Table Of ContentDrying 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
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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.
