了得網工業技術_Theory and Calculation of Heat Transfer in Furnaces(爐內傳熱

編輯推薦

通過該課程學習使同學掌握燃氣、燃油、燃煤鍋爐的爐內傳熱計算和國內水動力學計算，為將來從事能源動力行業大型蒸汽發生器（即鍋爐，是熱力發電站的三大主機之一，這三大主機分別為鍋爐、汽輪機和發電機）的設計奠定基礎。

內容簡介

本書簡明而繫統地闡述了爐內傳熱的基本原理、計算方法。全書共分七章，包括輻射換熱的基本理論與計算，層燃爐、室燃爐和循環床鍋爐的爐膛傳熱計算方法，鍋爐熱力計算方法以及積灰、結渣對爐膛傳熱的影響等內容。本書作為銜接基礎課傳熱學和鍋爐課程設計之間的教材，對從基礎理論到工程實際的處理方法給予了充分的重視。結合實際的工程案例，提供了完整的爐膛傳熱和熱力計算的實例，並結合*的研究進展繫統介紹了氣固兩相流的傳熱和循環流化床鍋爐的傳熱計算。
本書可作為高等學校熱能工程類專業的高年級本科生教材或教學參考書，也可供相關專業工程技術人員參考。

作者簡介

張衍國，教授、博導，《工業加熱》編委，全國第四屆“發明獎”榮獲者。長期致力於劣質燃料的燃燒、餘熱利用、固體燃料的熱轉化等技術的開發和應用及節能改造等技術服務，並及時跟蹤前沿課題，開發高爐渣干法粒化技術、可燃固體廢棄物超臨界熱處理、生物質碳化、固體燃料微型熱發電等技術。同時還致力於研究各種低品位燃料燃燒及熱轉化過程中的化學反應規律、物流組織和污染控制等。主持並參加了多項973、自然科學基金、科技重大專項和省校合作課題，承擔數十項企業研發、應用課題。出版專著《垃圾清潔焚燒發電技術》、《爐內傳熱原理與計算》和《Theory and Calculation of Heat Transfer in Furnaces》，發表文章百餘篇，其中SCI 30餘篇、EI收錄 60餘篇，獲授權發明專利30餘項

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

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

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

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

前言

PrefacePreface
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

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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

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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