Intermittent and Continuous Drying of Red Beech Timber From the Green Condition

Abstract

Intermittent and continuous schedules for drying New Zealand's indigenous red beech timber (Nothofagus fusca) from the green condition have been compared. Both schedules can be used to dry red beech with good timber quality. Continuous schedules are appropriate for use in conventional kilns, where better humidity control can be used to minimize timber degrade and equalize moisture contents. Intermittent schedules can be adapted for use in dehumidifiers, where the lower achievable humidities—often a result of poor insulation and air leakages—can be compensated for by the relaxation periods, when the fans and heaters are switched off intermittently to relieve drying-induced stresses. However, equalization cannot be easily applied in a dehumidifier. In this case, a presort of the green timber into two classes—a heartwood heavy class and a mixed heartwood light and sapwood class—would then prove beneficial to address the issue of significant timber property and green moisture content variations that occur in red beech timber.

Keywords:

• Degrade
• Equalization
• Hardwood
• Lumber
• Presorting

ACKNOWLEDGMENTS

We thank Neville Clark and Mike Wilson (Belfast Timber Kilns Ltd., New Zealand), Nigel Pink (School of Forestry, University of Canterbury), and Per Sorensen for their technical assistance; Associate Professor Shusheng Pang (Chemical and Process Engineering Department, University of Canterbury) for his academic support; and the Sub-committee of the Indigenous Forestry Advisory Group (New Zealand) for their expert advice. This work has been supported by a New Zealand Sustainable Farming Fund grant (07/133).