Principl of Enhanced Heat Transfer

Transcription

1 Principl of Enhanced Heat Transfer SECOND EDITION Ralph L Webb Nae-Hyun Kim Taylor & Francis Taylor & Francis Group Boca Raton London New York Singapore

2 TABLE OF CONTENTS PREFACE xxi CHAPTER 1: INTRODUCTION TO ENHANCED HEAT TRANSFER INTRODUCTION THE ENHANCEMENT TECHNIQUES Passive Techniques Active Techniques Technique vs. Mode PUBLISHED LITERATURE General Remarks U.S. Patent Literature Manufacturer's Information BENEFITS OF ENHANCEMENT COMMERCIAL APPLICATIONS OF ENHANCED SURFACES Heat (and Mass) Exchanger Types of Interest Illustrations of Enhanced Tubular Surfaces Enhanced Fin Geometries for Gases Plate-Type Heat Exchangers Cooling Tower Packings Distillation and Column Packings Factors Affecting Commercial Development DEFINITION OF HEAT TRANSFER AREA POTENTIAL FOR ENHANCEMENT PEC Example

3 vi I Table of Contents PEC Example NOMENCLATURE 30 REFERENCES, 31 CHAPTER 2: HEAT TRANSFER FUNDAMENTALS INTRODUCTION HEAT EXCHANGER DESIGN THEORY Thermal Analysis Heat Exchanger Design Methods Comparison of LMTD and NTU Design Methods FIN EFFICIENCY HEAT TRANSFER COEFFICIENTS AND FRICTION FACTORS Laminar Flow over Flat Plate Laminar Flow in Ducts Turbulent Flow in Ducts Tube Banks (Single-Phase Flow) Film Condensation Nucleate Boiling CORRECTION FOR VARIATION OF FLUID PROPERTIES Effect of Changing Fluid Temperature Effect Local Property Variation REYNOLDS ANALOGY FOULING OF HEAT TRANSFER SURFACES CONCLUSIONS 52 NOMENCLATURE 52 REFERENCES 54 CHAPTER 3: PERFORMANCE EVALUATION CRITERIA FOR SINGLE-PHASE FLOW PERFORMANCE EVALUATION CRITERIA (PEC) PEC FOR HEAT EXCHANGERS PEC FOR SINGLE-PHASE FLOW Objective Function and Constraints Algebraic Formulation of the PEC Simple Surface Performance Comparison Constant Flow Rate Fixed Flow Area 60

4 Table of Contents I vii 3.4 THERMAL RESISTANCE ON BOTH SIDES RELATIONS FOR St AND/ HEAT EXCHANGER EFFECTIVENESS EFFECT OF REDUCED EXCHANGER FLOW RATE FLOW NORMAL TO FINNED TUBE BANKS VARIANTS OF THE PEC COMMENTS ON OTHER PERFORMANCE INDICATORS Shah Soland and Colleagues EXERGY-BASED PEC ANALYSIS CONCLUSIONS 72 NOMENCLATURE 72 REFERENCES 74 CHAPTER 4: PERFORMANCE EVALUATION CRITERIA FOR TWO-PHASE HEAT EXCHANGERS INTRODUCTION OPERATING CHARACTERISTICS OF TWO-PHASE HEAT EXCHANGERS ENHANCEMENT IN TWO-PHASE HEAT EXCHANGE SYSTEMS Work-Consuming Systems Work-Producing Systems Heat-Actuated Systems PEC FOR TWO-PHASE HEAT EXCHANGE SYSTEMS PEC CALCULATION METHOD PEC Example PEC Example CONCLUSIONS 85 NOMENCLATURE 86 REFERENCES 87 CHAPTER 5: PLATE-AND-FIN EXTENDED SURFACES INTRODUCTION 89

