Development of a computationally efficient bubble column simulation approach by way of statistical bubble micro-flow modelling

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dc.contributor.advisorRawatlal, Randhiren_ZA
dc.contributor.advisorCoetzer, Roelof LJen_ZA
dc.contributor.authorCoetzee, Waldoen_ZA
dc.date.accessioned2014-07-31T11:13:15Z
dc.date.available2014-07-31T11:13:15Z
dc.date.issued2013en_ZA
dc.descriptionIncludes abstract.
dc.descriptionIncludes bibliographical references.
dc.description.abstractThe intimate contact achieved between the gas and liquid phases in bubble columns, coupled with the inherent efficient mixing these reactors offer, yield excellent heat and mass transfer characteristics. These attributes have been exploited commercially for decades, however, due to the complexity of the underlying hydrodynamics, the prediction of bubble columns based on empirical models can be unreliable outside of the operating ranges used to fit these models. Computational Fluid Dynamics (CFD) has emerged as an attractive tool for simulating these reactors and is based on numerically approximating the fundamentally based Navier-Stokes equations on a discretized domain. The application of CFD has become more practical as the cost of computational resources has declined and has lead to the establishment of three distinct modelling approaches which have been evaluated for the purpose of bubble column simulation in a number of research papers over the past two decades. Here the Euler-Euler approach has been recommended for the simulation of large scale columns, however, this approach is based on the most assumptions and yields the least amount of flow field information. The Euler-Lagrange approach treats bubbles as discrete particles which allows for the incorporation of a deterministic bubble size distribution and the direct consideration of heat and mass transfer effects. The most fundamental approach, Direct Numerical Simulation (DNS), predicts flow properties at the bubble scale, however, is extremely computationally expensive and is therefore only practically applicable to the investigation of a very small number of bubbles. The objective of this study is to contribute to the simulation of gasliquid flow interaction occurring in bubble columns by proposing a novel technique for simulating bubble scale flow information at a significantly reduced computational expense. For this purpose, it is proposed to predict the micro-flow fields around individual bubbles, within an Euler-Lagrange framework, with an algebraic model termed the Bubble Cell Model (BCM). The high gradient regions around individual bubbles are thereby accounted for with an algebraic flow model that can be rapidly evaluated as opposed to the two-phase partial differential Navier-Stokes equations, thereby reducing the numerical complexity of the problem. Since no such flow models currently exist and accuracy and fast evaluation are imperative, a statistical approach to the construction of the BCM is justified.en_ZA
dc.identifier.apacitationCoetzee, W. (2013). <i>Development of a computationally efficient bubble column simulation approach by way of statistical bubble micro-flow modelling</i>. (Thesis). University of Cape Town ,Faculty of Engineering & the Built Environment ,Department of Chemical Engineering. Retrieved from http://hdl.handle.net/11427/5368en_ZA
dc.identifier.chicagocitationCoetzee, Waldo. <i>"Development of a computationally efficient bubble column simulation approach by way of statistical bubble micro-flow modelling."</i> Thesis., University of Cape Town ,Faculty of Engineering & the Built Environment ,Department of Chemical Engineering, 2013. http://hdl.handle.net/11427/5368en_ZA
dc.identifier.citationCoetzee, W. 2013. Development of a computationally efficient bubble column simulation approach by way of statistical bubble micro-flow modelling. University of Cape Town.en_ZA
dc.identifier.risTY - Thesis / Dissertation AU - Coetzee, Waldo AB - The intimate contact achieved between the gas and liquid phases in bubble columns, coupled with the inherent efficient mixing these reactors offer, yield excellent heat and mass transfer characteristics. These attributes have been exploited commercially for decades, however, due to the complexity of the underlying hydrodynamics, the prediction of bubble columns based on empirical models can be unreliable outside of the operating ranges used to fit these models. Computational Fluid Dynamics (CFD) has emerged as an attractive tool for simulating these reactors and is based on numerically approximating the fundamentally based Navier-Stokes equations on a discretized domain. The application of CFD has become more practical as the cost of computational resources has declined and has lead to the establishment of three distinct modelling approaches which have been evaluated for the purpose of bubble column simulation in a number of research papers over the past two decades. Here the Euler-Euler approach has been recommended for the simulation of large scale columns, however, this approach is based on the most assumptions and yields the least amount of flow field information. The Euler-Lagrange approach treats bubbles as discrete particles which allows for the incorporation of a deterministic bubble size distribution and the direct consideration of heat and mass transfer effects. The most fundamental approach, Direct Numerical Simulation (DNS), predicts flow properties at the bubble scale, however, is extremely computationally expensive and is therefore only practically applicable to the investigation of a very small number of bubbles. The objective of this study is to contribute to the simulation of gasliquid flow interaction occurring in bubble columns by proposing a novel technique for simulating bubble scale flow information at a significantly reduced computational expense. For this purpose, it is proposed to predict the micro-flow fields around individual bubbles, within an Euler-Lagrange framework, with an algebraic model termed the Bubble Cell Model (BCM). The high gradient regions around individual bubbles are thereby accounted for with an algebraic flow model that can be rapidly evaluated as opposed to the two-phase partial differential Navier-Stokes equations, thereby reducing the numerical complexity of the problem. Since no such flow models currently exist and accuracy and fast evaluation are imperative, a statistical approach to the construction of the BCM is justified. DA - 2013 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 2013 T1 - Development of a computationally efficient bubble column simulation approach by way of statistical bubble micro-flow modelling TI - Development of a computationally efficient bubble column simulation approach by way of statistical bubble micro-flow modelling UR - http://hdl.handle.net/11427/5368 ER -en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/5368
dc.identifier.vancouvercitationCoetzee W. Development of a computationally efficient bubble column simulation approach by way of statistical bubble micro-flow modelling. [Thesis]. University of Cape Town ,Faculty of Engineering & the Built Environment ,Department of Chemical Engineering, 2013 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/5368en_ZA
dc.language.isoengen_ZA
dc.publisher.departmentCentre for Bioprocess Engineering Researchen_ZA
dc.publisher.facultyFaculty of Engineering and the Built Environment
dc.publisher.institutionUniversity of Cape Town
dc.subject.otherBioprocess Engineeringen_ZA
dc.titleDevelopment of a computationally efficient bubble column simulation approach by way of statistical bubble micro-flow modellingen_ZA
dc.typeDoctoral Thesis
dc.type.qualificationlevelDoctoral
dc.type.qualificationnamePhDen_ZA
uct.type.filetypeText
uct.type.filetypeImage
uct.type.publicationResearchen_ZA
uct.type.resourceThesisen_ZA
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