A zonal model for radiation heat transfer in coal-fired boiler furnaces

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dc.contributor.advisorRousseau, Pieteren_ZA
dc.contributor.authorMonnaemang, Whitney Ogalaletsengen_ZA
dc.date.accessioned2016-06-22T08:58:31Z
dc.date.available2016-06-22T08:58:31Z
dc.date.issued2015en_ZA
dc.description.abstractProblems associated with boilers are a major contributor to load losses in coal-fired power plants. The boiler furnace exit temperature is a key indicator of the combustion and heat transfer processes taking place and has a profound impact on the operation of the heat exchangers downstream of the furnace. Having a model that can predict the furnace exit temperature and heat flux distributions may enable furnace performance to be predicted without having to conduct extensive experimentation. Also, comparing the results with measurements taken on the plant may enable the identification of operating problems and potential sources of losses. Thermal radiation is the dominant mode of heat transfer in the boiler furnace. The primary objective of this study is to develop and implement a radiation heat transfer network solution methodology based on the zonal method that may be applied to boiler furnace modelling. The zonal method allows for the prediction of heat flux and temperature distributions on the walls, inside, and at the exit of the furnace. Direct exchange areas are the basis of the zonal method and are a function of the furnace geometry and radiative properties of the walls and the participating medium that fills the furnace volume. The evaluation of direct exchange areas is done by discrete numerical integration, after which it needs to be smoothed to satisfy energy conservation. After evaluating two different smoothing techniques, the least squares technique using Lagrange multipliers was selected for this study. Following this, the solution of the radiation heat transfer network was implemented for an emitting-absorbing-scattering participating medium for two different scenarios, namely (i) solving surface and volume heat fluxes for known surface and medium temperatures, and (ii) solving surface heat fluxes and medium temperature distributions for known surface temperatures and volume heat source terms. Intermediate verification and validation steps throughout the development process show good agreement with other numerical techniques and correlations available in literature. In order to illustrate the applicability of the final model, a number of case studies are conducted. These include an illustration of the effect of slagging on the furnace walls, of a faulty burner and of changes in the radiative properties of the participating medium. The results of the case studies show that the trends of the heat flux and temperature distributions obtained with the new model are in agreement with those found in literature.en_ZA
dc.identifier.apacitationMonnaemang, W. O. (2015). <i>A zonal model for radiation heat transfer in coal-fired boiler furnaces</i>. (Thesis). University of Cape Town ,Faculty of Engineering & the Built Environment ,Department of Mechanical Engineering. Retrieved from http://hdl.handle.net/11427/20092en_ZA
dc.identifier.chicagocitationMonnaemang, Whitney Ogalaletseng. <i>"A zonal model for radiation heat transfer in coal-fired boiler furnaces."</i> Thesis., University of Cape Town ,Faculty of Engineering & the Built Environment ,Department of Mechanical Engineering, 2015. http://hdl.handle.net/11427/20092en_ZA
dc.identifier.citationMonnaemang, W. 2015. A zonal model for radiation heat transfer in coal-fired boiler furnaces. University of Cape Town.en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Monnaemang, Whitney Ogalaletseng AB - Problems associated with boilers are a major contributor to load losses in coal-fired power plants. The boiler furnace exit temperature is a key indicator of the combustion and heat transfer processes taking place and has a profound impact on the operation of the heat exchangers downstream of the furnace. Having a model that can predict the furnace exit temperature and heat flux distributions may enable furnace performance to be predicted without having to conduct extensive experimentation. Also, comparing the results with measurements taken on the plant may enable the identification of operating problems and potential sources of losses. Thermal radiation is the dominant mode of heat transfer in the boiler furnace. The primary objective of this study is to develop and implement a radiation heat transfer network solution methodology based on the zonal method that may be applied to boiler furnace modelling. The zonal method allows for the prediction of heat flux and temperature distributions on the walls, inside, and at the exit of the furnace. Direct exchange areas are the basis of the zonal method and are a function of the furnace geometry and radiative properties of the walls and the participating medium that fills the furnace volume. The evaluation of direct exchange areas is done by discrete numerical integration, after which it needs to be smoothed to satisfy energy conservation. After evaluating two different smoothing techniques, the least squares technique using Lagrange multipliers was selected for this study. Following this, the solution of the radiation heat transfer network was implemented for an emitting-absorbing-scattering participating medium for two different scenarios, namely (i) solving surface and volume heat fluxes for known surface and medium temperatures, and (ii) solving surface heat fluxes and medium temperature distributions for known surface temperatures and volume heat source terms. Intermediate verification and validation steps throughout the development process show good agreement with other numerical techniques and correlations available in literature. In order to illustrate the applicability of the final model, a number of case studies are conducted. These include an illustration of the effect of slagging on the furnace walls, of a faulty burner and of changes in the radiative properties of the participating medium. The results of the case studies show that the trends of the heat flux and temperature distributions obtained with the new model are in agreement with those found in literature. DA - 2015 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 2015 T1 - A zonal model for radiation heat transfer in coal-fired boiler furnaces TI - A zonal model for radiation heat transfer in coal-fired boiler furnaces UR - http://hdl.handle.net/11427/20092 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/20092
dc.identifier.vancouvercitationMonnaemang WO. A zonal model for radiation heat transfer in coal-fired boiler furnaces. [Thesis]. University of Cape Town ,Faculty of Engineering & the Built Environment ,Department of Mechanical Engineering, 2015 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/20092en_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.titleA zonal model for radiation heat transfer in coal-fired boiler furnacesen_ZA
dc.typeMaster Thesis
dc.type.qualificationlevelMasters
dc.type.qualificationnameMSc (Eng)en_ZA
uct.type.filetypeText
uct.type.filetypeImage
uct.type.publicationResearchen_ZA
uct.type.resourceThesisen_ZA
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