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Bubble wake dynamics in liquids and liquid—solid suspensions
105
Powder Technology, 66 (1991) 105-106
Book Reviews Bubble Wake Dynamics in Liquids and LiquidSolid Suspensions by Liang-Shih Fan and Katsumi Tsuchiya, published by Butterworth-Heinemann, 1990; f70.00; ISBN 0 409 90286 861. The complex interactions between the components of multiphase systems are responsible for the success or failure of a multitude of processes. They control many important flow conditions, virtually all mass transfer operations and a great part of chemical reaction engineering. Indeed, when Brodkey’s book, The Phenomena of Fluid Motions, was published twenty or so years ago, at least one reviewer regretted the absence of discussion of wake flows from that text. It is appropriate that the gap is at last filled by this book which also originates from Ohio State University. Almost as a result of definition, the mainstream literature of fluid mechanics in continua has neglected wake flows, and the greater part of published work relating to wake phenomena concerns single bubbles, drops and particles. The situations which arise in real processes are almost invariably more complex. Knowledge of the wake flows generated within the dispersion or suspension will ultimately provide the key to the interactions at the heart of many separation and entrainment processes. This is a cheering field for the experimentalist. The contributions of rigorous theoretical analysis are strictly limited; extended wake systems are unpredictable and wayward. Analytical and numerical solutions are largely confined to the near field, whereas many of the effects, especially those influencing other bubbles or particles, are far field and essentially cannot be predicted in detail. The book starts, almost inevitably, by considering the behaviour of single bubbles and the characteristics of wake structure, stability and size. The text takes us onward from this point, discussing how the wake changes the underlying flow field, perhaps adding turbulent components and inducing lateral or vertical mixing. The trajectories of nearby or following bubbles or suspended particles are modified, often inducing heterogeneity in a relatively homogeneous dispersion. Bubble break-up and coalescence mechanisms are considered in some detail, as is the more complex problem of the interactions in a three-phase liquid-bubble-solid system. The processes which occur in suspension and fluidised bed reactors which lead to local accumulation or denudation in the
The suspension, are covered thoroughly. experimental and theoretical evidence for the underlying centrifugal and pressure fields which are responsible for these separation processes is clearly presented. Likewise, the important implications of wake flows for mixing, entrainment and mass transfer in bubbly fluids and suspensions are thoroughly discussed; it is to be hoped that these lessons on the significance of hydrodynamic effects for chemical reaction engineering do not go unremarked. This is an important and welcome addition to the literature, presenting the reader with an extensive and authoritative review of the phenomena in the liquid phase of bubbly systems. It is one of the problems of presenting a work dealingwith a ‘difficult’ area - and three-phase systems certainly come into that category - that it is impossible to provide solutions to all the problems that arise in practice. But then, if these authors had achieved that, there would be no research left to be done and the rest of us would be out of a job. John M. Smith Particle Size Measurement by T. Allen, published by Chapman and Hall, 2 Boundary
Row, London SE1 8HN, U.K.; 832 pp., f85.00, ISBN 0 412 350 70X.
This is the fourth edition of the book that has become the standard reference on Particle Size Measurement since it was first published in 1968. Each subsequent edition has extended and amplified the coverage, by bringing the bibliography up to date and describing new instruments. Twenty chapters cover all aspects of particle size measurement. Emphasis is placed on obtaining a representative sample from bulk powders, from fluid/particle streams and from the atmosphere and on preparing the sample for analysis using correct dispersion techniques. All standard methods of particle size analysis are very well described, including sieving, microscopy, sedimentation, electrical sensing zone method (Coulter Principle) and light interaction (single particle light scattering) methods. Additionally, very good chapters review measurement of specific surface by gas adsorption and permeametry. One feature of the new edition is a rewritten, expanded chapter on on-line particle size analysis divided into stream scanning techniques and field scanning techniques,
Elsevier Sequoia/Printed
in The Netherlands
Powder Technology, 66 (1991) 105-106
Book Reviews Bubble Wake Dynamics in Liquids and LiquidSolid Suspensions by Liang-Shih Fan and Katsumi Tsuchiya, published by Butterworth-Heinemann, 1990; f70.00; ISBN 0 409 90286 861. The complex interactions between the components of multiphase systems are responsible for the success or failure of a multitude of processes. They control many important flow conditions, virtually all mass transfer operations and a great part of chemical reaction engineering. Indeed, when Brodkey’s book, The Phenomena of Fluid Motions, was published twenty or so years ago, at least one reviewer regretted the absence of discussion of wake flows from that text. It is appropriate that the gap is at last filled by this book which also originates from Ohio State University. Almost as a result of definition, the mainstream literature of fluid mechanics in continua has neglected wake flows, and the greater part of published work relating to wake phenomena concerns single bubbles, drops and particles. The situations which arise in real processes are almost invariably more complex. Knowledge of the wake flows generated within the dispersion or suspension will ultimately provide the key to the interactions at the heart of many separation and entrainment processes. This is a cheering field for the experimentalist. The contributions of rigorous theoretical analysis are strictly limited; extended wake systems are unpredictable and wayward. Analytical and numerical solutions are largely confined to the near field, whereas many of the effects, especially those influencing other bubbles or particles, are far field and essentially cannot be predicted in detail. The book starts, almost inevitably, by considering the behaviour of single bubbles and the characteristics of wake structure, stability and size. The text takes us onward from this point, discussing how the wake changes the underlying flow field, perhaps adding turbulent components and inducing lateral or vertical mixing. The trajectories of nearby or following bubbles or suspended particles are modified, often inducing heterogeneity in a relatively homogeneous dispersion. Bubble break-up and coalescence mechanisms are considered in some detail, as is the more complex problem of the interactions in a three-phase liquid-bubble-solid system. The processes which occur in suspension and fluidised bed reactors which lead to local accumulation or denudation in the
The suspension, are covered thoroughly. experimental and theoretical evidence for the underlying centrifugal and pressure fields which are responsible for these separation processes is clearly presented. Likewise, the important implications of wake flows for mixing, entrainment and mass transfer in bubbly fluids and suspensions are thoroughly discussed; it is to be hoped that these lessons on the significance of hydrodynamic effects for chemical reaction engineering do not go unremarked. This is an important and welcome addition to the literature, presenting the reader with an extensive and authoritative review of the phenomena in the liquid phase of bubbly systems. It is one of the problems of presenting a work dealingwith a ‘difficult’ area - and three-phase systems certainly come into that category - that it is impossible to provide solutions to all the problems that arise in practice. But then, if these authors had achieved that, there would be no research left to be done and the rest of us would be out of a job. John M. Smith Particle Size Measurement by T. Allen, published by Chapman and Hall, 2 Boundary
Row, London SE1 8HN, U.K.; 832 pp., f85.00, ISBN 0 412 350 70X.
This is the fourth edition of the book that has become the standard reference on Particle Size Measurement since it was first published in 1968. Each subsequent edition has extended and amplified the coverage, by bringing the bibliography up to date and describing new instruments. Twenty chapters cover all aspects of particle size measurement. Emphasis is placed on obtaining a representative sample from bulk powders, from fluid/particle streams and from the atmosphere and on preparing the sample for analysis using correct dispersion techniques. All standard methods of particle size analysis are very well described, including sieving, microscopy, sedimentation, electrical sensing zone method (Coulter Principle) and light interaction (single particle light scattering) methods. Additionally, very good chapters review measurement of specific surface by gas adsorption and permeametry. One feature of the new edition is a rewritten, expanded chapter on on-line particle size analysis divided into stream scanning techniques and field scanning techniques,
Elsevier Sequoia/Printed
in The Netherlands