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Drying of Porous Materials Drying of Porous Materials Edited by Stefan Jan Kowalski Poznan´ University of Technology, Poland Reprinted from Transport in Porous Media, Volume 66(1–2), 2007 123 AC.I.P.CataloguerecordforthisbookisavailablefromthelibraryofCongress. ISBN-978-1-4020-5479-2(HB) ISBN-978-1-4020-5480-8(e-book) PublishedbySpringer, P.O.Box17,3300AADordrecht,TheNetherlands. www.springer.com CoverIllustration(background) Photoofwoodsampleafterdrying(photographtakenbyAndrzejRybicki) Printedonacid-freepaper AllRightsReserved (cid:2)2007Springer Nopartofthisworkmaybereproduced,storedinaretrievalsystem,ortransmitted inanyformorbyanymeans,electronic,mechanical,photocopying,microfilming,recording orotherwise,withoutwrittenpermissionfromthePublisher,withtheexception ofanymaterialsuppliedspecificallyforthepurposeofbeingentered andexecutedonacomputersystem,forexclusiveusebythepurchaserofthework. PrintedintheNetherlands. CONTENTS STEFANJANKOWALSKI/Preface 1 ARUN S. MUJUMDAR / An Overview of Innovation in Industrial Drying: CurrentStatusandR&DNeeds 3 ZDZISŁAWPAKOWSKI/ModernMethodsofDryingNanomaterials 19 YOSHINORIITAYA,SHIGERUUCHIYAMAandSHIGEKATSUMORI/ Internal Heating Effect and Enhancement of Drying of Ceramics by MicrowaveHeatingwithDynamicControl 29 STEFANJANKOWALSKIandANDRZEJRYBICKI/TheVapour–Liquid InterfaceandStressesinDriedBodies 43 PATRICK PERRE´ / Multiscale Aspects of Heat and Mass Transfer During Drying 59 STANISŁAWPABIS/TheoreticalModelsofVegetableDryingbyConvection 77 MARCIN PIATKOWSKI and IRENEUSZ ZBICINSKI / Analysis of the MechanismofCounter-CurrentSprayDrying 89 THOMAS METZGER, MARZENA KWAPINSKA, MIRKO PEGLOW, GABRIELA SAAGE and EVANGELOS TSOTSAS / Modern ModellingMethodsinDrying 103 MUSIELAK GRZEGORZ and BANASZAK JACEK / Non-linear Heat and Mass Transfer During Convective Drying of Kaolin Cylinder under Non-steadyConditions 121 WIESLAW OLEK and JERZY WERES / Effects of the Method of Identification of the Diffusion Coefficient on Accuracy of Modeling BoundWaterTransferinWood 135 STEFAN JAN KOWALSKI and ANNA SMOCZKIEWICZ-WOJCIE- CHOWSKA / Stresses in Dried Wood. Modelling and Experimental Identification 145 JAN STAWCZYK, SHENG LI, DOROTA WITROWA-RAJCHERT and ANNAFABISIAK/KineticsofAtmosphericFreeze-DryingofApple 159 MICHAL ARASZKIEWICZ, ANTONI KOZIOL, ANITA LUPINSKA and MICHALLUPINSKI/MicrowaveDryingofVariousShapeParticles SuspendedinanAirStream 173 ROMAN G. SZAFRAN and ANDRZEJ KMIEC / Periodic Fluctuations of FlowandPorosityinSpoutedBeds 187 _ J.F. NASTAJ and B. AMBROZEK / Modeling of Vacuum Desorption of MulticomponentMoistureinFreezeDrying 201 ARTURPOS´WIATAandZBIGNIEWSZWAST/OptimizationofFineSolid DryinginBubbleFluidizedBed 219 STEFANJANKOWALSKI/Referees 233 TranspPorousMed(2007)66:1–2 DOI10.1007/s11242-006-9008-0 PREFACE Preface StefanJanKowalski Publishedonline:10October2006 ©SpringerScience+BusinessMediaB.V.2006 I am very pleased to act as Guest Editor for this Special Issue of the International JournalTransportinPorousMedia,entitledDryingofPorousMaterials.ThisSpecial IssueconsistsofselectedpaperspresentedattheXIPolishDryingSymposium,held inPoznan´,ahistoricandbeautifulcityinWesternPoland,onSeptember13–16,2005. TheSymposium,organizedjointlybytheDryingSectionoftheCommitteeofChem- ical and Process Engineering of the Polish Academy of Sciences, the Polish Drying Association,Poznan´ UniversityofTechnologyandAugustCieszkowskiAgricultural UniversityofPoznan´,attracted94participants,includingforeignguestsfrom13coun- tries.ThePolishDryingSymposiumserieswasinitiatedin1972byProfessorCzesław Stumiłło,theHonorablePresidentofthisSymposium. TheSymposiumlanguagewasEnglish,bothforlecturesandposterpresentations. This allowed extended foreign participation and a fruitful exchange of ideas be- tweenPolishandinternationalparticipants.Severalprominentscientistswerepresent, including,amongothers,A.S.Mujumdar,P.Perre,Y.Itaya,T.Kudra,G.Srzednicki, A.E.Djomeh,O.Yaldiz,T.MetzgerfromabroadandCz.Strumiłło,Z.Pakowski,I. Zbicin´ski,S.Pabis,P.P.Lewicki,A.KmiecfromPoland.Altogether,34lecturesand7 