33
Edited by Evangelos Tsotsas and Arun S. Mujumdar Modern Drying Technology
Edited by
Evangelos Tsotsas and
Arun S. Mujumdar
Modern Drying Technology
Modern Drying Technology
Edited by E. Tsotsas and A. Mujumdar
Other Volumes
Volume 1: Computational Tools at Different ScalesISBN: 978-3-527-31556-7
Volume 2: Experimental TechniquesISBN: 978-3-527-31557-4
Volume 3: Product Quality and FormulationISBN: 978-3-527-31558-1
Volume 4: Energy SavingsISBN: 978-3-527-31559-8
Modern Drying Technology Set (Volumes 1 – 5)ISBN: 978-3-527-31554-3
Edited byEvangelos Tsotsas and Arun S. Mujumdar
Modern Drying Technology
Volume 5: Process Intensification
The Editors:
Prof. Evangelos TsotsasOtto von Guericke UniversityThermal Process EngineeringUniversitätsplatz 239106 MagdeburgGermany
Prof. Arun S. MujumdarNational University of SingaporeMechanical Engineering/Block EA 07-09 Engineering Drive 1Singapore 117576Singapore
All books published byWiley-VCH are carefullyproduced. Nevertheless, authors, editors, andpublisher do not warrant the information containedin these books, including this book, to be free oferrors. Readers are advised to keep in mind thatstatements, data, illustrations, procedural details orother items may inadvertently be inaccurate.
Library of Congress Card No.: applied for
British Library Cataloguing-in-Publication DataA catalogue record for this book is available from theBritish Library.
Bibliographic information published by the DeutscheNationalbibliothekThe Deutsche Nationalbibliothek lists thispublication in the Deutsche Nationalbibliografie;detailed bibliographic data are available on theInternet at < http:// dnb.d-nb.d e> .
# 2014 Wiley-VCH Verlag GmbH & Co. KGaA,Boschstr. 12, 69469 Weinheim, Germany
All rights reserved (including those of translation intoother languages). No part of this book may bereproduced in any form – by photoprinting,microfilm, or any other means – nor transmitted ortranslated into a machine language without writtenpermission from the publishers. Registered names,trademarks, etc. used in this book, even when notspecifically marked as such, are not to be consideredunprotected by law.
Print ISBN: 978-3-527-31560-4ePDF ISBN: 978-3-527-63171-1ePub ISBN: 978-3-527-65140-5Mobi ISBN: 978-3-527-65139-9oBook ISBN: 978-3-527-63170-4
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Printed on acid-free paperPrinted in the Federal Republic of Germany
Contents
Series Preface XIPreface of Volume 5 XVList of Contributors XIXRecommended Notation XXIIIEFCE Working Party on Drying: Address List XXIX
1 Impinging Jet Drying 1Eckehard Specht
1.1 Application 11.2 Single Nozzle 41.3 Nozzle Fields 71.3.1 Arrays of Single Nozzles 71.3.2 Hole Channels 121.3.3 Perforated Plates 131.3.4 Nozzles for Cylindrical Bodies 141.4 Summary of the Nusselt Functions 161.5 Design of Nozzle Field 171.6 Conclusion 23
References 24
2 Pulse Combustion Drying 27Ireneusz Zbicinski, Tadeusz Kudra, and Xiangdong Liu
2.1 Principle of Pulse Combustion 272.2 Pulse Combustors: Design and Operation 322.2.1 Pulse Combustors with Mechanical Valves 322.2.2 Pulse Combustors with Aerodynamic Valves 342.2.3 Frequency-Tunable Pulsed Combustors 352.3 Aerodynamics, Heat and Mass Transfer 362.3.1 Atomization 372.3.2 Heat and Mass Transfer 382.4 Modeling of Pulse Combustion Drying 422.5 Pulse Combustion in Drying 48
References 53
jV
3 Superheated Steam Drying of Foods and Biomaterials 57Sakamon Devahastin and Arun S. Mujumdar
3.1 Introduction 573.2 Principle of Superheated Steam Drying (SSD) 583.3 Atmospheric-Pressure Superheated Steam Drying 613.4 Low-Pressure Superheated Steam Drying (LPSSD) 693.5 Application of LPSSD to Improve the Quality of Foods and
Biomaterials 763.6 Concluding Remarks 82
References 83
4 Intensification of Fluidized-Bed Processes for Drying andFormulation 85Evangelos Tsotsas, Stefan Heinrich, Michael Jacob, Mirko Peglow,and Lothar M€orl
4.1 Introduction 854.2 Intensification by Apparatus and Flow Design 864.2.1 Different Types of Spouted Bed 864.2.2 Operating Characteristics of Spouted Beds 934.2.3 Mass and Heat Transfer in ProCell Units 1004.2.4 Discrete Particle Modeling 1074.3 Intensification by Contact Heating 1124.3.1 General Principle 1124.3.2 Main Effects and Influences 1144.3.3 Further Remarks on Modeling 1214.4 Further Methods of Intensification 1264.5 Conclusion 127
References 128
5 Intensification of Freeze-Drying for the Pharmaceutical and FoodIndustries 131Roberto Pisano, Davide Fissore, and Antonello A. Barresi
5.1 Introduction 1315.2 Exergetic Analysis (and Optimization) of the Freeze-Drying Process 1335.3 Process Intensification in Vacuum Freeze-Drying of Liquids 1395.3.1 Regulation of Nucleation Temperature During Freezing 1405.3.2 Use of Organic Solvents and Cosolvents 1445.4 Atmospheric Freeze-Drying 1465.5 Use of Combined Technologies for Drying Heat-Sensitive
Products 1505.5.1 Microwave-Assisted Drying 1505.5.2 Ultrasound-Assisted Drying 1525.6 Continuous Freeze-Drying 1545.7 Conclusions 155
References 157
VIj Contents
6 Drying of Foamed Materials 163Ireneusz Zbicinski, Julia Rabaeva, and Artur Lewandowski
6.1 Introduction 1636.2 Foam Properties 1646.3 Foam Spray Drying 1676.3.1 Processing Principles 1676.3.2 Final Product Properties 1726.4 Foam-Mat Drying 1816.5 Summary 187
References 188
7 Process-Induced Minimization of Mass Transfer Barriersfor Improved Drying 191Henry J€ager, Katharina Sch€ossler, and Dietrich Knorr
7.1 Introduction 1917.2 Structural Characterization of Plant Raw Materials and Impact of PEF
and Ultrasound 1927.2.1 Methods for Analysis of Tissue Structure and Quantification
