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Abstract(s)
O conforto térmico é cada vez mais equacionado como um requisito obrigatório, tanto a nível de edifícios de comércio e serviços, como de edifícios de habitação. Hoje em dia, é raro encontrar-se edifícios novos, até 5 anos de idade, sem um sistema de ar condicionado. Existem dois tipos de climatização por compressão de vapor: expansão direta e indireta. A solução de expansão indireta, recorre a um fluido secundário para realizar a permuta térmica, que na maioria das vezes é a água. Este sistema é designado como hidrónico. Este trabalho pretende efetuar uma análise comparativa entre duas soluções centralizadas de climatização: sistema de expansão direta e o sistema hidrónico. A escolha deste tema deveu-se a ser um assunto bastante debatido com inúmeros argumentos válidos em ambos os casos, não existindo uma solução correta, mas sim a solução mais adequada consoante o tipo de aplicação. Neste sentido, foram definidos dois tópicos mensuráveis, considerados dos mais importantes na implementação de um sistema de AVAC. Estes são: o fator económico, que envolve os custos desde a aquisição dos equipamentos até ao fim da vida útil dos mesmos, e o fator ambiental, com base no regulamento F-gas, que pretende regulamentar e diminuir os gases fluorados utilizados, tornando-se assim crucial a escolha de uma solução com baixo Potencial de Aquecimento Global (GWP). Foi selecionado o edifício M do Instituto Superior de Engenharia de Lisboa (ISEL), para o estudo em questão. Nesta escolha também existiu a preocupação de se ajudar esta instituição, providenciando duas soluções possíveis de se aplicar. Definiu-se um perfil climático referente à localização e importância do edifício. Através do levantamento realizado verifica-se que o edifício não cumpre muitos dos requisitos mínimos e das exigências funcionais dos vários elementos construtivos, havendo perdas ou ganhos térmicos através das envolventes que influenciam muito o seu consumo energético. Os sistemas de climatização existentes no edifício utilizam fluidos frigorigéneos com elevado GWP e com utilização já interdita que perante a legislação em vigor, caso se intervenha no circuito frigorífico é obrigatório a recuperação e destruição de todo esse fluido e substituição por outro. Constata-se que para manter os requisitos mínimos de conforto terá de haver intervenção a nível da envolvente do edifício. Tendo em conta as potências de aquecimento e arrefecimento obtidas verifica-se que entre as duas soluções, o sistema hidrónico irá trazer mais vantagens a longo prazo, apesar do seu custo inicial ser mais elevado e de ocupar mais espaço. É possível comprovar que o sistema hidrónico tem uma maior sustentabilidade ao longo do ciclo de vida pois utiliza a água como fluido principal para a troca térmica, enquanto o VRF utiliza fluido frigorigéneo em toda a sua instalação, logo maior quantidade de fluido a circular. De referir que, o GWP do R410A é superior ao do R134a, este pertencente aos equipamentos hidrónicos, e o sistema de expansão direta detém uma quantidade de fluido frigorigéneo maior, o que se traduz numa carga de toneladas equivalentes de CO2 igualmente superior.
