Modelagem, simulação e otimização de secadores convectivos de grãos : determinação da eficiência energética

Detalhes bibliográficos
Autor(a) principal: Johann, Gracielle
Data de Publicação: 2016
Tipo de documento: Tese
Idioma: por
Título da fonte: Repositório Institucional da Universidade Estadual de Maringá (RI-UEM)
dARK ID: ark:/35916/001300000231c
Texto Completo: http://repositorio.uem.br:8080/jspui/handle/1/3659
Resumo: Brazilian agribusiness is one of the most important sources of riches for Brazil, so that the country has a great potential for agricultural production. This, in turn, has increased significantly in recent decades, with a view to inclusion of new production technologies. However, this good productive performance is not accompanied by improvements in post-harvest activities, such as drying, processing, and especially in grain storage. The function of the storage of agricultural products is to ensure the continuous supply of this production in the consumer centers. Thus, the practice of storage and the associated operations, such as cleaning, drying and prophylactic treatments of grains, are part of a strategic planning context, essential for ensuring social and economic stability of any country. Theoretical analysis and modeling grain dryers activities are complex due to the number of factors involved. Obtaining phenomenological models that describe the drying process is of great interest, since they can be used to predict the drying time, when it is carried out at different processing conditions. Since the evaluation of the energy consumption in drying, objective look into the drying conditions that lead to lower energy consumption, where for maintaining the quality of the final product and the lowest processing cost. Thus, this thesis proposes the numerical study of grain drying processes of grapes, Cabernet Sauvignon, and crambe, including modeling, simulation and optimization of dryers in forced convection. It was studied numerically the thin layer drying of grape grains, with distributed parameters, and tested two drying rates. For the employment of the first drying rate, the coefficients effective mass diffusivity and drying constant were estimated. Since, for the second drying rate were adjusted values of the effective mass diffusivity coefficient and the convective mass transfer coefficient. Finally, we tested the equilibrium boundary condition on the surface of the grains. The model that best suited to the experimental data was one in which were estimated the coefficient of effective mass diffusivity and the mass convective transfer coefficient. With these values, it was proved the equivalence of the results obtained using the model of distributed parameters and the concentrated parameters. To this end, it was employed the values of effective mass diffusivity and convective mass transfer coefficient, obtained in thin layer drying study of grape grain with distributed parameters, in the deep bed and lumped parameters model, with double resistance to mass transfer. Energy optimization of the grape and crambe grains drying process in fixed bed, with and without recirculation of exhaust air of the convective dryer, was studied. The behavior of the energy efficiency, defined as the ratio between the amount of energy used in the removal of moisture, to the energy required to heat the drying air, from ambient to the dryer operating temperature, was similar for both grains. The simulations were conducted until the bed of grains reached 13% of average humidity, and set restrictions on the process was 50°C≤TGfeed≤80 °C, 1 m/s≤v≤5 m/s, 0%≤q≤100%. The increased energy efficiency, disregarding the recycling of the drying air, was obtained at 50 °C and 1 m/s. These were milder drying conditions imposed by the set of constraints considered. For the grape grains, maximum efficiency was 2,27% and for the crambe grain 3,06%. The specific energy consumption was lower as was the lower the air flow in the dryer. In the case of grape grains, energy efficiency, generated by reusing the exhaust air was 12,07% and crambe grain 13,26%, both for the dryer operating at 80 °C and 1 m/s, and 99 and 97% recirculation ratio, respectively. Thus, it was concluded that the use of lower drying air flow are recommended for convective drying of grains both in conventional dryers, as those operated with recirculation of the bed air outlet. Since also for both grains, when the dryer was operated conventionally without exhaust air recycling, greater efficiencies have been achieved at lower temperatures. However, when the device was provided with recirculation of exhaust air, the higher the operating temperature of the process, the higher the efficiency.