of Cell Damage 1927.2.2 PEF: Principles and Impact on Plant Tissue Structure 1957.2.2.1 Introduction to PEF Technology 1957.2.2.2 PEF: Impact on Plant Tissue Structure 1967.2.3 Ultrasound: Principles and Impact on Plant Tissue Structure 1997.2.3.1 Introduction to Ultrasound Technology 1997.2.3.2 Ultrasound: Impact on Plant Tissue Structure 2007.3 Pulsed Electric Field (PEF) Application as a Pretreatment 2047.3.1 Osmotic Dehydration 2057.3.2 Air Drying 2067.3.3 Impact of PEF on Freezing and Freeze-Drying Behavior of Raw
Materials 2087.3.4 Quality Characteristics Affected by PEF Pretreatment 2117.4 Contact Ultrasound for Combined Drying Processes 2167.4.1 Ultrasound in Osmotic Dehydration 2177.4.2 Contact Ultrasound in Air Drying 2187.4.3 Contact Ultrasound in Freeze-Drying 2217.4.4 Quality Characteristics Affected by Ultrasound-Combined Drying
Processes 2247.5 Conclusion 226
References 230
8 Drying Assisted by Power Ultrasound 237Juan Andr�es C�arcel, Jos�e Vicente García-P�erez, Enrique Riera,Carmen Rossell�o, and Antonio Mulet
8.1 Introduction 2378.2 Ultrasound 239
Contents jVII
8.2.1 Ultrasound Waves 2398.2.1.1 Power 2398.2.1.2 Frequency 2408.2.1.3 Attenuation 2408.2.1.4 Acoustic Impedance 2408.2.2 Effects of Ultrasound on Mass Transfer 2418.3 Ultrasonic Equipment 2428.3.1 Source of Energy 2438.3.2 Transducers 2438.3.3 Application Systems 2458.3.3.1 Treatments in Liquid Media 2458.3.3.2 Treatments in Gas Media 2478.4 Influence of the Main Process Variables on Drying Intensification
by Ultrasound 2508.4.1 Ultrasonic Power Applied 2508.4.1.1 Ultrasonic Field Measurements 2518.4.1.2 Ultrasonic Intensity and Effects 2528.4.1.3 Influence of the Characteristics of the Medium on Ultrasonic
Intensity 2588.4.2 Drying Air Temperature 2638.4.3 Ultrasound–Sample Interaction 2668.5 Conclusions 272
References 273
9 Microwave-Assisted Drying of Foods – Equipment, Processand Product Quality 279Yingqiang Wang, Min Zhang, and Arun S. Mujumdar
9.1 Introduction 2799.2 Microwave-Assisted Drying of Foods 2819.2.1 Basic Principles of Microwave-Assisted Drying 2819.2.2 Energy Absorption by Products During Dielectric Heating 2839.2.3 Dielectric Properties 2839.2.4 Penetration Depth 2859.3 Microwave-Assisted Drying Equipment 2859.3.1 Microwave-Assisted Convective Drying Equipment 2869.3.2 Microwave-Assisted Vacuum Drying Equipment 2879.3.3 Microwave-Assisted Freeze-Drying Equipment 2909.3.4 Microwave-Assisted Spouted Bed Drying Equipment 2919.4 Microwave-Assisted Drying Process 2929.4.1 Moisture Loss 2939.4.2 Temperature Distributions 2959.4.2.1 Temperature Variations at Fixed Levels of Microwave Power 2969.4.2.2 Temperature Variations at Variable Microwave Power without
Controlling Temperature 298
VIIIj Contents
9.4.2.3 Temperature Change with Time-Adjusted Power in FeedbackTemperature Control 299
9.4.3 Energy Consumption 2999.4.4 Dielectric Breakdown 3029.4.5 Changes in Dielectric Properties 3049.4.6 Quality Changes in Food during Microwave-Assisted Drying 3059.5 Microwave-Assisted Drying Process Control and Optimal
Operation 3089.5.1 Factors Controlling Microwave-Assisted Drying Processes 3089.5.2 Optimal Operation Strategy 3089.6 Concluding Remarks 310
References 312
10 Infrared Drying 317German Efremov
10.1 Introduction 31710.2 Radiation Heat Transfer 31810.2.1 General Principles 31810.2.2 Reflection, Absorption, and Transmission 31910.2.3 Infrared Spectrum 32110.3 Classification, Research, and Applications of Radiation Drying 32310.3.1 Classification 32310.3.2 Solar Drying 32510.3.3 Infrared Drying 32610.3.4 Catalytic Infrared Drying 32910.4 Types of Radiators 33210.4.1 General Considerations 33210.4.2 Electric Radiators 33310.4.3 Gas-Heated IR Radiators 33510.5 Interaction between Matter and Infrared Radiation 33710.5.1 General Relationships 33710.5.2 Radiation Properties of Materials 33910.6 Kinetics of Infrared Drying 34210.7 Infrared Drying Combined with other Types of Drying 34510.7.1 IR and Convective Drying 34610.7.2 IR and Microwave Drying 34710.7.3 IR and Freeze-Drying 34810.7.4 IR with other Types of Drying 34810.8 Conclusions 351
References 352
Index 357
Contents jIX
Series Preface
The present series is dedicated to drying, that is, to the process of removingmoisturefrom solids. Drying has been conducted empirically since the dawn of the humanrace. In traditional scientific terms it is a unit operation in chemical engineering.The reason for the continuing interest in drying and, hence, the motivation for theseries, concerns the challenges and opportunities. A permanent challenge isconnected to the sheer amount and value of products that must be dried – eitherto attain their functionalities, or because moisture would damage the materialduring subsequent processing and storage, or simply because customers are notwilling to pay for water. This comprises almost every material used in solid form,from foods to pharmaceuticals, from minerals to detergents, from polymers topaper. Raw materials and commodities with a low price per kilogram, but withextremely high production rates, and also highly formulated, rather rare but veryexpensive specialties have to be dried.This permanent demand is accompanied by the challenge of sustainable devel-
opment providing welfare, or at least a decent living standard, to a still-growinghumanity. On the other hand, opportunities emerge for drying, as well as for anyother aspect of science or living, from either the incremental or disruptive develop-ment of available tools. This duality is reflected in the structure of the book series,which is planned for five volumes in total, namely:
Volume 1: Computational tools at different scalesVolume 2: Experimental techniquesVolume 3: Product quality and formulationVolume 4: Energy savingsVolume 5: Process intensification.
