HEAT TRANSFER. PHI Learning PfcO too1. Principles and Applications BINAY K. DUTTA. Delhi Kolkata. West Bengal Pollution Control Board

Transcription

1 HEAT TRANSFER Principles and Applications BINAY K. DUTTA West Bengal Pollution Control Board Kolkata PHI Learning PfcO too1 Delhi

2 Contents Preface Notations ix xiii 1. Introduction Modes of Heat Transfer Conduction Convection Radiation Heat Transfer Equipment Systems of Measurement, Units and Dimensions English Engineering System The International System (SI) of Units (The Systeme Internationale (SI) de Unites) Examples of Unit Conversion 6 2. Steady State Conduction in One Dimension The Basic Law of Heat Conduction Fourier's Law Thermal Conductivity Steady State Conduction of Heat through a Composite Solid Steady State Heat Conduction through a Variable Area The Cylinder The Sphere Steady State Heat Conduction in Bodies with Heat Sources The Plane Wall The Cylinder The Sphere Average Temperature of a Solid Application of Conduction Calculation 40 Short Questions 42 Problems 44 References and Further Reading Heat Transfer Coefficient Convective Heat Transfer and the Concept of Heat Transfer Coefficient Overall Heat Transfer Coefficient Heat Transfer between Fluids Separated by Heat Transfer between Fluids Separated by a Cylindrical Wall 59 a Plane Wall 57 iii

3 iv CONTENTS 3.3 Heat Transfer from Extended Surfaces The Fins Thermal Contact Resistance Critical Insulation Thickness Economic (or Optimum) Insulation Thickness 85 Short Questions 89 Problems 90 References and Further Reading Forced Convection Forced Convection in Systems of Simple Geometries Flow over a Flat Plate Thermal Boundary Layer Flow across a Cylinder Dimensional Analysis Statement of Buckingham Pi Theorem Dimensionless Groups in Convective Heat Transfer to a Fluid Flowing through a Circular Pipe Dimensionless Groups in Heat Transfer Experimental Determination of the Heat Transfer Coefficient Correlations for the Heat Transfer Coefficient Internal Flows Laminar Flow through a Circular Pipe Turbulent Flow through a Circular Pipe Flow through a Non-circular Duct Correlations for the Heat Transfer Coefficient External Flows Flow over a Flat Plate Flow across a Cylinder Flow past a Sphese Flow across a Bank of Tubes Heat Transfer Coefficient in a Packed and a Fluidized Bed Heat Transfer with a Variable Driving Force Cocurrent and Countercurrent Operations Momentum and Heat Transfer Analogies 136 Short Questions 142 Problems 143 References and Further Reading Free Convection Qualitative Description of Free Convection Flows Heat Transfer Correlations for Free Convection Free Convection from a Flat Surface Free Convection from a Cylinder Free Convection from a Sphere Free Convection in an Enclosure Combined Free and Forced Convection 162 Short Questions 164 Problems 165 References and Further Reading 169

4 CONTENTS V 6. Boiling and Condensation The Boiling Phenomenon Hysteresis in the Boiling Curve The Mechanism of Nucleate Boiling Correlations for Pool Boiling Heat Transfer Nucleate Boiling Critical Heat Flux Stable Film Boiling Forced Convection Boiling The Condensation Phenomenon Film Condensation on a Vertical Surface Turbulent Film Condensation Condensation Outside a Horizontal Tube or a Tube Bank Condensation Inside a Horizontal Tube Effect of Non-condensable Gases Dropwise Condensation 202 Short Questions 202 Problems 203 References and Further Reading Radiation Heat Transfer Basic Concepts of Radiation from a Surface Blackbody Radiation Planck's Law Wein's Displacement Law The Stefan-Boltzmann Law Kirchhoff s Law Gray Body Radiation Intensity of a Blackbody Spectral Emissive Power of a Blackbody over a Hemisphere Radiative Heat Exchange between Surfaces The View Factor View Factor Algebra Rate of Radiation Exchange between Blackbodies Exchange of Radiation between Diffuse Gray Surfaces Radiation Exchange in a Gray Enclosure Radiation Exchange in a Two-surface Gray Enclosure Emissivity Factor A Gray Enclosure with Re-radiating Surfaces Use of the Network Diagram to Calculate Radiation Exchange Radiation Shield Radiation Combined with Conduction and Convection Absorption and Emission in a Gaseous Medium The Absorptivity and Emissivity of a Gas Radiation Exchange between a Non-luminous Gas and Black Surface of Enclosing Walls Greenhouse Effect 267 Short Questions 268 Problems 269 References and Further Reading 274

