Quality assessment of lumber after low temperature drying from the view of stochastic process characteristics
The quality of lumber drying is traditionally evaluated after the process. This paper proposes the algorithm of quality assessment of low-temperature convection lumber drying in accordance with the target values of the average final moisture content and its dispersion in the stack. The stochastic model of the process with random initial and boundary conditions, which allows calculating the dispersion of the final moisture content (MC) was proposed. To describe the kinetics of the wood drying process in the low-temperature chamber in view of the thermodynamic characteristics, 34 processes of drying of oak and pine lumber with the thickness of 30, 40 and 50 mm were made at the wood-processing enterprises in Ukraine. The theoretical equations of lumber low-temperature drying and the values of the coefficients that characterize the influence of material thickness, temperature and moisture fields’ distribution in the material during the drying process were obtained. The check of the proposed models on the uniformity of the average values and dispersion of the current moisture content showed a slight difference between the experimental and calculated values. These models allow predicting the quality of the low-temperature drying on the spread of target moisture content, which enables selection of rational drying schedules.