Descrição matemática do transporte simultâneo de calor e massa no processo dinâmico de secagem de madeira de Pinus elliottii

Abstract

In general, industrial drying of wood is characterized by being a process that requires a large investment due to high energy consumption and by requiring a slow operation. Its operational control is complex because it is strongly based on empirical parameters due to the intrinsic characteristics of the wood. Computational models for drying process analysis that use and accurately calculate system-related clinical effect levels, which is an important basis for business analysis and economic savings using costs and risks. In this work, the phenomenon of simultaneous heat and mass transfer during the wood drying process is analyzed by computer simulation. The used mathematical model describes the phenomenon as intrinsically diffusive but considering the influence of environmental drying conditions, such as temperature and equilibrium temperature of the airflow inside the greenhouse. The model consisting of a system of algebraic-differential equations describes the heat balances and the variation of thermodynamic variations. Its resolution is performed by implementing an algorithm that uses the integration of timeless system equations and the finite difference method to discretize the spatial direction. An analysis of the combined heat and mass transfer (moisture) was studied for a Pinus elliottii wood slab subjected to conditions typical of conventional oven drying. The thermophysical and operational parameters used in the model, as well as their correlations with the system variables, were shown in the literature. Validation was performed by comparison with experimental data from the literature and its evaluation shows significant similarity, obtaining linear correlations above 0.9. The behavior of mass and energy transport phenomena with the admission of different drying schedules was also studied. Thermodynamic properties were employed in the process efficiency analysis. Admission of gradual variations in operating conditions during the drying process resulted in positive effects on the quality and efficiency parameters of the process, increasing the drying rate and reducing the tendency for structural damage to the material.