Drying of multiphase single droplets in ultrasonic levitator [Elektronische Ressource] / vorgelegt von Belal Ali Al Zaitone

Belal Ali Al Zaitone

Informations

• Publié par: technischen_universitat_darmstadt
• Publié le: 01 janvier 2009
• Nombre de lectures: 67
• Langue: English
• Poids de l'ouvrage: 18 Mo

Extrait

Drying of Multiphase Single Droplets in
Ultrasonic Levitator
Vom Fachbereich Maschinenbau
an der Technischen Universität Darmstadt
zur
Erlangung des Grades eines Doktor-Ingenieurs
(Dr.-Ing.)
genehmigte
D i s s e r t a t i o n
vorgelegt von
M.Sc. BelalAliAlZaitone
ausSouf,Jordanien
Berichterstatter: Prof. Dr.-Ing. C.Tropea
Mitberichterstatter: Prof. Dr.-Ing. P.Stephan
TagderEinreichung: 01. March2009
TagdermündlichenPrüfung: 20. May2009
Darmstadt,2009
D17For my mother and father with love and gratitudeAcknowledgments
The present research work has been conducted at Chair of Fluid Mechanics and Aero-
dynamics,TechnischeUniversitätDarmstadtbetweenAugust2005andFebruary2009.
First of all I would like to take this opportunity to express my heartfelt thanks and
appreciation to my advisor Prof. Dr.-Ing. C. Tropea for his invaluable guidance, en-
couragement, and patience. The confidence he offered me beside his inspiring ideas
provided a great opportunity to develop my research skills and gain experience in ex-
perimentalwork.
I want to thank Prof. Dr.-Ing. P. Stephan, Chair of Technical Thermodynamics, Tech-
nischeUniversitätDarmstadt,forhispromptwillingnesstoreviewthisdissertation.
ThefinancialsupportofDeutscheForschungsgemeinschaft "DFG"throughthe
Graduiertenkolleg "Optische Messtechniken für die Charakterisierung von Transport-
prozessen an Grenzflächen" (GRK1114) is gratefully acknowledged. I would like also
tothankProf. Dr.-Ing. NilsDamaschke,ChristianHeinisch,FrauMonikaMedinaand
KarlWunderlefortheirsupportandthecooperationwithinGRK1114.
I am grateful to Dr. Guillaume Castanet for his assistance during the first year of
my doctoral research; I admire his help, motivation and illuminating instructions. I
am more than grateful for Prof. A. Yarin for the fruitful discussions, advice and his
significanthelp.
I would like to thank Dr. Bruno Frackowiak for his suggestions and contribution
that definitely helped me to advance my work. I owe special thanks for Dr. Hubert
Marschallforhishelpandbeingreadytoanswermyquestions.
IwouldlikealsotothankothercolleaguesNilsvanHinsberg,AndreasLembach,Lars
Opfer and Erika Saffer for their help. I would like also to thank Mrs. S. Lath and Ms.
S.Wallenrforthearrangementofmanyadministrativematters.
I would like to thank my friends. Especially the people I have met while in gradu-
ate school either in Erlangen or Darmstadt, who have become my closest and dearest
friends, their support to this work is not insignificant, and to all I give my love and
VIIthanks.
Iwouldliketoendbythankingmydearestfamily. Myparentshavealwaysinspiredme
and helped me reach my goals. I owe them everything and I wish I could show them
justhowmuchIloveandappreciatethem. Ihopethatthisworkmakethemproud.
Darmstadt,February2009 BelalAliAlZaitone
VIIIAbstract
Spraydryingiswidelyusedinmanyindustries,e.g. chemical,foodandpharmaceutical
processing, in which the spray generation is followed by solvent/liquid evaporation
leadingtoafinalpowderproduct.
As the liquid component evaporates, the droplet weight decreases. This evaporation
process is accompanied by phase change of the volatile component. For a multiphase
droplet,solidmaterialissuspendedordissolvedintheliquidphase. Insuchcases,itis
important to have knowledge of transport phenomena for single droplets as it pertains
totheirevaporationandcomponentdistribution.
The investigation of the evaporation of single droplets is particularly applicable to the
study of spray drying and atomization. There are several different measurement tech-
niquesthatcanbeusedtoanalyzedropletsofvariouscomponentssuchaspureliquids,
mixtures,solutions,andcolloidalsuspensions.
The principle of ultrasonic levitation is unique in that it allows the isolation of a sin-
gle droplet in space rather than a myriad of droplets. Having a multiphase droplet
suspended in the acoustic field facilitates the study of the drying rate at different op-
erational parameters, and tracking the morphological changes during the course of the
dryingprocess.
The experiments conducted in this work were performed for a single droplet or sep-
aration of two single droplets. Single droplet analysis allows for characterization of
thedropletsdryingrate. Themulti-dropletanalysisispertinenttosoundpressurelevel
calibration.
Understanding the sub-models for these processes is largely beneficial to the advance
ofmodelingtheoverallspraydryingprocess.
In the present work, the drying of further example systems has been studied, and a
characterization of the outer crust formed at the end of the first drying stage is pre-
sented. These are accompanied by "quasi" 2-D model formulations for the simulation
of individual drop drying to describe the solid concentration profiles and the creation
of the crust at the end of the constant rate period, when the solids concentration at the
surfaceexceedthesaturationconcentration.
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