5 viii I Table of Contents 5.2 OFFSET-STRIP FIN Enhancement Principle PEC Example Analytically Based Models fory and/vs. Re Transition from Laminar to Turbulent Region Correlations forj and/vs. Re Use of OSF with Liquids Effect,of Percent Fin Offset Effect of Burred Edges LOUVER FIN Heat Transfer and Friction Correlations Flow Structure in the Louver Fin Array Analytical Model for Heat Transfer and Friction PEC Example CONVEX LOUVER FIN WAVY FIN THREE-DIMENSIONAL CORRUGATED FINS PERFORATED FIN PIN FINS AND WIRE MESH VORTEX GENERATORS Types of Vortex Generators Vortex Generators on a Plate-Fin Surface METAL FOAM FIN PLAIN FIN PEC Example ENTRANCE LENGTH EFFECTS PACKINGS FOR GAS-GAS REGENERATORS NUMERICAL SIMULATION Offset-Strip Fins Louver Fins Wavy Channels Chevron Plates Summary CONCLUSIONS 137 NOMENCLATURE 137 REFERENCES 139

6 Table of Contents I ix CHAPTER 6: EXTERNALLY FINNED TUBES INTRODUCTION THE GEOMETRIC PARAMETERS AND THE REYNOLDS NUMBER Dimensionless Variables Definition of Reynolds Number Definition of the Friction Factor Sources of Data PLAIN PLATE-FINS ON ROUND TUBES Effect of Fin Spacing Correlations for Staggered Tube Geometries Correlations for Inline Tube Geometries PLAIN INDIVIDUALLY FINNED TUBES Circular Fins with Staggered Tubes Low Integral-Fin Tubes ENHANCED PLATE FIN GEOMETRIES WITH ROUND TUBES Wavy Fin Offset Strip Fins Convex Louver Fins LouveredFin Perforated Fins Mesh Fins Vortex Generators ENHANCED CIRCULAR FIN GEOMETRIES Illustrations of Enhanced Fin Geometries Spine or Segmented Fins Wire Loop Fins OVAL AND FLAT TUBE GEOMETRIES Oval vs. Circular Individually Finned Tubes Flat Extruded Aluminum Tubes with Internal Membranes Plate-and-Fin Automotive Radiators Vortex Generators on Flat or Oval Fin-Tube Geometry ROW EFFECTS STAGGERED AND INLINE LAYOUTS HEAT TRANSFER COEFFICIENT DISTRIBUTION (PLAIN FINS) Experimental Methods Plate Fin-and-Tube Measurements Circular Fin-and-Tube Measurements 186

7 x I Table of Contents 6.10 PERFORMANCE COMPARISON OF DIFFERENT GEOMETRIES Geometries Compared Analysis Method Calculated Results PROGRESS ON NUMERICAL SIMULATION RECENT PATENTS ON ADVANCED FIN GEOMETRIES HYDROPHII^C COATINGS CONCLUSIONS 197 NOMENCLATURE 198 REFERENCES 201 CHAPTER 7: INSERT DEVICES FOR SINGLE-PHASE FLOW INTRODUCTION TWISTED TAPE INSERT Laminar Flow Data Predictive Methods for Laminar Flow Turbulent Flow PEC Example Twisted Tapes in Annuli Twisted Tapes in Rough Tubes SEGMENTED TWISTED TAPE INSERT DISPLACED ENHANCEMENT DEVICES Turbulent Flow Laminar Flow PEC Example WIRE COIL INSERTS Laminar Flow Turbulent Flow EXTENDED SURFACE INSERT TANGENTIAL INJECTION DEVICES CONCLUSIONS 238 NOMENCLATURE 239 REFERENCES 241 CHAPTER 8: INTERNALLY FINNED TUBES AND ANNULI INTRODUCTION 245

