Moisture Migration in Wood Under Heating Measured by Thermal Neutron Radiography

Abstract

The article addresses the transport of moisture due to high-temperature gradients resulting from heating by means of thermal neutron radiography. Moisture migration due to heating is quantified along the orthotropic directions of two wood species, spruce and beech, with high spatial and moisture content resolution. As the heat wave is propagating into the wood, the moisture content in the heated zone rapidly decreases, and moisture is transported due to the high-temperature gradient ahead of the heated zone, resulting in a zone with higher moisture content. Both the drying and the moisture accumulation areas evolve non-uniformly, depending on wood microstructure and orientation.

Keywords:

• neutron imaging
• moisture migration
• heat transfer
• wood
• microstructure

Acknowledgments

The authors acknowledge the support of SNF Sinergia (grant 127467). The experiments were carried out at the NEUTRA beamline of the Paul Scherrer Institute, Villigen, Switzerland, with the helpful support of Jan Hovind, and the gratefully acknowledged participation of the technicians of EMPA: Stephan Carl, Roger Vonbank, Rudi Blessing, and Daniel Heer.