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Particle Deposition Studies in a Laminar Wall Jet - The Hydrodynamic Influence on the Kinetics of Colloidal Deposition

Göransson, Anders LU (2001)
Abstract (Swedish)
Popular Abstract in Swedish

Inom forskningen kring rengöring och processhygien är det viktigt att förstå de bakomliggande mekanismerna för depositionen av partiklar och makromolekyler på ytor. Depositionsprocessen kan beskrivas som transporten av partiklar till ytan och den påföljande adhesionen. Om de hydrodynamiska krafterna är tillräckligt starka kan partiklarna åter transporteras bort från ytan.



I denna avhandling har depositionen av partiklar studerats <i>in situ</i>. En experimentell uppställning med en walljetcell användes för att erhålla en väldefinierbar masstransport av partiklar till en glasyta. En modellösning med polystyren-latexpartiklar med två partikelradier, 0,23 um respektive... (More)
Popular Abstract in Swedish

Inom forskningen kring rengöring och processhygien är det viktigt att förstå de bakomliggande mekanismerna för depositionen av partiklar och makromolekyler på ytor. Depositionsprocessen kan beskrivas som transporten av partiklar till ytan och den påföljande adhesionen. Om de hydrodynamiska krafterna är tillräckligt starka kan partiklarna åter transporteras bort från ytan.



I denna avhandling har depositionen av partiklar studerats <i>in situ</i>. En experimentell uppställning med en walljetcell användes för att erhålla en väldefinierbar masstransport av partiklar till en glasyta. En modellösning med polystyren-latexpartiklar med två partikelradier, 0,23 um respektive 0,38 um, användes i experimenten. Depositionsförloppet i flödescellen kunde mätas med hjälp av en teknik, total internal reflection microscopy, varigenom man mäter ljusspridningen av de infästa partiklarna. Cellens konstruktion möjliggjorde att partikeldepositionen kunde följas vid positioner med olika väggskjuvhastigheter i ett och samma experiment.



En depositionsmodell användes för att öka förståelsen av de olika fenomen som styr partikeldepositionen. I modellen kunde transporten av partiklar till och från ytan kombineras genom att en transportterm användes som beskriver partikelfluxet till ytan, och därtill en term som uttrycker frigörandet av partiklar. I den transportterm som användes inkluderades en så kallad skuggningsfunktion. Fenomenet med skuggning av ytan kunde förklara den avtagande depositionshastigheten.



Genom att använda en datoralgoritm som baserades på en så kallad <i>random sequential adsorption</i> kunde studiet av skuggningsfenomenet utvidgas. Det visade sig att storleken på det skuggade området ökade med en ökande väggskjuvhastighet, liksom med en minskande partikelkoncentration. (Less)
Abstract
In the research area of cleaning and process hygiene it is important to understand the underlying mechanisms behind the deposition of particles and macromolecules onto surfaces. The deposition process is described as the transport of particles to the surface followed by attachment. If the hydrodynamic forces are strong enough, the particles can be re-entrained.



In this work particle deposition was studied <i>in situ</i>. In order to obtain a well-defined mass transfer to a glass surface covered with indium-tin oxide onto which deposition was to occur, an experimental setup consisting of a wall-jet cell was employed. Model solutions consisting of polystyrene latex particles of two particle radii, 0.23 um and... (More)
In the research area of cleaning and process hygiene it is important to understand the underlying mechanisms behind the deposition of particles and macromolecules onto surfaces. The deposition process is described as the transport of particles to the surface followed by attachment. If the hydrodynamic forces are strong enough, the particles can be re-entrained.



In this work particle deposition was studied <i>in situ</i>. In order to obtain a well-defined mass transfer to a glass surface covered with indium-tin oxide onto which deposition was to occur, an experimental setup consisting of a wall-jet cell was employed. Model solutions consisting of polystyrene latex particles of two particle radii, 0.23 um and 0.38 um, were used in the deposition experiments. The deposited particles were visualized by total internal reflection microscopy. The construction of the cell made it possible to radially scan the surface and thus follow the deposition of particles at positions exposed to different wall shear rates in one single experiment.



To be able to better understand the different phenomena which are thought to affect deposition a model was employed. By using a transport term describing the particle flux to the surface and another term expressing the detachment of particles, transport to and from the collector surface could be included in the model. The flux term to the surface included a so-called shielding function. The phenomenon of surface shielding was used to explain the decrease in deposition rate.



The study of shielding was expanded by applying a computer algorithm based on the concept of random sequential adsorption. It was found that the size of the shielded area increased with increasing wall shear rate, as well as with decreasing bulk particle concentration. (Less)
Please use this url to cite or link to this publication:
author
opponent
  • Professor Melo, Luis, University of Porto, Porto, Portugal
organization
publishing date
type
Thesis
publication status
published
subject
keywords
shielding function, surface blocking, total internal reflection microscopy, laminar wall jet, random sequential adsorption, colloidal deposition, Food and drink technology, Livsmedelsteknik
pages
139 pages
publisher
Food Engineering, Lund Univeristy
defense location
Lecture hall A, Center for Chemistry and Chemical Engineering
defense date
2001-11-16 13:15
external identifiers
  • Other:ISRN: LUTKDH/(TKLT-1034)1-60
ISBN
91-7874-155-6
language
English
LU publication?
yes
id
f9c27a48-2eb3-4555-b7c6-9d9c5fb019ce (old id 42022)
date added to LUP
2007-06-21 13:02:27
date last changed
2016-09-19 08:45:09
@misc{f9c27a48-2eb3-4555-b7c6-9d9c5fb019ce,
  abstract     = {In the research area of cleaning and process hygiene it is important to understand the underlying mechanisms behind the deposition of particles and macromolecules onto surfaces. The deposition process is described as the transport of particles to the surface followed by attachment. If the hydrodynamic forces are strong enough, the particles can be re-entrained.<br/><br>
<br/><br>
In this work particle deposition was studied &lt;i&gt;in situ&lt;/i&gt;. In order to obtain a well-defined mass transfer to a glass surface covered with indium-tin oxide onto which deposition was to occur, an experimental setup consisting of a wall-jet cell was employed. Model solutions consisting of polystyrene latex particles of two particle radii, 0.23 um and 0.38 um, were used in the deposition experiments. The deposited particles were visualized by total internal reflection microscopy. The construction of the cell made it possible to radially scan the surface and thus follow the deposition of particles at positions exposed to different wall shear rates in one single experiment.<br/><br>
<br/><br>
To be able to better understand the different phenomena which are thought to affect deposition a model was employed. By using a transport term describing the particle flux to the surface and another term expressing the detachment of particles, transport to and from the collector surface could be included in the model. The flux term to the surface included a so-called shielding function. The phenomenon of surface shielding was used to explain the decrease in deposition rate.<br/><br>
<br/><br>
The study of shielding was expanded by applying a computer algorithm based on the concept of random sequential adsorption. It was found that the size of the shielded area increased with increasing wall shear rate, as well as with decreasing bulk particle concentration.},
  author       = {Göransson, Anders},
  isbn         = {91-7874-155-6},
  keyword      = {shielding function,surface blocking,total internal reflection microscopy,laminar wall jet,random sequential adsorption,colloidal deposition,Food and drink technology,Livsmedelsteknik},
  language     = {eng},
  pages        = {139},
  publisher    = {ARRAY(0xb507a98)},
  title        = {Particle Deposition Studies in a Laminar Wall Jet - The Hydrodynamic Influence on the Kinetics of Colloidal Deposition},
  year         = {2001},
}