• Journal of Biosystems Engineering
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• 제38권1호
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• pp.41-47
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• 2013

Purpose: The objectives of this study were to construct the solar drying system with evacuated tubular solar collector and to investigate its performance in comparison with indoor and outdoor dryings. Methods: Solar drying system was constructed with using CPC (compound parabolic concentrator) evacuated tubular solar collector. Solar drying system is mainly composed of evacuated tubular solar collector with CPC reflector, storage tank, water-to-air heat exchanger, auxiliary heater, and drying chamber. Performance test of solar drying system was conducted with drying of agricultural products such as sliced radish, potato, carrot, and oyster mushroom. Drying characteristics of agricultural products in solar drying system were compared with those of indoor and outdoor ones. Results: Solar drying system showed considerable effect on reducing the half drying time for all drying samples. However, outdoor drying was more effective than indoor drying on shortening the half drying time for all of drying samples. Solar drying system and outdoor drying for oyster mushroom showed the same half drying time. Conclusions: Oyster mushroom could be dried easily under outdoor drying until MR (Moisture Ratio) was reached to about 0.2. However, solar drying system showed great effect on drying for most samples compared with indoor and outdoor dryings, when MR was less than 0.5.

• Journal of Biosystems Engineering
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• 제41권4호
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• pp.357-364
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• 2016

Purpose: This study was performed to define the drying characteristics of sorghum by developing thin layer drying equations and evaluating various grain drying equations. Thin layer drying equations lay the foundation characteristics to establish the thick layer drying equations, which can be adopted to determine the design conditions for an agricultural dryer. Methods: The drying rate of sorghum was measured under three levels of drying temperature ($40^{\circ}C$, $50^{\circ}C$, and $60^{\circ}C$) and relative humidity (30%, 40%, and 50%) to analyze the drying process and investigate the drying conditions. The drying experiment was performed until the weight of sorghum became constant. The experimental constants of four thin layer drying models were determined by developing a non-linear regression model along with the drying experiment results. Result: The half response time (moisture ratio = 0.5) of drying, which is an index of the drying rate, was increased as the drying temperature was high and relative humidity was low. When the drying temperature was $40^{\circ}C$ at a relative humidity (RH) of 50%, the maximum half response time of drying was 2.8 h. Contrastingly, the maximum half response time of drying was 1.2 h when the drying temperature was $60^{\circ}C$ at 30% RH. The coefficient of determination for the Lewis model, simplified diffusion model, Page model, and Thompson model was respectively 0.9976, 0.9977, 0.9340, and 0.9783. The Lewis model and the simplified diffusion model satisfied the drying conditions by showing the average coefficient of determination of the experimental constants and predicted values of the model as 0.9976 and Root Mean Square Error (RMSE) of 0.0236. Conclusion: The simplified diffusion model was the most suitable for every drying condition of drying temperature and relative humidity, and the model for the thin layer drying is expected to be useful to develop the thick layer drying model.

• 한국의류산업학회지
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• 제10권6호
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• pp.1058-1063
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• 2008

The use of clothes dryers is increasing in Korea and throughout Asia, because of preference for the drum type washer dryer. Clothes dryers consume more energy than almost any other home appliance. This paper suggests efficient ways for drying laundry with condensing clothes drier. We dried cotton fabrics with the condensing clothes dryers and observed the energy input, temperature and RH of the dryer during the drying process. In the early stages of drying process, the air temperature inside the clothes dryer decreased and the RH and the drying time increased as the weight of fabrics increased. We found that it was important to consider the total weight of the fabrics that included heat-sensitive fibers. It took more than half the drying time and the energy input for a 2.5 kg load that it did for a 5 kg load. Therefore, drying larger one load was more efficient than divided smaller loads, because increasing the weight of the fabrics reduced the energy input per kg of drying clothes. The lower the initial moisture regains of the fabrics were, the lower the energy input and the drying time were. The energy input for spinning after washing was much less than that for drying in the dryer. Consequently, it is more efficient to reduce the moisture content of the clothes by lengthening the spinning time of the washer to reduce the energy consumption and the drying time. During the drying process opening the door twice for 30 seconds each time lowered the air temperature and the RH of the dryer, but did not affect the moisture regain of the fabrics, the drying time, and the energy input.