As the titles indicate, we start with the opportunities in terms of moderncomputational and experimental tools in Volumes 1 and 2, respectively. How theseopportunities can be used in fulfilling the challenges, in creating better and newproducts, in reducing the consumption of energy, in significantly improvingexisting or introducing new processes will be discussed in Volumes 3, 4 and 5. Inthis sense, the first two volumes of the series will be driven by science; the last
jXI
three will try to show how engineering science and technology can be translatedinto progress.In total, the series is designed to have both common aspects with and essential
differences from an extended textbook or a handbook. Textbooks and handbooksusually refer to well-established knowledge, prepared and organized either forlearning or for application in practice, respectively. On the contrary, the ambitionof the present series is to move at the frontier of “modern drying technology”,describing things that have recently emerged, mapping things that are about toemerge, and also anticipating some things that may or should emerge in the nearfuture. Consequently, the series is much closer to research than textbooks orhandbooks can be. On the other hand, it was never intended as an anthology ofresearch papers or keynotes – this segment being well covered by periodicals andconference proceedings. Therefore, our continuing effort will be to stay as close aspossible to a textbook in terms of understandable presentation and as close aspossible to a handbook in terms of applicability.Another feature in commonwith an extended textbook or a handbook is the rather
complete coverage of the topic by the entire series. Certainly, not every volume orchapter will be equally interesting for every reader, but we do hope that severalchapters and volumes will be of value for graduate students, for researchers who areyoung in age or thinking, and for practitioners from industries that are manu-facturing or using drying equipment. We also hope that the readers and owners ofthe entire series will have a comprehensive access not to all, but to manysignificant recent advances in drying science and technology. Such readers willquickly realize that modern drying technology is quite interdisciplinary, profitinggreatly from other branches of engineering and science. In the opposite direction,not only chemical engineers, but also people from food, mechanical, environ-mental or medical engineering, material science, applied chemistry or physics,computing and mathematics may find one or the other interesting and usefulresults or ideas in the series.The mentioned interdisciplinary approach implies that drying experts are keen to
abandon the traditional chemical engineering concept of unit operations for the sakeof a less rigid and more creative canon. However, they have difficulties of identifi-cation with just one of the two new major trends in chemical engineering, namelyprocess-systems engineering or product engineering. Efficient drying can becompletely valueless in a process system that is not efficiently tuned as a whole,while efficient processing is certainly valueless if it does not fulfill the demands ofthe market (the customer) regarding the properties of the product. There are fewtopics more appropriate in order to demonstrate the necessity of simultaneoustreatment of product and process quality than drying. The series will try to work outchances that emerge from this crossroads position.One further objective is to motivate readers in putting together modules (chapters
from different volumes) relevant to their interests, creating in this manner individ-ual, task-oriented threads trough the series. An example of one such thematic threadset by the editors refers to simultaneous particle formation and drying, with a focus
XIIj Series Preface
on spray fluidized beds. From the point of view of process-systems engineering, thisis process integration – several “unit operations” take place in the same equipment.On the other hand, it is product engineering, creating structures – in many casesnanostructures – that correlate with the desired application properties. Suchproperties are distributed over the ensemble (population) of particles, so that itis necessary to discuss mathematical methods (population balances) and numericaltools able to resolve the respective distributions in one chapter of Volume 1.Measuring techniques providing access to properties and states of the particlesystem will be treated in one chapter of Volume 2. In Volume 3, we will attempt tocombine the previously introduced theoretical and experimental tools with the goalof product design. Finally, important issues of energy consumption and processintensification will appear in chapters of Volumes 4 and 5. Our hope is that somethematic combinations we have not even thought about in our choice of contents willarise in a similar way.As the present series is a series of edited books, it can not be as uniform in either
writing style or notation as good textbooks are. In the case of notation, a list ofsymbols has been developed and will be printed in the beginning of every volume.This list is not rigid but foresees options, at least partially accounting for the habits indifferent parts of the world. It has been recently adopted as a recommendation by theWorking Party on Drying of the European Federation of Chemical Engineering(EFCE). However, the opportunity of placing short lists of additional or deviantsymbols at the end of every chapter has been given to all authors. The symbols usedare also explained in the text of every chapter, so that we do not expect any seriousdifficulties in reading and understanding.The above indicates that the clear priority in the edited series was not in
uniformity of style, but in the quality of contents that are very close to currentinternational research from academia and, where possible, also from industry.Not every potentially interesting topic is included in the series, and not everyexcellent researcher working on drying contributes to it. However, we arevery confident about the excellence of all research groups that we were able togather together, and we are very grateful for the good cooperation with all chapterauthors. The quality of the series as a whole is set mainly by them; the success ofthe series will primarily be theirs. We would also like to express our acknowl-edgments to the team of Wiley-VCH who have done a great job in supporting theseries from the first idea to realization. Furthermore, our thanks go to Mrs NicolleDegen for her additional work, and to our families for their tolerance andcontinuing support.Last but not least, we are grateful to the members of the Working Party on Drying
of the EFCE for various reasons. First, the idea about the series came up during theannual technical and business meeting of the working party 2005 in Paris. Secondly,many chapter authors could be recruited among its members. Finally, the WorkingParty continues to serve as a panel for discussion, checking and readjustment of ourconceptions about the series. The list of the members of the working party with theiraffiliations is included in every volume of the series in the sense of acknowledgment,
Series Preface jXIII
but also in order to promote networking and to provide access to national workingparties, groups and individuals. The present edited books are complementary to theregular activities of the EFCE Working Party on Drying, as they are also comple-mentary to various other regular activities of the international drying community,including well-known periodicals, handbooks, and the International DryingSymposia.
