Heat Transfer – Basics and Practice

Heat Transfer – Basics and Practice
اسم المؤلف
Peter von Bockh, Thomas Wetzel
التاريخ
1 مارس 2020
المشاهدات
التقييم
(لا توجد تقييمات)
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Heat Transfer – Basics and Practice
Peter von Bockh, Thomas Wetzel
Contents
List of ymbols xi
1 Introduction and definitions 1
1.1 Modes of heat transfer . 3
1.2 Definitions 4
1.2.1 Heat (transfer) rate and heat flux . 4
1.2.2 Heat transfer coefficients and overall heat transfer coefficients . 4
1.2.3 Rate equations . 6
1.2.4 Energy balance equations 6
1.2.5 Log mean temperature difference 7
1.2.6 Thermal conductivity 9
1.3 Methodology of solving problems . 9
2 Thermal conduction in static materials 17
2.1 Steady-state thermal conduction 17
2.1.1 Thermal conduction in a plane wall 18
2.1.2 Heat transfer through multiple plane walls . 22
2.1.3 Thermal conduction in a hollow cylinder .25
2.1.4 Hollow cylinder with multiple layers 29
2.1.5 Thermal conduction in a hollow sphere 32
2.1.6 Thermal conduction with heat flux to extended surfaces 35
2.1.6.1 Temperature distribution in the fin . 36
2.1.6.2 Temperature at the fin tip . 38
2.1.6.3 Heat rate at the fin foot . 38
2.1.6.4 Fin efficiency 39
2.1.6.5 Applicability for other geometries . 40
2.2 Transient thermal conduction .44
2.2.1 One-dimensional transient thermal conduction . 44
2.2.1.1 Determination of the temporal change of temperature . 44
2.2.1.2 Determination of transferred heat 47
2.2.1.3 Special solutions for short periods of time . 58
2.2.2 Coupled systems 60
2.2.3 Special cases at Bi = 0 and Bi = ? . 62
vii
Sviii Contents
2.2.4 Temperature changes at small Biot numbers . 62
2.2.4.1 A small body immersed in a fluid with large mass 63
2.2.4.2 A body is immersed into a fluid of similar mass 65
2.2.4.3 Heat transfer to a static fluid by a flowing heat carrier 68
2.2.5 Numerical solution of transient thermal conduction equations .70
2.2.5.1 Discretization 70
2.2.5.2 Numerical solution . 73
2.2.5.3 Selection of the grid spacing and of the time interval 74
3 Forced convection 77
3.1 Dimensionless parameters .78
3.1.1 Continuity equation .79
3.1.2 Equation of motion 80
3.1.3 Equation of energy 81
3.2 Determination of heat transfer coefficients 83
3.2.1 Flow in a circular tube .83
3.2.1.1 Turbulent flow in circular tubes .83
3.2.1.2 Laminar flow in circular tubes at constant wall temperature .85
3.2.1.3 Equations for the transition from laminar to turbulent . 86
3.2.1.3 Flow in tubes and channels of non-circular cross-sections 94
3.2.2 Flat plate in parallel flow . 98
3.2.3 Single bodies in perpendicular cross-flow 99
3.2.4 Perpendicular cross-flow in tube bundles .103
3.2.5 Tube bundle with baffle plates 109
3.3 Finned tubes . 110
3.3.1 Annular fins . 112
4 Free convection 119
4.1 Free convection at plain vertical walls 120
4.1.1 Inclined plane surfaces 126
4.2 Horizontal plane surfaces .128
4.3 Free convection on contoured surface areas 128
4.3.1 Horizontal cylinder 129
4.3.2 Sphere 130
4.4 Interaction of free and forced convection 130
5 Condensation of pure vapors 131
5.1 Film condensation of pure, static vapor .131
5.1.1 Laminar film condensation 131
5.1.1.1 Condensation of saturated vapor on a vertical wall .131
5.1.1.2 Influence of the changing wall temperature .135
5.1.1.3 Condensation of wet and superheated vapor 136
5.1.1.4 Condensation on inclined walls 137
5.1.1.5 Condensation on horizontal tubes 137Contents ix
5.1.2 Turbulent film condensation on vertical surfaces .137
5.2 Dimensionless similarity numbers .137
5.2.1 Local heat transfer coefficients .138
5.2.2 Mean heat transfer coefficients .139
5.2.3 Condensation on horizontal tubes .139
5.2.4 Procedure for the determination of heat transfer coefficients .140
5.2.5 Pressure drop in tube bundles 147
5.3 Condensation of pure vapor in tube flow 151
5.3.1 Condensation in vertical tubes 152
5.3.1.1 Parallel-flow (vapor flow downward) 153
5.2.1.2 Counterflow (vapor flow upward) .154
5.3.2 Condensation in horizontal tubes 158
6 Boiling heat transfer 171
6.1 Pool boiling 171
6.1.1 Sub-cooled convection boiling .173
6.1.2 Nucleate boiling 173
6.2 Boiling at forced convection 182
6.2.1 Sub-cooled boiling 182
6.2.2 Convection boiling 183
7 Thermal radiation 189
7.1 Basic law of thermal radiation .190
7.2 Determination of the heat flux of radiation .191
7.2.1 Intensity and directional distribution of the radiation .192
7.2.2 Emissivities of technical surfaces 193
7.2.3 Heat transfer between two surfaces .194
7.2.3.1 Parallel gray plates with identical surface area size .196
7.2.3.2 Surrounded bodies 197
7.3 Thermal radiation of gases .206
7.3.1 Emissivities of flue gases 207
7.3.1.1 Emissivity of water vapor .207
7.3.1.2 Emissivity of carbon dioxide 208
7.3.2 Heat transfer between gas and wall .208
8 Heat exchangers 215
8.1 Definitions and basic equations .215
8.2 Calculation concepts 218
8.2.1 Cell method .218
8.2.2 Analysis with the log mean temperature method 223
8.3 Fouling resistance 236
8.4 Tube vibrations 240
8.4.1 Critical tube oscillations 240
8.4.2 Acoustic resonance 242x Contents
Appendix 245
A1: Important physical constants 245
A2: Thermal properties of sub-cooled water at 1 bar pressure .246
A3: Thermal properties of saturated water and steam .248
A4: Thermal properties of water and steam 250
A5: Thermal properties of saturated Freon 134a 252
A6: Thermal properties of air at 1 bar pressure 254
A7: Thermal properties of solid matter .255
A8: Thermal properties of thermal oils .256
A9: Thermal properties of fuels at 1.013 bar 257
A10: Emissivity of surfaces 258
A11: Formulary .261
Index 275
Bibliography 27
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