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Abstract(s)
O ressurgimento recente de ciclos frigoríficos de CO2 é justificado quer por razões ambientais, quer por razões económicas e legais devido às restrições impostas pela comissão europeia, nomeadamente, através da regulamentação para a utilização de gases fluorados, designada por F-gas. Na presente dissertação, foi desenvolvido o projeto de uma bomba de calor ar-água de 50 kW para aquecimento de água sanitárias (AQS), utilizando como fluido frigorigéneo, CO2 em regime transcrítico. Este sistema tem ganho preponderância no mercado mundial de equipamentos destinados à produção de AQS, graças à sua elevada eficiência energética que se traduz na redução de consumo energético nos setores dos edifícios de habitação, comércio e serviços. A fase inicial de trabalho, começou pela identificação e análise das tecnologias atuais de ciclos transcríticos para a produção de água quente sanitária, estudo este que permitiu definir o esquema de princípio a adotar no projeto da bomba de calor. De forma a analisar o desempenho e variações de funcionamento do ciclo frigorifico e também, de obter os parâmetros necessários para seleção dos vários equipamentos, foi desenvolvida uma ferramenta de cálculo da bomba de calor (FCBC), implementada no Excel, modelada com recurso a correlações experimentais, tabelas de propriedades termodinâmicas do CO2, e equações termodinâmicas aplicadas no ciclo transcrítico de CO2. Com base nos dados de entrada, ou seja, nas condições de operação, a FCBC tem como dados de saída, o caudal mássico, a relação de compressão, o rendimento isentrópico e volumétrico, o COP, a potência calorífica do gas cooler e do evaporador. Os resultados obtidos nassimulações na FCBC, mostraram que a bomba de calor garante os 50 kW requeridos, para a condição limite de temperatura ambiente de 5°C e temperatura de saída de água a 90°C, onde teria um COP de 2,5. O COP máximo obtido foi de 4,63, para a condição de operação de temperatura de saída de água de 55°C e temperatura ambiente de 35°C. Verificou-se que o aumento da temperatura ambiente e a diminuição da temperatura de saída de água requerida, implica um aumento do COP da bomba de calor. Por último, com os dados de saída da FCBC foi possível selecionar os componentes principais da bomba de calor. Definido os equipamentos, é ainda enquadrado a bomba de calor perante os requisitos mínimos de eficiência de acordo com a legislação portuguesa, assim como da elegibilidade da mesma no contributo renovável de energia.
The recent reappearing of CO2 systems is justified either by environmental reasons, economic and legal reasons, as a consequence of the restrictions imposed by the European Commission, specifically as the regulation for the use of fluorinated greenhouse gases, designated by F-gas. The present dissertation developed the project of an air-water heat pump of 50kW for sanitary water heating production, using, as refrigerant fluid, CO2 in a transcritical regime. This system has been earning recognition and strength in the global market of sanitary water heating production equipment, thanks to its significant energy efficiency that contributes to the reduction of energy consumption in areas such as residential, commercial, and service buildings. The initial phase of work began with the identification and analysis of current technologies of transcritical cycles towards the process of getting hot sanitary water, a study that defined the principle to be followed in the heating water pump project. As a way to analyze the system's performance and functioning variations of the refrigeration cycle and additionally, to obtain the required parameters for the selection of the necessary equipment, has been implemented in Microsoft Excel a heat pump calculation tool, modeled as a resource of experimental correlations, databases, and equations of thermodynamics applied in the transcritical cycle of CO2. Based on input data, that is, the operating conditions, the heat pump calculation tool has as output data, mass flow, compression ratio, isentropic and volumetric yield, COP, and the heating power of gas cooler and evaporator. The results obtained from the simulations in the heat pump calculation tool have shown that the heating pump guarantees the required 50kW, for the ambient temperature limit condition of 5°C and the water outlet temperature at 90°C, where there would be a COP of 2,5. The maximum COP obtained was 4,63, as for the operating condition of water outlet temperature of 55°C and ambient temperature of 35°C. It was found that the increase in the ambient temperature and decrease in the temperature of the required water outlet, implies an increase in the COP of the heat pump. Last, with the obtained outlet data in the heat pump calculation tool, was possible to select the main components of the heat pump. After defining the equipment, it still framed the heat pump to the minimum efficiency requirements according to the Portuguese legislation, as well as gives it eligibility for the renewable energy contribution.
The recent reappearing of CO2 systems is justified either by environmental reasons, economic and legal reasons, as a consequence of the restrictions imposed by the European Commission, specifically as the regulation for the use of fluorinated greenhouse gases, designated by F-gas. The present dissertation developed the project of an air-water heat pump of 50kW for sanitary water heating production, using, as refrigerant fluid, CO2 in a transcritical regime. This system has been earning recognition and strength in the global market of sanitary water heating production equipment, thanks to its significant energy efficiency that contributes to the reduction of energy consumption in areas such as residential, commercial, and service buildings. The initial phase of work began with the identification and analysis of current technologies of transcritical cycles towards the process of getting hot sanitary water, a study that defined the principle to be followed in the heating water pump project. As a way to analyze the system's performance and functioning variations of the refrigeration cycle and additionally, to obtain the required parameters for the selection of the necessary equipment, has been implemented in Microsoft Excel a heat pump calculation tool, modeled as a resource of experimental correlations, databases, and equations of thermodynamics applied in the transcritical cycle of CO2. Based on input data, that is, the operating conditions, the heat pump calculation tool has as output data, mass flow, compression ratio, isentropic and volumetric yield, COP, and the heating power of gas cooler and evaporator. The results obtained from the simulations in the heat pump calculation tool have shown that the heating pump guarantees the required 50kW, for the ambient temperature limit condition of 5°C and the water outlet temperature at 90°C, where there would be a COP of 2,5. The maximum COP obtained was 4,63, as for the operating condition of water outlet temperature of 55°C and ambient temperature of 35°C. It was found that the increase in the ambient temperature and decrease in the temperature of the required water outlet, implies an increase in the COP of the heat pump. Last, with the obtained outlet data in the heat pump calculation tool, was possible to select the main components of the heat pump. After defining the equipment, it still framed the heat pump to the minimum efficiency requirements according to the Portuguese legislation, as well as gives it eligibility for the renewable energy contribution.
Description
Keywords
Bomba de Calor CO2 Regime transcrítico COP Heat pump Transcritical regime