December 2006 Evangelos TsotsasArun S. Mujumdar
XIVj Series Preface
Preface of Volume 5
Volume 5 of “Modern Drying Technology” is dedicated to “Process intensification”.This is a natural conclusion for the series. “Computational tools at different scales”and “Experimental techniques”, presented in Vol. 1 and Vol. 2, respectively, wereused to discuss “Product quality and formulation” in Vol. 3, and “Energy savings” inVol. 4. Now the goal is not as specific as in Vol. 4, but more general and quiteambitious; namely, to use as intensive drying processes as possible in order toreduce the drying time and hence the equipment size. Insights from all previousvolumes of the series must be implemented and applied to this purpose, leading tothe following ten chapters of Vol. 5:
Chapter 1: Impinging jet dryingChapter 2: Pulse combustion dryingChapter 3: Superheated steam drying of foods and biomaterialsChapter 4: Intensification of fluidized-bed processes for drying and formulationChapter 5: Intensification of freeze-drying for the pharmaceutical and food
industriesChapter 6: Drying of foamed materialsChapter 7: Process-induced minimization of mass transfer barriers for improved
dryingChapter 8: Drying assisted by power ultrasoundChapter 9: Microwave-assisted drying of foods – Equipment, process and product
qualityChapter 10: Infrared drying
Frequent mention of foods, biomaterials and pharmaceuticals in the list of contentsshows that process intensification is not a stand-alone perspective, but a challengewhich usually must be addressed under serious constraints set by the qualityrequirements of valuable products that might suffer damage during processing.On the other hand, the list of contents of this final volume is longer than the lists ofprevious volumes in this series, indicating that a large variety of approaches andmethods can lead to process intensification in practice, and that the internationaldrying community is continually and persistently working on their further devel-opment and implementation.
jXV
External, gas-side heat andmass transfer resistances can seriously limit the rate ofdrying processes, but they can also be radically reduced by high velocity flowimpingement on the surface of the material to be dried. This is easy to implementfor flat products such as paper, textiles, tissues, tiles or wood veneer, but connectedwith questions about how many nozzles shall be used, and how these nozzles shallbe placed and operated. Answers to those questions are provided in Chapter 1, in aconcise way that refrains from the consideration of less significant details and aimsat immediate engineering applicability.The same purpose of lowering external heat and mass transfer resistances can be
achieved by imposing, instead of a steady turbulent flow, an oscillatory flow of dryinggas around thematerial to be dried. This can be realized by drying in flue gas comingfrom a special, pulse burner via a tailpipe to the drying chamber. Intensification ofthe external heat and mass transfer may not be as spectacular as in case ofimpinging jets, but the method is applicable to virtually any kind of convectivedryer, i.e. it is not restricted to flat products. Construction and operation of therespective combustors, enhancement of heat and mass transfer, and modeling arediscussed in Chapter 2.In Chapter 3, the focus is shifted to the use of superheated steam, instead of hot air
of flue gas, as the drying agent, which has an influence on both, the external and theinternal heat and mass transfer. A major advantage of this process is that energy canmuch easier be recovered from exhaust steam, than from the wet exhaust air ofconventional drying processes. The necessity of operating above the boiling point ofthe liquid to be removed, usually water, may be turned into an advantage bycombining the drying process with, e.g., sterilization or cooking of foods andbiomaterials. Damage that such materials might suffer at the boiling temperature ofwater at ambient pressure can be prevented by reducing the operating pressure, i.e.by low-pressure superheated steam drying.Alternatively, drying rates can be boosted in fluidized beds by combining heat
transfer from the fluidization air with indirect heat transfer, usually from immersedsteam tubes. Fundamentals and applications of respective processes are discussed inChapter 4. It is pointed out that the resulting process intensification can be used forincreasing the capacity of the dryer, or for reducing the temperature level in order toprotect thermally sensitive products. Moreover, the process can be significantlyintensified by applying spouted beds, instead of conventional fluidized beds. Thebackground of this behavior is that regions of extremely high gas velocity can berealized in specially designed spouted beds with adjustable air inlet.However, there are foods and pharmaceuticals which are so sensitive, that they
must be dried from the frozen state. Purposeful use of the notoriously slow processof freeze drying increases the necessity and urgency of process intensificationmeasures. Various suchmeasures are available, as discussed in Chapter 5, includingautomatic control for better drying cycles, favorable templating of the solid matrix tobe dried by controlled freezing, the use of organic solvents, freeze drying underatmospheric conditions, or the transition from batch to the continuous operationmode. Moreover, hybrid processes can be applied, such as microwave or ultrasoundassisted freeze drying.