excellentkeynotelectureswerepresentedandthepostersessionaccommodated43 posters. ThesubjectoftheSymposiumhasbeentraditionallysharedbyagri/food(ca.35%) and all other drying subjects. Among agri/food subjects, the drying of wood was strongly represented and a considerable number of papers covered drying process simulation and parameter identification. A brief survey of all presentations indi- catesthatthereisnonationalbiasorspecialtycharacterizingPolishdryingresearch. Instead,itcanbenoticedthatitencompassesamajorityoftopicsrepresentedatall dryingconferences,includingthewellknownIDS(InternationalDryingSymposium). B S.J.Kowalski( ) PoznanUniversityofTechnology,InstituteofTechnologyandChemicalEngineering, pl.MariiSklodowskiejCurie2,60–965Poznan, Poland e-mail: [email protected] 2 TranspPorousMed(2007)66:1–2 ThisindicatesthatPolishdryingresearchcloselyfollowsglobalcuttingedgeresearch on subjects of drying, including such emerging areas as CFD (Computational Fluid Dynamics) application, drying of nanomaterials, microencapsulation, supercritical drying,etc. The papers selected for inclusion in this special issue concern mostly drying of liquid-saturatedporousmaterials,butnotexclusively.ThepaperbyA.S.Mujumdar “An Overview of Global R&D in Industrial Drying: Current Status and Future” presentsareviewofthecurrentproblemsconcerningresearchanddevelopmenton drying,andparticularlyonindustrialdrying.Severalpapersdealwithspraydrying,or dryinginabubblingfluidizedbed,whosemodelingisquitesimilartothatencountered inthetheoryoftheliquid-saturatedporousmedia. The Editor of TIPM kindly agreed to publish this special issue of the Journal, with several unpublished papers reflecting some aspects of the theory of saturated porous media applied to heat and mass transfer in drying, as well as an analysis of dryinginducedstresses.Outof84paperspresentedattheSymposium,theScientific Committee and the specialists on porous materials, both from Poland and abroad, whoactedasthereviewers,haveselected16papersforthisSpecialIssue.Anumber oforiginalpapersconcerningdrying,butnotnecessarilydryingofporousmaterials, presentedattheSymposium,willbepublishedinaspecialissueofDryingTechnol- ogy–anInternationalJournalaswellasinaregularissueofthejournalChemicaland ProcessEngineering. As theGuestEditor, I wouldlike to takethis opportunityto expressmycordial thankstoProf.JerzyWeres,theco-chairmanoftheSymposiumandhisco-workers from the August Cieszkowski Agricultural University in Poznan´, for their help in organizingtheSymposium.Ialsoaddressmysincerethankstomyco-workersfrom theDepartmentofProcessEngineeringoftheInstituteofTechnologyandChemical Engineering,Poznan´ UniversityofTechnologyfortheireffortsandprecioushelpin allaspectsoftheSymposium’sorganization. Financial support for the Symposium from the following sponsors is gratefully acknowledged: • RectorofPoznan´ UniversityofTechnology, • MinistryofNationalEducationandSport, • FoundationonBehalfofDevelopmentofPoznan´ UniversityofTechnology, • InternationalTobaccoMachineryPolandLtd.inRadom. TranspPorousMed(2007)66:3–18 DOI10.1007/s11242-006-9018-y ORIGINAL PAPER An overview of innovation in industrial drying: current status and R&D needs ArunS.Mujumdar Received:30November2005/Accepted:26March2006/ Publishedonline:30August2006 ©SpringerScience+BusinessMediaB.V.2006 Abstract Overthepastthreedecadestherehasbeennearlyexponentialgrowthin dryingR&Donaglobalscale.Althoughthermaldryinghadalwaysbeenthework- horseofalmostallmajorindustrialsectors,theneedforandopportunitiesinbasicas wellasindustrialresearchbecameclearonlyaftertheenergycrisisoftheearly1970s. Althoughthepriceofoildiddropsubsequentlytheawarenessofthesignificanceof improving the drying operation to save energy, improve product quality as well as reduce environmental effect remained and indeed has flourished over recent