|Airflow Flow Distribution||Flow Variations in 2 Wood Stacks||Temperature and Moisture Distribution in the Wood|
The uniformity of drying and the quality of the wood in a kiln are strongly influenced by the drying schedule and by the uniformity of the airflow. The uniformity of the airflow has an important effect on the final moisture distribution and the reduction of wood defects and is influenced by such parameters as the geometry of the kiln plenum, air ducts, roof design, the proper stacking of each wood package, and lumber dimensional control. A uniform airflow ensures uniformity of drying temperature and humidity, avoids moisture build-up through regions of stagnation in part of the packages, and minimises prolonged periods of moisture equalisation. Minimisation of airflow variations requires a proper understanding of the mechanisms that contribute to airflow non-uniformities.
To achieve the optimisation of a drying kiln and to improve the quality of wood products, simultaneous modelling of the mass transfer and heat transfer in the wood and in the air is required, as these factors are interdependent. The UBC modelling group is currently developing a kiln model to optimise kiln designs, help improve kiln operations, and address the requirements of the industry regarding the reduction of wood defects and the lowering of the deviation in moisture content. A three-dimensional airflow kiln model has been developed in conjunction with a three-dimensional wood-drying model. Coupling between the airflow and wood drying models and the development of statistical variations in wood package geometry and wood properties are currently under development.
PSL currently applies the woodkiln model to address the influence of kiln design on air uniformity and drying conditions. Problems resulting from improper packaging of the lumber and the influence of the air velocity, temperature, and humidity control on the moisture distribution within lumber packages during the drying schedule will soon be available.