Page 10 - Modelling in Transport Phenomena A Conceptual Approach

Preface

During their undergraduate education, students take various courses on fluid flow,
heat transfer, mass transfer, chemical reaction engineering and thermodynamics.
Most of the students, however, are unable to understand the links between the
concepts covered in these courses and have difficulty in formulating equations,
even of the simplest nature. This is a typical example of not seeing the forest for
the trees.
The pathway from the real problem to the mathematical problem has two
stages: perception and formulation. The difliculties encountered in both of these
stages can be easily resolved if students recognize the forest first. Examination of
trees one by one comes at a later stage.
In science and engineering, the forest is represented by the basic concepts,
i.e., conservation of chemical species, conservation of mass, conservation of momen-
tum, and conservation of energy. For each one of these conserved quantities, the
following inventory rate equation can be written to describe the transformation of
the particular conserved quantity cp :
Rate of Rate of Rate of cp Rate of cp
( cp in ) - ( cp out ) + ( generation ) = ( accumulation
in which the term cp may stand for chemical species, mass, momentum or energy.
My main purpose in writing this textbook is to show students how to translate
the inventory rate equation into mathematical terms at both the macroscopic and
microscopic levels. It is not my intention to exploit various numerical techniques
to solve the governing equations in momentum, energy and mass transport. The
emphasis is on obtaining the equation representing a physical phenomenon and its
interpretation.
I have been using the draft chapters of this text in my third year Mathematical
Modelling in Chemical Engineering course for the last two years. It is intended as an
undergraduate textbook to be used in an (Introduction to) Transport Phenomena
course in the junior year. This book can also be used in unit operations courses in
conjunction with standard textbooks. Although it is written for students majoring
in chemical engineering, it can also be used as a reference or supplementary text
in environmental, mechanical, petroleum and civil engineering courses.
The overview of the manuscript is shown schematically in the figure below.

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