years. Newdryingtechnologies,betteroperationalstrategiesandcontrolofindustrialdry- ers,aswellasimprovedandmorereliablescale-upmethodologieshavecontributed to better cost-effectiveness and better quality dried products. Yet there is no uni- versallyorevenwidelyapplicabledryingtheoryonthehorizon.Mostmathematical modelsofdryingremainproduct-equipmentspecificforavarietyofreasons.Inthis paper,weexaminetheroleofinnovationindryinginvariousindustrialsectors,e.g. paper,wood,foods,agriculture,wastemanagement,etc.Progressmadeoverthepast threedecadesandthechallengesaheadareoutlined.Someareasinneedoffurther researchareidentified.Examplesofintensificationofinnovationindryerdesignsvia mathematicalmodelingarediscussed.Finally,theneedforcloserinteractionbetween academiaandindustryisstressedasthekeytosuccessfuldryingR&Dinthecoming decade. Keywords Innovation · Intensification of innovation · Mathematical models · Energyaspects·Environmentalimpact·Noveldryers·Researchanddevelopment needs B A.S.Mujumdar( ) DepartmentofMechanicalEngineering, NationalUniversityofSingapore, 9EngineeringDrive1,117576Singapore,Singapore e-mail: [email protected] 4 ArunS.Mujumdar 1 Introduction Thermal drying has beenrecognized as an importantunit operation as it is energy- intensive and has a decisive effect on the quality of most products that are dried commercially.Escalatingenergycosts,demandforeco-friendlyandsustainabletech- nologies as well as the rising consumer demand for higher quality products, have givenfreshincentivestoindustryandacademiatodevotegreatefforttodryingR&D. Fortunately,thisareadoesnotdemandamassiveperfusionofR&Dfundstocome upwithvaluableinsightsandinnovations,withonlyafewexceptions.Indeed,there isalreadyasustainablelevelofR&Dsupport—bothintermsofhumanandfinancial resources—aroundtheworld.Emergingeconomiesoftheworld,suchasChina,Bra- zil,India,etc,havepickeduptheslackcausedbythefullydevelopedeconomiesof thewestmovingtowardsnanotechnologies.Overall,theglobalR&Defforthasbeen risingdespiteprecipitousdropsinNorthAmericaandEurope.With12–25%ofthe nationalindustrialenergyconsumptionattributabletoindustrialdryingindeveloped countries, it is only a matter of time before high energy costs will stimulate further R&Dindrying. Thefactthattensofthousandsofproductsneedtobedriedinovera100variants of dryers provides major and ample opportunities for innovation. In this paper, we startwiththedefinitionofinnovationandhowitmaybeintensified.Thisisfollowed by a discussion of some new technologies in comparison with the traditional ones, which still dominate the market. The need for industry–academia interaction and a pro-active role of industry—the ultimate beneficiary of all R&D regardless of its origin—isstressed. 2 NeedforandroleofR&D Researchers in academia as well as industry along with granting agencies consis- tentlyagreeontheneedformoreR&Dfunds.TheyarguethatR&Dfundsshould be rightfully considered as investment rather than expenditure. In either case, it is necessarytoaccountfortheoutlaysonR&Dintermsofitseconomicand/orsocial benefits. It is essential to look critically at the cost/benefit ratio for R&D funds in general and provide appropriate justification for such expenditures or investments. Thisismorereadily—notnecessarilyeasilyorreliably—achievedinthebusinessor industrial world. When public funds are used for R&D—a major source for most nations—itisamuchmoredifficulttask. Thereismuchscholarlyliteratureontheeconomicreturnsonpubliclyfundedbasic research(e.g.A.J.SalterandBenR.Martin,ResearchPolicy,Vol.30,2001,pp.509– 532).Astheseauthorspointout,researchoutputmaybeinformationorknowledge that can be used to economic advantage; they postulate that much of the publicly fundedR&Doutputisofinformationalnatureandtheknowledgecreatedis“non- rival” and “non-excludable”. Non-rival knowledge is defined as that which others canuse“withoutdetractingfromtheknowledgeoftheproducers”.Non-excludable implies that no one can be stopped from using this knowledge—even competitors