Drying on the Board- and Boxed Heart Squares-larch Lumbers within an Opaque Solar Drying House Covered by a Composite Surface

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Two sorts of lumber drying house covered by a composite surface consisting of three layer transparent films and a carbon-fibre sheet (CF-sheet; looks like a semi-opaque) were invented and developed. One of them was built in Ashoro-cho, the eastern part of Hokkaido, Japan (the first proving site), and the other was built in Asahikawa-shi, the central part of Hokkaido (the second proving site). The dimension of each drying houses is a frontage of 4.5 m, depth of 5.0 m and height of 3.4 m (the 1st site) and the same frontage and depth as the former, but height of 3.8 m (the 2nd site), respectively. Two types of models of the drying house (East-West type and South-North-type) were desinged. The former is shaped like a half Quonset hut and the latter a just Quonset hut. All of the surfaces including the roof and walls except for a north wall of both models are covered by a composite surface. The composite surface is specially consisted by a triple transparent film from upper side and a CF-sheet to bottom side between which there are a few space of air layers. As a result of mutual effect of a spectral radiation properties of the films and the CF-sheet, a total solar radiation incident upon the drying house with cubic body composed of multi-surface from all the sky globally, can be collected into the house as solar rays volumetrically, converted into infrared radiation and trapped inside the drying house as solar heat passively, without any electric power. Moreover, the moist air inside the house being evaporated when drying green lumber can be naturally exhausted through two insulated cylinders (chimney) outside the drying house according to a principle of the thermo-siphon. From these reasons, “An opaque solar lumber drying house covered by a composite surface consisting of a triple-transparent film and a CF-sheet” could be called “A fully passive solar lumber drying house” in other word.In this paper, after explained the principle of drying mechanism due to solar radiation and heat rays, the experimental procedures and the results at the proving test, on a board-larch lumber at the 1st proving site and a boxed heart squares-larch lumber for pillar material at the 2nd proving site, were described and discussed thoroughly.