Annular Two-Phase Flow - 1st Edition - ISBN: 9780080157979, 9781483285238

Annular Two-Phase Flow

1st Edition

Authors: Geoffrey Hewitt
eBook ISBN: 9781483285238
Imprint: Pergamon
Published Date: 17th December 1970
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Annular Two-Phase Flow presents the wide range of industrial applications of annular two-phase flow regimes. This book discusses the fluid dynamics and heat transfer aspects of the flow pattern. Organized into 12 chapters, this book begins with an overview of the classification of the various types of interface distribution observed in practice. This text then examines the various regimes of two-phase flow with emphasis on the regions of occurrence of the annular flow regime. Other chapters consider the single momentum and energy balances, which illustrate the differences and analogies between single- and two-phase flows. This book discusses as well the simple modes for annular flow with consideration to the calculation of the profile of shear stress in the liquid film. The final chapter deals with the techniques that are developed for the measurement of flow pattern, entrainment, and film thickness. This book is a valuable resource for chemical engineers.

Table of Contents


1. Introduction

2. Regimes of Flow

2.1 Introduction

2.2 Flow Regimes in Vertical Flow

2.3 Flow Regimes in Horizontal and Inclined Flow

2.4 Flow Regime Maps

2.5 Flow Pattern Transitions in Vertical Flow

2.5.1 The Bubbly Flow-Slug Flow Transition

2.5.2 Flooding and Flow Reversal

2.5.3 The Slug Flow-Churn Flow Transition

2.5.4 The Churn Flow-Annular Flow Transition

2.5.5 Transition to Wispy-Annular Flow

2.6 Regimes of Flow in a Boiling Channel

3. Simple Momentum and Energy Balances and their Applications

3.1 Introduction

3.2 Single-Phase Flow

3.2.1 Force (Momentum) Balance for Single-Phase Flow

3.2.2 Single-Phase Energy Balance

3.3 Two-Phase Flow

3.3.1 General Momentum and Energy Balances for Two-Phase Flow Systems

3.3.2 Separated Flow Models

3.3.3 Separated Annular Flow with Liquid Entrainment

3.3.4 Experimental Determination of Individual Components of Pressure Gradient

3.4 The Homogeneous Model

3.5 The Lockhart-Martinelli Model

3.6 Pressure Losses in Expansions, Contractions, Orifices, Bends and Valves

3.6.1 Pressure Change at a Sharp Expansion

3.6.2 Pressure Change at a Sudden Contraction

3.6.3 Two-Phase Flow through Orifices

3.6.4 Flow in Bends, T's, Valves, etc.

3.7 Critical Two-Phase Flow

3.7.1 Overall Models

3.7.2 Detailed Examination of Interface Heat and Mass Transfer Processes

4. Simple Analytical Models of Annular Two-Phase Flow and their Applications

4.1 Introduction

4.2 Single-Phase Flow

4.3 Application of Single-Phase Flow Concepts to the Prediction of Annular Two-Phase Flow

4.3.1 Evaluation of Interfacial Shear Stress

4.3.2 Shear Stress Distribution in the Liquid Film

4.3.3 Velocity Profile and Mass Flowrate in Laminar Film Flow in a Vertical Tube

4.3.4 Velocity Profile and Mass Flowrate in Turbulent Film Flow

4.4 Applications of the Smooth Film Theories

4.4.1 Direct Tests of the Triangular Interrelationship between Liquid Film Flowrate, Liquid Film Thickness and Pressure Gradient