XVIj Preface of Volume 5
Sometimes, product quality requirements meet with the goal of more intensedrying processes for hard-to-dry products, such as fruit pulps, juices, or dairy. Foamdrying techniques provide attractive solutions for such cases. Foamed products canbe produced in spray dryers by injecting inert gas to the feed of the dryer, before orduring atomization. Alternatively, solutions or dispersions can be whipped to foamthat is subsequently dried in any appropriate type of equipment, which is denoted byfoam-mat drying. Respective process configurations, enhancement of drying byincreased surface area and more open structures, and resulting product propertiesare discussed in Chapter 6.In some other cases, biological materials to be dried contain natural barriers to
mass transfer, such as cell membranes. Then, drying can be enhanced by applyingpulsed electric fields to create pores in the membranes or disintegrate the cells,followed by osmotic dehydration, hot-air drying, or freeze drying. Similar effects canbe attained by application of ultrasound to support and assist the mentioned dryingprocesses. Principles and results of these novel technologies are presented inChapter 7, along with methods for the structural and textural characterization ofthe materials, and quality characteristics of the resulting products.A more detailed treatment of the application of ultrasound is provided in
Chapter 8, along with a discussion of the principles of generation and transmissionof ultrasound energy to the material to be treated. It is pointed out that powerultrasound can be used to assist both, liquid-solid processes, such as brinetreatment, and drying. The acoustic field is shown to enhance, by a number ofmechanisms, both, the external and the internal mass transfer when combined withhot air or atmospheric freeze drying of vegetables and fruits. The more porous thematerial, and the lower the permissible temperature and gas velocity, the higher isthe intensification that can be reached by application of power ultrasound.Another method of hybrid or assisted processing is to support hot-air drying,
vacuum drying, freeze drying, or spouted bed drying by microwaves. Microwaveshave the unique property of targeting heat supply to the consumer, i.e. to the wetinterior of dryingmaterials. Respective processes, equipment, and the enhancementof drying rate that can be achieved by means of the microwaves are thoroughlypresented in Chapter 9. Moreover, issues of energy consumption, automatic control,and product quality are addressed. Agricultural products and food materials are,again, in the focus of the discussion.Infrared radiation usually does not penetrate deep into materials, but it can
significantly intensify drying processes by supplying significant and well controlla-ble amounts of energy to the surface. In a comprehensive treatment of infrareddrying in Chapter 10 different types of radiators, including gas-fired ones, arepresented, the necessity of matching the infrared spectrum used with the propertiesof the material to be dried is stressed, and opportunities to improve product qualityby intermittent radiation supply are pointed out. Combinations of infrared heatsupply with hot-air drying, microwave drying, freeze drying, and heat-pump dryingare discussed.Volume 5 brings several thematic threads set in previous volumes, for instance on
fluidized bed drying or food processing, to their contemporary completion. It
Preface of Volume 5 jXVII
reflects the interdisciplinary and multi-scale character of modern drying technologyin a similar way as the previous volumes of the series. Therefore, we hope that thisfinal volume and the entire series have at least partially attained the goal of providingall people working on drying in industry and research with a map that shows wheredrying science and technology are, where they are presently growing to cope withincreasing challenges and application demands, and where they may be in thefuture. In other words, we hope that the series can contribute to the solution ofspecific, well defined practical tasks (“improve quality, save energy, cut costs”, aspromised in the flyer of the publisher), but that it can also motivate furtherexploratory work and inspire to innovation in an important and rewarding fieldof engineering science. In this farewell preface, we would like to renew ourprofound acknowledgement of all persons who have made this series possible -our families and co-workers, the excellent editorial team of the publisher, all ouroutstanding and esteemed colleagues and friends who have served as chapterauthors, the countless engineers and scientists whose contributions are quotedin the book series, but also those who have contributed to drying science and practicewithout finding individual citation.
