Persistent Link:
http://hdl.handle.net/10150/194528
Title:
Electrically-Driven Natural Convection in Colloidal Suspensions
Author:
Safier, Paul Alan
Issue Date:
2005
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
A basic physical model of electrodecantation has been developed and tested. Experimental data of Belongia (1999) were used to compare with computational results obtained from the model. The model was developed to calculate the transient velocity field, electric potential and particle distribution for the parameter space encountered in stable colloidal dispersions. The model included the effects of a spatially nonuniform electric field that existed in the experiments of Belongia (1999) because of the type and position of the electrodes used. As a result, the model required numerical methods for its solution. The problem was found to depend largely on three dimensionless groups: Re, a Reynolds number, Pe an electric Péclet number and ¤ a large dimensionless parameter denoting the Grashof number divided by the Reynolds number. Because A^(1/3) >> 1, nonuniform computational meshes were needed to resolve the exceedingly thin natural convection boundary layers that occur. Additionally, because Pe >> 1, a flux-limiting (FCT) numerical method was used to solve the particle transport equation. Results from the basic physical model show excellent agreement with the scaling of the experimental data but exhibit about 80% relative error when compared with experimental data on the decantation time. Consequently, a physicochemical model of electrodecantation was developed to include electrical conductivity variations that develop as ions transport during electrodecantation. Results show markedly better agreement (about 10% relative error) with experimental data concerning the decantation rate. Additionally, the physicochemical model is able to predict the pH and electrical conductivity stratification that was measured experimentally by Belongia (1999). A problem concerning the electrohydrodynamic deformation of miscible fluids, with differing electromechanical properties (electrical conductivity and dielectric constant), was also investigated. Numerical results predicting the sense and extent of deformation for various values of the two fluids’ electrical conductivity ratio compare well (less than 10% relative error) with measurements by Rhodes, et al. (1989). The role of dielectric constant differences in electrohydrodynamic deformations was also investigated. It was determined that an O(1) difference in the fluids’ dielectric constants is necessary to produce electrohydrodynamic deformations on the time scales reported by Rhodes, et al. (1989) and Trau, et al. (1995).
Type:
text; Electronic Dissertation
Keywords:
convection; stratification; fluid dynamics; mass transfer
Degree Name:
PhD
Degree Level:
doctoral
Degree Program:
Chemical Engineering; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Baygents, James C
Committee Chair:
Baygents, James C

Full metadata record

DC FieldValue Language
dc.language.isoENen_US
dc.titleElectrically-Driven Natural Convection in Colloidal Suspensionsen_US
dc.creatorSafier, Paul Alanen_US
dc.contributor.authorSafier, Paul Alanen_US
dc.date.issued2005en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractA basic physical model of electrodecantation has been developed and tested. Experimental data of Belongia (1999) were used to compare with computational results obtained from the model. The model was developed to calculate the transient velocity field, electric potential and particle distribution for the parameter space encountered in stable colloidal dispersions. The model included the effects of a spatially nonuniform electric field that existed in the experiments of Belongia (1999) because of the type and position of the electrodes used. As a result, the model required numerical methods for its solution. The problem was found to depend largely on three dimensionless groups: Re, a Reynolds number, Pe an electric Péclet number and ¤ a large dimensionless parameter denoting the Grashof number divided by the Reynolds number. Because A^(1/3) >> 1, nonuniform computational meshes were needed to resolve the exceedingly thin natural convection boundary layers that occur. Additionally, because Pe >> 1, a flux-limiting (FCT) numerical method was used to solve the particle transport equation. Results from the basic physical model show excellent agreement with the scaling of the experimental data but exhibit about 80% relative error when compared with experimental data on the decantation time. Consequently, a physicochemical model of electrodecantation was developed to include electrical conductivity variations that develop as ions transport during electrodecantation. Results show markedly better agreement (about 10% relative error) with experimental data concerning the decantation rate. Additionally, the physicochemical model is able to predict the pH and electrical conductivity stratification that was measured experimentally by Belongia (1999). A problem concerning the electrohydrodynamic deformation of miscible fluids, with differing electromechanical properties (electrical conductivity and dielectric constant), was also investigated. Numerical results predicting the sense and extent of deformation for various values of the two fluids’ electrical conductivity ratio compare well (less than 10% relative error) with measurements by Rhodes, et al. (1989). The role of dielectric constant differences in electrohydrodynamic deformations was also investigated. It was determined that an O(1) difference in the fluids’ dielectric constants is necessary to produce electrohydrodynamic deformations on the time scales reported by Rhodes, et al. (1989) and Trau, et al. (1995).en_US
dc.typetexten_US
dc.typeElectronic Dissertationen_US
dc.subjectconvectionen_US
dc.subjectstratificationen_US
dc.subjectfluid dynamicsen_US
dc.subjectmass transferen_US
thesis.degree.namePhDen_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineChemical Engineeringen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorBaygents, James Cen_US
dc.contributor.chairBaygents, James Cen_US
dc.contributor.committeememberGuzman, Robertoen_US
dc.contributor.committeememberSaez, A. Eduardoen_US
dc.contributor.committeememberChan, Cho Liken_US
dc.identifier.proquest1122en_US
dc.identifier.oclc137354074en_US
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