Multiphase CFD modelling of stirred tanks

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dc.contributor.advisorDeglon, Daviden_ZA
dc.contributor.advisorMeyer, CJen_ZA
dc.contributor.authorAppa, Harishen_ZA
dc.date.accessioned2014-07-31T11:22:22Z
dc.date.available2014-07-31T11:22:22Z
dc.date.issued2007en_ZA
dc.descriptionIncludes bibliographical references (p. 67-70).
dc.description.abstractStirred tanks agitated with Rushton turbines are commonly used in industry, for instance mixing processes and flotation systems. The need for more efficient systems in industries has led to the study of fluid flow within the tanks upon agitation; so that a better understanding of the phenomena can help in the optimisation of the tanks. In the recent years, efforts have been made towards the development of predictive methods using computational fluid dynamics (CFD). Among the various numerical works presented, emphasis was laid mainly on single phase systems. However, due to the various processes involving gas-liquid systems, the need for multiphase modelling of stirred tanks became increasingly important. This has led to more research studies involving multiphase flows. Most of the work reported showed good prediction of the velocity data and the power draw, reasonable turbulence parameters. But, the prediction of the gas hold-up was rarely well established. Therefore, the aim of this thesis, based on the numerical work presented by Engelbrecht (2006), is to investigate the discrepancies reported and to develop a multiphase model of a stirred tank agitated by a Rushton turbine. The commercially available CFD code FLUENT@ was used to model the agitated gas-liquid system. The results were validated with the numerical work of Engelbrecht (2006) and the experimental work presented by Deglon (1998). Two main cases were investigated, with a steady state and a transient approach. The QUICK scheme was used for the discretisation of the volume fraction and momentum and the first order upwind scheme for the discretisation of the turbulent kinetic energy and dissipation rate. The standard k - E turbulence model was used to account for the turbulent flow regime. A steady state MRF model was used for the investigation of the discrepancy reported by Engelbrecht (2006). The author reported that no convergence was achieved with such models. Solving the problem would have resulted in a good modelling approach for the prediction of gas dispersion, since steady state models are not computationally intensive. Three different boundary conditions, namely, a pressure outlet, an outflow and a velocity inlet, were used to model the outlet of the tank. The Euler-Euler multiphase model was used to simulate the gas-liquid system for the steady state model.en_ZA
dc.identifier.apacitationAppa, H. (2007). <i>Multiphase CFD modelling of stirred tanks</i>. (Thesis). University of Cape Town ,Faculty of Engineering & the Built Environment ,Department of Mechanical Engineering. Retrieved from http://hdl.handle.net/11427/5548en_ZA
dc.identifier.chicagocitationAppa, Harish. <i>"Multiphase CFD modelling of stirred tanks."</i> Thesis., University of Cape Town ,Faculty of Engineering & the Built Environment ,Department of Mechanical Engineering, 2007. http://hdl.handle.net/11427/5548en_ZA
dc.identifier.citationAppa, H. 2007. Multiphase CFD modelling of stirred tanks. University of Cape Town.en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Appa, Harish AB - Stirred tanks agitated with Rushton turbines are commonly used in industry, for instance mixing processes and flotation systems. The need for more efficient systems in industries has led to the study of fluid flow within the tanks upon agitation; so that a better understanding of the phenomena can help in the optimisation of the tanks. In the recent years, efforts have been made towards the development of predictive methods using computational fluid dynamics (CFD). Among the various numerical works presented, emphasis was laid mainly on single phase systems. However, due to the various processes involving gas-liquid systems, the need for multiphase modelling of stirred tanks became increasingly important. This has led to more research studies involving multiphase flows. Most of the work reported showed good prediction of the velocity data and the power draw, reasonable turbulence parameters. But, the prediction of the gas hold-up was rarely well established. Therefore, the aim of this thesis, based on the numerical work presented by Engelbrecht (2006), is to investigate the discrepancies reported and to develop a multiphase model of a stirred tank agitated by a Rushton turbine. The commercially available CFD code FLUENT@ was used to model the agitated gas-liquid system. The results were validated with the numerical work of Engelbrecht (2006) and the experimental work presented by Deglon (1998). Two main cases were investigated, with a steady state and a transient approach. The QUICK scheme was used for the discretisation of the volume fraction and momentum and the first order upwind scheme for the discretisation of the turbulent kinetic energy and dissipation rate. The standard k - E turbulence model was used to account for the turbulent flow regime. A steady state MRF model was used for the investigation of the discrepancy reported by Engelbrecht (2006). The author reported that no convergence was achieved with such models. Solving the problem would have resulted in a good modelling approach for the prediction of gas dispersion, since steady state models are not computationally intensive. Three different boundary conditions, namely, a pressure outlet, an outflow and a velocity inlet, were used to model the outlet of the tank. The Euler-Euler multiphase model was used to simulate the gas-liquid system for the steady state model. DA - 2007 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 2007 T1 - Multiphase CFD modelling of stirred tanks TI - Multiphase CFD modelling of stirred tanks UR - http://hdl.handle.net/11427/5548 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/5548
dc.identifier.vancouvercitationAppa H. Multiphase CFD modelling of stirred tanks. [Thesis]. University of Cape Town ,Faculty of Engineering & the Built Environment ,Department of Mechanical Engineering, 2007 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/5548en_ZA
dc.language.isoengen_ZA
dc.publisher.departmentDepartment of Mechanical Engineeringen_ZA
dc.publisher.facultyFaculty of Engineering and the Built Environment
dc.publisher.institutionUniversity of Cape Town
dc.subject.otherMechanical Engineeringen_ZA
dc.titleMultiphase CFD modelling of stirred tanksen_ZA
dc.typeMaster Thesis
dc.type.qualificationlevelMasters
dc.type.qualificationnameMScen_ZA
uct.type.filetypeText
uct.type.filetypeImage
uct.type.publicationResearchen_ZA
uct.type.resourceThesisen_ZA
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