Summer 2013 Evangelos TsotsasArun S. Mujumdar
XVIIIj Preface of Volume 5
List of Contributo rs
Editors
Prof. Evangelos TsotsasOtto von Guericke UniversityMagdeburgThermal Process EngineeringPSF 412039106 MagdeburgGermanyEmail: [email protected]
Prof. Arun S. MujumdarMcGill UniversityDepartment of BioresourceEngineering2111 Lakeshore RoadSainte-Anne-de-BellevueQuebec H9X 3V9CanadaEmail: [email protected]
Authors
Prof. Antonello A. BarresiPolitecnico di TorinoDipartimento di Scienza Applicata eTecnologiaCorso Duca degli Abruzzi 2410129 TorinoItalyEmail: [email protected]
Prof. Juan Andr�es C �arcelUniversidad Polit�ecnica de ValenciaDepartamento de Tecnología deAlimentosCami de Vera s/n46022 ValenciaSpainEmail: [email protected]
Prof. Sakamon DevahastinKing Mongkut’ s University ofTechnology ThonburiDepartment of Food Engineering126 Pracha u-tid RoadBangkok 10140ThailandEmail: [email protected]
Prof. German EfremovMoscow State Open UniversityStreet Krasnogo Mayaka 13acor. 2, app. 71117570 MoscowRussiaEmail: [email protected]
Dr. Davide FissorePolitecnico di TorinoDipartimento di Scienza Applicata eTecnologiaCorso Duca degli Abruzzi 2410129 TorinoItalyEmail: davide. [email protected]
jXIX
Prof. Jos�e Vicente García-P�erezUniversidad Polit�ecnica de ValenciaDepartamento de Tecnología deAlimentosCami de Vera s/n46022 ValenciaSpainEmail: [email protected]
Prof. Stefan HeinrichHamburg University of TechnologyInstitute of Solids ProcessEngineering and Particle TechnologyDenickestrasse 1521073 HamburgGermanyEmail: [email protected]
Dr. Michael JacobGlatt Ingenieurtechnik GmbHNordstrasse1299427 WeimarGermanyEmail: [email protected]
Dr. Henry J €agerTechnische Universit€at BerlinDepartment of Food Biotechnologyand Food Process EngineeringKoenigin-Luise-Strasse 2214195 BerlinGermanyEmail: [email protected]
Prof. Dietrich KnorrTechnische Universit€at BerlinDepartment of Food Biotechnologyand Food Process EngineeringKoenigin-Luise-Strasse 2214195 BerlinGermanyEmail: [email protected]
Dr. Tadeusz KudraCanmetENERGY957 de SalieresSt. Jean-sur-RichelieuQuebec J2W 1A3CanadaEmail: [email protected]
Artur LewandowskiLodz University of TechnologyFaculty of Process and EnvironmentalEngineeringul. Wolczanska 21393-924 LodzPolandEmail: [email protected]
Prof. Xiangdong LiuChina Agricultural UniversityCollege of Engineering17 Qinghua East Rd.Beijing 100083P. R. ChinaEmail: [email protected]
Prof. Lothar M€orlOtto von Guericke UniversityMagdeburgChemical Equipment DesignPSF 412039106 MagdeburgGermanyEmail: [email protected]
Prof. Arun S. MujumdarMcGill UniversityDepartment of BioresourceEngineering2111 Lakeshore RoadSainte-Anne-de-BellevueQuebec H9X 3V9CanadaEmail: [email protected]
XXj List of Contributors
Prof. Mirko PeglowIPT-PERGANDE GmbHWilfried-Pergande-Platz 106369 Weißandt-G €olzauGermanyEmail: [email protected]
Dr. Roberto PisanoPolitecnico di TorinoDipartimento di Scienza Applicata eTecnologiaCorso Duca degli Abruzzi 2410129 TorinoItalyEmail: [email protected]
Prof. Antonio Mulet PonsUniversidad Polit�ecnica de ValenciaDepartamento de Tecnología deAlimentosCami de Vera s/n46022 ValenciaSpainEmail: [email protected]
Dr. Julia RabaevaLodz University of TechnologyFaculty of Process and EnvironmentalEngineeringul. Wolczanska 21393-924 LodzPolandEmail: [email protected]
Dr. Enrique RieraInstituto de Seguridad de laInformaci �on (ISI)Grupo de Sistemas Ultras �onicosCSICSerrano 14428006 MadridSpainEmail: [email protected]
Prof. Carmen Rossell�oEnglish University of Illes BalearsSpanish Departamentode QuímicaCtra. Valldemossa km 7.507122 Palma MallorcaSpainEmail: [email protected]
Dr. Katharina Sch€osslerTechnische Universit€at BerlinDepartment of Food Biotechnologyand Food Process EngineeringKoenigin-Luise-Strasse 2214195 BerlinGermanyEmail: [email protected]
Prof. Eckehard SpechtOtto von Guericke UniversityMagdeburgThermodynamics and CombustionPSF 412039106 MagdeburgGermanyEmail: [email protected]
Prof. Evangelos TsotsasOtto von Guericke UniversityMagdeburgThermal Process EngineeringPSF 412039106 MagdeburgGermanyEmail: [email protected]
List of Contributors jXXI
Dr. Yingqiang WangJiangnan UniversitySchool of Food Science andTechnology214122 WuxiJiangsu ProvinceP. R. China
and
Longdong UniversityCollege of Agriculture and ForestryLanzhou Road 45745000 QingyangGansu ProvinceP. R. ChinaEmail: [email protected]
Prof. Ireneusz ZbicinskiLodz University of TechnologyFaculty of Process and EnvironmentalEngineeringul. Wolczanska 21393-924 LodzPolandEmail: [email protected]
Prof. Min ZhangJiangnan UniversitySchool of Food Science andTechnology214122 WuxiJiangsu ProvinceP. R. ChinaEmail: [email protected]
XXIIj List of Contributors
Recommended Notation
� Alternative symbols are given in brackets� Vectors are denoted by bold symbols, a single bar, an arrow or an index
(e.g., index: i)� Tensors are denoted by bold symbols, a double bar or a double index (e.g., index:
i, j)� Multiple subscripts should be separated by colon (e.g., rp;dry: density of dry
particle)
A surface area m�2
aw water activity –
B nucleation rate kg�1 m�1 s�1
b breakage function m�3
C (K) constant or coefficient variousc specific heat capacity J kg�1K�1