havefreeaccesstoitalthoughtheydidnotpayforitdirectly.Thisisalsothenature ofinformationandknowledgedisseminatedbyjournalssuchasDryingTechnology. Utilization of “free” informational knowledge requires significant investment to understandanduseittoadvantage.Thus,scientificknowledgeisreallynotavailable “freely”butonlytothosewhohavethenecessaryexpertisetoaccessit.AnOECD Anoverviewofinnovationinindustrialdrying:currentstatusandR&Dneeds 5 Report(1996)states:“Knowledgeandinformationabound;itisthecapacitytouseit thatisscarce”.Informationisavailabletoall,butonlythosewiththerightcapabilities canconvertittoknowledgeanduseittoinnovate. Ipostulatethattherateoftechnologicalinnovationdependsdirectlyontherate ofgenerationofinformationalknowledgeandtheeffectivenessofitsutilization;the latter is a measure of the ability to assimilate or exploit the knowledge. Efficient dissemination of knowledge is important but it is equally important to develop the abilitytoutilizeit.Academicinstitutionsareresponsiblefordevelopingsuchability.If theycanalsomakeavaluablecontributiontothegenerationofnewknowledge,then theyareveryeffectiveinenhancingtherateofinnovation,whichdrivestheeconomic growthofnations. Talkingaboutsustainabledevelopmentisinvoguethesedays.Clearly,itmakesa lotofsenseandtheworldwillbeabetterplaceifalldevelopmentweretrulysustain- able.Ibelievethatthisconceptisapplicabletoresearchanddevelopmenteffortas well,beitinacademiaorinindustry. WeareconcernedaboutthecontinuallyshrinkingR&Dfundingpiealmostallover theworld.Grantingbodieshavetriedtocutthepieinmanydifferentways.Usually, areasthatarecurrentlypopularorfashionablereceivelargersharesofthepie,thus reducing the funding for some other key or core areas—or worse, even eliminating funding for many of the so-called traditional areas of research. The implication is thatenoughR&Dhasalreadybeenconductedinareasthathaveexistedforlonger periods. New is automatically assumed to be innovative, creative and thus valuable for the future development of the economy. Larger portions of R&D funding have goneintoenergytechnologies,environmentalissues,bio-technology,IT,etc.overthe pasttwodecades,andmorerecentlyintonano-scienceandnano-technology.Clearly, alltheseareasareimportantanddeservefunding.Theissueishowmuchandatwhat costtotheotherareas.Willitcausesomecoreincompetenciesinfuture? This is where I think, we need to examine my idea of sustainable research level. Justforillustration,ifallinstitutionsaroundtheworldfocustheireffortondevelop- ing nano-technology, are there enough opportunities for so many to make original contributions?Also,isthemarketlargeenoughforalltheplayerstoobtainadequate returns on their investments? Some institutions will lead and outpace most others as a result of their access to higher levels of human and financial resources. At the sametime,areasthatindustrycurrentlyneedsandtechnologiesthatformthelifeline of current businesses will be penalized as no new funding is made available for the new R&D areas. Overcrowding of pre-selected research areas is as risky as under- populatingthemwithunder-funding.Over-fundingdoesnotassuredevelopmentof innovativeideas;itmayevenimpedeitasfundingbecomeseasiertoobtainandhence non-competitive.Also,projectionsofpotentialmajorwindfallfromnewtechnologies arefraughtwithuncertainties. Iwishtopostulatethatforeachresearchfieldatanygiventimeandanygivenloca- tion,thereisasustainablelevelofR&Dfundingsupportbeyondwhichthereturns on investment will necessarily decline. The opportunity cost of not doing R&D is otherareaswillriseaswell.Dryingisconsideredamaturearea:inmanywaysitis. However, there are still many unsolved, complex problems that deserve attention andofferchallengestoresearchers.ThereturnonthemodestlevelsofR&Dfund- ingneededtocarryoutdryingresearchcanbesubstantialsincethisoperationisso energy-intensive and has a direct impact on product quality and the environment. Whatisneededisafocusedeffortwithcollaborationbetweenindustryandacademia.
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