• Journal of Advanced Marine Engineering and Technology
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• 제25권3호
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• pp.588-594
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• 2001

The aim of this paper is to develop the low temperature vacuum dryer, with low initial investments and operating costs, easy operating method and trouble-free operation Usally operations just below atmospheric pressure, as with direct dryers, but some are built for vacuum operation with pressure as low 50 mmHg abs. The lowers the boiling point to $39^{\circ}C$ The experimental data of quantitative analysis for using practically were obtained by the constant drying rate period and reducing drying rate period according to the temperature of hot water which is the experimental parameters of present experiment. As the results, it took about 20 hours for material to reach about 18% of the final moisture content is order to store products for a long time about 450% of the early moisture content at the beginning of drying and maximum drying rate comes to about 0.30 kg/m2hr at about 350% of the moisture content.

• Journal of Forest and Environmental Science
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• 제12권1호
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• pp.1-12
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• 1996

강원도산(江原道産) 참나무과(科) 4수종(樹種)의 건조특성(乾操特性)을 파악코져 $100^{\circ}C$에서 급속건조(急速乾操)를 실시하여 건조중(乾操中) 함수율(含水率)과 건조경과(乾操經過), 초기할열(初期割裂)(목구할열(木口割裂)과 표면할열(表面割裂)), 찌그러짐, 내부할열(內部割裂) 등의 건조결함(乾操缺陷)을 조사하여 추정건조(推定乾操)스케쥴을 작성한 결과(結果)는 다음과 같다. 건조시간별(乾操時間別) 건조중(乾操中) 함수율(含水率)은 초기함수율(初期含水率)이 높은 판재일수록 급속(急速)한 곡선적(曲線的) 감소(減少)를 나타내었고 건조소요시간(乾操所要時間)은 두께가 두꺼울수록, 초기함수율(初期含水率)이 높을수록, 건조중(乾操中) 함수율(含水率) 변화( 變化)가 느린 수종(樹種)일수록 길었다. 또한, 두께가 두꺼울수록 할열(割裂)의 발생량(發生量)이 증가하므로 건조초기(乾操初期)의 조건(條件)을 완화하게 해야 함을 알 수 있었다.

• Journal of Biosystems Engineering
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• 제41권4호
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• pp.342-356
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• 2016

Purpose: The drying of a thin layer of native cassava starch in a tray dryer was modeled to establish an equation for predicting the drying behavior under given conditions. Methods: Drying tests were performed using samples of native cassava starch over a temperature range of $40-60^{\circ}C$. We investigated the variation in the drying time, dynamic equilibrium moisture content, drying rate period, critical moisture content, and effective diffusivity of the starch with temperature. The starch diffusion coefficient and drying activation energy were determined. A modification of the model developed by Hii et al. was devised and tested alongside fourteen other models. Results: For starch with an initial moisture content of 82% (db), the drying time and dynamic equilibrium moisture content decreased as the temperature increased. The constant drying rate phase preceded the falling rate phase between $40-55^{\circ}C$. Drying at $60^{\circ}C$ occurred only in the falling rate phase. The critical moisture content was observed in the $40-55^{\circ}C$ range and increased with the temperature. The effective diffusivity of the starch increased as the drying temperature increased from 40 to $60^{\circ}C$. The modified Hii et al. model produced randomized residual plots, the highest $R^2$, and the lowest standard error of estimates. Conclusions: Drying time decreased linearly with an increase in the temperature, while the decrease in the moisture content was linear between $40-55^{\circ}C$. The constant drying rate phase occurred without any period of induction over a temperature range of $40-55^{\circ}C$ prior to the falling rate period, while drying at $60^{\circ}C$ took place only in the falling rate phase. The effective diffusivity had an Arrhenius relationship with the temperature. The modified Hii et al. model proved to be optimum for predicting the drying behavior of the starch in the tray dryer.

• 한국가구학회지
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• 제19권2호
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• pp.116-123
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• 2008

Kiln schedule development was based on two schedule phases, the first being to determine the maximum safe kiln temperature during the check prone initial stage of drying, with the second stage determining how to accelerate drying once the danger of checking had passed. This was achieved by using 38 mm thick boards which were pre-screened for susceptibility to internal checking, and then drying matched sample boards over a range of kiln temperatures. Research has shown that below 50% MC there is no further risk of internal checking. However, difference in drying rate due to board width and the increased occurrence of wet patches in wide boards means that it is essential to modify the basic schedule according to the maximum board width. A condition of 52/40 $^{\circ}C$ was selected for the checking-free initial kiln drying step and a 5-step kiln-schedule dried the boards from 109% to 8% MC for 72.5 hours without internal checking.

