描述
开 本: 32开纸 张: 胶版纸包 装: 平装-胶订是否套装: 否国际标准书号ISBN: 9787302470694
本书可作为高等学校热能工程类专业的高年级本科生教材或教学参考书，也可供相关专业工程技术人员参考。
Contents
Foreword v Preface vii Symbols ix
1. Theoretical Foundation and Basic Properties of Thermal Radiation
1.1. Thermal Radiation Theory—Planck’s Law 3
1.2. Emissive Power and Radiation Characteristics 6
1.2.1. Description of Radiant Energy 6
1.2.2. Physical Radiation Characteristics 9
1.2.3. Monochromatic and Directional Radiation 11
1.3. Basic Laws of Thermal Radiation 12
1.3.1. Planck’s Law and Corollaries 12
1.3.2. Lambert’s Law 15
1.3.3. Kirchhoff’s Law 16
1.4. Radiativity of Solid Surfaces 17
1.4.1. Difference Between Real Surfaces and Blackbody Surfaces 17
1.4.2. Graybody 19
1.4.3. Diffuse Surfaces 19
1.5. Thermal Radiation Energy 21
1.5.1. Thermal Radiation Forms 21
1.5.2. Radiosity 22
1.6. Radiative Geometric Con. guration Factors 24
1.6.1. De. nition of the Con. guration Factor 24
1.6.2. Con. guration Factor Properties 27
1.6.3. Con. guration Factor Calculation 29
1.7. Simpli.ed Treatment of Radiative Heat Exchange in Engineering Calculations
41
1.7.1. Simpli. cation Treatment of Radiation Heat Transfer in Common Engineering Calculations 41
1.7.2. Discussion on Simpli. ed Conditions 41
2. Emission and Absorption of Thermal Radiation
2.1. Emission and Absorption Mechanisms 46
2.1.1. Molecular Spectrum Characteristics 46
2.1.2. Absorption and Radiation of Media 47
i
2.2. Radiativity of Absorbing and Scattering Media 49
2.2.1. Absorbing and Scattering Characteristics of Media 49
2.3. Scattering 50
2.4. Absorption and Scattering of Flue Gas 50
2.4.1. Radiation Intensity Characteristics 50
2.4.2. Exchange and Conservation of Radiant Energy 54
2.4.3. Mean Beam Length, Absorptivity, and Emissivity of Media 59
2.4.4. Gas Absorptivity and Emissivity 65
2.4.5. Flue Gas and Flame Emissivity 71
3. Radiation Heat Exchange Between Isothermal Surfaces
3.1. Radiative Heat Exchange Between Surfaces in Transparent Media 76
3.1.1. Radiative Heat Transfer of a Closed System Composed of Two Surfaces 76
3.1.2. Radiation Transfer of a Closed System Composed of Multiple Surfaces 80
3.1.3. Hole Radiative Heat Transfer 82
3.1.4. Radiative Heat Transfer of Hot Surface, Water Wall, and Furnace Wall 86
3.2. Radiative Heat Exchange Between an Isothermal Medium and a Surface 88
3.2.1. Heat Transfer Between a Medium and a Heating Surface 89
3.2.2. Heat Transfer Between a Medium and a Furnace 90
3.2.3. Calculating Radiative Heat Transfer According to Projected Heat 93
3.3. Radiative Heat Exchange Between a Flue Gas and a Heating Surface with Convection 95
4. Heat Transfer in Fluidized Beds
4.1. Fundamental Concepts of Fluidized Beds 101
4.1.1. De. nition and Characteristics of Fluidized Beds 101
4.1.2. Basic CFB Boiler Structure 103
4.1.3. Different Types of CFB Boilers 105
4.1.4. CFB Boiler Characteristics 107
4.2. Convective Heat Transfer in Gas–Solid Flow 112
4.2.1. Two-Phase Flow Heat Transfer Mechanism 114
4.2.2. Factors Impacting Two-Phase Heat Transfer 114
4.2.3. Two-Phase Flow Convective Heat Transfer 118
4.3. Radiative Heat Transfer in Gas–Solid Flow 122
4.4. Heat Transfer Calculation in a Circulating Fluidized Bed 124
4.4.1. In. uence of Heating Surface Size on Heat Transfer 125
4.4.2. CFB Boiler Gas Side Heat Transfer Coef. cient 127
Contents iii
5. Heat Transfer Calculation in Furnaces
5.1. Heat Transfer in Furnaces 132
5.1.1. Processes in the Furnace 132
5.1.2. Classi. cation of Heat Transfer Calculation Methods 133
5.1.3. Furnace Heat Transfer Calculation Equation 134
5.1.4. Flame Temperature 135
5.2. Heat Transfer Calculation in Suspension-Firing Furnaces 139
5.2.1. Gurvich Method 139
5.2.2. Calculation Method Instructions 140
5.2.3. Furnace Heat Transfer Calculation Examples 143
5.3. Heat Transfer Calculation in Grate Furnaces 143
5.3.1. Heat Transfer Calculation in Grate Furnaces in China 143
5.3.2. Heat Transfer Calculation in Grate-Firing Furnaces 149
5.4. Heat Transfer Calculation in Fluidized Bed Furnaces 152
5.4.1. Heat Transfer Calculation in Bubbling Fluidized Bed (BFB) Furnaces 152
5.4.2. CFB Furnace Structure and Characteristics 153
5.4.3. Heat Transfer Calculation in CFB Furnaces 157
5.5. Heat Transfer Calculation in Back-End Heating Surfaces 160
5.5.1. Basic Heat Transfer Equations 161
5.5.2. Heat Transfer Coef. cient 162
5.6. Thermal Calculation of the Boiler 165
5.6.1. Basic De. nitions of Boiler Heating Surfaces 165
5.6.2. Thermal Calculation Methods for Boilers 169
