Este trabalho apresenta a comparação das técnicas de resolução numérica de Diferenças Finitas e Runge-Kutta-Gill de 4a ordem com passo de integração variável para a simulação do modelo de transferência de calor em regime transiente bidimensional em coordenadas cilíndricas e unidimensional em coordenadas esféricas, aplicado a alimentos enlatados processados em autoclave, observando-se a rapidez e a precisão de integração comparados aos perfis reais de tempo/temperatura, incluindo desvios de processo. Além disso, uma análise de sensibilidade paramétrica na difusividade térmica foi realizada na tentativa de quantificar a influência que essa propriedade possui na resolução numérica. Para tanto, foram realizados ensaios de penetração de calor em autoclave a vapor, utilizando-se latas cilíndricas de 75x90 e 100x110 contendo simulantes de alimentos com características de aquecimento por condução e convecção. This work presents a comparison of the integration quickness and precision between the techniques of numerical resolution of Finite Differences and Runge-Kutta-Gill of fourth order with variable integration pass, to do simulation of the unsteady-state heat transfer model, two-dimensional in cylindrical coordinates and one-dimensional in spherical coordinates, applied to canned foods processed in retorts, showing advantages for the technique of Runge-Kutta-Gill. It was also accomplished a parametric sensitivity analysis in the thermal diffusivity indicating a great influence of this parameter in the numerical solution. The mathematical simulation were compared with results of real heat penetration tests done in steam retort, using cylindrical cans filled with bentonite suspensions simulating foods with heat characteristics resembling heat conduction and heat convection
LaTi1−xFexO3 (x = 0, 0.2, 0.4, 0.6, 0.8 and 1) perovskite-type oxide samples were synthesized by the solid state reaction method and characterized, and their photocatalytic activity was tested in the degradation of Acid Orange 7 under ultraviolet and visible light. The oxides were successfully synthesized and the XRD results showed a phase change from monoclinic to orthorhombic, with an increase in Fe content (x), with LaTi0.8Fe0.2O3 and LaTi0.6Fe0.4O3 samples presenting both phases. All samples presented low photocatalytic activity under visible light radiation, with a maximum Abs484nm removal of 2.9% for LaFeO3 after one hour. The best results were obtained under ultraviolet radiation, for all samples, with the best photocatalytic activity exhibited by the La2Ti2O7 perovskite, with 44.6% Abs484nm removal after one hour.
Keywords: perovskites, LaTi1−xFexO3, photocatalysis, Acid Orange 7
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