8 Table of Contents I xi 8.2 INTERNALLY FINNED TUBES Laminar Flow Turbulent Flow PEC Example SPIRALLY FLUTED TUBES Spirally Fluted Tube Spirally Indented Tube ADVANCED INTERNAL FIN GEOMETRIES FINNED ANNULI CONCLUSIONS 277 NOMENCLATURE 278 REFERENCES 280 CHAPTER 9: INTEGRAL ROUGHNESS INTRODUCTION ROUGHNESS WITH LAMINAR FLOW Laminar Flow in Roughened Circular Tubes Laminar Flow in Roughened Flat Tubes HEAT-MOMENTUM TRANSFER ANALOGY CORRELATION Friction Similarity Law PEC Example Heat Transfer Similarity Law TWO-DIMENSIONAL ROUGHNESS Transverse Rib Roughness Integral Helical-Rib Roughness Wire Coil Inserts Corrugated Tube Roughness PEC Example THREE-DIMENSIONAL ROUGHNESS PRACTICAL ROUGHNESS APPLICATIONS Tubes with Inside Roughness Rod Bundles and Annuli Rectangular Channels Outside Roughness for Cross Flow GENERAL PERFORMANCE CHARACTERISTICS St and/vs. Reynolds Number 326

9 xii I Table of Contents Other Correlating Methods Prandtl Number Dependence HEAT TRANSFER DESIGN METHODS Design Method Design Method PREFERRED ROUGHNESS TYPE AND SIZE Roughness Type PEC Example NUMERICAL SIMULATION Predictions for Transverse-Rib Roughness Effect of Rib Shape The Discrete-Element Predictive Model CONCLUSIONS 346 NOMENCLATURE 347 REFERENCES 350 CHAPTER 10: FOULING ON ENHANCED SURFACES INTRODUCTION FOULING FUNDAMENTALS Paniculate Fouling FOULING OF GASES ON FINNED SURFACES SHELL-SIDE FOULING OF LIQUIDS Low Radial Fins Axial Fins and Ribs in Annulus Ribs in Rod Bundle FOULING OF LIQUIDS IN INTERNALLY FINNED TUBES LIQUID FOULING IN ROUGH TUBES Accelerated Paniculate Fouling Long-Term Fouling LIQUID FOULING IN PLATE-FIN GEOMETRY CORRELATIONS FOR FOULING IN ROUGH TUBES MODELING OF FOULING IN ENHANCED TUBES Example Problem FOULING IN PLATE HEAT EXCHANGERS CONCLUSIONS 384

10 Table of Contents I xiii NOMENCLATURE 384 REFERENCES 386 CHAPTER 11: POOL BOILING AND THIN FILM EVAPORATION INTRODUCTION EARLY WORK ON ENHANCEMENT ( ) SUPPORTING FUNDAMENTAL STUDIES TECHNIQUES EMPLOYED FOR ENHANCEMENT Abrasive Treatment Open Grooves Three-Dimensional Cavities Etched Surfaces Electroplating Pierced Three-Dimensional Cover Sheets Attached Wire and Screen Promoters Nonwetting Coatings Oxide and Ceramic Coatings Porous Surfaces Structured Surfaces (Integral Roughness) Combination of Structured and Porous Surfaces Composite Surfaces SINGLE-TUBE POOL BOILING TESTS OF ENHANCED SXURFACES THEORETICAL FUNDAMENTALS Liquid Superheat Effect of Cavity Shape and Contact Angle on Superheat Entrapment of Vapor in Cavities Effect of Dissolved Gases Nucleation at a Surface Cavity Bubble Departure Diameter Bubble Dynamics BOILING HYSTERESIS AND ORIENTATION EFFECTS Hysteresis Effects Size and Orientation Effects BOILING MECHANISM ON ENHANCED SURFACES Basic Principles Employed Visualization of Boiling in Subsurface Tunnels Boiling Mechanism in Subsurface Tunnels Chien and Webb Parametric Boiling Studies 438

