• Journal of the Korean Wood Science and Technology
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• v.42 no.1
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• pp.49-57
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• 2014

The pre-air-drying of Korean pine before the high-temperature and low-humidity drying was shown to be effective in uniform moisture content distribution and prevention of surface check. Our results suggest that initial moisture content of the timber also plays important role in high-temperature and low-humidity drying method. The pre-air-drying also helps in the reduction of surface checks in Korean pine when compared to the Korean pine dried by only high-temperature and low-humidity. End-coating was not effective in the prevention of twist, shrinkage, case hardening and internal checks. The pre-air-drying reduces the internal tension stresses which occur during high-temperature and low-humidity drying thus decreasing case hardening and also preventing internal checks. The pre-air-drying decreases the moisture content and causes shrinkage which leads to increased twist in the Korean pine.

• Journal of the Korean Wood Science and Technology
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• v.25 no.4
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• pp.22-28
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• 1997

This research was carried out to obtain the fundamental data for the development of the technology and practical use of far-infrared radiation(IR) drying of quarter-sliced decorative veneers of walnut and red oak. The average drying rates of IR drying were about one and half to four times those of kiln drying and this tendency was prominent in thin veneer. The end wavinesses of the IR-dried veneers were smaller than those of kiln-dried veneers. These were largely recovered by the cold treatments after drying. The consumed electric power for IR drying was about one-fifth to two-fifthes compared to that for kiln drying.

• Journal of the Korean Wood Science and Technology
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• v.48 no.2
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• pp.121-135
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• 2020

This study aims to evaluate applicability for the continuous drying process using saturated and superheated steam for large-square timber. During drying of the boxed heart square timber, changes in moisture content were examined through the slices of the surface, inner and core layers. The results showed that there was a large moisture content difference between the surface and inner layers during saturated steam drying and between the inner and core layers during superheated steam drying. However, despite the moisture content difference between the layers, no surface check occurred, and an internal check occurred only near the pith or juvenile parts of the wood. The maximum value of the drying stress of the dried larch boxed heart square timber, calculated from the elastic strain of the slice and the tangential elastic modulus of the larch, was 1.30 MPa. The tangential tensile strength of the larch was estimated at 5.21 MPa under temperature and moisture content conditions when drying stress was at a maximum. That is, in the continuous drying process, the saturated and superheated steam did not generate a check in the surface because the drying stress of the wood did not exceed the tangential tensile strength. In further studies, the superheated steam drying conditions will need to be relaxed to suppress the occurrence of internal checks. Such studies would make the continuous drying process using saturated and superheated steam available for the drying of large-square timber.

• Journal of the Korean Wood Science and Technology
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• v.39 no.2
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• pp.132-139
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• 2011

This study examined the characteristics of radio-frequency/vacuum dried Korean red pine ($Pinus$ $densoflora$) heavy timbers with 250 ${\times}$ 250 mm (S), 300 ${\times}$ 300 mm (L) in cross section and 300 mm in diameter, and 3,600 mm in length, which were subjected to compressive loading after a kerf pretreatment. The following results were obtained : The drying time was short and the drying rate was high in spite of the large cross section of specimens. The moisture gradient inall specimens was gentle in both longitudinal and transverse directions owing to dielectric heating. The shrinkage of the width in the direction perpendicular to was 21 percent ~ 76 percent of that of the thickness of square timbers in the direction parallel to the mechanical pressure. The casehardening for all specimens was very slight because of significantly reduced ratio of the tangential to radial shrinkage of specimens and kerfing. The surface checks somewhat severely occurred although the occurrence extent of the surface checks on the kerfed specimens was slight compared withthat on the control specimen.

• Journal of the Korean Wood Science and Technology
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• v.39 no.2
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• pp.117-124
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• 2011

The possibility of using the properties of an ultrasonic wave as a means for monitoring the moisture content of a board during drying was investigated. The ultrasonic wave signals are influenced by moisture content and other factors such as temperature, moisture gradient and coupling area. The effect of temperature was examined by measuring the transit times, amplitudes and velocities of ultrasonic waves transmitted through air, a metal bar and a board at various temperatures. The effect of a moisture gradient was studied using a model specimen composing five wood pieces of various moisture contents. The velocity and amplitude of the ultrasonic waves transmitted through air increase with temperature, while those through a metal bar and a board decrease. It was confirmed that the temperature effect is partially attributed to the change of transducer's properties. The effect of a moisture gradient on the velocity of an ultrasonic wave varies with the average moisture content of a board. As the dimension of the end face of a board increases the velocity of an ultrasonic wave increases and low frequency components more dominates than high frequency components. The transit times of ultrasonic waves transmitted through a board during kiln drying reflect the temperature steps in the drying schedule and the transducer temperatures.

• Journal of the Korean Wood Science and Technology
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• v.2 no.2
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• pp.13-21
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• 1974

1. In the past, the smoke-pipe type dry kiln being characterized by the low cost of installation and easy operation was only used by the small scale of wood processing enterprisers for drying softwood and finishing air-dried stocks that were belonged to easy drying properties. The smoke-pipe type dry kiln usually was not suitable for drying hardwoods and green woods because of the difficulties of controlling drying conditions. 2. However, the smoke-pipe type dry kiln heated with smokeless coal which was designed and constructed by the authers was demonstrated to maintain higher accuracy of controlling temperature and humidity than the other smillar types of kiln. Also, since it was constructed with home made equipments, it is supposed to offer the opportunity to install the kiln by the small scale of wood processing enterprisers who could not install the dry kiln because of economical and technical difficulties. Thus, it is expected that promoting the spread of installing the dry kiln will realize the rational use of wood.

• Journal of the Korean Wood Science and Technology
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• v.25 no.4
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• pp.51-60
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• 1997

We investigated the characteristics of air-and vacuum-drying heated by hot plates for 8~14cm-diameter logs or 6~12cm-thick pillars of Pinus koraiensis. And we evaluated the effects of longitudinal kerf and vacuum drying heated by hot plates. The vacuum drying times from green to 10.9~18.6% MC were 15 days, and these times were one-fifth compared to the air-drying times. The longitudinal kerfing had no significant, effect on drying rates during both air-drying and vacuum drying. But drying defects such as surface checks and V-shaped cracks were effectively prevented during air-drying and vacuum drying by longitudinal kerfing. The vacuum drying was more advantageous than air-drying for preventing of surface checks, end checks and V-shaped cracks, and especially, the vacuum dried pillars with longitudinal kerf were almost free from drying defects. In accelerated weathering conditions the resin did not exude for all specimens.

• Journal of the Korean Wood Science and Technology
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• v.23 no.3
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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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• v.35 no.1
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• pp.11-16
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• 2007

This study was carried out to investigate the effect of Vapor-dam treatment on drying drying rates, prevention of checks and V-shaped split during air circulating oven drying bamboo (Phyllostachys pubescens Mazel et Z) tube. It was shown that the drying time from green to around 7~8 % of moisture content was required less as drying schedule was more severe, and distinctly dominated by the drying rate during the initial drying stage. Area shrinkages in cross section and thickness shrinkages measured during air circulating oven drying test were very large. Surface checks and V-shaped splits were occurred in untreated samples just after the beginning of drying, while sixty seven percentages of all the Vapor-dam treated samples could be produced without drying defects. The V-shaped splits occurred in the Vapor-dam treated samples were influenced more by the sealing of the vapor evaporation through the cross section than drying schedule.

• Journal of the Korean Wood Science and Technology
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• v.11 no.2
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• pp.3-9
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• 1983