Drying of sugi [Cryptomeria japonica] square lumber with high temperature heating by radio frequency under vacuum after treating of local steam explosion
2002
Noji, K. (Kochi-ken. Forest Experiment Station, Tosayamada (Japan)) | Masaoka, H. | Suzaki, K. | Kanagawa, Y. | Fujiwara, S.
Sugi (Cryptomeria japonica D. DON) square lumbers were dried in high temperature heating at about 90degC by the radio-frequency under vacuum of 18.6kPa (140mmHg) after local steam explosion as a pretreatment of drying. The temperature was 120degC and the repetition of the explosion was 31 times. As a result, the following points were clarified. Drying time was significantly reduced to two days, which was about a half of drying time in usual radio-frequency vacuum drying. Average initial moisture content of 47% and 60% became about 12% at the end of drying. Though internal checks occurred, the few surface checks were observed. Amount of the drained water in evacuation tended to be 8 or 9% less than the weight loss of lumber. A moisture content change in drying process can be evaluated by two factors of the amount of the drained water and the expected specific gravity of 0.35.
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