Study on Moisture Movement in Wood with X-ray CT scanner.

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Moisture distribution in drying were non-destructively detected with X-ray CT scanner. In the first stage of this research, methods were investigated to distinguish CT number attributed the moisture only from total CT number obtained directly with CT scanner and to improve the accuracy of moisture measurment using silicon rubber bags surrounding the sample. Moisture contents on internal cross section could be non-destructively measured in the finest of 1% below 40% range.In the second stage, applying the method to detect the moisture distribution of Douglas-fir thick quarter sawn lumber (6 cm thickness) in drying, change of moisture distribution in thickness direction was measured. The sample had probbably a homogeneous property for moisture movement. Also, it was assumed that the diffusion coefficient was continuously changing with moisture content. On this assumption, moisture contents on the surface of sample were reversely calculated from the relationship between diffusion coefficient and moisture content. Moisture content on the surface should be set the higher value of about 6% in high moisture content range and the higher value of 3-4% in low range than equilibrium moisture contents, in solving the Fick's 2nd law with the finite difference method. Describing moisture movement with moisture content as driving force, the diffusion coefficient was almost constant with moisture content change.