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Abstract(s)
A eficiência energética assume atualmente uma das maiores preocupações da sociedade, aos pequenos e grandes consumidores de energia exige-se o uso racional e eficiente das fontes de produção existentes, e aos fabricantes de sistemas elétricos exige-se o desenvolvimento e produção de equipamentos energeticamente eficientes. A refrigeração assume uma das frações mais significativas do consumo energético a nível mundial, pelo que o aumento da eficiência dos sistemas de refrigeração é um desafio no seio da engenharia.
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 evaporador, operem 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 remoção 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.
Com o presente trabalho analisou-se a influência da temperatura do ar, humidade do ar e caudal volúmico do ar na formação de gelo num permutador de calor. A acoplação deste componente a uma unidade de tratamento de ar permitiu com o auxílio de uma unidade de ar condicionado e uma unidade de arrefecimento a variação das condições de ensaio. A adequada monitorização de todo o sistema possibilitou a observação minuciosa da formação de gelo nas diversas situações distintas. Adicionalmente realizaram-se dois ensaios com interrupção da unidade de arrefecimento com intuito de observar a eficácia de uma medida de atenuação da formação de gelo inovadora proposta neste trabalho.
Dos resultados obtidos concluiu-se que a formação de gelo acentua-se com o aumento da humidade relativa do ar, com a diminuição da temperatura do ar ou com a diminuição do caudal volúmico do ar. Verificou-se ainda que a existência de um ciclo de descongelação estratégico durante o tempo de funcionamento é benéfico para o sistema de refrigeração em estudo, atenuando significativamente a formação de gelo no permutador de calor.
The energy efficiency currently takes one of the largest concerns of society, for small and large consumers of energy it’s required the rational and efficient use of existing production sources, and to the manufacturers of electrical systems it’s required the development and production of energy-efficient equipment. The cooling takes on a significant fraction of the energy consumption in the world, for that the increase of the efficiency of the refrigeration systems is a challenge in engineering. 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. The present study examined the influence of air temperature, air humidity and volume flow of air in ice formation in a heat exchanger. The union of this component to an air handler allowed, with the assistance of an air conditioner unit and a cooling unit, the variation in the testing conditions. A proper monitoring of the entire system allowed the thorough observation of the ice formation in distinct situations. Additionally, two trials were conducted with interruption of the cooling unit in order to observe a measure of attenuation in ice formation. From the results obtained it was concluded that the ice formation is accentuated with the increase of relative air humidity, with a decrease in the air temperature or with decreasing the volume flow of air. It was also found that the existence of a defrosting cycle during the operation time is beneficial for the cooling system in study, significantly reducing the ice formation in the heat exchanger.
The energy efficiency currently takes one of the largest concerns of society, for small and large consumers of energy it’s required the rational and efficient use of existing production sources, and to the manufacturers of electrical systems it’s required the development and production of energy-efficient equipment. The cooling takes on a significant fraction of the energy consumption in the world, for that the increase of the efficiency of the refrigeration systems is a challenge in engineering. 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. The present study examined the influence of air temperature, air humidity and volume flow of air in ice formation in a heat exchanger. The union of this component to an air handler allowed, with the assistance of an air conditioner unit and a cooling unit, the variation in the testing conditions. A proper monitoring of the entire system allowed the thorough observation of the ice formation in distinct situations. Additionally, two trials were conducted with interruption of the cooling unit in order to observe a measure of attenuation in ice formation. From the results obtained it was concluded that the ice formation is accentuated with the increase of relative air humidity, with a decrease in the air temperature or with decreasing the volume flow of air. It was also found that the existence of a defrosting cycle during the operation time is beneficial for the cooling system in study, significantly reducing the ice formation in the heat exchanger.
Description
Keywords
Evaporador Formação de Gelo Permutador de Calor Sistema de Refrigeração