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spelling Modelagem, simulação e otimização de secadores convectivos de grãos : determinação da eficiência energéticaModeling, simulation and optimization of convective grain dryers: determination of energetic efficiencySecador de grãosConvecção forçadaModelagem e otimizaçãoBrasil.Grain dryersForced convectionModeling and optimizationBrazil.EngenhariasEngenharia QuímicaBrazilian agribusiness is one of the most important sources of riches for Brazil, so that the country has a great potential for agricultural production. This, in turn, has increased significantly in recent decades, with a view to inclusion of new production technologies. However, this good productive performance is not accompanied by improvements in post-harvest activities, such as drying, processing, and especially in grain storage. The function of the storage of agricultural products is to ensure the continuous supply of this production in the consumer centers. Thus, the practice of storage and the associated operations, such as cleaning, drying and prophylactic treatments of grains, are part of a strategic planning context, essential for ensuring social and economic stability of any country. Theoretical analysis and modeling grain dryers activities are complex due to the number of factors involved. Obtaining phenomenological models that describe the drying process is of great interest, since they can be used to predict the drying time, when it is carried out at different processing conditions. Since the evaluation of the energy consumption in drying, objective look into the drying conditions that lead to lower energy consumption, where for maintaining the quality of the final product and the lowest processing cost. Thus, this thesis proposes the numerical study of grain drying processes of grapes, Cabernet Sauvignon, and crambe, including modeling, simulation and optimization of dryers in forced convection. It was studied numerically the thin layer drying of grape grains, with distributed parameters, and tested two drying rates. For the employment of the first drying rate, the coefficients effective mass diffusivity and drying constant were estimated. Since, for the second drying rate were adjusted values of the effective mass diffusivity coefficient and the convective mass transfer coefficient. Finally, we tested the equilibrium boundary condition on the surface of the grains. The model that best suited to the experimental data was one in which were estimated the coefficient of effective mass diffusivity and the mass convective transfer coefficient. With these values, it was proved the equivalence of the results obtained using the model of distributed parameters and the concentrated parameters. To this end, it was employed the values of effective mass diffusivity and convective mass transfer coefficient, obtained in thin layer drying study of grape grain with distributed parameters, in the deep bed and lumped parameters model, with double resistance to mass transfer. Energy optimization of the grape and crambe grains drying process in fixed bed, with and without recirculation of exhaust air of the convective dryer, was studied. The behavior of the energy efficiency, defined as the ratio between the amount of energy used in the removal of moisture, to the energy required to heat the drying air, from ambient to the dryer operating temperature, was similar for both grains. The simulations were conducted until the bed of grains reached 13% of average humidity, and set restrictions on the process was 50°C≤TGfeed≤80 °C, 1 m/s≤v≤5 m/s, 0%≤q≤100%. The increased energy efficiency, disregarding the recycling of the drying air, was obtained at 50 °C and 1 m/s. These were milder drying conditions imposed by the set of constraints considered. For the grape grains, maximum efficiency was 2,27% and for the crambe grain 3,06%. The specific energy consumption was lower as was the lower the air flow in the dryer. In the case of grape grains, energy efficiency, generated by reusing