This work is aimed at modeling the heat transfer mechanism in a fluidized bed of grass seeds (Brachiaria brizantha) for supporting further works on simulating the drying of these seeds in such a bed. The three-phase heat transfer model, developed by Vitor et al. (2004), is the one used for this proposal. This model is modified to uncouple one of the four adjusted model parameters from the gas temperature. Using the first set of experiments, carried out in a laboratory scale batch fluidized bed, the four adjusted model parameters are determined, generating the heat transfer coefficient between particles and gas phase, as well as the heat transfer coefficient between the column wall and ambient air. The second set of experiments, performed in the same unit at different conditions, validates the modified model.

Este trabalho teve como objetivo investigar o efeito da distribuição granulométrica sobre parâmetros de permeabilidade, porosidade aparente e secagem de concretos refratários de alta alumina. Verificou-se a influência de ambas as distribuições discreta e acumulada, baseadas no modelo de empacotamento de Andreasen. Ensaios de permeabilidade ao ar à temperatura ambiente permitiram correlacionar os tipos de poros presentes no concreto com a facilidade de escoamento de fluidos. Ensaios de permeabilidade em temperaturas elevadas foram utilizados para acompanhar a decomposição de hidratos. A análise termogravimétrica permitiu associar as características da estrutura com a facilidade de eliminação de água durante o processo de secagem. Os resultados mostraram que o aumento no teor de agregados favorece a permeabilidade e a secagem do concreto. A composição formulada com matriz grossa e agregados finos foi a que apresentou melhor desempenho global de secagem.

The objective of this work was to evaluate the influence of the particle size distribution of raw materials on the permeability, porosity and drying parameters of ultra-low cement high-alumina refractory castables. Both cumulative and discrete distributions were varied, following Andreasen's model for particle packing. Results have shown that the permeability is strongly affected by the fraction of aggregates in the composition due to the formation of pores at the matrix-aggregate interface. Porosity and permeability in the matrix were affected by the size of the matrix particles. Thermoanalysis has shown that the larger the aggregate content, the faster is elimination of water. Composition with q = 0.31 made of fine aggregates and coarse matrix yielded the castable with better performance during drying tests.