5.6.3. Thermal Calculation According to Different Furnace Types 170
6. Effects of Ash Deposition and Slagging on Heat Transfer
6.1. Ash Deposition and Slagging Processes and Characteristics 173
6.1.1. Deposition and Slagging 173
6.1.2. Formation and Characteristics of Deposition and Slagging 175
6.1.3. Damage of Deposition and Slagging 178
6.1.4. Ash Composition 179
6.2. Effects of Ash Deposition and Slagging on Heat Transfer in Furnaces 179
6.2.1. Heat Transfer Characteristics and Ash Layer Calculation with Slagging 182
6.2.2. Heat Transfer Calculation with Deposition and Slagging 184
6.3. Effects of Ash Deposition and Slagging on Heat Transfer in Convective Heating Surfaces 185
6.3.1. Effects of Severe Ash Deposition and Slagging 185
6.3.2. Basic Heat Transfer Equation for Convective Heating Surfaces 185
6.3.3. Coef. cients Evaluating the Ash Deposition Effect 188
7. Measuring Heat Transfer in the Furnace
7.1. Flame Emissivity Measurement 194
7.1.1. Bichromatic Optical Pyrometer 194
7.1.2. Auxiliary Radiative Resources 196
7.2. Radiative Flux Measurement 197
7.2.1. Conductive Radiation Heat Flux Meter 198
7.2.2. Capacitive Radiation Heat Flux Meter 199
7.2.3. Calorimetric Radiation Heat Flux Meter 200
7.3. Two Other Types of Heat Flux Meter 200
7.3.1. Heat Pipe Heat Flux Meter 201
7.3.2. Measuring Local Heat Transfer Coef. cient in CFB Furnaces 202
Appendix A. Common Physical Constants of Heat Radiation 205 Appendix B. Common Con. guration Factor Calculation Formulas 207 Appendix C. Example of Thermal Calculation of 113.89 kg/s (410 t/h)
Ultra-High-Pressure, Coal-Fired Boiler 219 Appendix D. Supplementary Materials 293
References 323 Subject Index 325
Energy, communication, and material are basic elements which push modern so-ciety forward in the processes of industrialization, electri.cation, and informa-tion development. Most energy and power for modern devices come from fossil fuels, which are combusted in furnaces to release heat by chemical reaction. In a boiler furnace, radiation is the dominant mechanism of transferring heat from . ame and . ue gas to the heating surface, combined with convection—the heat is delivered from the surface to the inner media by conduction of the tube wall. The physical and chemical processes in a furnace are a combination of combus-tion, heat transfer, and .ows, all of which are limited by engineering factors. All devices related to combustion (including not only power plant boilers, turbines, and engines, but several other industry boilers and stoves) must satisfy environ-mental protection and economic demands. This book was written based on a course on Heat Transfer in Furnaces taught by the authors at Tsinghua University, Beijing, for several years. The author would suggest that the reader .rst learn the basic scienti.c concepts of heat transfer. This book provides a connection between fundamental theories on the subject and real-world engineering applications, and the authors sincerely hope it will serve as a helpful reference for the reader during complex engineer-ing design endeavors. This book contains seven chapters in total. After a brief introduction to the essentials and basic principles of radiation in chapter: Theoretical Foundation and Basic Properties of Thermal Radiation , radiative characteristics of . ame and .ue gas (with walls) are examined in chapter: Emission and Absorption of Thermal Radiation and chapter: Radiation Heat Exchange Between Isother-mal Surfaces . Chapter: Heat Transfer in Fluidized Beds describes the relatively novel concept of heat transfer in .uidized beds, which differs notably from heat transfer in stock boilers or pulverized coal boilers. Chapter: Heat Transfer Calculation in Furnaces provides thermal calculations for furnaces in three typi-cal types of boilers. Chapter: Effects of Ash Deposition and Slagging on Heat Transfer illustrates the effects of ash deposition and slagging on the heat trans-fer of heating surfaces, and chapter: Measuring Heat Transfer in the Furnace discusses furnace heat transfer measurement, including .ame emissivity and heat . ux meters. I strongly feel that this book contains unique and valuable characteristics, including clear and accurate depiction of relevant concepts, simple and .uent
language, and a fascinating and practical extension of the authors’ combined experience in engineering. I am happy to recommend it to the reader, and hope that students and practitioners of boiler technology will .nd this book inspiring and useful. Academician of Chinese Academy of Sciences, Buxuan Wang Department of Thermal Engineering Tsinghua University