the exhaust air was 12,07% and crambe grain 13,26%, both for the dryer operating at 80 °C and 1 m/s, and 99 and 97% recirculation ratio, respectively. Thus, it was concluded that the use of lower drying air flow are recommended for convective drying of grains both in conventional dryers, as those operated with recirculation of the bed air outlet. Since also for both grains, when the dryer was operated conventionally without exhaust air recycling, greater efficiencies have been achieved at lower temperatures. However, when the device was provided with recirculation of exhaust air, the higher the operating temperature of the process, the higher the efficiency.O agronegócio brasileiro é uma das mais importantes fontes geradoras de riquezas para o Brasil, de modo que o país apresenta grande potencial de produção agrícola. Este, por sua vez, vem crescendo significativamente nas últimas décadas. No entanto, esse bom desempenho produtivo não é acompanhado por melhorias nas atividades de pós colheita, como na secagem, no beneficiamento e, principalmente, no armazenamento de grãos. A função da armazenagem dos produtos agrícolas é garantir a oferta contínua dessa produção nos centros consumidores. Dessa forma, a prática de armazenamento e as operações associadas, tais como limpeza, secagem e tratamentos profiláticos dos grãos, se inserem num contexto de planejamento estratégico, fundamental para garantir a estabilidade social e econômica de qualquer país. A análise teórica e a modelagem de secadores de grãos são atividades complexas, devido ao número de fatores envolvidos. A obtenção de modelos fenomenológicos que descrevam o processo de secagem é de grande interesse, uma vez que podem ser utilizados para predição do tempo de secagem, quando esta é conduzida em diferentes condições de processamento. Já a avaliação do consumo de energia na secagem, objetiva averiguar as condições de secagem que levem ao menor consumo energético, sempre garantindo a manutenção da qualidade final do produto e o menor custo de processamento. Assim, o presente trabalho propôs o estudo numérico do processo de secagem de grãos de uva, variedade Cabernet Sauvignon, e de crambe, abrangendo a modelagem, simulação e otimização de secadores em convecção forçada. Foi estudada numericamente a secagem em camada fina, com parâmetros distribuídos, de grãos de uva, e testadas duas taxas de secagem. Para o emprego da primeira taxa de secagem, foram estimados os coeficientes difusividade mássica efetiva e constante de secagem. Já, para a segunda taxa de secagem, foram ajustados os valores do coeficiente de difusividade mássica efetiva e do coeficiente de transferência convectiva de massa. Por fim, foi testada a condição de contorno de equilíbrio na superfície dos grãos. O modelo que melhor se adequou aos dados experimentais foi aquele em que foram estimados o coeficiente de difusividade mássica efetiva e o coeficiente de transferência convectiva de massa. De posse desses valores, foi provada a equivalência entre os resultados obtidos empregando o modelo de parâmetros distribuídos e o de parâmetros concentrados. Para tal, empregaram-se os valores da difusividade mássica efetiva e do coeficiente de transferência convectiva de massa, obtidos no estudo de secagem de grãos de uva em camada fina com parâmetros distribuídos, no modelo de leito profundo e de parâmetros concentrados, com dupla resistência à transferência de massa. Foi estudada a otimização energética do processo de secagem de grãos de uva e de crambe em leito fixo, sem e com a recirculação do ar de exaustão do secador convectivo. O comportamento da eficiência energética, definida como sendo a razão entre a quantidade de energia empregada na remoção da umidade, pela energia requerida para aquecer o ar de secagem, da temperatura ambiente até a temperatura de operação do secador, foi similar para ambos os grãos. As simulações foram conduzidas até que o leito de grãos atingisse 13% de umidade média, e conjunto de restrições impostas ao processo foi 50°C≤TGfeed≤80 °C, 1 m/s≤v≤5 