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Advisor(s)
Abstract(s)
A refrigeração é fundamental na vida do Homem e, devido à sua importância, é responsável
por impactos significativos sobre o meio ambiente. Alterações legislativas recentes forçam
o setor da refrigeração a convergir por um caminho mais sustentável e ecológico, tornandose
importante adotar alternativas à utilização de hidrofluorocarbonetos.
Numa primeira fase, foi desenvolvida uma ferramenta de projeto com o intuito de calcular a
potência térmica das câmaras frigoríficas destinadas à congelação ou conservação, positiva
ou negativa, de produtos. O método comparativo foi utilizado para validar a ferramenta,
comparando-se os resultados de quatro casos práticos com os valores obtidos por outras
cinco ferramentas de cálculo. Através deste método, os desvios relativos entre a ferramenta
desenvolvida e os restantes programas, variaram entre 12,5% e -39,6%. Porém, aferiu-se que
os desvios se encontram, maioritariamente, associados a pressupostos existentes nos
diferentes programas. Nos casos de conservação a gama de desvios obtida para os dois
programas mais similares encontra-se entre os 4,7% e os -9,8%, valores enquadrados com
os desvios máximos de ±10% recomendados pela literatura do setor. Relativamente ao caso
prático de congelação uma das ferramentas apresentou um desvio de 1,9% relativo à carga
térmica total, porém nas cargas térmicas parcelares atingiram-se desvios de 39%, mostrando
que não é viável analisar apenas os desvios das cargas totais.
Na segunda fase, procurou-se adotar soluções compatíveis com a utilização de
hidrocarbonetos nos circuitos de frio. Verificou-se que o mercado ainda se encontra a
caminhar para estas soluções, tendo a solução encontrada sido a utilização de unidades
compactas adequadas à utilização de R290 e R1270. Porém, esta solução não permite efetuar
a seleção individualizada dos seus componentes.
Este estudo permitiu identificar que existem, oportunidades de melhoria no modelo de
cálculo de ganhos de calor através do solo, assim como, desenvolvimentos para a conceção
do sistema de frio com fluidos naturais.
Refrigeration is crucial in the man’s life, and because of its importance, is responsible for significant impacts on the environment. Recent legislative changes force the refrigeration sector to converge for a more sustainable and environmentally friendly, making it important to adopt alternatives to the use of hydrofluorocarbons. In the first phase, a design tool was developed to calculate the thermal power of the refrigerating chambers intended for freezing or conservation, positive or negative, of products. The comparative method was used to validate the tool, comparing the results of four practical cases with values obtained for five other design tools. The deviations between the developed tool and other design tools, were in the range from, -39.6% to +12.5%. However, it was noted that deviations are mostly associated with the assumptions of each design tool. For the conservation chambers, the range of deviations obtained were lying between -9.8% and +4.7%, which are in per the maximum deviation of ± 10% of the sector recommended literature. Regarding the freezing case, one of the tools presented a deviation of 1.9% relative to the total thermal load, but regarding its various partial thermal loads, was found a deviation of 39%, which means that it is not feasible to analyze only the total deviations for validating the refrigeration chamber design tools. In the second phase, it was tried to adopt equipment solutions compatible with the use of hydrocarbons. It was found that the market is still heading for these solutions, and so the chosen solutions were compact units appropriate to the use of R290 and R1270. However, these solutions do not allow to make the individualized selection of its components. This study revealed that there are opportunities for improvement in heat gains calculation model through the soil, as well as developments for the design of the cooling system with natural fluids.
Refrigeration is crucial in the man’s life, and because of its importance, is responsible for significant impacts on the environment. Recent legislative changes force the refrigeration sector to converge for a more sustainable and environmentally friendly, making it important to adopt alternatives to the use of hydrofluorocarbons. In the first phase, a design tool was developed to calculate the thermal power of the refrigerating chambers intended for freezing or conservation, positive or negative, of products. The comparative method was used to validate the tool, comparing the results of four practical cases with values obtained for five other design tools. The deviations between the developed tool and other design tools, were in the range from, -39.6% to +12.5%. However, it was noted that deviations are mostly associated with the assumptions of each design tool. For the conservation chambers, the range of deviations obtained were lying between -9.8% and +4.7%, which are in per the maximum deviation of ± 10% of the sector recommended literature. Regarding the freezing case, one of the tools presented a deviation of 1.9% relative to the total thermal load, but regarding its various partial thermal loads, was found a deviation of 39%, which means that it is not feasible to analyze only the total deviations for validating the refrigeration chamber design tools. In the second phase, it was tried to adopt equipment solutions compatible with the use of hydrocarbons. It was found that the market is still heading for these solutions, and so the chosen solutions were compact units appropriate to the use of R290 and R1270. However, these solutions do not allow to make the individualized selection of its components. This study revealed that there are opportunities for improvement in heat gains calculation model through the soil, as well as developments for the design of the cooling system with natural fluids.
Description
Keywords
Câmara de refrigeração Congelação Carga Frigorífica Fluidos Frigorigéneos Naturais R290 Freezing Natural Refrigerant Refrigeration Chamber Thermal Loads