The Dynamics of Aerocolloidal Systems

International Reviews in Aerosol Physics and Chemistry

1st Edition - January 1, 1970
Authors: G. M. Hidy, J. R. Brock
Language: English
eBook ISBN:
9 7 8 - 1 - 4 8 3 1 - 4 6 0 5 - 8

The Dynamics of Aerocolloidal Systems, Volume 1 is concerned with the dynamical behavior of idealized aerosol particles in the light of developments in classical mechanics. The… Read more

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The Dynamics of Aerocolloidal Systems, Volume 1 is concerned with the dynamical behavior of idealized aerosol particles in the light of developments in classical mechanics. The idealization is based on the assumption that the solid or liquid particles suspended in a gas can be modeled as macroscopically smooth, chemically inert, spherical bodies. Topics covered include transport processes, single particles, and generation and behavior of clouds. Emphasis is placed on fluid dynamics from the continuum regime to the free molecule regime. This book is comprised of 10 chapters and begins with an overview of definitions and classifications of aerocolloidal suspensions. The next chapter deals with the characteristics of aerial dispersions as provided for in the hard, smooth sphere picture. The basic mechanical parameters of an aerocolloidal system is described, along with certain different regimes of the idealized aerosol and various solutions of the Boltzmann equation. The reader is methodically introduced to the dynamics of single particles in the continuum approximation; heat and mass transfer to single particles in a continuum; formation of aerosols by nucleation of supersaturated vapor; and diffusion and dispersion of aerosol particles. The final chapter considers the interaction between aerosol particles, paying particular attention to the collision of inert spheres whose sticking probability is unity. This volume will be useful to scholars, practicing scientists, and graduate students as well as those who would consider teaching aerosol mechanics as part of a curriculum in the atmospheric sciences, or in other applied sciences including applied physical chemistry, and engineering.

