• Journal of the Korean Wood Science and Technology
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• 제19권2호
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• pp.30-39
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• 1991

Internal moisture gradients of 3cm-thick radiata pine (Pinus radiata) sapwood and meranti(Shorea spp.) heartwood were determined by using slicing method during drying and were predicted by Hart's Sorption Simulation. The shapes of internal moisture gradients. moisture contents and drying rates, which were obtained by the slicing method. were compared with those predicted by Sorption Simulation. After the 2nd fitting attempts. the differences between the gravimetric drying rates and the drying rates predicted by Sorption Simulation were less than 0.021%/hr for radiata pine and 0.043%/hr for meranti. The shapes of the internal moisture gradients predicted by Sorption Simulation were in good agreement with those obtained by the slicing method. It could be concluded that Sorption Simulation be an excellent tool to predict internal moisture gradients of wood.

• Journal of the Korean Wood Science and Technology
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• 제20권2호
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• pp.73-80
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• 1992

The effect of presteaming on native oak specimens(Quercus serrata) of 2.5cm thick were investigated by measuring specific gravities, internal moisture gradients, residual extractives, and transport rates of free and bound water. The specific gravities and internal moisture gradients of the presteamed samples did not much deviate from those of the controls, but after presteaming discrepancy in moisture content between specimens lessened. The amount of residual hot-water extractives of the presteamed samples were less than those of the controls by 25%. The transport rates of bound water were determined by measuring steady-state diffusion coefficients with a vapormeter cup. After presteaming the diffusion coefficients in radial direction increased by 35%, but decreased those in the tangential direction.

• Journal of the Korean Wood Science and Technology
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• 제23권3호
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• pp.28-32
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• 1995

The presteamed or prefrozen persimmon blocks of 10cm ${\times}$ 10cm ${\times}$ 15cm were air-dried at room temperature until about 30% moisture content, and then were dried in a MW oven. During drying their internal temperatures were monitored with thermo-couple probes. The presteamed and prefrozen blocks didn't show any improvement in drying rate and moisture gradient when compared with the controls. Checks appeared on the surfaces of most presteamed blocks during air-drying. It has been clearly revealed that the maximum weight, loss must, be less than 2g/min during MW drying to prevent internal checking and that MW drying reduced moisture gradients inside blocks. MW dried the persimmon blocks 440 times faster than conventional kiln.

• Journal of the Korean Wood Science and Technology
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• 제26권3호
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• pp.1-8
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• 1998

Western redcedar timber, 26 by 26cm in cross section and by 200cm long, was dried in a laboratory radio-frequency/vacuum kiln under 65torr of ambient pressure and a fixed frequency of 6.78MHz for the potential rapidly dry large timber. All process data were collected and saved in a computer through a data acquisition system. The temperature in the middle of timber was higher than temperature at the quarter point of timber length and thickness. Temperature gradients developed in the longitudinal and transverse direction of timber. The pressure in the middle of timber was higher than pressure at the quarter point of timber length. The pressure in the middle of timber was lower in the early stage of drying, and higher in the latter stage of drying than pressure at the quarter point of timber thickness. Power density was very highest during heating period and then gradually decreased. The drying curve was approximately linear and the total drying time was 27 hours from an initial moisture content(MC) of 48.6 percent to a final Me of 19.2 percent with only a few mild internal checks in the middle location of timber.