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Advisor(s)
Abstract(s)
A refrigeração, numa perspetiva doméstica ou industrial, assume um papel preponderante na
sociedade. Possuindo como principal objetivo a minimização dos processos de de organismos bacteriais, despontou nas civilizações antigas como um processo de
armazenamento de gelo natural no inverno, para utilização posterior no verão. Hoje em dia,
grande parte dos processos de refrigeração são dirigidos principalmente, ao armazenamento
de produtos alimentares e ao arrefecimento de espaços fechados.
A necessidade de obtenção de temperaturas inferiores às existentes no meio ambiente para
conforto térmico e conservação de alimentos é atualmente inevitável. Assim, exige-se que os
sistemas de refrigeração, em particular o componente permutador de calor, opere a
temperaturas inferiores às do ponto de congelação da água, facto que inequivocamente
propicia a formação de gelo nas suas superfícies. A formação de gelo é prejudicial para o
sistema a nível energético e térmico pelo que, a sua atenuação ou remoço é essencial, de
modo a garantir as condições de funcionamento desejadas. Para determinar as medidas de
atenuação da formação de gelo mais eficientes, é importante perceber quais os fatores que
influenciam a sua formação e qual a sua contribuição individual.
É no contexto da otimização de sistemas de refrigeração, que surge o desenvolvimento da
presente dissertação, onde foram estudadas condições de operação no sentido de aumentar a
estabilidade da potência térmica do banco de evaporadores em estudo. Foi feita também uma
análise minuciosa de todos os parâmetros críticos da formação de gelo, como por exemplo os
valores de humidade relativa e de temperatura dos fluidos refrigerantes no sentido de se
determinar qual das condições permite um melhor desempenho.
Os resultados do estudo experimental desenvolvido, revelam que as condições de operação com
desativação estratégica da circulação de fluido no permutador de calor revelou ser uma
condição de operação viável, uma vez que permitiu um prolongamento do processo de
arrefecimento e a potência térmica se manteve estável.
Refrigeration, in a domestic or industrial point of view, takes a very important role in society. Once its main objective is the minimization of the formation of bacterial entities, it blunted in the old civilizations as a process of natural ice storage in the winter, for subsequent use in the summer. Nowadays, a big portion of the refrigeration processes are taken into account in the food and drinks storage, and also in the cooling of closed spaces. The need to obtain lower temperatures that exists in the environment for thermal comfort and food preservation is now inevitable, therefore it is required that the cooling systems, in particular the evaporator component, operate at lower temperatures than the water freezing point, a fact which clearly favors the formation of ice on their surfaces. The ice formation is detrimental to the system at thermal and energy level’s, reason why its mitigation or removal is essential to ensure the desired operating conditions. In order to determinate the most efficient attenuation measurements in the ice formation it’s important to realize which factors influence it’s formation and what is their contribution. It is in the context of the optimization of refrigeration systems that the development of the present dissertation arises, where two operating conditions were studied in order to increase the stability thermal power of the evaporator bank under study. A thorough analysis was also made of all critical ice formation parameters, such as the relative humidity and coolant temperature values in order to determine which offers a better performance. The results of the experimental study showed the operating conditions with the strategic deactivation of the refrigerant circulation proved to be a viable operating condition since it allowed a prolongation of the refrigeration cycle and thermal power was stable during the operating time.
Refrigeration, in a domestic or industrial point of view, takes a very important role in society. Once its main objective is the minimization of the formation of bacterial entities, it blunted in the old civilizations as a process of natural ice storage in the winter, for subsequent use in the summer. Nowadays, a big portion of the refrigeration processes are taken into account in the food and drinks storage, and also in the cooling of closed spaces. The need to obtain lower temperatures that exists in the environment for thermal comfort and food preservation is now inevitable, therefore it is required that the cooling systems, in particular the evaporator component, operate at lower temperatures than the water freezing point, a fact which clearly favors the formation of ice on their surfaces. The ice formation is detrimental to the system at thermal and energy level’s, reason why its mitigation or removal is essential to ensure the desired operating conditions. In order to determinate the most efficient attenuation measurements in the ice formation it’s important to realize which factors influence it’s formation and what is their contribution. It is in the context of the optimization of refrigeration systems that the development of the present dissertation arises, where two operating conditions were studied in order to increase the stability thermal power of the evaporator bank under study. A thorough analysis was also made of all critical ice formation parameters, such as the relative humidity and coolant temperature values in order to determine which offers a better performance. The results of the experimental study showed the operating conditions with the strategic deactivation of the refrigerant circulation proved to be a viable operating condition since it allowed a prolongation of the refrigeration cycle and thermal power was stable during the operating time.
Description
Keywords
Atenuação Descongelação Evaporador Formação de Gelo Permutador de Calor Potência Térmica Refrigeração