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Introduction to industrial drying operations
The Chemuzal Engmeermg Journal, 19 (1980) 83 @ Elsevler Sequoia &A , Lausanne - Prmted m the Netherlands
83
Book Review
Introduction
to Industrial Drying Operations
by R B Keey, Pergamon Press, Oxford, 1978, XIX + 376 pp Price, paperback U S.$l6.50, hardcover U S $44 00
The author hopes “that this book will find a useful place, not only as a students’ text on prmciples of drymg, but also as an engineer’s guide to the better design and operation of drymg plant”. Anyone who has read the book will acknowledge that the author did attempt to fulfil his promise, with respect to drying operations by means of heat. The book draws exhaustively on the most recent research results in the technology of drymg This 1s commendable but mtegration of the new material with existmg knowledge presents a very demanding challenge. We know that every research result usually uncovers problems of which we have been unaware and 1slikely to call for revision of some of the existing knowledge. The first four chapters are devoted to the presentation of the basic knowledge of thermophysics required for the calculation of heat and material balances. In this part of the book the author famlliarises the reader with almost all possible types of computation likely to occur m the technology of drying. In doing so, he should perhaps have placed less emphasis on the use of formulae for domg even the most simple calculations, where the answer should follow from an understanding of the basis concepts. Such an approach does not encourage students to think for themselves. For instance, m an example on page 63 in which absolute humidity is to be calculated, the reader is referred to eqn. 2.10. Any student of average ability should be able to solve this kind of problem without such aids, whether it is a single calculation or whether he is to design a computer programme for repetitive calculations. This reliance on formulae features throughout the book.
Chapter five introduces the reader to the process of drymg. The author deals very briefly with theories of drying and related problems. His treatment of the mechanism of moisture movement m solids is too brief - for example, only porous structures are dealt with. The statement at the bottom of page 149 describes a section ABC of the curve m Fig. 5.3 as “constant rate period” whereas only the section from A to B should be thus described. The last three chapters deal with drymg equipment performance. To be able to fully understand the various exercises used to Illustrate the SubJect the reader will need to be already famihar with the equipment. Here the author considers the effect of a multitude of factors and operating conditions on the performance of the equipment. The concept of mass transfer coefficients, the operatmg efficiency in terms of transfer units and a variety of various correction factors are used to evaluate the performance of driers. An mexpenenced reader could form the impression that the design of driers is already a scientifically established procedure, while m fact it IS mainly still an art. The book will help a critical reader m making him aware of most of the computational problems and techniques in the technology of drying. It will be less helpful in studying physical aspects of drying, particularly the behaviour of moisture m the material being dried. This knowledge however is very relevant to the making of a correct choice of equipment for a given material to be dried. The book, despite some uncorrected typing errors and unnoticed mistakes and omissions, makes highly stimulatmg reading for a serious student of the technology of drying.
W. F CATUS
83
Book Review
Introduction
to Industrial Drying Operations
by R B Keey, Pergamon Press, Oxford, 1978, XIX + 376 pp Price, paperback U S.$l6.50, hardcover U S $44 00
The author hopes “that this book will find a useful place, not only as a students’ text on prmciples of drymg, but also as an engineer’s guide to the better design and operation of drymg plant”. Anyone who has read the book will acknowledge that the author did attempt to fulfil his promise, with respect to drying operations by means of heat. The book draws exhaustively on the most recent research results in the technology of drymg This 1s commendable but mtegration of the new material with existmg knowledge presents a very demanding challenge. We know that every research result usually uncovers problems of which we have been unaware and 1slikely to call for revision of some of the existing knowledge. The first four chapters are devoted to the presentation of the basic knowledge of thermophysics required for the calculation of heat and material balances. In this part of the book the author famlliarises the reader with almost all possible types of computation likely to occur m the technology of drying. In doing so, he should perhaps have placed less emphasis on the use of formulae for domg even the most simple calculations, where the answer should follow from an understanding of the basis concepts. Such an approach does not encourage students to think for themselves. For instance, m an example on page 63 in which absolute humidity is to be calculated, the reader is referred to eqn. 2.10. Any student of average ability should be able to solve this kind of problem without such aids, whether it is a single calculation or whether he is to design a computer programme for repetitive calculations. This reliance on formulae features throughout the book.
Chapter five introduces the reader to the process of drymg. The author deals very briefly with theories of drying and related problems. His treatment of the mechanism of moisture movement m solids is too brief - for example, only porous structures are dealt with. The statement at the bottom of page 149 describes a section ABC of the curve m Fig. 5.3 as “constant rate period” whereas only the section from A to B should be thus described. The last three chapters deal with drymg equipment performance. To be able to fully understand the various exercises used to Illustrate the SubJect the reader will need to be already famihar with the equipment. Here the author considers the effect of a multitude of factors and operating conditions on the performance of the equipment. The concept of mass transfer coefficients, the operatmg efficiency in terms of transfer units and a variety of various correction factors are used to evaluate the performance of driers. An mexpenenced reader could form the impression that the design of driers is already a scientifically established procedure, while m fact it IS mainly still an art. The book will help a critical reader m making him aware of most of the computational problems and techniques in the technology of drying. It will be less helpful in studying physical aspects of drying, particularly the behaviour of moisture m the material being dried. This knowledge however is very relevant to the making of a correct choice of equipment for a given material to be dried. The book, despite some uncorrected typing errors and unnoticed mistakes and omissions, makes highly stimulatmg reading for a serious student of the technology of drying.
W. F CATUS