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Abstract(s)
A presente dissertação tem como objetivo efetuar uma avaliação do sistema de climatização dos navios da Classe Vasco da Gama em ambientes tropicais. Sendo projetados para navegar em águas com temperaturas inferiores a 27 °C, acima destes valores, o sistema de refrigeração tende alterar os parâmetros de funcionamento. A potência máxima disponível é de 960 kW e a potência necessária ronda os 640 kW quando operado dentro dos parâmetros de projeto.
Sendo uma preocupação com o meio ambiente cada vez mais globalizada, a necessidade de efetuar trocas dos refrigerantes nos sistemas de refrigeração. Pretende-se reduzir as emissões de gases com potencial de aquecimento global, ou que esse valor (de potencial de aquecimento) seja menor nos refrigerantes utilizados.
Face aos problemas verificados no funcionamento do sistema em ambientes tropicais e na necessidade de efetuar a troca do refrigerante usado atualmente efetuou-se uma análise do sistema com o refrigerante de projeto, R22, o refrigerante atualmente em uso, R404a e com possíveis substitutos.
A análise, passa por avaliar o sistema de refrigeração, e pela sua ligação com o sistema de distribuição de ar. Desenvolveu-se um modelo do sistema de bordo através de um software com as propriedades termodinâmicas dos diferentes refrigerantes. Efetuou-se a resolução das diferentes equações que descrevem o modelo, e obteve-se os resultados necessários para a sua avaliação. O R407C apresenta capacidade de refrigeração e características operacionais muito próximas do R22.O R404a sendo limitado pelas suas características e pela potência do motor elétrico não permite melhores capacidades de refrigeração. Além disso, tem pressões na alta pressão elevadas o que é um problema por se aproximar do valor máximo de dimensionamento do condensador.
A solução principal passa por substituir o sistema com o R407C, ou alterar o sistema atualmente instalado, para que ele possa funcionar em condições mais extremas (ambientes tropicais).
The present dissertation aims to evaluate the air conditioning system of Vasco da Gama Class warships in tropical environments. Being ships essentially designed to sail in waters with temperatures below 27 ° C, above these values, the cooling system significantly changes their operation. The maximum available power is 960 kW, and power required for 640 kW when operated within the design parameters. Concern about the environment is increasingly globalized, requiring the exchange of refrigerants in refrigeration systems. It is intended to reduce emissions of gases with a high global warming potential (GWP) and to replace them with refrigerants with lower GWP. In view of the problems encountered in the operation of the air conditioning system in tropical environments, and the need to replace the refrigerant currently used, an analysis was made of the system already implemented with the current refrigerant and then with possible substitutes. The system model considered the refrigeration system, the load interconnection network and the air distribution system. For this, a software was used with the thermodynamic properties of the different refrigerants, the different equations describing the model were solved, and the necessary results were obtained for its evaluation. In order to guarantee a near capacity during the system to work with the design refrigerant, the solutions / alterations to be equated will be given. The R22 has the best capabilities for the currently installed system. The R407C when presenting capacities, as well as its operating characteristics very close to the R22, is considered the alternative. The R404a being limited by the power of the electric motor does not allow for better cooling capabilities. In addition the working pressure starts to be a problem, since, it is close to the maximum that the condenser supports. The solution has been to replace the system with the R407C, or to change the system currently installed, so that it can work in more extreme conditions (tropical environments).
The present dissertation aims to evaluate the air conditioning system of Vasco da Gama Class warships in tropical environments. Being ships essentially designed to sail in waters with temperatures below 27 ° C, above these values, the cooling system significantly changes their operation. The maximum available power is 960 kW, and power required for 640 kW when operated within the design parameters. Concern about the environment is increasingly globalized, requiring the exchange of refrigerants in refrigeration systems. It is intended to reduce emissions of gases with a high global warming potential (GWP) and to replace them with refrigerants with lower GWP. In view of the problems encountered in the operation of the air conditioning system in tropical environments, and the need to replace the refrigerant currently used, an analysis was made of the system already implemented with the current refrigerant and then with possible substitutes. The system model considered the refrigeration system, the load interconnection network and the air distribution system. For this, a software was used with the thermodynamic properties of the different refrigerants, the different equations describing the model were solved, and the necessary results were obtained for its evaluation. In order to guarantee a near capacity during the system to work with the design refrigerant, the solutions / alterations to be equated will be given. The R22 has the best capabilities for the currently installed system. The R407C when presenting capacities, as well as its operating characteristics very close to the R22, is considered the alternative. The R404a being limited by the power of the electric motor does not allow for better cooling capabilities. In addition the working pressure starts to be a problem, since, it is close to the maximum that the condenser supports. The solution has been to replace the system with the R407C, or to change the system currently installed, so that it can work in more extreme conditions (tropical environments).
Description
Keywords
Tropical Refrigerante Potencial Análise Soluções Tropical Refrigerant Potential Analysis Solutions