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Abstract(s)
Esta tese teve como objetivo o desenvolvimento de um algoritmo de otimização do dimensionamento de secadores de alimentos por bomba de calor a ar. Seu desenvolvimento serviu para o apoio ao projeto de um protótipo de uma máquina de secagem de alimentos de pequeno porte, focada no mercado doméstico. O algoritmo focou-se na redução do tempo de cálculo para a seleção de componentes em função das dimensões do secador e do tipo de alimento.
A tese apresenta toda a base teórica utilizada para produzir este algortimo, nos ambitos da psicrometria, da transferência de calor e de massa e de como o alimento se comporta quando exposto ao ar quente para secagem. Equações de transferência de calor, de massa e de curvas de secagem, oriundas dos prícipios de conservação de massa e de energia, são indicadas e explicadas para justificar sua aplicação.
O algoritmo possui 3 etapas: cálculo psicrométrico, cálculo de carga térmica e cálculo de secagem. A lógica da sequência de ações é apontada, com o intuito de exclarecer ao leitor o funcionamento sequencial entre estas etapas que resultam no dimensionamento. Esta explicação do desenvolvimento do algoritmo é independente do código, para permitir aplicação em qualquer meio ou linguagem de programação.
Finalmente, a tese apresenta os resultados que foram obtidos pela simulação da atuação ideal de uma máquina, por meio da implementação do algoritmo em um código de MatLab. Esta simulação foi iniciada com base num desenho da arca de um frigorífico, resultando no valor do caudal mássico de fluido refrigerante necessário.
No caso foram dimensionados secadores para as seguintes massas de cogumelos: 45kg, 123kg, 200kg, 277kg e 355kg. Com o caudal obtido, foram encontrados três compressores compatíveis da EMBRACO sendo as suas potências 610W, 990W e 1445W. O primeiro compressor atendeu um secador de 45kg, o segundo até 123kg e o terceiro atende até o maior valor de 355kg.
O algoritmo resultou na publicação do artigo “Heat Pump Dryer Design Optimization Algorithm”. Além disso, foi feito o refinamento dos tempos de secagem da simulação com o uso de modelos de previsão melhores, que foram de 6 horas para uma secagem de cogumelos completa a 60°C (temperatura utilizada nos experimentos), condizentes com os valores obtidos experimentalmente e publicados de 5 horas para secagem (dado que a paragem feita experimentalmente não segue parametros tão pequenos como a simulação), o que reforça a solidez do modelo apresentado.
This thesis focused on the development of a heat pump air based dryer’s design optimization algorithm. Its development was intended to support the project development of a prototype of a home appliance type of machine. This meant that the algorithm had to reduce the time spent on calculating the parameters based on the input of the machine’s dimensions. At first the thesis present the theoretical basis used in the algorithm: from psychrometry, to heat and mass transfer and finally the hot air drying dynamics. Each of the equations that define these phenomena and plot the drying curves are pointed and its use is explained. The aforementioned equations are placed within parts of the algorithm which itself is explained and organized with commentary. The structure of the algorithm is constructed though the presentation of the inputs and outputs of each step and its equations forming the logic of the algorithm beyond any programming language. Finally the thesis presents the results of the algorithm applied in a MatLab simulation of a theoretical machine. This code used designs that were desired for a home-appliance machine and simulated the required mass flow rate of refrigerant. The total mass of mushrooms simulated to be dried were: 45kg, 123kg, 200kg, 277kg e 355kg. With the calculated mass, three compatible compressors were selected, all from EMBRACO. With their respective power output: 610W, 990W e 1445W. The first compressor can just power the 45kg dryer, the second can power up to 123kg and the third can power a drier filled with all the options, up to 355 kg. To ensure the quality of its results the algorithm was validated by the publication of the article named “Heat Pump Dryer Design Optimization Algorithm”. Also, the algorithm was refined by the improved precision of the simulation of the drying time, which was found to be 6 hours for a complete drying of mushrooms at 60°C, value that matches the ones obtained experimentally. In the experiments the drying time was of 5 hours but the parameters are slightly different since the experiment stopped when the mushroom seemed dry while the simulation stops with a pre-specified parameter.
This thesis focused on the development of a heat pump air based dryer’s design optimization algorithm. Its development was intended to support the project development of a prototype of a home appliance type of machine. This meant that the algorithm had to reduce the time spent on calculating the parameters based on the input of the machine’s dimensions. At first the thesis present the theoretical basis used in the algorithm: from psychrometry, to heat and mass transfer and finally the hot air drying dynamics. Each of the equations that define these phenomena and plot the drying curves are pointed and its use is explained. The aforementioned equations are placed within parts of the algorithm which itself is explained and organized with commentary. The structure of the algorithm is constructed though the presentation of the inputs and outputs of each step and its equations forming the logic of the algorithm beyond any programming language. Finally the thesis presents the results of the algorithm applied in a MatLab simulation of a theoretical machine. This code used designs that were desired for a home-appliance machine and simulated the required mass flow rate of refrigerant. The total mass of mushrooms simulated to be dried were: 45kg, 123kg, 200kg, 277kg e 355kg. With the calculated mass, three compatible compressors were selected, all from EMBRACO. With their respective power output: 610W, 990W e 1445W. The first compressor can just power the 45kg dryer, the second can power up to 123kg and the third can power a drier filled with all the options, up to 355 kg. To ensure the quality of its results the algorithm was validated by the publication of the article named “Heat Pump Dryer Design Optimization Algorithm”. Also, the algorithm was refined by the improved precision of the simulation of the drying time, which was found to be 6 hours for a complete drying of mushrooms at 60°C, value that matches the ones obtained experimentally. In the experiments the drying time was of 5 hours but the parameters are slightly different since the experiment stopped when the mushroom seemed dry while the simulation stops with a pre-specified parameter.
Description
Mestrado de dupla diplomação com o Centro Federal de Educação Tecnológica Celso Suckow da Fonseca - CEFET/RJ
Keywords
Secadores de alimentos Bomba de calor