11 xiv I Table of Contents 11.9 PREDICTIVE METHODS FOR STRUCTURED SURFACES Empirical Correlations Nakayama et al. [1980b] Model Chien and Webb Model Ramaswamy et al. Model Jiang et al. Model Other Models Evaluation of Models BOILING MECHANISM ON POROUS SURFACES O'Neill et al. Thin Film Concept Kovalev et al. Concept PREDICTIVE METHODS FOR POROUS SURFACES O'Neill et al. Model Kovalov et al. Model Nishikawa et al. Correlation Zhang and Zhang Correlation CRITICAL HEAT FLUX ENHANCEMENT OF THIN FILM EVAPORATION CONCLUSIONS 463 NOMENCLATURE 464 REFERENCES 466 CHAPTER 12: VAPOR SPACE CONDENSATION INTRODUCTION Condensation Fundamentals Basic Approaches to Enhanced Film Condensation DROPWISE CONDENSATION SURVEY OF ENHANCEMENT METHODS Coated Surfaces Roughness Horizontal Integral-Fin Tubes Corrugated Tubes Surface Tension Drainage Electric Fields SURFACE TENSION DRAINED CONDENSATION Fundamentals Adamek [1981] Generalized Analysis 506

12 Table of Contents I xv "Practical" Fin Profiles Prediction for Trapezoidal Fin Shapes HORIZONTAL INTEGRAL-FIN TUBE The Beatty and Katz [1948] Model Precise Surface Tension-Drained Models Approximate Surface Tension-Drained Models Comparison of Theory and Experiment HORIZONTAL TUBE BANKS Condensation with Vapor Shear Condensate Inundation without Vapor Shear Condensate Drainage Pattern Prediction of the Condensation Coefficient CONCLUSIONS 533 APPENDIX 12.A: THE KEDZIERSKI AND WEBB FIN PROFILE SHAPES 534 APPENDIX 12.B: FIN EFFICIENCY IN THE FLOODED REGION 535 NOMENCLATURE 535 REFERENCES 538 CHAPTER 13: CONVECTIVE VAPORIZATION INTRODUCTION FUNDAMENTALS Flow Patterns Convective Vaporization in Tubes Two-Phase Pressure Drop Effect of Flow Orientation on Flow Pattern Convective Vaporization in Tube Bundles Critical Heat Flux ENHANCEMENT TECHNIQUES IN TUBES Internal Fins Swirl Flow Devices Roughness Coated Surfaces Perforated Foil Inserts Porous Media Coiled Tubes and Return Bends THE MICROFIN TUBE Early Work on the Microfin Tube 572

13 xvi I Table of Contents Recent Work on the Microfin Tube Special Microfin Geometries Microfin Vaporization Data MINICHANNELS CRITICAL HEAT FLUX (CHF) Twisted Tape Grooved Tubes Corrugated Tubes Mesh Inserts PREDICTIVE METHODS FOR IN-TUBE FLOW High Internal Fins Microfins Twisted Tape Inserts Corrugated Tubes Porous Coatings TUBE BUNDLES Convective Effects in Tube Bundles Tube Bundle Convective Vaporization Data Effect of Spacing between Tubes Convective Vaporization Models Starting Hysteresis in Tube Bundles PLATE-FIN HEAT EXCHANGERS THIN FILM EVAPORATION Horizontal Tubes Vertical Tubes CONCLUSIONS 609 NOMENCLATURE 610 REFERENCES 612 CHAPTER 14: CONVECTIVE CONDENSATION INTRODUCTION FORCED CONDENSATION INSIDE TUBES MICROFIN TUBE Internally Finned Geometry Twisted-Tape Inserts Roughness Wire Coil Inserts Coiled Tubes and Return Bends