D equipment diameter mD (d) diffusion coefficient m2 s�1
d diameter or size of solids mE energy JF mass flux function –
Fð _VÞ volumetric flow rate m�3s�1
f relative (normalized) drying rate –
f multidimensional number density –
G shear function or modulus PaG growth rate kg s�1
g acceleration due to gravity m s�2
H height mH enthalpy JH Heaviside step function –
h specific enthalpy (dry basis) J kg�1
h (a) heat-transfer coefficient W m�2 K�1
~h ðhNÞ molar enthalpy J mol�1
Dhv specific enthalpy of evaporation J kg�1
I total number of intervals –
jXXIII
J numerical flux function –
J Jacobian matrix variousj ð _m; JÞ mass flux, drying rate kg m�2 s�1
K dilatation function or bulk modulus Pak (b) mass transfer coefficient m s�1
L length mM (m) mass kg~M (M, MN) molecular mass kg kmol�1
_M ðWÞ mass flow rate kg s�1
_m ðJ; jÞ mass flux, drying rate kg m�2 s�1
_m volumetric rate of evaporation kg m�3 s�1
N number –
N molar amount mol_N ðWNÞ molar flow rate mol s�1
n molar density, molar concentration mol m�3
n number density m�3
n outward normal unit vector_n ðJNÞ molar flux mol m�2 s�1
P power WP total pressure kg m�1 s�2
p partial pressure/vapor pressureof component
kg m�1 s�2
_Q ðQÞ heat flow rate W_q ðqÞ heat flux W m�2
R equipment radius mR individual gas constant J kg�1 K�1
~R ðRNÞ universal gas constant J kmol�1 K�1
r radial coordinate mr pore (throat) radius mS saturation –
S selection function s�1
s boundary-layer thickness mT temperature K,�Ct time su velocity, usually in z-direction m s�1
u displacement mV volume, averaging volume m3
_V ðFÞ volumetric flow rate m3 s�1
v specific volume m3 kg�1
v general velocity, velocity in x-direction m s�1
W weight force NW ð _MÞ mass flow rate kg s�1
w velocity, usually in y-direction m s�1
X solids moisture content (dry basis) –
x mass fraction in liquid phase –
XXIVj Recommended Notation
x particle volume in population balances m3
x general Eulerian coordinate, coordinate(usually lateral)
m
x0 general Lagrangian coordinate m~x ðxNÞ molar fraction in liquid phase –
Y gas moisture content (dry basis) –
y spatial coordinate (usually lateral) my (v) mass fraction in gas phase –
~y ðyNÞ molar fraction in gas phase –
z spatial coordinate (usually axial) mOperators! gradient operator! divergence operatorD difference operatorGreek lettersa (h) heat-transfer coefficient W m�2 K�1
b (k) mass-transfer coefficient m s�1
b aggregation kernel s�1
d Dirac-delta distributiond (D) diffusion coefficient m2 s�1
e voidage –
e emissivity –
e small-scale parameter for periodic media –
e strain –
h efficiency –
u angle, angular coordinate radk thermal diffusivity m2 s�1
l thermal conductivity W m�1K�1
m dynamic viscosity kg m�1 s�1
m moment of the particle-size distribution variousn kinematic viscosity m2 s�1
p circular constant –
r density, mass concentration kg m�3
S summation operators surface tension N m�1
s Stefan–Boltzmann constant for radiativeheat transfer
W m�2 K�4
s standard deviation (of pore-size distribution) ms stress Pat dimensionless time –
F characteristic moisture content –
w relative humidity –
w phase potential Pav angular velocity radv (y) mass fraction in gas phase –
Recommended Notation jXXV
Subscriptsa at ambient conditionsas at adiabatic saturation conditionsb bound waterbed bedc cross sectionc capillarycr at critical moisture contentD dragdry drydp at dewpointeff effectiveeq equilibrium (moisture content)f frictiong gas (dry)H wet (humid) gasI inneri, 1, 2, . . . component index, particle indexi, j, k coordinate index, i,j,k = 1 to 3in inlet valuel liquid (alternative: as a superscript)m mean valuemax maximummf at minimum fluidizationmin minimumN molar quantityo outerout outlet valueP at constant pressurep particlepbe population balance equationph at the interfacer radiationrel relative velocitys solid (compact solid phase), alternative: as a
superscriptS at saturation conditionssurf surfaceV based on volumev vapor, evaporationw waterw wallwb at wet-bulb conditionswet wet1 at large distance from interface
XXVIj Recommended Notation
Superscripts, Special symbolsv volumetric strain� rheological strain� at saturation conditions� or h i average, phase average�a or h ia intrinsic phase average� spatial deviation variable
Recommended Notation jXXVII
EFCE Working Party on Drying: Add ress List
Prof. Odilio Alves-FilhoNorwegian University of Science andTechnologyDepartment of Energy and ProcessEngineeringKolbjørn Hejes vei 1B7491 TrondheimNorwayodilo. [email protected]
Prof. Julien Andrieu (delegate)UCB Lyon I/ESCPELAGEP UMR CNRS 5007 batiment308 G43 boulevard du 11 novembre 191869622 Villeurbanne [email protected]
Dr. Paul Avontuur (guest industry)Glaxo Smith KlineNew Frontiers Science Park H89Harlow CM19 5AWUnited [email protected]
Prof. Christopher G. J. BakerDrying AssociatesHarwell InternationalBusiness Centre404/13 Harwell DidcotOxfordshire OX11 ORAUnited [email protected]
Prof. Antonello Barresi (delegate)Dip. Scienza dei Materiali eIngegneria ChimicaPolitecnico di TorinoCorso Duca degli Abruzzi 2410129 [email protected]
Dr. Rainer Bellinghausen (delegate)Bayer Technology Services GmbHBTS-PT-PT-PDSPBuilding E 4151368 [email protected]
