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Abstract(s)
De forma a garantir que uma central de refrigeração opere com segurança e fiabilidade, a sua estrutura deve estar corretamente projetada para garantir que esta resiste aos esforços aplicados durante o seu funcionamento, como o peso dos componentes, as vibrações causadas pelos compressores e os esforços durante o seu levantamento no transporte. O Método dos Elementos Finitos (MEF), devido à sua versatilidade e acessibilidade, tem sido amplamente utilizado por projetistas, utilizando software comercial para estudar o comportamento de estruturas de geometria complexa, a problemas muito diversos. Nesta dissertação reuniu-se informações sobre o MEF e o funcionamento de centrais de refrigeração de CO2 a funcionar no regime transcrítico, com o intuito de dimensionar e otimizar as estruturas de duas centrais. Enquanto a primeira central já tinha uma estrutura, componentes e parâmetros de funcionamento definidos, a segunda estrutura foi construída do zero, sendo necessário um processo de seleção dos componentes em função das restrições geométricas impostas. Realizou-se os estudos dos casos de carga para a estrutura da central inicial, determinando-se a flecha máxima para o caso de carga habitual e casos de carga de transporte, 2,529 e 13,37 mm, respetivamente. As tensões máximas localizaram-se junto aos apoios e nas ligações aos olhais. Otimizou-se a estrutura inicial, levando a redução do peso em cerca de 32,7%. Nos estudos, obteve-se uma redução dos deslocamentos significativa para o caso de carga habitual, enquanto para os casos referentes ao transporte da central, esta redução foi mais ligeira. Analisando os estudos referentes à central transcrítica compacta, validou-se o design projetado, sendo o coeficiente de segurança igual a 2,99.
In order to ensure that a refrigeration system operates safely and reliably, its structure must be correctly designed to ensure that it resists the stresses applied during its operation, such as the weight of the components, the vibrations caused by the compressors and the efforts during their lifting in transport. The Finite Element Method (FEM), due to its versatility and accessibility, has been widely used by designers, using commercial software to study the behavior of complex geometry structures, to very diverse problems. This dissertation gathered information on the MEF and the processes of CO2 refrigeration systems operating in the transcritical regime, in order to size and optimize the structures of two systems. While the first system already had a defined structure, components and operating parameters, the second structure was constructed from scratch, and a component selection process was required according to the geometric constraints imposed. Load case studies were carried out for the initial refrigeration system structure, determining the maximum deflection for the usual load case and transport load cases, 2.529 and 13.37 mm, respectively. The maximum stresses were located at the supports and at the padeyes bases. The initial structure was optimized, leading to a weight reduction of about 32.7%. In the studies, there was a significant reduction in displacements for the usual load case, while for the cases referring to the transport of the refrigeration system, this reduction was slighter. Analyzing the studies referring to the compact transcritical system, the projected design was validated, with a factor of safety equal to 2.99.
In order to ensure that a refrigeration system operates safely and reliably, its structure must be correctly designed to ensure that it resists the stresses applied during its operation, such as the weight of the components, the vibrations caused by the compressors and the efforts during their lifting in transport. The Finite Element Method (FEM), due to its versatility and accessibility, has been widely used by designers, using commercial software to study the behavior of complex geometry structures, to very diverse problems. This dissertation gathered information on the MEF and the processes of CO2 refrigeration systems operating in the transcritical regime, in order to size and optimize the structures of two systems. While the first system already had a defined structure, components and operating parameters, the second structure was constructed from scratch, and a component selection process was required according to the geometric constraints imposed. Load case studies were carried out for the initial refrigeration system structure, determining the maximum deflection for the usual load case and transport load cases, 2.529 and 13.37 mm, respectively. The maximum stresses were located at the supports and at the padeyes bases. The initial structure was optimized, leading to a weight reduction of about 32.7%. In the studies, there was a significant reduction in displacements for the usual load case, while for the cases referring to the transport of the refrigeration system, this reduction was slighter. Analyzing the studies referring to the compact transcritical system, the projected design was validated, with a factor of safety equal to 2.99.
Description
Keywords
MEF Elemento Finito Central de Refrigeração Estrutura Análise Estática CAD/CAE FEM Finite Element Refrigeration System Structure Static Analysis