Sistema pneumático de secagem de grãos com gerenciamento termodinâmico do processo
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Data
2009-03-20
Autores
Faria, Antonio Eduardo de [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
Neste trabalho de pesquisa foi realizadas uma análise do comportamento de grãos de arroz submetidos à passagem de fluxos de ar com variadas condições termodinâmicas (temperatura, umidade relativa / absoluta, entalpia). Esta análise foi feita utilizando-se um recipiente com capacidade para confinar 5 litros de grãos, sendo o ar forçado a escoar pela ação da sucção de uma bomba de vácuo, promovendo assim pressões relativas menores que a atmosférica no ar de secagem, proporcionando uma migração mais facilitada das moléculas de água. Como resultado deste experimento foi obtido um consumo de energia em torno de 30 % dos sistemas convencionais de secagem à lenha com tempos de processamento de 2 horas, menores que os convencionais que consomem até 6 horas. Também foi possível determinar a distância ótima de escoamento do ar de secagem pelos grãos, em torno de 16 cm, pela análise da distribuição de pressões e temperaturas medidas através do secador protótipo . Devido ao fato do processo de secagem ser extremamente dinâmico devido as variações das características do ar ambiente (temperatura, umidade, entalpia, massa específica, etc), dos grãos provenientes do campo (arroz, feijão, milho, etc) e do combustível (lenha, casca de arroz, gás natural, etc) a ser utilizado como fonte térmica, torna-se necessária a implementação de um sistema de controle capaz de promover um gerenciamento termodinâmico do processo, ou seja, monitorar as taxas de transferência de calor e água entre os grãos e o ar de secagem em tempo real, promovendo ajustes na temperatura e intensidade do fluxo de ar de secagem, assim como a velocidade de homogeneização dos grãos dentro do leito.
In this research work an analysis of the behavior of grains of rice of the field was accomplished submitted to the passage of flows of air with several thermodynamic conditions (temperature, relative humidity / absolute, entalpia). This analysis was made being used a recipient with capacity to confine 5 liters of grains, being the forced air to drain like this for the action of the suction of a vacuum pump, promoting smaller relative pressures than the atmospheric in the drying air, promoting a facilitated migration of the molecules of water. As a result of this experiment was obtained a consumption of energy around 30% of the conventional firewood systems with times of processing of 2 hours, smaller that the conventional ones that consume 6 hours. It was also possible to determine the larger distance of drainage of the drying air for the grains around 16 cm, through the analysis of the distribution of pressures and temperatures measured through the volume. Due to the fact of the drying process to be extremely dynamic due to the variations of the characteristics of the environmental air (temperature, humidity, entalpia, specific mass, etc), grains coming of the field (rice, bean, corn, etc) and of the fuel (firewood, peel of rice, natural gas, etc) to be used as thermal source, it becomes necessary the implementation of a control system capable of promoting an thermodynamic management of the process, in other words, to follow the rates of transfer of heat and water between the grains and the drying air in real time, promoting adjustment in the temperature and intensity of the flow of drying air, as well as the speed to homogenize the grains inside of the bed.
In this research work an analysis of the behavior of grains of rice of the field was accomplished submitted to the passage of flows of air with several thermodynamic conditions (temperature, relative humidity / absolute, entalpia). This analysis was made being used a recipient with capacity to confine 5 liters of grains, being the forced air to drain like this for the action of the suction of a vacuum pump, promoting smaller relative pressures than the atmospheric in the drying air, promoting a facilitated migration of the molecules of water. As a result of this experiment was obtained a consumption of energy around 30% of the conventional firewood systems with times of processing of 2 hours, smaller that the conventional ones that consume 6 hours. It was also possible to determine the larger distance of drainage of the drying air for the grains around 16 cm, through the analysis of the distribution of pressures and temperatures measured through the volume. Due to the fact of the drying process to be extremely dynamic due to the variations of the characteristics of the environmental air (temperature, humidity, entalpia, specific mass, etc), grains coming of the field (rice, bean, corn, etc) and of the fuel (firewood, peel of rice, natural gas, etc) to be used as thermal source, it becomes necessary the implementation of a control system capable of promoting an thermodynamic management of the process, in other words, to follow the rates of transfer of heat and water between the grains and the drying air in real time, promoting adjustment in the temperature and intensity of the flow of drying air, as well as the speed to homogenize the grains inside of the bed.
Descrição
Palavras-chave
Cereais - Secagem, Termodinamica, Grãos - Processos de secagem, Grains - Drying process
Como citar
FARIA, Antonio Eduardo de. Sistema pneumático de secagem de grãos com gerenciamento termodinâmico do processo. 2009. 124 f. Tese (doutorado) - Universidade Estadual Paulista, Faculdade de Engenharia de Guaratinguetá, 2009.