Table Of ContentSolid–Liquid Two Phase Flow
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Solid–Liquid Two Phase Flow
Sümer M. Peker
S¸erife S¸. Helvacı
Department of Chemical Engineering,
˙
Ege University, Izmir, Turkey
with contributions by
H. Banu Yener
·
Berrin Ikizler
Alp Alparslan
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First edition 2008
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This book is dedicated to the remembrance of
˙
Iffet and Hayri Peker
and
to the dear parents
of all who contributed to the writing of this book.
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Preface
Being an ‘underpinning technology’, fluid flow closely reflects and sometimes precedes
the developments of the ‘core technologies’of the time. Only in the second half of 19th
century that the term ‘two-phase flow’was pronounced and added as a chapter to fluid
mechanics and unit operations books. At that time, two-phase flow term was used pre-
dominantly to denote gas–liquid flow,which is not coincidental,as the leading technolo-
gies were nuclear and thermal, addressing mainly vapor–liquid systems. Development of
secondary and tertiary oil recovery technologies in 1980s focused the attention of the sci-
entific world on surfactants and liquid–liquid systems incorporating surfactants. The new
millennium brought with it a vision toward a change in the scale of processes and dimen-
sions from macroscale to microscale. Along with it came the need for a fundamental
understanding of processes in the molecular scale,in place of empirical models.
The subject of solid–liquid two-phase flow is something we live with. Man is acquainted
with solid–liquid mixtures since he first made his brick house, and she, her bread.
Solid–liquid systems are within us,as our blood,around us in our everyday living and in
fundamental technologies such as ceramics,cement,plastics,and grain-based food indus-
tries. However,the outlook on solid–liquid systems has changed in the meantime,in par-
allel with the advancement in the global interests and technologies. The excellent books
written on solid–liquid two-phase flow about two decades ago addressed particulate tech-
nologies of noncolloidal materials. Reduction in the scale of the particulate materials
brought with it inevitable involvement in surface sciences. Inspection of the foresight and
research framework contents gives an insight into the powerful role of liquid–solid inter-
actions and two phase flow in the technologies of the future. Some new concepts are
expected to be introduced in the future; for example,the ‘solid wall’was generally meant
to be the metal pipe wall,or a particle of a mineral. In the future,it may mean a surfactant
bilayer,the cell membrane,or a tissue. Until that time there is a great gap to be covered.
Solid–liquid two-phase flow in its present state of development is a multidisciplinary
subject: The size of the particles being processed in the developing technologies has
reduced from the order of micrometers to nanometers. Solid–particle interactions in this scale
are investigated in the field of colloid and surface science. Interfacial phenomenon is an
indispensable counterpart of the rheology of colloidal suspensions. The nonlinear rheo-
logical behavior,in turn,affects the fluid dynamics of solid–liquid mixtures. On the other
hand particles of noncolloidal dimensions settle under the action of gravity. Transport phe-
nomena together with the averaging techniques are required to analyze the flow problems
of settling suspensions. The analysis of the flow of settling slurries is still not free of
empiricism brought by the use of drag coefficients and friction factors.
Thirty years of experience of one of the authors in teaching fluid mechanics showed us
that a thorough understanding of fluid mechanics is possible only when the mechanism
underlying empirical results can be explained on a molecular scale. Models can then be
used for the prediction of the phenomena. The present book is written with this
understanding. The Solid–Liquid Two Phase Flow book consists mainly of three parts.
vii
viii Preface
The first three chapters handle the flow behavior of micron and submicron particles. The
next three chapters are related with particle sizes where Brownian motions are negligible.
The final two chapters are related with mixing and separation processes that are an insep-
arable part of solid–liquid flow. Within this context,a coherent and consistent approach is
adopted in interrelating the individual chapters.
Chapter 1 deals with the formation of the particulate phase of colloidal suspensions
starting with the molecular interactions. The role of surface forces in the aggregation of
primary particles is then taken up. This chapter is fundamental in the understanding of the
behavior of solid–liquid suspensions on all concentration levels and frequently referred to
in the subsequent chapters.
Chapter 2 gives the fundamentals of non-Newtonian flow together with examples for the
visualization of flow in channels of various geometries.
Chapter 3 is founded on the concepts given in Chapters 1 and 2 and extends these con-
cepts to concentrated suspensions where the interactions between particles predominate the
flow behavior. The chapter also deals with the effect of viscoelasticity of the suspending
medium and the particulate phase and recapitulates these effects in the most complicated of
all the flow systems,that of blood flow.
Chapter 4 takes up the motion of primary and aggregated particles. In parallel with the
contents of Chapter 1, the motion of porous, fractal aggregates and the particles with a
nonuniform density distribution and shape are also taken into consideration. This chapter
is closely interrelated with Chapters 6–8.
Chapter 5 reviews mathematical tools such as Eulerian and Lagrangian approaches and
averaging techniques that can be used in transport equations in analyzing dispersed systems
on microscale and macroscale.
Chapter 6 deals with the flow behavior of settling solids based on the concepts given in
Chapters 4 and 5. The flow patterns, concentration distribution of particles in each flow
pattern and the pressure losses are taken up in this chapter.
Chapter 7 takes up the introduction of solids into the liquid phase. The interfacial phe-
nomena associated with the dispersion of solids is taken up first followed by the introduc-
tion of the solid phase into the liquid phase. Principles of macroscale mixing in agitated
vessels,static mixers and micromixers are then given.
Chapter 8 deals with the classification of particles according to their sizes and its exten-
sion, separation of solids from the liquid phase. Principles of continuous classification
processes in sedimentation, fluidization, and hydrocyclones are given as frequently used
macroscale processes. Examples of novel separation processes in the microscale are also
introduced in this chapter.
With this content,the book gives an overview of the recent developments in solid–liquid
two-phase flow. In writing the book,we tried to reach all the available literature on subjects
within the scope of this book, to the best of our knowledge. We looked for experimental
work supported by theoretical development or modeling work supported with experiments
in the selection of material to be included within the text,whenever possible. We hope that
it will be a useful guide to graduate students,researchers and professionals working in the
industry who are interested in solid–liquid systems.
We are grateful for the enthusiasm and support given by our graduate students,Alp
.
Alparslan, H. Banu Yener, and Berrin Ikizler who contributed so much in shaping up
Preface ix
this book. The help of our graduate students Volkan Çakır and Selin S¸arkaya are grate-
fully acknowledged. We deeply appreciate the peaceful working environment provided
by Prof. Dr. Süheyda Atalay,the Head of the Chemical Engineering Department during
the writing of this book. We are grateful to Prof. Dr. Mustafa Demirciog(cid:2)lu for critical
reading of some of the chapters Prof. Dr. Deniz Üner for her helpful suggestions and to
Pakize Peker for her help extended in the drawing of the Figures. Suggestions by the
academic members of Clinical Biochemistry and Hematology Divisions of Faculty of
Medicine of Ege University are highly appreciated.
This book would have never been written if it were not for the positive energy of
Sybrand Boer-Iwema, Publishing Editor of Chemistry and Chemical Engineering of
Elsevier Science Ltd. to whom we are deeply indebted. We also thank our Editors Joan
Anuels and Kristi Green for their helpful suggestions,guidance and support throughout the
writing of this book and Dr. M.S. Rajkumar for the careful typesetting. Finally we are
thankful to our families and friends who waited patiently for us to finish the writing of this
book symbolized as “Chapter 4”.
Sümer M. Peker
S¸erife S¸. Helvacı
