Hybrid drying with high-frequency heating and hot air under atmospheric pressure IV: water movement in <Emphasis Type="Italic">Cryptomeria japonica</Emphasis> wood during high-frequency heating |
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| Authors: | Y Kawai Y Kobayashi M Norimoto |
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| Institution: | (1) Institute of Wood Technology, Akita Prefectural University, 11-1 Kaieizaka, Noshiro, Akita 016-0876, Japan Tel. +81-185-52-6985; Fax +81-185-52-6976 e-mail: kawai@iwt.akita-pu.ac.jp, JP;(2) Wood Research Institute, Kyoto University, Kyoto 611-0011, Japan, JP |
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| Abstract: | The relations among internal temperature, internal pressure, and moisture content distribution in sugi square lumber during
high-frequency (HF) heating were determined to clarify the mechanism of water movement during the combination of HF heating
and hot air exposure. Green sugi square lumbers were subjected to HF heating under atmospheric pressure. The water movement
and pathways in the lumber during HF heating were also investigated. Results showed that internal pressure is the driving
force of water movement. HF heating causes a rise in the internal temperature and internal pressure in sugi square lumber.
Ordinarily, water in lumber evaporates from the surfaces of lumber during hot air drying. However, with HF heating the internal
pressure is generated by the increased temperature, and liquid water is driven not only parallel to the grain but also perpendicular
to the grain of the lumber. The ratio of the amount of liquid flow in the parallel and perpendicular directions ranged from
2 : 3 to 1 : 3. When the movement of water in the lumber was traced with a 0.5% aqueous solution of acid fuchsin, water was
found to move through the lumber in the longitudinal direction and then flow in a direction perpendicular to the grain or
in the radial and tangential directions.
Received: June 15, 2001 / Accepted: February 8, 2002
Acknowledgment The authors thank Dr. O.R. Pulido, Institute of Wood Technology, Akita Prefectural University, for discussions and for proofreading
this paper.
Part of this research was presented at the 51st Annual Meeting of the Japan Wood Research Society, Tokyo, April 2001
Correspondence to:Y. Kawai |
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| Keywords: | Water movement HF heating Sugi (Cryptomeria japonica D Don) Internal pressure Internal temperature |
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