Chapter 1
Theoretical Foundation and Basic Properties of Thermal Radiation
Chapter Outline 1.1 Thermal Radiation 1.5 Thermal Radiation Energy 21 Theory—Planck’s Law 3 1.5.1 Thermal Radiation 1.2 Emissive Power and Radiation Forms 21 Characteristics 6 1.5.2 Radiosity 22 1.2.1 Description 1.6 Radiative Geometric of Radiant Energy 6 Con. guration Factors 24 1.2.2 Physical Radiation 1.6.1 De. nition of the Characteristics 9 Con. guration Factor 24 1.2.3 Monochromatic and 1.6.2 Con. guration Factor Directional Radiation 11 Properties 27 1.3 Basic Laws of Thermal 1.6.3 Con. guration Factor Radiation 12 Calculation 29 1.3.1 Planck’s Law and 1.7 Simpli. ed Treatment of Corollaries 12 Radiative Heat Exchange in 1.3.2 Lambert’s Law 15 Engineering Calculations 41 1.3.3 Kirchhoff’s Law 16 1.7.1 Simpli. cation 1.4 Radiativity of Solid Surfaces 17 Treatment of Radiation 1.4.1 Difference Between Real Heat Transfer in Surfaces and Blackbody Common Engineering Surfaces 17 Calculations 41 1.4.2 Graybody 19 1.7.2 Discussion on 1.4.3 Diffuse Surfaces 19 Simpli. ed Conditions 41
All substances continuously emit and absorb electromagnetic energy when their molecules or atoms are excited by factors associated with internal energy (such as heating, illumination, chemical reaction, or particle collision). This process is called radiation. Radiation is considered a series of electromagnetic waves in classic physical theory, while modern physics considers it light quanta, that is, the transport of photons. Strictly speaking, radiation exhibits wave-particle duality, possessing properties of not only particles but also waves; this work 1
considers these to be the same, that is, “radiation” refers simultaneously to both photons and electromagnetic waves. At equilibrium, the internal energy of a substance is related to its tempera-ture – the higher the temperature, the greater the internal energy. The emitted radiation covers the entire electromagnetic wave spectrum, as illustrated sche-matically in Fig. 1.1 . Thermal energy is the energy possessed by a substance due to the random and irregular motion of its atoms or molecules. Thermal radiation is the trans-formation of energy from thermal energy to radiant energy by emission of rays. The wavelength range encompassed by thermal radiation is approximately from 0.1 to 1000 .m, which can be divided into three subranges: the infrared from 0.7 to 1000 .m, the visible from 0.4 to 0.7 .m, and the near ultraviolet from 0.1 to 0.4 .m. Thermal radiation is a form of heat transfer between objects, character-ized by the exchange of energy by emitting and absorbing thermal rays. Consider, for example, two concentric spherical shells with different ini-tial temperatures (t1 < t2) separated by a vacuum, as shown in Fig. 1.2 . The temperature of sphere shell 2 increases as a result of heat exchange by thermal radiation between the two shells, since there is no heat conduction or heat con-vection between them.
This chapter will brie.y outline the essential characteristics of thermal ra-diation, and the fundamental parameters that describe thermal radiation prop-erties. The description of the basic laws of thermal radiation and the general methods used in thermal radiation transfer calculation are emphasized, as these are the theoretical foundation for solving heat radiation transfer problems and conducting related engineering calculations. 1.1 THERMAL RADIATION THEORY—PLANCK’S LAW [1,2,23,24] At the end of the 19th century, classical physics had encountered two major roadblocks: the problem of relative motion between ether and measurable ob-jects, and the spectrum law of blackbody radiation, that is, the failure of the en-ergy equipartition law. The solution to the .rst problem led to relativity theory, and the second problem was solved after the establishment of quantum theory. Quantum theory also solved the problems of blackbody radiation, photoelectric effect, and Compton scattering. In quantum mechanics, a particle’s state at a de. nite time can be described by wave function Ψ(r), and the motion of the particle can be described by the change of the wave function with time Ψ(r,t). The wave function Ψ(r,t ) satis. es the following Schrodinger equation: . .
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