- Email: [email protected]
Principles of flow in disperse systems
Powder Technobgy, 77 (1993) 321
321
Book Review
Principles of Flow In Disperse Systems Edited by Otto Molerus, published by Chapman and Hall, London, 1993, 320 pp.; ISBN O-412-40630-6; f55.
This book by Molerus is a fine compilation of various areas of study to which he has contributed over his career in dealing with disperse systems. The book begins with discussions on single particles and ends with fluidized bed systems. Professor Molerus has been a significant contributor in all these areas. The approach is a very rational one in that fundamentals are used when possible to develop understanding of these systems; when the complexity is amplified, empirical correlations are relied on but always aiming at a basic explanation of the phenomena being studied. In many cases, the limits of applicability of the analyses are stated to prevent the reader from misusing the information presented. The use of the word ‘strands’ appears various times in describing dispersed phase systems, and the author at the outset tries to warn the reader to distinguish carefully between the various definitions of strand-type flows. Consistent nondimensional groups are used throughout, and are clearly explained. Both spherical and the more common nonspherical particles are treated throughout the book. Analysis is also made of agitated vessels used to disperse particles, bubbles and drops. Design factors for minimum stirrer speeds and limits of applicability are presented. The agitated vessel is modeled in terms of pump characteristics. For the chemical engineer the bubble column is well treated in Chapter 4. Models, experimental set-up and data processing are dealt with. Chapter 5 has a good compilation of non-dimensional numbers with particular emphasis on dispersed phase systems and even including reduced gravity effects. Chapter 6 is entitled “Gas/solid flows with partial phase
separation” and spans regular pneumatic transport with particular concentration on strand flow and including the recirculating or fast fluid bed. To cover these two topics together makes sense, since one is an extension of the other. This chapter also has several sections dedicated to the modeling of fluidized beds including mass and momentum transport. Stability analysis is also presented, along with comparisons with experimental results. Chapter 7 is uniquely that of Professor Molerus and his use of vibration-induced pneumatic conveying which is a novel way of conveying fragile material without the need for a transport gas. Chapter 4 addresses the flow behavior of powders, an important issue in putting dispersed systems together. Both cohesive and non cohesive powder theory is developed, again with comparison with experimental results. The important issue of the effect of the presence of fine particles on flow behavior is also presented. Most of the material in this section comes from Molerus’ own developments in this field. Particles in dispersed systems can generally improve heat transfer depending on the characteristics of the powders. Fluidization and recirculating heat transfer topics are covered, with particular attention paid to the Geldart classification of powders for mechanisms and results. Some detailed particle-wall experimental findings lend a basic flavor to the heat transfer analysis. Chapters 10 and 11 give a brief coverage of gas fluidization, with some discussion of local structure and bubble behavior. Overall, I recommend this book to people who are serious about solids processing since it has a wide scope and includes some unique developments which Professor Molerus himself has spearheaded. George E. Klinzing
Elsevier Sequoia
321
Book Review
Principles of Flow In Disperse Systems Edited by Otto Molerus, published by Chapman and Hall, London, 1993, 320 pp.; ISBN O-412-40630-6; f55.
This book by Molerus is a fine compilation of various areas of study to which he has contributed over his career in dealing with disperse systems. The book begins with discussions on single particles and ends with fluidized bed systems. Professor Molerus has been a significant contributor in all these areas. The approach is a very rational one in that fundamentals are used when possible to develop understanding of these systems; when the complexity is amplified, empirical correlations are relied on but always aiming at a basic explanation of the phenomena being studied. In many cases, the limits of applicability of the analyses are stated to prevent the reader from misusing the information presented. The use of the word ‘strands’ appears various times in describing dispersed phase systems, and the author at the outset tries to warn the reader to distinguish carefully between the various definitions of strand-type flows. Consistent nondimensional groups are used throughout, and are clearly explained. Both spherical and the more common nonspherical particles are treated throughout the book. Analysis is also made of agitated vessels used to disperse particles, bubbles and drops. Design factors for minimum stirrer speeds and limits of applicability are presented. The agitated vessel is modeled in terms of pump characteristics. For the chemical engineer the bubble column is well treated in Chapter 4. Models, experimental set-up and data processing are dealt with. Chapter 5 has a good compilation of non-dimensional numbers with particular emphasis on dispersed phase systems and even including reduced gravity effects. Chapter 6 is entitled “Gas/solid flows with partial phase
separation” and spans regular pneumatic transport with particular concentration on strand flow and including the recirculating or fast fluid bed. To cover these two topics together makes sense, since one is an extension of the other. This chapter also has several sections dedicated to the modeling of fluidized beds including mass and momentum transport. Stability analysis is also presented, along with comparisons with experimental results. Chapter 7 is uniquely that of Professor Molerus and his use of vibration-induced pneumatic conveying which is a novel way of conveying fragile material without the need for a transport gas. Chapter 4 addresses the flow behavior of powders, an important issue in putting dispersed systems together. Both cohesive and non cohesive powder theory is developed, again with comparison with experimental results. The important issue of the effect of the presence of fine particles on flow behavior is also presented. Most of the material in this section comes from Molerus’ own developments in this field. Particles in dispersed systems can generally improve heat transfer depending on the characteristics of the powders. Fluidization and recirculating heat transfer topics are covered, with particular attention paid to the Geldart classification of powders for mechanisms and results. Some detailed particle-wall experimental findings lend a basic flavor to the heat transfer analysis. Chapters 10 and 11 give a brief coverage of gas fluidization, with some discussion of local structure and bubble behavior. Overall, I recommend this book to people who are serious about solids processing since it has a wide scope and includes some unique developments which Professor Molerus himself has spearheaded. George E. Klinzing
Elsevier Sequoia