The development of moisture and strain profiles during predrying of<i>Eucalyptus nitens</i>

Abstract

This article describes one of a series of studies carried out at the University of Bio-Bio in Chile with the objective of characterizing the response of Eucalyptus nitens to drying. The ultimate goal is to minimize collapse and internal intra-ring checking in the industrial drying of Eucalyptus nitens, which currently prevents the lumber manufacturing industry in Chile from producing a large number of commercial solid wood products from this species. This study focuses, however, on the drying conditions that have been shown in previous studies and are known in the industry to minimize collapse and internal intra-ring checking. For these conditions, this study reports the development of moisture content and internal strain profiles during drying. In addition, a simple diffusion model based on the concept of effective diffusion coefficient was proposed to compare the drying rates in the radial and tangential directions. The results showed that the diffusion coefficient in the radial direction was approximately 50% higher than that in the tangential direction. Internal strains, on the other hand, developed approximately at the same time, regardless of the annual ring orientation. This indicates that it would be feasible to apply strain relief strategies simultaneously to all boards regardless of their annual ring orientation in order avoid internal intra-ring checking during predrying. This finding could be used as a benchmarking tool in the industrial drying for solid wood products of Eucalyptus nitens.