m/s, 0%≤q≤100%. A maior eficiência energética, desconsiderando o reciclo do ar de secagem, foi obtida em 50 °C e 1 m/s. Essas foram as condições mais amenas de secagem impostas pelo conjunto de restrições considerado. Para os grãos de uva, a eficiência máxima foi de 2,27% e para os grãos de crambe 3,06%. O consumo específico de energia foi tão menor quanto menor foi o fluxo de ar no secador. Para o caso dos grãos de uva, a eficiência energética, gerada pelo reaproveitamento do ar de exaustão foi de 12,07%, e para os grãos de crambe 13,26%, ambos para o secador operando a 80 °C e 1 m/s, e 99 e 97% de razão de recirculação, respectivamente. Assim, concluiu-se que o emprego de menores vazões de ar de secagem são recomendadas, para a secagem convectiva de ambos os grãos, tanto em secadores convencionais, quanto naqueles operados com recirculação do ar de saída do leito. Já, também para ambos os grãos, quando o secador foi operado de forma convencional, sem reaproveitamento do ar de exaustão, maiores eficiências foram alcançadas com menores temperaturas. Entretanto, quando o equipamento foi provido de recirculação do ar de exaustão, quanto maior foi a temperatura de operação do processo, maior foi a eficiência.1 CD-ROM (xv, 147 f.)Universidade Estadual de MaringáBrasilDepartamento de Engenharia QuímicaPrograma de Pós-Graduação em Engenharia QuímicaUEMMaringá, PRCentro de TecnologiaNehemias Curvelo PereiraEdson Antonio da Silva - UEMIvo Neitzel - FATEBMaraísa Lopes de Menezes - UTFPREsdras Penêdo de Carvalho - UEMJohann, Gracielle2018-04-17T17:39:54Z2018-04-17T17:39:54Z2016info:eu-repo/semantics/publishedVersioninfo:eu-repo/semantics/doctoralThesishttp://repositorio.uem.br:8080/jspui/handle/1/3659ark:/35916/001300000231cporinfo:eu-repo/semantics/openAccessreponame:Repositório Institucional da Universidade Estadual de Maringá (RI-UEM)instname:Universidade Estadual de Maringá (UEM)instacron:UEM2018-10-15T18:12:13Zoai:localhost:1/3659Repositório InstitucionalPUBhttp://repositorio.uem.br:8080/oai/requestopendoar:2024-04-23T14:56:48.445734Repositório Institucional da Universidade Estadual de Maringá (RI-UEM) - Universidade Estadual de Maringá (UEM)false
dc.title.none.fl_str_mv Modelagem, simulação e otimização de secadores convectivos de grãos : determinação da eficiência energética
Modeling, simulation and optimization of convective grain dryers: determination of energetic efficiency
title Modelagem, simulação e otimização de secadores convectivos de grãos : determinação da eficiência energética
spellingShingle Modelagem, simulação e otimização de secadores convectivos de grãos : determinação da eficiência energética
Johann, Gracielle
Secador de grãos
Convecção forçada
Modelagem e otimização
Brasil.
Grain dryers
Forced convection
Modeling and optimization
Brazil.
Engenharias
Engenharia Química
title_short Modelagem, simulação e otimização de secadores convectivos de grãos : determinação da eficiência energética
title_full Modelagem, simulação e otimização de secadores convectivos de grãos : determinação da eficiência energética
title_fullStr Modelagem, simulação e otimização de secadores convectivos de grãos : determinação da eficiência energética
title_full_unstemmed Modelagem, simulação e otimização de secadores convectivos de grãos : determinação da eficiência energética
title_sort Modelagem, simulação e otimização de secadores convectivos de grãos : determinação da eficiência energética
author Johann, Gracielle
author_facet Johann, Gracielle
author_role author
dc.contributor.none.fl_str_mv Nehemias Curvelo Pereira
Edson Antonio da Silva - UEM
Ivo Neitzel - FATEB
Maraísa Lopes de Menezes - UTFPR
Esdras Penêdo de Carvalho - UEM
dc.contributor.author.fl_str_mv Johann, Gracielle
dc.subject.por.fl_str_mv Secador de grãos
Convecção forçada
Modelagem e otimização
Brasil.
Grain dryers
Forced convection
Modeling and optimization
Brazil.
Engenharias
Engenharia Química
topic Secador de grãos
Convecção forçada
Modelagem e otimização
Brasil.
Grain dryers
Forced convection
Modeling and optimization
Brazil.