4.4.2 Minimum Pressure Drop and Zero Wall Shear Stress

4.4.3 Flooding

4.4.4 Empirical Correlation of Flooding for Liquids of Low Viscosity

4.4.5 Results and Correlations for Viscous Liquids

4.5 Horizontal Annular Flow (Liquid Film Distribution)

5. Empirical Relationships for Annular Flow

5.1 Introduction

5.2 Empirical Correlations Inherently Based on the Triangular Relationship

5.2.1 Simplified Form of the Triangular Relationship in Terms of Friction Factor

5.2.2 Empirical Correlations Relating Pressure Drop and Void Fraction

5.2.3 Comparison of Empirical Correlations with Experimental Data

5.3 Gas Phase Distribution and Interfacial Interaction

5.3.1 Gas Flow Distribution

5.3.2 Correlation Between Interfacial Roughness and Film Thickness

6. Interfacial Waves

6.1 Introduction

6.2 The Kelvin-Helmholtz Instability

6.3 The Critical Layer

6.4 The Effect of Viscosity

6.5 An Example of an Interfacial Stability Calculation

6.6 Wave Velocity

6.7 Experimental Observations of the Interface in Annular or Stratified Flow

6.7.1 Vertical Upward Co-Current Annular Flow

6.7.2 Vertical Annular Flow (Co-Current Downwards)

6.7.3 Horizontal Parallel Flow

6.7.4 Horizontal Annular Flow

7. Stability Against De-Wetting

7.1 Introduction

7.2 The Effects of Flow on Re-Wetting

7.2.1 Wetting in Annular Flow

7.2.2 The Stability of Rivulet Flow

7.3 Film Breakdown Under Conditions of Heat and Mass Transfer

7.4 The Role of Nucleate Boiling and "Sputtering" in the Wetting of Hot Surfaces

7.5 Conclusion

8. The Creation and Behavior of Entrained Droplets in Annular Flow

8.1 Introduction

8.2 Mechanisms of Droplet Entrainment

8.2.1 Wave Entrainment

8.2.2 Entrainment by Release of Bubbles

8.3 Onset of Droplet Entrainment

8.3.1 Definition of the Point of Onset of Entrainment

8.3.2 Experimental Observations of the Onset of Droplet Entrainment

8.3.3 Dimensional Analysis of the Onset of Liquid Entrainment

8.4 Observations and Correlations of Entrained Fraction

8.4.1 Effect of Liquid and Gas Flowrates on Liquid Entrainment

8.4.2 Correlation of Entrained Fraction

8.5 Distribution of Entrained Droplet Flow

8.6 Droplet Size and Breakup

8.7 Droplet Mass Transfer

8.7.1 Introduction

8.7.2 Particle Deposition: General

8.7.3 Measurements of Droplet Interchange Rate in Annular Two-Phase Flow

8.7.4 Droplet Mass Transfer in the Absence of Re-Entrainment

9. Introduction to Two-Phase Heat Transfer

9.1 Vapour-Liquid Equilibrium

9.2 Vapour Generation and Boiling

9.2.1 Bubble Nucleation

9.2.2 Bubble Growth and Departure

9.2.3 Terminology Used in the Description of Boiling

9.2.4 A General Qualitative Description of Pool Boiling

9.2.5 Forced Convective Boiling

9.3 Condensation

9.3.1 Droplet Nucleation

9.3.2 Modes of Condensation

10. Heat transfer in annular flow

10.1 Introduction

10.2 Heat Transfer through the Liquid Film

10.2.1 Heat Transfer in the Absence of Nucleation

10.2.2 Onset and Suppression of Nucleate Boiling

10.2.3 Heat Transfer in the Presence of Nucleation

10.3 Temperature Difference Across the Interface in Evaporation or Condensation

10.4 Heat and Mass Transfer in the Gas Core

11. Burnout

11.1 Introduction

11.2 Comparison of Burnout in Pool Boiling and Channel Flow

11.3 Studies of Mechanisms of Burnout in Annular Flow

11.3.1 Visual Studies

11.3.2 Liquid Film Flowrate Measurement

11.3.3 The Entrainment Curve and its Applications

11.3.4 Droplet Deposition Control

11.4 Parametric Effects

11.5 Burnout Correlations for Water

11.5.1 Burnout Correlations for Water Flow in Vertical Round Tubes

11.5.2 Rectangular Channels

11.5.3 Annuli and Rod Bundles

12. Experimental Techniques for Annular Flow

12.1 Introduction

12.2 The Determination of Flow Pattern

12.2.1 Photographic Methods

12.2.2 Pressure Drop Methods

12.2.3 Probe Methods

12.3 Measurements of Liquid Film Thickness

12.3.1 Film Average Methods

12.3.2 Localized Methods

12.3.3 Point Methods

12.4 Measurements of Entrainment and Droplet Size

12.4.1 Measurement of Total Entrainment Flow

12.4.2 Sampling and Isokinetic Probe Studies

12.4.3 Droplet Size Measurement

12.5 Pressure Drop Measurement



Appendix: S.I. Unit Conversion Table for Chemical Engineering



© Pergamon 1970
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About the Author

Geoffrey Hewitt

Professor Hewitt is an Emeritus Professor of Chemical Engineering at Imperial College London. Professor Hewitt has worked on a variety of subjects in the general field of chemical engineering but his speciality for several decades now has been in mutliphase flow systems, with particular reference to channel flow and heat transfer. He has published many papers and books in this industrially important area and has lectured on the subject widely throughout the world. He has had a wide experience of industrial application through extensive consultancy and contract work and through his founding of the Heat Transfer and Fluid Flow Service (HTFS) at Harwell and Hexxcell Ltd., a spin-out of Imperial College London operating in the area of heat transfer and energy efficiency. Professor Hewitt's contributions to the field have been recognised by his election to the Royal Academy of Engineering (1985), the Royal Society (1990), and the US National Academy of Engineering (1998) in addition to several international awards including Donald Q. Kern Award by AIChE (1981), Max Jakob Award by ASME (1995), and the Luikov Medal by ICHMT (1997). In 2007, he was presented the Global Energy Prize by Vladimir Putin at the World Economic Forum.

Affiliations and Expertise

Emeritus Professor of Chemical Engineering, Imperial College, London, UK

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