• Journal of the Korean Wood Science and Technology
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• 제13권3호
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• pp.27-33
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• 1985

Air-drying tests were carried out on green taun (Pometia pinnata f glabra) for 25-mm and 50-mm thickness to elucidate drying characteristics on air-drying rate, time and defects in spring and air-drying calendar. The results of this study were as follows: 1. The air-dried lumber for 25-mm thickness from an initial average moisture content (MC) of $58.3{\pm}3.5$ percent reached 30 percent MC in 17 days, 25 percent MC in 24 days, 20 percent MC in 38 days and 15 percent MC in 84 days. 2. The air-dried lumber for 50-mm thickness from an initial average MC of $59.6{\pm}5.0$ percent reached 30 percent MC in 39 days, 25 percent MC in 55 days and 20 percent MC in 84 days. 3. Air-drying calendar that could be useful in estimating drying times for each month developed by the use of climatological data for Suwon. Total number of effective air-drying days during a year were 243.5 days and the major determinant of the effect air-drying days was temperature. 4. The air-drying rates for 25-mm and 50-mm coated lumber were slight1y slower than those of uncoated lumber. The number and total length of both end checks and surface checks for end coated lumber were less severe than those of uncoated lumber.

• Journal of the Korean Wood Science and Technology
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• 제25권1호
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• pp.28-36
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• 1997

Several thick board and dimension lumbers of Japanese larch(Larix leptolepis), Dahurian larch(Larix gmelini) and radiata pine(Pinus radiata) air-dried in four different seasons to compare air-drying process. Patterns of air-drying curves were influenced by climatological conditions and limber thickness. The initial drying rates of summer were the highest, followed those of fall, spring and winter. The drying times to equilibrium moisture contents for four seasons were nearly the same except for winter. However, the drying time for winter required twice more time than the other seasons. The drying time of dimension lumbers required 1.3 times more than boards. The final moisture contents were lowest during spring, highest during winter and similar between summer and fall.

• Journal of Biosystems Engineering
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• 제13권3호
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• pp.59-70
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• 1988

A computer simulation model for rice circulating concurrent-flow dryer was developed and verified by conduction a series of pilot-scale experiment. The effects of design parameter and operating conditions on dryer performance were analyzed by using simulation. The results indicated that the developed model was found suitable for analyzing operating characteristics. The other results from simulation also showed that; 1) an increse in the initial moisture content resulted in an increase in the drying rate and a reduction in the grain temperature and total energy requirements. 2) an increase in the drying air temperature resulted in an increase in the drying rate and grain temperature. 3) an increase in air flow rate resulted in an radical increase in drying rate, fan power requirements and total energy requirements but an radical decrease in final head rice yield. 4) an increase in the bed depth resulted in an increase in fan power requirements and a lowering of the final head rice yield.

• 한국수산과학회지
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• 제15권3호
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• pp.207-210
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• 1982

갑오징어 우리나라에서 비교적 맏이 어획되어 대부분 천연건조에 의해 가공되고 있다. 갑오징어의 고정층 건조를 실시하여 건조 속도 및 Shirai식에 의한 건조 속도 상수 (k) 를 구하고, Arrhenius' plot에 의해 온도 의존성을 관찰하여 다음과 같은 결론을 얻었다. 1. 갑오징어의 수분 함량을 $40\%$이하로 낮추는데 본 실험의 경구 4시간이내가 소요되어 고정층 건조방법이 배등의 열풍건조법보다 효과적인 방법으로 판단된다. 2. 시료의 세분화, 껍질 제거, 열풍의 온도 상승 및 방향 조정 등으로 건조시간을 2시간으로 단축할 수 있었다. 3. 본 실험의 결과는 Shirai식과 Arrhenius' law에 잘 적용되었다.

• 환경위생공학
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• 제13권3호
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• pp.133-140
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• 1998

The food wastes from a refectory and an eating house were heated in domestic microwave oven(700W) equipped with a fan and the drying rates and destruction of microorganisms were investigated. The drying rate was decreased with the size of food waste and the food wastes in polypropylene basket were dried faster than that on glass dish. The rate was increased with lower initial moisture content. Death rate of microorganisms was also decreased with the size of food waste. Ninety eight percent of reduction in viable cell numbers for the 400g of food waste could be achieved in 240sec of microwave irradiation. The growth of microorganisms in food wastes after microwave irradiated was observed at $32^{\circ}C$ and 95% relative humidity after 7days and the cell numbers in microwave irradiated food wastes were found to be 1/2 ~ 1/20 of the numbers in untreated wastes in accordance with the mass and the length of exposed time to microwave. To minimize the moisture and microorganisms in food wastes, the use of microwave oven are recommended.

• 미생물학회지
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• 제16권3호
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• pp.103-110
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• 1978

Saccharomyces cerevisiae strain M. was cultured in a molasses-containing media with different amounts of phosphorous and nitrogen sources. The effects of constituents of the cell on the functional activity as well as sensitivity of it were investigated, the results obtained being summarised as follows : Both the thermotolerance and dry tolerance of the yeast cell were higher when the more carbohydrate and thehalose were present in the yeast cell. During the drying, the rate of dead cell was noted increasing and the fermentability decreasing, but it was more remarkable at early stage of the decreasing rate of drying, and at the same time increasing rate of dead cell and decrease of fermentability were more remarkable in the yeast cell containing much protein. In this case the speed of drying was slower. The trehalose content in the yeast cell increased during early stage of the drying and this increase was higher when content of trehalose and carbohydrate in the initial yeast cell was relatively high.