Radio Frequency/vacuum Drying of B.c. Softwoods; Preliminary Experiments

Five exploratory drying runs were carried out in a commercial size (23 m3), radio frequency/vacuum hardwood kiln. The species investigated were Pacific coast hemlock, Douglas-fir and western red cedar of different sizes and grades. Evaluation of the dried lumber showed that the three species can be dried in very short times and low amount of degrade irrespective of thickness with the exception of clear cedar which exhibited severe internal honeycombing; indicating the need to develop proper kiln schedules for this drying process. A thermodynamic and sensitivity analyses were performed which showed that above certain efficiency levels, RF/V drying is economical and fast. That was in particular true with lumber over 8 cm in thickness.