14 Table of Contents I xvii Microfin Geometry Details Optimization of Internal Geometry Condensation Mechanism in Microfin Tubes Convective Condensation in Special Microfin Geometries FLAT TUBE AUTOMOTIVE CONDENSERS Condensation Data for Flat, Extruded Tubes Other Predictive Methods of Condensation in Flat Tubes PLATE-TYPE HEAT EXCHANGERS NONCONDENSIBLE GASES PREDICTIVE METHODS FOR CIRCULAR TUBES High Internal Fins Wire Loop Internal Fins Twisted Tapes Roughness Microfins CONCLUSIONS 657 NOMENCLATURE 658 REFERENCES 659 CHAPTER 15: ENHANCEMENT USING ELECTRIC FIELDS 665 * 15.1 INTRODUCTION ELECTRODE DESIGN AND PLACEMENT SINGLE-PHASE FLUIDS Enhancement on Gas Flow Enhancement on Liquid Flow Numerical Studies CONDENSATION Fundamental Understanding Vapor Space Condensation In-Tube Condensation Falling Film Evaporation Correlations BOILING Fundamental Understanding Pool Boiling Convective Vaporization Critical Heat Flux Correlations 683

15 xviii I Table of Contents 15.6 CONCLUSIONS 684 NOMENCLATURE 684 REFERENCES 685 CHAPTER 16: SIMULTANEOUS HEAT AND MASS TRANSFER INTRODUCTION MASS TRANIJFER RESISTANCE IN THE GAS PHASE Condensation with Noncondensible Gases Evaporation into Air Dehumidifying Finned-Tube Heat Exchangers Water Film Enhancement of Finned-Tube Exchanger CONTROLLING RESISTANCE IN LIQUID PHASE SIGNIFICANT RESISTANCE IN BOTH PHASES CONCLUSIONS 702 NOMENCLATURE 703 REFERENCES 704 CHAPTER 17: ADDITIVES FOR GASES AND LIQUIDS INTRODUCTION ADDITIVES FOR SINGLE-PHASE LIQUIDS Solid Particles PEC Example Gas Bubbles Suspensions in Dilute Polymer and Surfactant Solutions ADDITIVES FOR SINGLE-PHASE GASES Solid Additives Liquid Additives ADDITIVES FOR BOILING ADDITIVES FOR CONDENSATION AND ABSORPTION CONCLUSIONS 719 NOMENCLATURE 719 REFERENCES 720 CHAPTER 18: MICROCHANNELS INTRODUCTION FRICTION IN SINGLE MICROCHANNELS 725

16 Table of Contents I xix 18.3 FRICTION IN A SINGLE CHANNEL VS. MULTICHANNELS SINGLE-PHASE HEAT TRANSFER IN MICROCHANNELS Single Channel Flow Heat Transfer in Multiple Microchannels MANIFOLD SELECTION AND DESIGN Single-Phase Flow Two-Phase Flow NUMERICAL SIMULATION OF FLOW IN MANIFOLDS TWO-PHASE HEAT TRANSFER IN MICROCHANNELS CONCLUSIONS 741 NOMENCLATURE 742 REFERENCES 743 CHAPTER 19: ELECTRONIC COOLING HEAT TRANSFER INTRODUCTION COMPONENT THERMAL RESISTANCES LIMITS ON DIRECT HEAT REMOVAL WITH AIR-COOLING PEC Example 19.1, Enhanced Fin Geometry Heat Sink SECOND GENERATION IndHR DEVICES FOR HEAT REMOVAL AT HOT SOURCE Single-Phase Fluids Two-Phase Fluids Heat Pipe Nucleate Boiling Forced Convection Vaporization Spray Cooling DISCUSSION OF ADVANCED HEAT REMOVAL CONCEPTS Jet Impingement/Spray Cooling Devices Single-Phase MicroChannel Cooling Two-Phase MicroChannel Cooling Enhanced Two-Phase Forced Convection Cooling REMOTE HEAT-EXCHANGERS FOR IndHR Air-Cooled Ambient Heat Exchangers Condensing Surfaces Design for Multiple Heat Sources SYSTEM PERFORMANCE FOR THE IndHR SYSTEM 771

17 xx I Table of Contents 19.8 CONCLUSIONS 772 NOMENCLATURE 772 REFERENCES 773 PROBLEM SUPPLEMENT 775 INDEX 789