Heat and mass transfer characteristics: design and optimisation of absorption refrigeration machines

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dc.contributor.advisorGryzagoridis, Jassonen_ZA
dc.contributor.authorVicatos, Georgeen_ZA
dc.date.accessioned2016-03-04T16:44:46Z
dc.date.available2016-03-04T16:44:46Z
dc.date.issued1995en_ZA
dc.descriptionBibliography: pages 205-209.en_ZA
dc.description.abstractAn extensive literature study on the subject of absorption refrigeration has revealed that there is no proven methodology that can be used to design, optimise and size a plant. On the contrary there are numerous methods which analyse the performance of an existing plant from collected data. These methods however, do not provide any means of predicting how the analysed plant would perform if one or more of its working conditions should change. This work provides a complete design for an ammonia-water absorption refrigeration plant. The ranges of the working conditions in the evaporator and condenser are from -5°C to -55°C and from 5°C to 45°C respectively. For any combination of temperatures within these ranges, the temperature of the generator is optimised for maximum performance of the plant. Depending on the refrigeration capacity, the components are sized and designed. The proper design of the various components takes into account both heat and mass transfer correlations, something which has not been considered in the past as a necessary step for absorption refrigeration machines. Literature indicates that there is a vast amount of research into the absorption of gases into liquids and two-phase flows through tubes of various sections. The correlations cited in these studies have been used in designing the absorption column, evaporator and generator. The proposed optimisation method is a novel approach in designing a plant and stems from the fact that the performance of the absorption refrigerator reaches a maximum at a specific generator temperature. For this, optimisation curves have been developed, which for a particular combination of evaporator and cooling environment temperatures, both the optimum generator temperature and the maximum performance of the plant are predicted. The equations used in the computerised simulation procedure are based on the well-established enthalpy-concentration chart for the ammonia-water mixtures. Thus the properties of the mixture at various points in the plant are accurately predicted. Published computerised procedures in the past have been proven inaccurate in predicting the properties of the mixtures at near pure-ammonia concentrations. The validity of the simulation model is verified by tests performed on a laboratory size absorption plant. The plant was built from design parameters predicted by the simulation model for a refrigeration capacity of 1 kW at -l5°C evaporator coil and 25°C condensate temperatures. Thereafter the unit was operated for a range of evaporator conditions while the generator temperature was varied.en_ZA
dc.identifier.apacitationVicatos, G. (1995). <i>Heat and mass transfer characteristics: design and optimisation of absorption refrigeration machines</i>. (Thesis). University of Cape Town ,Faculty of Engineering & the Built Environment ,Department of Mechanical Engineering. Retrieved from http://hdl.handle.net/11427/17476en_ZA
dc.identifier.chicagocitationVicatos, George. <i>"Heat and mass transfer characteristics: design and optimisation of absorption refrigeration machines."</i> Thesis., University of Cape Town ,Faculty of Engineering & the Built Environment ,Department of Mechanical Engineering, 1995. http://hdl.handle.net/11427/17476en_ZA
dc.identifier.citationVicatos, G. 1995. Heat and mass transfer characteristics: design and optimisation of absorption refrigeration machines. University of Cape Town.en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Vicatos, George AB - An extensive literature study on the subject of absorption refrigeration has revealed that there is no proven methodology that can be used to design, optimise and size a plant. On the contrary there are numerous methods which analyse the performance of an existing plant from collected data. These methods however, do not provide any means of predicting how the analysed plant would perform if one or more of its working conditions should change. This work provides a complete design for an ammonia-water absorption refrigeration plant. The ranges of the working conditions in the evaporator and condenser are from -5°C to -55°C and from 5°C to 45°C respectively. For any combination of temperatures within these ranges, the temperature of the generator is optimised for maximum performance of the plant. Depending on the refrigeration capacity, the components are sized and designed. The proper design of the various components takes into account both heat and mass transfer correlations, something which has not been considered in the past as a necessary step for absorption refrigeration machines. Literature indicates that there is a vast amount of research into the absorption of gases into liquids and two-phase flows through tubes of various sections. The correlations cited in these studies have been used in designing the absorption column, evaporator and generator. The proposed optimisation method is a novel approach in designing a plant and stems from the fact that the performance of the absorption refrigerator reaches a maximum at a specific generator temperature. For this, optimisation curves have been developed, which for a particular combination of evaporator and cooling environment temperatures, both the optimum generator temperature and the maximum performance of the plant are predicted. The equations used in the computerised simulation procedure are based on the well-established enthalpy-concentration chart for the ammonia-water mixtures. Thus the properties of the mixture at various points in the plant are accurately predicted. Published computerised procedures in the past have been proven inaccurate in predicting the properties of the mixtures at near pure-ammonia concentrations. The validity of the simulation model is verified by tests performed on a laboratory size absorption plant. The plant was built from design parameters predicted by the simulation model for a refrigeration capacity of 1 kW at -l5°C evaporator coil and 25°C condensate temperatures. Thereafter the unit was operated for a range of evaporator conditions while the generator temperature was varied. DA - 1995 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 1995 T1 - Heat and mass transfer characteristics: design and optimisation of absorption refrigeration machines TI - Heat and mass transfer characteristics: design and optimisation of absorption refrigeration machines UR - http://hdl.handle.net/11427/17476 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/17476
dc.identifier.vancouvercitationVicatos G. Heat and mass transfer characteristics: design and optimisation of absorption refrigeration machines. [Thesis]. University of Cape Town ,Faculty of Engineering & the Built Environment ,Department of Mechanical Engineering, 1995 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/17476en_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.subject.otherRefrigerationen_ZA
dc.titleHeat and mass transfer characteristics: design and optimisation of absorption refrigeration machinesen_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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