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Advisor(s)
Abstract(s)
A realização do presente trabalho passou por determinar a tecnologia mais eficiente para a conservação de produtos frutícolas com temperaturas positivas e com potências frigoríficas até 250 kW. Desta forma apresentaram-se soluções industriais para preservar determinados bens de primeira necessidade através de ciclos termodinâmicos nomeadamente, ciclos de compressão de vapor, tendo em consideração que são os mais utilizados na conservação alimentar. A seleção dos fluidos frigorígenos para combater as alterações climáticas passa por adotar fluidos naturais, fluidos HFO e misturas HFC-HFO com reduzido GWP e nulo OPD. Relativamente à análise de produtos frutícolas, evidenciou-se que a produção de laranjas apresentou um crescimento gradual entre 2016 e 2021 de 21,5 %, pelo que exibiu a segunda maior produção em 2021 com 363 918 t. A produção deste fruto encontra-se focalizada na região do Algarve com 77,6%, tendo sido este o fruto selecionado para conservar. Estudos realizados à operacionalidade dos sistemas de compressão simples permitiram observar o impacto que os mesmos têm sobre a eficiência energética. Realizaram-se análises ao impacto das temperaturas de condensação, das temperaturas de evaporação, dos sobreaquecimentos útil e não útil, do subarrefecimento e dos múltiplos estágios de compressão. Construiu-se um sistema aplicável para determinar qual o fluido mais eficiente tanto energética com exergeticamente. Inferiu-se que o sistema aplicável com o fluido R-717 apresenta-se como a melhor solução com um 𝐶𝑂𝑃𝑅𝑒𝑎𝑙 de 3,38 (4,44 com o adiabático em funcionamento). Para além disso o funcionamento do sistema aplicável com R-717 exibiu a menor energia destruída com 47,0 kW (29,5 kW com adiabático). Para as condições de funcionamento impostas para a conservação de laranjas, as propriedades termodinâmicas do R-717 destacam-se sobre os outros fluidos analisados. Os custos de investimento e de manutenção com a utilização do R-717 foram os mais acessíveis. No dimensionamento da instalação refrigerada inferiu-se que, para a área das câmaras de conservação e para o número apresentado de trabalhadores, não existem restrições à quantidade de R-717 utilizado no sistema. Concluiu-se, através da realização de um balanço térmico, que é possível conservar uma quantidade aproximada de laranjas de 104,37 t.
The realization of the present work involved determining the most efficient technology for the conservation of fruit products at positive temperatures and with refrigerating powers of up to 250 kW. In this way, industrial solutions were presented to preserve certain essential goods through thermodynamic cycles, namely, steam compression cycles, taking into account that they are the most used in food preservation. The selection of refrigerants to combat climate change involves adopting natural fluids, HFO fluids and HFC-HFO blends with low GWP and zero OPD. Regarding the analysis of fruit products, it was evidenced that the production of oranges showed a gradual growth between 2016 and 2021 of 21.5%, so it exhibited the second highest production in 2021 with 363,918 t. The production of this fruit is focused on the Algarve region with 77.6%, and this was the fruit selected for conservation. Studies carried out on the operation of simple compression systems allowed observing the impact they have on energy efficiency. Analyzes were carried out on the impact of condensing temperatures, evaporation temperatures, useful and non-useful superheating, subcooling and multiple stages of compression. An applicable system was built to determine which fluid is the most efficient both energetically and exergetically. It was inferred that the system applicable with the fluid R-717 presents itself as the best solution with a 𝐶𝑂𝑃𝑅𝑒𝑎𝑙 of 3.38 (4.44 with the adiabatic in operation). Furthermore, the operation of the applicable system with R-717 exhibited the lowest exergy destroyed with 47.0 kW (29.5 kW with adiabatic). For the operating conditions imposed for the conservation of oranges, the thermodynamic properties of R-717 stand out over the other fluids analyzed. Investment and maintenance costs with the use of R-717 were the most affordable. In the dimensioning of the refrigerated installation, it was inferred that, for the area of the conservation chambers and for the number of workers presented, there are no restrictions on the charge of R-717 used in the system. It was concluded, by carrying out a thermal balance, that it is possible to preserve an approximate quantity of oranges of 104.37 t.
The realization of the present work involved determining the most efficient technology for the conservation of fruit products at positive temperatures and with refrigerating powers of up to 250 kW. In this way, industrial solutions were presented to preserve certain essential goods through thermodynamic cycles, namely, steam compression cycles, taking into account that they are the most used in food preservation. The selection of refrigerants to combat climate change involves adopting natural fluids, HFO fluids and HFC-HFO blends with low GWP and zero OPD. Regarding the analysis of fruit products, it was evidenced that the production of oranges showed a gradual growth between 2016 and 2021 of 21.5%, so it exhibited the second highest production in 2021 with 363,918 t. The production of this fruit is focused on the Algarve region with 77.6%, and this was the fruit selected for conservation. Studies carried out on the operation of simple compression systems allowed observing the impact they have on energy efficiency. Analyzes were carried out on the impact of condensing temperatures, evaporation temperatures, useful and non-useful superheating, subcooling and multiple stages of compression. An applicable system was built to determine which fluid is the most efficient both energetically and exergetically. It was inferred that the system applicable with the fluid R-717 presents itself as the best solution with a 𝐶𝑂𝑃𝑅𝑒𝑎𝑙 of 3.38 (4.44 with the adiabatic in operation). Furthermore, the operation of the applicable system with R-717 exhibited the lowest exergy destroyed with 47.0 kW (29.5 kW with adiabatic). For the operating conditions imposed for the conservation of oranges, the thermodynamic properties of R-717 stand out over the other fluids analyzed. Investment and maintenance costs with the use of R-717 were the most affordable. In the dimensioning of the refrigerated installation, it was inferred that, for the area of the conservation chambers and for the number of workers presented, there are no restrictions on the charge of R-717 used in the system. It was concluded, by carrying out a thermal balance, that it is possible to preserve an approximate quantity of oranges of 104.37 t.
Description
Estágio de natureza profissional para obtenção do grau de Mestre em Engenharia Mecânica.
Keywords
Ciclo de compressão de vapor Fluidos frigorígenos Laranjas Eficiência energética Energia Sistema de refrigeração Vapor compression cycle Refrigerant fluids Oranges Energy efficiency Energy Refrigeration system
Citation
PEREIRA, José Emanuel Alves Dinis - Seleção da tecnologia mais eficiente para instalações refrigeradas sem temperaturas negativas para potências até 250 kW. Lisboa: Instituto Superior de Engenharia de Lisboa, 2022. Dissertação de Mestrado.