Dr. Carl-Gustav BergAbo AkademiProcess Design LaboratoryBiskopsgatan 820500 [email protected]
Dr. Catherine Bonazzi (delegate)AgroParisTech - INRAJRU for Food Process Engineering1 Avenue des Olympiades91744 Massy [email protected]
jXXIX
Paul Deckers M.Sc. (delegate)BodecProcess Optimization andDevelopmentIndustrial Area ‘t ZandBedrijfsweg 15683 CM BestThe [email protected]
Henk van Deventer M.Sc. (delegate)TNOUtrechtseweg 483704 HE ZeistThe [email protected]
Dr. German I. EfremovPavla Korchagina 22129278 [email protected]
Prof. Trygve EikevikNorwegian University of Scienceand TechnologyDep. of Energy and ProcessEngineeringKolbjørn Hejes vei 1B7491 [email protected]
Dr.-Ing. Ioannis EvripidisDow Deutschland GmbH & Co. OHGP.O. Box 112021677 [email protected]
Prof. Dr. Istvan Farkas (chairman)Szent Istvan UniversityDep. of Physics and Process ControlPater K. u. 12103 [email protected]
Dr. Dietrich GehrmannWilhelm-Hastrich-Str. 1251381 [email protected]
Prof. Adrian-Gabriel Ghiaus (delegate)Thermal Engineering DepartmentTechnical University of CivilEngineeringBd. P. Protopopescu 66021414 [email protected]
Prof. Gheorghita JinescuUniversity “Politehnica ” dinBucurestiDepartment of ChemicalEngineering1 Polizu street, Room F21078126 [email protected]
Prof. Dr. Gligor KanevceSt. Kliment Ohridski UniversityFaculty of Technical Sciencesul. Ivo Ribar Lola b.b.BitolaFYR of [email protected]
XXXj EFCE Working Party on Drying: Address List
Ir. Ian C. Kemp (delegate)Glaxo SmithKline, R&DGunnels Wood RoadStevenage SG1 2NYUnited [email protected]
Prof. Matthias KindKarlsruhe Institute of TechnologyInstitut f €ur ThermischeVerfahrenstechnikKaiserstr. 1276128 [email protected]
Prof. Stefan J. KowalskiPoznan University of TechnologyInstitute of Technology and ChemicalEngineeringul. Marii Sklodowskiej Cuvie 260965 [email protected]
Prof. Magdalini Krokida (delegate)National Technical University ofAthensDepartment of ChemicalEngineeringPolitechnioupoli, Zografou Campus15780 [email protected]
Dr. Ir. Ang�elique L�eonard (delegate)Universit�e de Li�egeD�epartement de Chimie Appliqu�eeLaboratoire de G�enie ChimiqueBatiment B6c – Sart-Tilman4000 Li�[email protected]
Prof. Avi Levy (delegate)Ben-Gurion University of the NegevDepartment of MechnicalEngineeringBeer-Sheva [email protected]
Jean-Claude MassonRhodia Op�erations, CRTL-GI-DIPH85 Avenue des Fr�eres Perret69196 Saint-Font [email protected]
Prof. Natalia MenshutinaMendeleyev University of ChemicalTechnology of Russia (MUCTR)High Technology DepartmentMuisskaya sq.9125047 [email protected]
Dr. Thomas MetzgerBASF SEGCP/T T-L54067056 [email protected]
Prof. Antonio Mulet Pons (delegate)Universitat Politecnica de ValenciaDepartament de Tecnologiad’AlimentsCami de Vera s/n46071 [email protected]
EFCE Working Party on Drying: Address List jXXXI
Prof. Zdzislaw Pakowski (delegate)Lodz University of TechnologyFaculty of Process and EnvironmentalEngineeringul. Wolczanska 21390924 [email protected]
Prof. Patrick Perr�e (delegate)Ecole Centrale ParisLaboratoire de G�enie des Proc�ed�es etMa t �eriauxGrande Voie des Vignes92295 [email protected]
Dr. Romain R�emondAgroParisTech – ENGREF14, Rue Girardet54042 [email protected]
Dr. Roger Rentr€omKarlstad UniversityDepartment of Environmental andEnergy SystemsUniverstietsgatan 265188 [email protected]
Prof. Michel RoquesUniversite de Pau at des Paysde l’ Adour5 Rue Jules-FerryENSGTI64000 [email protected]
Prof. Carmen Rossell�o (delegate)University of Illes BalearesDep. QuimicaCtra. Valldemossa km 7.507122 Palma [email protected]
Dr. Panayiotis ScarlatosSusTchem Engineering LTD144 3rd September Street11251 [email protected]
Dr. Michael Sch€onherrBASF SEGCT/T – L 54067056 [email protected]
Dr. Andreas SchreinerNovartis Pharma AGWSJ-145.1.54Lichtstr. 354056 [email protected]
Dr. Milan StakicVin9ca Institute for Nuclear SciencesCenter NTIP.O. Box 52211001 [email protected]
Dr. Andrew Stapley (delegate)Loughborough UniversityDepartment of ChemicalEngineeringLoughborough, LeicestershireLE11 3TUUnited [email protected]
XXXIIj EFCE Working Party on Drying: Address List
Prof. Stig Stenstrom (delegate)Lund UniversityInstitute of TechnologyDepartment of ChemicalEngineeringP.O. Box 12422100 [email protected]
Prof. Ingvald Strommen (delegate)Norwegian University of Science andTechnologyDepartment of Energy and ProcessEngineeringKolbjørn Hejes vei 1b7491 [email protected]
Prof. Czeslaw Strumillo (delegate)Lodz University of TechnologyFaculty of Process and EnvironmentalEngineeringul. Wolczanska 21390924 [email protected]
Prof. Radivoje Topic (delegate)University of BelgradeFaculty of Mechanical Engineering27 Marta 8011000 [email protected]
Prof. Evangelos Tsotsas (delegate)Otto von Guericke UniversityThermal Process EngineeringP.O. Box 412039016 [email protected]
Thorvald Ullum M.Sc.GEA, NiroGladsaxevej 3052860 [email protected]
Dr. Bertrand Woinet (delegate)SANOFI-PASTEUR, CDPBatiment 860031-33 Quai Armand Barb�es69683 Neuville sur Saone [email protected]
Prof. Ireneusz ZbicinskiLodz University of TechnologyFaculty of Process and EnvironmentalEngineeringul. Wolczanska 21390924 [email protected]
EFCE Working Party on Drying: Address List jXXXIII
