Industrial Flow Modeling Group, iFMg at National Chemical Laboratory undertakes contract research and consultancy projects in the general area of reactor engineering. We use computational flow modeling to carry out these industrial projects. Computational flow modeling is a powerful tool for the design and analysis of industrial flow processes. Though it is routinely used as a design tool in aerospace engineering, chemical engineers have started exploiting the power of computational flow modeling only recently. Considering the central role played by reactors in chemical process industries, there is tremendous potential for applying computational flow-modeling tools to improve reactor engineering.

Through interactions with practicing engineers from industry, it has been realized that there is insufficient help available to harness state of the art computational flow modeling tools for complex, industrial reactor engineering applications. Many reactor engineers either consider that the flow complexities of industrial reactors are impossible to simulate, or expect miracles from off-the-shelf, commercial flow modeling tools. These two diverse views arise because of inadequate interactions between the flow modeling and industrial reactor engineering communities. It is essential to clearly understand the role of flow modeling in reactor engineering. It is necessary to relate the individual aspects of reactor engineering and computational flow modeling in a coherent and consistent way to realize the potential of computational flow modeling for reactor engineering research and practice. To assist practicing engineers in these aspects, workshops on 'computational flow modeling for chemical process industries' were started at the National Chemical Laboratory. The enthusiastic response to these workshops has encouraged me to write this book, which is an expanded and formalized presentation of workshop notes. I have tried to provide sufficient information to understand and to define the specific role of computational flow modeling for reactor engineering applications, to select appropriate tools and to apply these tools to link reactor hardware to reactor performance. The intended audience of the book is practicing chemical engineers working in industry as well as chemical engineering scientists and research students working in the area of reactor engineering. Some prior background in reactor engineering and numerical techniques is assumed.

The information in the book is organized to facilitate the central task of reactor engineer, that is, relating reactor hardware to reactor performance. Several steps to achieve such a task are discussed to clearly define the role of flow modeling in the overall reactor engineering activity. The necessity of using a hierarchy of modeling tools and establishing a clear relationship between the objectives of reactor engineering and the computational flow model is emphasized with the help of examples. The overall methodology of achieving the objectives of reactor engineering via computational flow modeling is discussed. Desirable characteristics and key issues in selecting appropriate computational fluid dynamics (CFD) codes are briefly discussed. A number of examples and case studies covering the four major reactor types used in chemical industries, namely, stirred reactors, bubble column reactors, flu-idized bed reactors and fixed bed reactors are included. In view of the wide range of reactor types, however, it is impossible to cover all the reactor types and flows relevant to these reactor types. Emphasis on certain topics and the selection of examples is biased and is directly related to my own research and consulting experience. Some topics, like radiative heat transfer, laminar reactive flows are completely omitted. I have, however, made an attempt to evolve general guidelines, which will be useful for solving practical reactor engineering problems. Some comments on future trends in computational flow modeling and its use by the chemical engineering community are also included.

The material included in this book may be used in several ways and at various stages of flow modeling projects. It may be used as a basic resource for making appropriate decisions about investment in the application of CFD to reactor engineering. It may be used as a study material for an in-house course to facilitate the appreciation and application of computational flow modeling for reactor engineering. It may be used as a companion book while solving practical reactor engineering problems. I hope that this book will encourage chemical engineers to exploit the potential of computational flow modeling and will eventually lead to better reactor engineering.

This book is essentially the outcome of my last fifteen years of association with this subject. I have received a great deal of help from numerous persons over these years in formulating and revising my views on both computational flow modeling and chemical reactor engineering. I am particularly indebted to my teacher and mentor, Professor J.B. Joshi, who has been one of the leading practitioners of process fluid dynamics for three decades. There are not adequate words to express his contributions to this book. I was fortunate to have an opportunity to work with Dr R.V. Chaudhari and Dr R.A. Mashelkar at the National Chemical Laboratory. Both of them always extended their full support and encouragement in my every endeavor. Without their support, it would not have been possible to develop our industrial flow modeling activity, on which this book is based. I would like to acknowledge the support provided by Professor H.E.A. van den Akker of Delft University of Technology and by

Professors G.F. Versteeg and J.A.M. Kuipers of University of Twente, The Netherlands. My brief stay at Professor van den Akker's laboratory at Delft introduced me to different commercial CFD solvers and expanded my horizons. The idea of this book was formalized during my second visit to The Netherlands at University of Twente. I would also like to thank Dr Bharatan Patel of Fluent Inc. and Mr Paresh Patel of Fluent India for their support.

I am grateful to my associates and collaborators with whom I worked on different industrial projects. In particular, I owe much to Professor J.R. Bourne, Mr Vaibhav Deshpande, Ms S.M.S. Dommeti and Mr Yatin Tayalia. My students, especially Kapil Girotra, Ashwin Sunthankar, Ranjit Utikar, Aravind Rammohan, Sachin Muthian, Avinash Khopkar, Prashant Gunjal, Vivek Buwa and Shishir Sable have contributed to this book in different ways. This includes technical contributions either in a direct or indirect way, helping me to collect the required information and reading the draft manuscript. My father, Mr V.B. Ranade also has painstakingly read the entire manuscript and suggested several ways to enhance the clarity of presentation. The manuscript was improved wherever their suggestions were incorporated. Any remaining errors or shortcomings are, needless to say, the responsibility of the author. Finally, I wish to thank my wife, Nanda, for her patience, understanding and enthusiastic support, which carried me through this long and arduous writing process.

Vivek V. Ranade December 2000 Pune

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