Solução numérica e implementação computacional da equação de difusão usando coordenadas generalizadas tridimensionais: aplicação na secagem de telhas ornamentais.

Abstract

This work has the objective to study theoretically and experimentally the diffusion process in three dimensions, for solids of arbitrary form. The study presents numerical and analytical solutions of the diffusion equation in the description of the transport of the greatness of interest for the boundary condition of the third type. The analytical tools consider the product with the parallelepiped form, while the numerical solution was developed for generically form solids. To use the numerical method, the solution of the three-dimensional diffusion equation was discretized using the finite volume method, with a fully implicit formulation, using generalized coordinates. A computational code developed in FORTRAN, using the CVF 6.6.0 studio was used and the results coupled to the software LS Optimizer to make the simulation, from experimental data of drying. Thus, the effective diffusion coefficient was determined as a function of the moisture ratio for several functions and also the value of the convective transfer coefficient. The tools were applied to the drying of ceramic tiles for four experimental conditions. The results have shown that by increasing the temperature or the speed of the drying air flow or both, the process time decreases. For the temperatures and speeds studied, the drying kinetics presented physically coherent results in the drying process. The values of the diffusive coefficients and convective transfers were obtained with the uncertainties and can be considered statistically coherent. In addition to this, the analysis and comparison of the results with data reported in the literature, for similar cases, showed that the presented solution provided coherent results for all cases investigated.