• Journal of Biosystems Engineering
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• 제27권1호
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• pp.45-50
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• 2002

This study was performed to develop thin layer drying equations fur short grain rough rice using far-infrared ray. Thin layer drying tests was conducted at four far-infrared ray temperature levels of 30, 40, 50, 60$^{\circ}C$ and two initial moisture content levels of 20.7, 26.2%(w.b.). The measured moisture ratios were fitted to Lewis and Page drying models by stepwise multiple regression analysis. Half response time of drying was affected by both drying temperature and initial moisture content at drying temperature of below 40$^{\circ}C$, but at above 40$^{\circ}C$ was mainly affected by drying temperature. Experimental constant(k) in Lewis model was a function of drying temperature, but K and N in Page model were function of drying temperature and initial moisture content. Moisture ratios predicted by two drying models agreed well with experimental values. But in the actual range of drying temperature above 30$^{\circ}C$ Page model was more suitable for predicting of drying rates.

• Journal of Biosystems Engineering
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• 제31권5호
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• pp.410-415
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• 2006

This study was performed to develop thin layer drying equations for green rice. Thin layer drying tests of green rice were conducted at three temperature levels of 30, 40, $50^{\circ}C$ and two relative humidity levels of 30, 50% respectively. The measured moisture ratio were fitted to the selected four drying models (Page, Thompson, Simplified diffusion and Lewis model) using stepwise multiple regression analysis. The overall drying rate increased as the drying air temperature and as relative humidity was increased, but the effect of temperature increase was dominant. Half response time (Moisture ratio=0.5) of drying was affected by both drying temperature and relative humidity Drying rate was mainly affected by relative humidity at drying temperature of $50^{\circ}C$. The results of comparing coefficients of determination and root mean square error of moisture ratio for four drying models showed the Page model was found to ft adequately to all drying test data.

• Journal of Biosystems Engineering
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• 제29권6호
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• pp.495-500
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• 2004

This study was performed to develop thin layer drying equations for low temperature. Thin layer drying tests of short grain rough rice were conducted at three low temperature levels of 15, 25, $35^{\circ}C$ and two relative humidity levels of 30, $50\%$, respectively. The measured moisture ratios were fitted to the selected four drying models (Page, Thompson, Simplified diffusion and Lewis model) using stepwise multiple regression analysis. The overall drying rate increased as the drying air temperature was increased and as relative humidity was decreased, but the effect of temperature increase was dominant. Half response time (Moisture ratio=0.5) of drying was affected by both drying temperature and relative humidity at drying temperature of below $25^{\circ}C$, but at $35^{\circ}C$ was mainly affected by drying temperature. The results of comparing coefficients of determination and root mean square error of moisture ratio for low drying models showed that Page model was found to fit adequately to all drying test data.

• Journal of Biosystems Engineering
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• 제6권2호
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• pp.48-57
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• 1982

In order to improve the quality of traditionally sun-dried red peppers and to increase the efficiency of drying performance, three types of solar dryers were designed and built, and drying performance of the solar dryers was compared to traditional sun drying. Results obtained from the experiment are summarized as fallows: 1. The air temperature and relative humidity profiles over a 8-hour period measured at the specified locations in the drying chamber of solar dryers appeared to have large variation in each dryer. The rate of drying increased with the temperature rise in the drying chamber of the solar dryer. 2. In general. drying with solar dryers proceeded faster than traditional sun drying. With A'-type of solar dryer developed in the second experiment it was possible to dry red peppers in seven days from an initial moisture content of 80% to safe storage conditions. The drying time with the A'-type solar drier was 50% shorter compared to traditional sun drying. 3. Red peppers appeared to have an increasing or constant-rate drying period until the weight of the product was reduced to about one half the initial weight, followed by a falling-rate drying period. When the dried red peppers were exposed to the atmospere during the night, the moisture content increased as much as 6%, which is much higher than for the grains. 4. It was suggested from the experiment that either a heat storage system or a supplemental heating system in the solar dryer was desirable for more efficient drying operation. 5. It was shown that the solar dryer developed in this study may be suitable for drying other vegetables and fishes, and also offered additional advantages of saving in drying time, maintaining sanitation and minimizing contamination by dust, insects and unfavorable weather condition.