Engenharias
Engenharia Química
description Brazilian agribusiness is one of the most important sources of riches for Brazil, so that the country has a great potential for agricultural production. This, in turn, has increased significantly in recent decades, with a view to inclusion of new production technologies. However, this good productive performance is not accompanied by improvements in post-harvest activities, such as drying, processing, and especially in grain storage. The function of the storage of agricultural products is to ensure the continuous supply of this production in the consumer centers. Thus, the practice of storage and the associated operations, such as cleaning, drying and prophylactic treatments of grains, are part of a strategic planning context, essential for ensuring social and economic stability of any country. Theoretical analysis and modeling grain dryers activities are complex due to the number of factors involved. Obtaining phenomenological models that describe the drying process is of great interest, since they can be used to predict the drying time, when it is carried out at different processing conditions. Since the evaluation of the energy consumption in drying, objective look into the drying conditions that lead to lower energy consumption, where for maintaining the quality of the final product and the lowest processing cost. Thus, this thesis proposes the numerical study of grain drying processes of grapes, Cabernet Sauvignon, and crambe, including modeling, simulation and optimization of dryers in forced convection. It was studied numerically the thin layer drying of grape grains, with distributed parameters, and tested two drying rates. For the employment of the first drying rate, the coefficients effective mass diffusivity and drying constant were estimated. Since, for the second drying rate were adjusted values of the effective mass diffusivity coefficient and the convective mass transfer coefficient. Finally, we tested the equilibrium boundary condition on the surface of the grains. The model that best suited to the experimental data was one in which were estimated the coefficient of effective mass diffusivity and the mass convective transfer coefficient. With these values, it was proved the equivalence of the results obtained using the model of distributed parameters and the concentrated parameters. To this end, it was employed the values of effective mass diffusivity and convective mass transfer coefficient, obtained in thin layer drying study of grape grain with distributed parameters, in the deep bed and lumped parameters model, with double resistance to mass transfer. Energy optimization of the grape and crambe grains drying process in fixed bed, with and without recirculation of exhaust air of the convective dryer, was studied. The behavior of the energy efficiency, defined as the ratio between the amount of energy used in the removal of moisture, to the energy required to heat the drying air, from ambient to the dryer operating temperature, was similar for both grains. The simulations were conducted until the bed of grains reached 13% of average humidity, and set restrictions on the process was 50°C≤TGfeed≤80 °C, 1 m/s≤v≤5 m/s, 0%≤q≤100%. The increased energy efficiency, disregarding the recycling of the drying air, was obtained at 50 °C and 1 m/s. These were milder drying conditions imposed by the set of constraints considered. For the grape grains, maximum efficiency was 2,27% and for the crambe grain 3,06%. The specific energy consumption was lower as was the lower the air flow in the dryer. In the case of grape grains, energy efficiency, generated by reusing the exhaust air was 12,07% and crambe grain 13,26%, both for the dryer operating at 80 °C and 1 m/s, and 99 and 97% recirculation ratio, respectively. Thus, it was concluded that the use of lower drying air flow are recommended for convective drying of grains both in conventional dryers, as those operated with recirculation of the bed air outlet. Since also for both grains, when the dryer was operated conventionally without exhaust air recycling, greater efficiencies have been achieved at lower temperatures. However, when the device was provided with recirculation of exhaust air, the higher the operating temperature of the process, the higher the efficiency.
publishDate 2016
dc.date.none.fl_str_mv 2016
2018-04-17T17:39:54Z
2018-04-17T17:39:54Z
dc.type.status.fl_str_mv info:eu-repo/semantics/publishedVersion
dc.type.driver.fl_str_mv info:eu-repo/semantics/doctoralThesis
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dc.identifier.uri.fl_str_mv http://repositorio.uem.br:8080/jspui/handle/1/3659
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url http://repositorio.uem.br:8080/jspui/handle/1/3659
identifier_str_mv ark:/35916/001300000231c
dc.language.iso.fl_str_mv por
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dc.rights.driver.fl_str_mv info:eu-repo/semantics/openAccess
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dc.publisher.none.fl_str_mv Universidade Estadual de Maringá
Brasil
Departamento de Engenharia Química
Programa de Pós-Graduação em Engenharia Química
UEM
Maringá, PR
Centro de Tecnologia
publisher.none.fl_str_mv Universidade Estadual de Maringá
Brasil
Departamento de Engenharia Química
Programa de Pós-Graduação em Engenharia Química
UEM
Maringá, PR
Centro de Tecnologia
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instname:Universidade Estadual de Maringá (UEM)
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instname_str Universidade Estadual de Maringá (UEM)
instacron_str UEM
institution UEM
reponame_str Repositório Institucional da Universidade Estadual de Maringá (RI-UEM)
collection Repositório Institucional da Universidade Estadual de Maringá (RI-UEM)
repository.name.fl_str_mv Repositório Institucional da Universidade Estadual de Maringá (RI-UEM) - Universidade Estadual de Maringá (UEM)
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