Simulação do processo de resfriamento de grãos usando a mecânica dos fluidos computacional

• Ano de defesa: 2009
• Autor(a) principal: Coelho, Marcelo Pereira
• Orientador(a): Lacerda Filho, Adílio Flauzino de
• Banca de defesa: Queiroz, Daniel Marçal de , Martins, José Helvécio , Monteiro, Paulo Marcos de Barros
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Viçosa
• Programa de Pós-Graduação: Mestrado em Engenharia Agrícola
• Departamento: Construções rurais e ambiência; Energia na agricultura; Mecanização agrícola; Processamento de produ
• País: BR
• Palavras-chave em Português: Escoamento em meios porosos; Resfriamento de grãos; Volumes finitos
• Palavras-chave em Inglês: Flow in porous media; Cooling grain; Finite volume
• Área do conhecimento CNPq: CNPQ::CIENCIAS AGRARIAS::ENGENHARIA AGRICOLA
• Link de acesso: http://locus.ufv.br/handle/123456789/3548

The cropping season of 2007/2008 was one of the highest in the history of Brazil, in which were produced around 143.87 millions of tons, emphasizing corn and soybeans which corresponds approximately 84 % of this total. Aeration process aims to maintain the initial quality of the grain during storage, with the goal to keep the temperature of the grain at low levels, inhibiting the plague development. However, in tropical or subtropical sites, is difficult to successfully use aeration with the air temperature, being necessary to cool the air in order to proceed to the aeration process. In this context, the computational fluid dynamics (CFD) is an important technique to predict, manipulate and study the cooling processes in grain storage systems. Being that stated, the objective of this work was to model the cooling process of stored bulk grains utilizing the CFD technique applied to porous media. An advection-diffusion transient one-dimensional case with a known analytical solution was simulated. The simulations were made varying the Péclet number (Pe), with the goal to verify if the program ANSYS CFX sp1 possesses any limitations regarding the solution of this kind of issues. The second case was a study of the air flow in a fixed porous bed, considering the porosity variation due to the grains compaction, in which the experimental measurements accomplished by Devilla et al. (2005) were compared with the obtained results provided by the simulations. The third studied case was a problem of soybeans cooling in a fixed bed, validated by experimental data. Concerning the first case, it was observed that lowest values of Pe led to higher scalar gradient between the entrance and exit of the column (predominance of the diffusive term). It was also observed that for high values of Pe, a downscaling of the mesh must be made to minimize the effect of false diffusion. Nonetheless, the software did not present any limitations that would not allow the analysis of the advective-diffusive problems. The obtained results through the proposed model on the second case presented a good fit in relation to the experimental data. The associated relative error is low (6.86 %) and the difference in relation to the experimental data can be explained due to the fact that the axial and radial porosity variation was not considered due to the fine accumulation. The proposed model is valid and allows the simulation of air flow systems in silos. The results of the third case demonstrate the good concordance among the experimental results, confirming the proposed model validity. Thus, it was concluded that the proposed thermo fluid dynamic model in porous media to cooling is valid and can be used in another studies of grain cooling systems.