RADIO FREQUENCY VACUUM DRYING OF WOOD. II. EXPERIMENTAL MODEL EVALUATION

Abstract

Thick specimens of two softwoods were dried in a laboratory radio frequency/vacuum (RF/V) dryer to investigate the evolution of internal moisture flow patterns. The total average moisture content and local temperatures and pressures were monitored as a function of time. A number of runs were carried out for different conditions of voltage, power density, ambient pressure, core temperature, and initial moisture content. The results obtained were compared with the ones predicted by a 1D simplified model. Despite the simplicity of the model, good agreement was obtained for a variety of drying conditions, especially in predicting the average moisture evolution and the drying time.

Keywords:

• Dielectric
• Evaporation
• Pressure
• Controlling resistances
• Transport mechanisms

ACKNOWLEDGMENTS

This research was financially supported by a Natural Sciences and Engineering Research Council Strategic Research Grant, a BC Science Council GREAT Award and by Heatwave Drying Systems Ltd. The help of Dr. Liping Cai with part of the experimental work is highly appreciated.