Model predicted and CT scanned moisture distribution in aPinus radiata board during drying

Abstract

Pinus radiata sapwood boards of 100 x 40 x 1200 mm were dried in a tube dryer at Lule~ University, using a computer tomography (CT) scanner to scan the wood during drying. The CT-scanned wet wood density can illustrate moisture distribution within wood when the wood basic density profile is known. The CT-scanned results were used to validate a 2-D single board drying model developed at the New Zealand Forest Research Institute. The validation has shown that the model is not only capable of predicting the average moisture content but also moisture content gradients in board thickness, width and within growth rings. To investigate the effects of sawing pattern and intrinsic wood properties on drying, the input parameters for the model include within-ring variations of wood density, green moisture content and wood permeability. The model can assist in understanding the causes of some drying defects and has potential for the development of drying schedules. Feuchteverteilung in einem Kiefernbrett w~herend des Trocknens, gesch~tzt nach einem Model/und 9emessen mittels Computertomographie (CT)Splintholzbretter von Pinus radiata (100 x 40 x 1200 mm) wurden getrocknet, wobei gleichzeitig mittels Computertomographie die Holzfeuchte verfolgt wurde. Die dabei erfat~te Dichteverteilung kann als Feuchteverteilung dargestellt werden, wenn das entsprechende Rohdichteprofil des Holzes bekannt ist. Die ermittelten Daten wurden verwendet um ein zweidimensionales Modell zu verifizieren, das am Holzforschungsinstitut in Neuseeland entwickelt worden ist. Es ergab sich, daft dieses ModeU nicht nur die durchschnittliche Holzfeuchte richtig vorhersagt, sondern auch Feuchtegradienten innerhalb des Brettes und zwar gemessen fiber die Breite, die Dicke und innerhalb der ]ahrringe. Um die Einfl/isse der Schnittparameter und der Holzeigenschaften zu untersuchen, enth~ilt das ModeU auch Angaben fiber Dichteverteilungen innerhalb der

On the use of X-ray computed tomography for determining wood properties: a review1This article is a contribution to the series The Role of Sensors in the New Forest Products Industry and Bioeconomy.

“…One may assume that the wood basic (dry) density profile is known (Pang and Wiberg 1998). Also, during wood drying, a change in wood volume (i.e., shrinkage) can occur.…”

“…One of the most important industrial applications of CT images is monitoring of wood moisture during the drying process. For modeling the kiln drying process of boards, CT images have been used to determine moisture flux and diffusion coefficients (e.g., Danvind and Morén 2004), to validate mathematical models in the case of radiata pine (Pinus radiata D. Don) (Pang and Wiberg 1998) or of Norway spruce (Picea abies (L.) Karst.) (Eriksson et al 2007), to assess wet-wood distributions in heartwood in the case of subalpine fir (Abies lasiocarpa (Hook.)…”

The contradictory effect of drying internal checks and moisture changes on the ultrasonic propagation in poplar wood (Populous nigra)

“…Nondestructive testing (NDT) can be a good and accurate tool to characterize wood during drying. Nuclear magnetic resonance (NMR, Quick et al 1990), X-ray spectroscopy (Tarmian et al 2009), X-ray computed tomography (CT) scanning (Pang and Wiberg 1999), gamma ray (Davis et al 1993), microwave method (Moschler et al 2007), magnetic resonance imaging (MRI, Rosenkilde et al 2004), thermal and ultrasonic techniques are some measurement methods for nondestructive evaluation of wood moisture content distribution during drying. Among them, ultrasonic inspection is a simple and low cost technique.…”

Identification of selected log characteristics from computed tomography images of sugar maple logs using maximum likelihood classifier and textural analysis

“…The scanner is set so that brighter regions, i.e., higher pixel GL values, correspond to regions of denser material. Besides the application to log breakdown optimization, the information derived from CT images has also been used for wood drying and quality control (Pang and Wiberg 1998).…”