focus on those topics that are of interest to the practicing engineer. It does not profess to be exhaustively comprehensive, but does attempt to provide references for the interested reader who would like more information on a particular subject. As most authors know, it is always a struggle about what to include and what not to include in a book. Here, the guideline that has been used is to minimize the theory and maximize the applications, while at the same time trying to at least touch on the relevant topics for heat transfer in industrial combustion. © 2000 by CRC Press LLC About the Author Charles E. Baukal, Jr., Ph.D., P.E., is the Director of the John Zink Company LLC R & D Test Center in Tulsa, OK. He has 20 years of experience in the fields of heat transfer and industrial combustion and has authored more than 50 publications in those fields, including editing the book Oxygen-Enhanced Combustion (CRC Press, Boca Raton, FL, 1998). He has a Ph.D. in mechanical engineering from the University of Pennsylvania, is a licensed Professional Engineer in the state of Pennsylvania, has been an adjunct instructor at several colleges, and has eight U.S. patents. © 2000 by CRC Press LLC Acknowledgment This book is dedicated to my wife Beth, to my children Christine, Caitlyn, and Courtney, and to my mother Elaine. This book is also dedicated to the memories of my father, Charles, Sr. and my brother, Jim, who have both gone on to be with their maker. The author would like to thank Tom Smith of Marsden, Inc. (Pennsauken, NJ) and Buddy Eleazer of Air Products (Allentown, PA) for the opportunities to learn firsthand about heat transfer in industrial combustion. The author would also like to thank David Koch and Dr. Roberto Ruiz of John Zink Company LLC (Tulsa, OK) for their support in the writing of this book. Last but not least, the author would like to thank the good Lord above, without whom this would not have been possible. Charles E. Baukal, Jr., Ph.D., P.E. © 2000 by CRC Press LLC Nomenclature Symbol Description Units 2 2 A Area ft or m c Speed of light ft/sec or m/sec cp Specific heat Btu/lb-°F or J/kg-K Cp Pitot-Static probe calibration constant dimensionless d Diameter in. or mm D Dimensionless diameter = d/dn dimensionless Da Damköhler number (see Eq. 2.19) dimensionless e Hemispherical emissive power Btu/hr-ft2 or kW/m2 E Error dimensionless E Hemispherical emissive power Btu/hr or kW F1-2 Radiation view factor from surface 1 to surface 2 dimensionless Gr Grashoff number (see Eq. 3.12) dimensionless 2 2 h Convection heat transfer coefficient Btu/hr-ft -°F or W/m -K C h Chemical enthalpy Btu/lb or J/kg hfusion Heat of fusion Btu/lb or J/kg S h Sensible enthalpy = ½cpdt Btu/lb or J/kg T C S h Total enthalpy = h + h Btu/lb or J/kg H Fuel heat content Btu/lb or kJ/kg 2 2 I Radiation intensity Btu/hr-ft -µm or W/m -µm k Thermal conductivity Btu/hr-ft-°F or W/m-K K Non-absorption factor for radiation dimensionless Ka Absorption coefficient for radiation dimensionless Ks Scattering coefficient for radiation dimensionless l Length in. or mm lv Potential core length for velocity in. or mm L Distance between the burner and the target = lj/dn dimensionless L Radiation path length through a gas ft or m Lm Mean beam length ft or m Le Lewis number = ρcpDi–mix/k dimensionless •m Mass flow rate lb/hr or kg/hr Ma Mach number = v/c dimensionless MW Molecular weight lb/lb-mole or g/g-mole Nu Nusselt number (see Eq. 3.3) dimensionless pst Static pressure psig or Pa pt Total pressure psig or Pa Pr Prandtl number = cpµ/k (see Eq. 3.2) dimensionless q Heat flow Btu/hr or kW q″ Heat flux Btu/hr-ft2 or kW/m2 qf Burner firing rate Btu/hr or kW qi Heat absorbed by calorimeter i Btu/hr or kW Q Gas flow rate ft3/hr or m3/hr r Radial distance from the burner centerline in.