Theory and Calculation of Heat Transfer in Furna

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