Development of steam injection drying method for lumber.

点击翻译按钮获取中文摘要

We developed the steam injection drying method in which super steam of over 100' was injected into laser incised holes of lumber. This new type of drying is supposed to be able to heat and dry whole lumber rapidly and evenly compared to conventional kiln drying. Furthermore, decompression and dehydration of water in lumber is supposed to happen by Bernoulli's theory. We also inspected whether a beam expander can control the shape of a hole or not. The results obtained in this research were as follows.1.We designed and made a jig for steam injection drying in order to prevent a leak of steam from a gap caused by shrinkage of lumber under fiber saturation point in moisture content. As the results, we could dry lumber to 15 % in moisture content without the leak of steam. Drying check was seen in lumber after quick drying. Therefore, a drying schedule must be developed even for this method to achieve a perfect drying.2.Drying speed increased with the laser incising density but the efficiency was doubled in case of lumber with four times of incising density. Therefore, it became clear not to raise the incising density blindly.3.The drying speed decreased only in case of incising pattern whose interval ratios are 1:2 and 1:5 for longitudinal and lateral directions. This phenomenon could not found both in higher and lower incising densities such as 2,000 holes/m^2 or 500 holes/m^2.4.The incising density of 1,000 holes/m^2 was most effective for perfect drying of lumber within this research.5.When an input diameter of a laser beam to a lens is expanded twice or three times compared to that of the original one with the beam expander made by this fund, a more slender hole could be made, though the depth of focus was shallow. Therefore, this technique is found to be more suitable for the laser incising of a lamina for glue lam.