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Drying is the most energy consuming process in the industrial transformation of wood. The current energy and climate crisis makes it imperative to adapt the process to energy availability, in terms of quantity, cost and temperature level. Wood drying schedules are historically based on practice. In the present work, a mechanistic drying model is used as a predictive tool to adapt conditions to specific situations. A multiscale computational model, Multi_Wood_DryS, has been combined with a probabilistic optimization code to propose tailor-made drying schedules that meet operators' expectations in terms of energy consumption, quality, drying time and cost. Optimizations of drying schedules of a stack of boards are proposed. The cost-optimized schedule is advantageous for all criteria with a 48% reduction in drying time. The resulting metamodel is a first step toward an intelligent controller for wood drying. [ABSTRACT FROM AUTHOR]

The paper brings new insights into nonsymmetrical convective drying, a configuration in which stresses induce a global change of the section shape of a wooden board with five insulated faces. Two experimental devices that allow to test simultaneously “twin” wooden boards have been developed: the first board is free and its curvature is collected vs. time; the second one is constrained and the force required to keep it flat is collected vs. time. Convective drying tests have been performed on radial specimens of spruce, 5 and 15 mm thick at 45 and 65°C. The results are commented and compared with simulation runs. For this purpose, a 1-D mechanical formulation is embedded in the computational code of heat and mass transfer TransPore. The objective of the comparison between numerical and experimental results is a better understanding of the coupled phenomena and the identification of some transfer and mechanical parameters. [ABSTRACT FROM AUTHOR]

This article proposes a dual-scale computational model of wood drying in a batch lumber kiln. The stack may consist of a large number of boards (typically 100) arranged in layers. Each single board of the stack is simulated using one module of TransPore , a comprehensive computational model for heat and mass transfer in porous media. Timber variability is taken into account by a Monte-Carlo method. Such a dual-scale model allows the drying simulation of a 100-board stack to be completed in less than 30 s on a PC with a 2.8-GHz Xeon processor. Sample simulations are presented to depict the great potential and prospects of this new tool. [ABSTRACT FROM AUTHOR]