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Effect of end-covering and low pressure steam explosion treatment on drying rate and checking during radio-frequency/vacuum drying of Japanese cedar log cross sections

2000; Forest Products Society; Volume: 50; Issue: 2 Linguagem: Inglês

2376-9637

Nam-Ho Lee, K. Hayashi,

Materials Engineering and Processing

This experiment was conducted to investigate the effect of end-covering and explosion treatment on the drying rate, checking, and shrinkage during radio-frequency/vacuum (RF/V) drying of 75-mm-thick Japanese cedar log cross sections (disks). The drying times were drastically shortened by explosion treatment, however, most of the disks were defected by heart checks during treatment. The initial drying rate of the explosion disks was dramatically higher than the others. The sum of tangential and radial shrinkage was about 40 to 70 percent less than that based on the American Society for Testing and Materials (ASTM) method. A reduction of tangential shrinkage by the RF/V drying process wash higher than that in radial shrinkage, and the difference between tangential and radial shrinkage, therefore, represents a very low value. The control disks and the end-covered disks could be dried with very slight heart checks and without V-cracks. The specific energy for water removal during the RF/V drying runs for the explosion disks was approximately 40 percent less above the fiber saturation point (FSP), and 20 percent less below FSP, than the run of control disks.