The thermal comfort is increasingly considered as a mandatory requirement, both in commercial and service buildings and in residential buildings. Nowadays, it is rare to find new buildings, up to 5 years old, without an air conditioning system. There are two types of air conditioning systems: direct and indirect expansion. The indirect expansion solution uses a secondary fluid to carry out the heat exchange, which in most cases is water. This type of systems are called hydronic. This work intends to carry out a comparative analysis of two possible centralized air conditioning solutions: direct expansion system and hydronic system. The choice of this theme was due to the fact that it is a subject that has been widely debated with numerous valid arguments in both cases, with no specific solution, but the most appropriate solution depending on the type of application. In this sense, two measurable topics were defined, considered among the most important in the implementation of an HVAC system. These are: the economic factor, which involves costs from the acquisition of equipment to the end of it’s useful life, and the environmental factor, which, in view of the F-gas regulation, which aims to regulate and reduce the fluorinated gases, it is crucial to choose the refrigerant with the lowest Global Warming Potential (GWP). The M building of the Instituto Superior de Engenharia de Lisboa (ISEL) was selected for this study. In this choice there was also a concern to help this institution, providing two possible solutions to apply. A climate profile was defined regarding the location and importance of the building. Through the inspection carried out, it was verified that it does not meet many of the minimum and functional requirements of the various construction elements, with thermal losses or gains through the surroundings that greatly influence its energy consumption. The current air conditioning systems in the building use refrigerants with a high GWP and whose use is already prohibited, which according to the legislation in force, if the refrigeration circuit is intervened, the recovery and destruction of all this fluid and replacement by another is mandatory. The analysis indicates that to maintain the minimum comfort requirements, there will be necessary an intervention in the building. Considering the heating and cooling power obtained, it is known that between the two solutions, the hydronic system will bring more benefits in the long term, even though the cost is higher and needs more space. It is proven that the hydronic system has a higher sustainability throughout its life cycle as it uses water as the main fluid for the heat exchanges, while the VRF uses refrigerant throughout its installation, which would represent a greater amount of fluid circulates. Should be referred that the GWP of R410A is higher than that of R134a, this belonging to hydronic equipment, and the direct expansion system contains a greater amount of refrigerant, which means into an equally greater load of equivalent tons of CO2.
The thermal comfort is increasingly considered as a mandatory requirement, both in commercial and service buildings and in residential buildings. Nowadays, it is rare to find new buildings, up to 5 years old, without an air conditioning system. There are two types of air conditioning systems: direct and indirect expansion. The indirect expansion solution uses a secondary fluid to carry out the heat exchange, which in most cases is water. This type of systems are called hydronic. This work intends to carry out a comparative analysis of two possible centralized air conditioning solutions: direct expansion system and hydronic system. The choice of this theme was due to the fact that it is a subject that has been widely debated with numerous valid arguments in both cases, with no specific solution, but the most appropriate solution depending on the type of application. In this sense, two measurable topics were defined, considered among the most important in the implementation of an HVAC system. These are: the economic factor, which involves costs from the acquisition of equipment to the end of it’s useful life, and the environmental factor, which, in view of the F-gas regulation, which aims to regulate and reduce the fluorinated gases, it is crucial to choose the refrigerant with the lowest Global Warming Potential (GWP). The M building of the Instituto Superior de Engenharia de Lisboa (ISEL) was selected for this study. In this choice there was also a concern to help this institution, providing two possible solutions to apply. A climate profile was defined regarding the location and importance of the building. Through the inspection carried out, it was verified that it does not meet many of the minimum and functional requirements of the various construction elements, with thermal losses or gains through the surroundings that greatly influence its energy consumption. The current air conditioning systems in the building use refrigerants with a high GWP and whose use is already prohibited, which according to the legislation in force, if the refrigeration circuit is intervened, the recovery and destruction of all this fluid and replacement by another is mandatory. The analysis indicates that to maintain the minimum comfort requirements, there will be necessary an intervention in the building. Considering the heating and cooling power obtained, it is known that between the two solutions, the hydronic system will bring more benefits in the long term, even though the cost is higher and needs more space. It is proven that the hydronic system has a higher sustainability throughout its life cycle as it uses water as the main fluid for the heat exchanges, while the VRF uses refrigerant throughout its installation, which would represent a greater amount of fluid circulates. Should be referred that the GWP of R410A is higher than that of R134a, this belonging to hydronic equipment, and the direct expansion system contains a greater amount of refrigerant, which means into an equally greater load of equivalent tons of CO2.
Description
Dissertação de natureza científica para obtenção do grau de Mestre em Engenharia Mecânica
Keywords
Conforto térmico AVAC Expansão direta Hidrónico GWP Sustentabilidade Thermal confort HVAC Direct expansion Hydronic GWP Sustainability
Citation
BARREIRA, Gustavo Castanheira Lopes Godinho - Análise comparativa dos sistemas de climatização: expansão direta vs hidrónico. Lisboa: Instituto Superior de Engenharia de Lisboa, 2022. Dissertação de Mestrado.