5 CONTENTS Heat Exchangers Construction of a Shell-and-Tube Heat Exchanger The Shell The Tubes The Tube Sheets The Bonnet and the Channel The Pass Partition Plate Nozzles Baffles Tie Rods and Baffle Spacers Flanges and Gaskets Expansion Joint Process Design Considerations Fouling of a Heat Exchanger The Dirt Factor or Fouling Factor Log Mean Temperature Difference Correction Factor Temperature Distribution in Multi-pass Exchangers and Temperature Cross The Caloric Temperature Individual and Overall Heat Transfer Coefficients Pressure Drop Calculation Double-pipe Heat Exchanger Design Procedure Energy Balance and Heat Duty Calculation The Design Procedure Shell-and-Tube Heat Exchanger Design Procedure The Effectiveness NTU'Method of Heat Exchanger Analysis Other Types of Shell-and-Tube Exchangers Floating-head Exchangers Heat Exchanger with a U-bundle Reboilers and Condensers The RODbaffle Exchanger Air-cooled Exchangers Classification of Shell-and-Tube Exchangers Materials of Construction Cleaning of Heat Exchangers Heat Transfer in an Agitated Vessel Heating and Cooling Arrangements Thermal Design of an Agitated Vessel Correlations for Individual Coefficients Compact Heat Exchangers Plate Heat Exchangers Spiral-plate and Spiral-tube Heat Exchangers Other Common Heat Exchange Devices Pipe Tracing Steam Jacketing Electrical Heating Steam Tracing Heat Transfer Fluids 353 Short Questions 354 Problems 356 References and Further Reading 358

6 CONTENTS vii 9. Evaporation and Evaporators Types of Evaporators Their Construction and Operation Natural-circulation Evaporators Forced-circulation Evaporators Falling-film Evaporators Climbing- or Rising-film Evaporator Agitated Thin-film Evaporators The Plate Evaporator Evaporator Auxiliaries Vacuum Devices Steam Traps Entrainment Separators Principles of Evaporation and Evaporators Single- and Multiple-effect Evaporators Capacity and Economy Boiling Point Elevation (BPE) Temperature Driving Force Heat Transfer Coefficient Enthalpy of a Solution Single-effect Evaporator Calculation Multiple-effect Evaporators Classification Based on the Mode of Feed Supply Comparison between the Forward and Backward Feed Modes Effect of Boiling Point Elevation in a Multiple-effect Evaporator Multiple-effect Evaporator Calculations Evaporator Selection Vapour Recompression 411 Short Questions 415 Problems 418 References and Further Reading Unsteady State and Multidimensional Heat Conduction Mathematical Formulation and Initial and Boundary Conditions Techniques of Analytical Solution Types of Boundary Conditions Determination of the Average Temperature of a Solid Numerical Calculation of Unsteady State Heat Conduction Unsteady or Steady State Heat Conduction in a Multidimensional Solid The Graetz Problem Similarity Solution Numerical Solution of Heat Conduction Problems 460 Short Questions 461 Problems 461 References and Further Reading 464

7 viii CONTENTS 11. Boundary Layer Heat Transfer The Equation of Continuity The Equation of Motion Boundary Layer Flow over a Flat Plate Differential Equations for Laminar Boundary Layer Flow Solution of the Boundary Layer Equations Boundary Layer Thickness and Drag Coefficient The Momentum Integral Equation Forced Convection Heat Transfer in Laminar Boundary Layer Flow over a Flat Plate Boundary Layer Temperature Equation The Energy Integral Equation Application to Free Convection Heat Transfer Heat Transfer in Turbulent Boundary Layer Flow Mean and Fluctuating Quantities The Concept of Eddy Viscosity The Prandtl Mixing-Length Theory The Prandtl Analogy The von Kantian Analogy 508 Short Questions 509 Problems 510 References and Further Reading 511 Answers to Selected Problems 513 liidi-x 521