Preface

Principal Nomenclature

1. Introduction

A. Preliminary Definitions and Classification

B. Scope and Limitations

2. Fundamental Considerations

2.1 Characterization of Aerocolloidal Systems

A. Definition of an Aerocolloidal System

B. Mechanical Regimes of Aerocolloidal Systems

C. A Single Particle in an Infinite Gas

D. Some Relevant Additional Dimensionless Parameters

E. Assemblies of Particles in a Gas

2.2 Quantitative Formulation of Aerosol Dynamics

A. The Physics of the Suspending Gas

B. Derivation of the Boltzmann Equation

C. Mechanics of Two-body Collisions

D. Conservation Laws

E. The Approach to Equilibrium

F. Some Solutions of the Boltzmann Equation for Extremes of Knudsen Number

G. Solutions which Apply to the Knudsen Transition Regime

2.3 Physicochemical Properties of Aerosol Particles

3. Dynamics of Single Particles in the Continuum Approximation

3.1 Steady Rectilinear Motion in a Homogeneous Gas

A. Stokes' Solution

B. Effects of External Forces and of Non-uniformities in the Gas

3.2 Accelerated Motion of Particles in a Moving Medium

A. Generalized Equations of Motion

B. Relaxation Time to Reach Steady Motion

C. Curvilinear Motion of Particles

D. Curvilinear Motion and Particle Deposition

E. Deposition of Particles in Electrical Fields

4. Heat and Mass Transfer to Single Particles in a Continuum

4.1 The Macroscopic Equations for Heat and Mass Transfer in a Continuum Regime

A. Laws of Conservation of Matter and Energy

B. Relations between Fluxes and Driving Forces

C. Maxwell's Diffusion Laws for Multicomponent Systems

D. Simplification of the Macroscopic Equations of Conservation

4.2 Diffusional Processes to a Particle in a Stagnant Gas

A. Growth by Condensation and Evaporation

B. Temperature Changes during Evaporation or Condensation

C. Non-steady State Transport Processes

4.3 Diffusional Processes to a Particle Moving Relative to the Gas Phase

A. Convective Transport at Conditions of Steady State

B. Quasi-stationary Evaporation and Growth of a Moving Droplet

4.4 Mass Transfer Coupled to Particle Motion

5. Transfer Processes to Single Particles: The Free Molecule and Transitions Regions of Knudsen Number

5.1 Transfer Processes to Single Particles from Moments of the Molecular Velocity Distribution Function

5.2 Transfer Processes in the Free Molecule Regime

A. Molecular and Heat Transfer Rates for Evaporating or Condensing Particles in the Free Molecule Region

B. Momentum Transfer to Particles in the Free Molecule Region

C. Summary

5.3 Transfer Processes in the Transition Regime

A. Mass and Heat Transfer in the Transition Region

B. Momentum Transfer in the Transition Region

C. Summary

6. Transfer Processes to an Aerosol Particle in the Slip Flow Region

6.1 The Slip Flow Procedure

A. Application of the Navier-Stokes Equations

6.2 Illustrations of the Slip Flow Procedure

A. Mass Transfer to an Aerosol Particle in a Stagnant Gas

B. Heat Transfer from an Aerosol Particle to a Stagnant Gas

C. Momentum Transfer to an Aerosol Particle in the Slip Flow Region

6.3 Summary

7. Diffusion and Dispersion of Aerosol Particles

7.1 General Properties of the Diffusion Equations

A. Some Concepts of Random Processes

B. Diffusion by Discontinuous Jumps

C. Diffusion of Particles by Brownian Motion

D. Diffusion in the Presence of an External Force Field

7.2 Deposition of Aerosols by Diffusion

A. Diffusion in a Stagnant Medium

B. Diffusion in a Gravity Field

7.3 Laminar Convection and Diffusion

A. Diffusion of Particles in a Slow, Uniform Velocity Field

B. Diffusion of Particles in Laminar Shearing Flows

C. Solutions for Convective Diffusion in Laminar Flows

D. Aerosol Filtration

7.4 Diffusion of Particles in a Turbulent Medium

A. Diffusion by Continuous Movements

8. Aerosol, Generation by Disintegration and Dispersal

8.1 Atomization and the Breakup of Liquids

A. Energetics of Breakup

B. Mechanics of Droplet Formation

C Mechanisms of Aerodynamic Atomization

8.2 Aerosols by Dispersal of Powders

A. Formation of Powders by Attrition or Impulsive Forces

B. Cohesive and Adhesive Forces

C. Entrainment of Particles from Surfaces

D. Dispersal of Powders by Air Jets

9. Formation of Aerosols by Nucleation of Supersaturated Vapor

9.1 Nucleation of Vapor in the Absence of Foreign Nuclei

A. Super saturation and Thermodynamic Equilibrium

B. The Kinetics of New Phase Formation

C. Solutions to the Kinetic Equations for Nucleation

D. The Formation of Solid Particles by Nucleation

E. Nucleation from Multicomponent Gases

F. Experimental Observations of Homogeneous Nucleation

9.2 Heterogeneous Nucleation

A. Condensation of Liquids on Ions

B. Nucleation on Foreign Particles

C. Nucleation of Liquids on Soluble Particles

D. Heterogeneous Nucleation to Form Crystalline Materials

9.3 Some Features of Aerosols Created by Spontaneous Condensation

A. Diffusional Growth of a Collection of Particles

B. Modeling the Size Distributions of Nucleating Aerosols

10. Interaction between Aerosol Particles—Growth by Coagulation or Coalescence

10.1 Brownian Motion of Electrostatically Charged and Uncharged Particles

A. Smoluchowski's Theory

B. Free Molecule Theory

C. The Region of Transition in Knudsen Number

10.2 Influences of Non-uniformities in the Suspending Gas and External Forces on Coagulation

A. Free Molecule Aerosols

B. Examples of Continuum Theory for Coagulation of Suspensions in Non-uniform Gases in External Fields of Force

10.3 Influences of Aerodynamic and Electrical Forces Arising from Interaction between Particles

A. Aerodynamic Forces

B. Collision Efficiencies Accounting for Induced Forces

10.4 The Evolution of the Size Distribution of a Coagulating Aerosol

A. Solutions for the Coagulation Equations

B. Asymptotic Behavior of the Size Spectrum

References

Author Index

Subject Index