• 한국환경농학회지
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• 제37권3호
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• pp.213-220
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• 2018

BACKGROUND: This study was carried out to determine characteristics of residual pesticides in time-dependent manner and calculate half-lives of the residual pesticides in fresh and dried Chinese matrimony vine. In addition, processing factors were calculated based on the residual concentrations in them. METHODS AND RESULTS: The test pesticides, etofenprox and fenitrothion, were sprayed onto the Chinese matrimony vine plants at once or twice (at seven-day interval) and then samples were collected at 0 (after 3 hours), 1, 3, 5 and 7 days after the last spraying. Dried samples were prepared in hot-air drying oven at $60^{\circ}C$ for 48 hours until water content of less than 20%. Residual concentrations of etofenprox in fresh and dried samples decreased by 54.0-60.9% after 7 days of the last pesticide-application. In case of fenitrothion, the concentrations were found to have decreased by 69.2-76.5%. Processing factors of etofenprox were 2.6-3.0 for the one-time spraying and 2.5-3.0 for the two-time spraying and those of fenitrothion were found to be 1.5-22 for the one-time spraying and 1.6-2.0 for the two-time spraying. First half-lives of etofenprox and fenitrothion in fresh and dried samples ranged from 5.0 to 6.3 and from 3.4 to 4.0 days, respectively. The third half-lives were found to be 15.0-18.9 and 10.2-12.1 days, respectively. CONCLUSION: Residual concentrations of the tested pesticides in the studied crop decreased, but those in the dried samples appeared to have increased. In addition, processing factor and half life were constant regardless of spraying times.

• 한국건축시공학회지
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• 제12권4호
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• pp.393-400
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• 2012

본 연구에서는 고로슬래그의 치환율이 80% 이상에 이르는 슬래그 대량 치환 콘크리트(High Volume Slag Concrete, HVSC)의 개발을 목표로 응결특성, 압축강도, 건조수축 및 중성화 저항성에 미치는 고로슬래그 치환율의 영향 및 알칼리 자극제의 효과에 대해 평가하였다. 고로슬래그 미분말의 치환율 증가에 따른 시험결과는 다음과 같다. 응결시간은 초결 및 종결 도달시간이 약 2~2.5 시간 지연되는 것으로 나타났으며 압축강도 발현특성은 초기 및 장기의 모든 재령에서 감소하였다. 건조수축은 치환율에 따른 뚜렷한 경향을 나타내지 않았으며 모든 배합에서 $6{\times}10^{-4}$ 이하의 값을 보여 매우 양호한 것으로 나타났다. 중성화는 현저히 증가하는 경향을 나타냈다. 한편 알칼리 자극제의 첨가에 따른 응결시간 및 초기강도 발현특성은 현저히 개선되었으며 건조수축에 기여하는 효과가 큰 것으로 나타났다. 반면 중성화 저항성에 미치는 영향은 크지 않은 것으로 나타났다.

• 공업화학
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• 제4권3호
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• pp.497-504
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• 1993

본 연구는 고온 구조재료 및 전자재료로 주목받고 있는 복합산화물인 mullite($3Al_2O_3${\cdot}2SiO_2$)를 금속알콕사이드에 의한 졸-겔법으로 합성함에 있어서 재활용품으로서의 aluminium foil을 aluminium 금속원으로 사용하여 알루미늄 알콕사이드를 제조하고 $Si(OC_2H_5)_4$와 혼합하여 가수분해 단계에서 건조조절화학첨가제(Drying Control Chemical Additives, DCCA)를 첨가함으로써 건조시간을 단축시키려는 시도를 하였으며 이러한 DCCA가 mullite 물성에 어떠한 영향을 주는지 검토하고자 하였다. 이때 DCCA로 N, N-dimethyl formamide (DMF), Glycerol, 1, 4-Dioxane과 Oxalic acid가 첨가되었으며 건조된 겔을 각 온도별로 소성하여 TG-DTA, FT-IR, XRD 및 SEM을 사용하여 결정의 전이과정 및 각 소성온도에서의 결정상태 등을 관찰하였다. DCCA를 첨가하여 건조시킨 결과 0.1mole의 DMF를 첨가하였을 경우 DCCA를 첨가하지 않았을 때보다 건조시간이 1/2 정도 단축되었으며 분석결과 mullite의 결정형성에 큰 영향을 미치지 않았음을 확인하였다.