• 한국산업융합학회 논문집
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• 제6권2호
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• pp.103-108
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• 2003

This study was performed to find out drying characteristics and develop waste heat recovery dryer. this system was initiated in order to recover discharged waste heat of drying air from drying chamber in agricultural products dryer and recycle for additional heat source that could save drying cost. The system consists of drying chamber, fan, burner, circulation pump and heat exchanger made of fins and tubes. For the system performance, drying experiments with fresh pepper were conducted, and comparisons on fuel consumption amount and drying performance were made between conventional dryer and the heat recovery system attached dryer.

• Journal of Biosystems Engineering
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• 제41권4호
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• pp.389-395
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• 2016

Purpose: Drying is one of the most widely used methods for preserving agricultural products or food. The main purpose of drying agricultural products is to reduce their water content for minimizing microbial spoilage and deterioration reaction during storage. Methods: Although numerous drying methods are successfully applied to dehydrate various agricultural products with little drying time, the final quality of dried samples in terms of appearance and shape cannot be guaranteed. Therefore, based on published literature, this review was conducted to study the drying characteristics of various agricultural products when different drying methods were applied. Results: An increase in the drying power of sources-for example, increase in hot air temperature or velocity, infrared or microwave power-and the combination of drying power levels can reduce the drying time of various agricultural products. In addition, energy efficiency in drying significantly relies on the compositions of the dried samples and drying conditions. Conclusions: The drying power source is the key factor to control entire drying process of different samples and final product quality. In addition, an appropriate drying method should be selected depending on the compositions of the agricultural products.

• Journal of Biosystems Engineering
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• 제29권1호
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• pp.37-44
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• 2004

This study was conducted to develop a new drying method far reducing the drying cost and time and to investigate the drying characteristics of oak mushroom. A far infrared dryer of down draft air flow type used for this experiment can control the drying parameters, such as far infrared heater temperature and aeration velocity. The far infrared drying tests were performed at aeration velocities of 0.3 and 0.6m/s under the temperature of 90 and 100$^{\circ}C$ in for infrared heater, respectively. The results were compared and analyzed with those of an heated air drying method used as a control in terms of properties representing the drying characteristics. such as shrinkage rate, color, energy consumption amino acid components, drying rate and moisture ratio. The results obtained from this research can be summarized as follows. 1. The drying rate of far infrared drying was faster than that of heated air drying. With high temperature of far infrared heater and slow aeration velocity, the far infrared drying of down draft air flow type was superior to the heated air drying. 2. Most of far infrared drying conditions required less energy consumption than heated air drying. 3. The shrinkage rates of heated air drying and far infrared drying were decreased by 17.0% and 18.2∼19.8%, respectively. 4. The difference of color on oak mushroom surface before and after drying can be represented as $\Delta$E. $\Delta$E values of far infrared drying and heated air drying were 2.39∼4.55 and 6.77, respectively. 5. The amounts of free amino acids were higher in the far infrared than in the heated air drying. In addition the amounts of Gln and Glu generally were increased and those of Ala, Leu, and Val were decreased in order.

• Food Science and Biotechnology
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• 제14권5호
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• pp.661-666
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• 2005

The specific objectives of this study were to dry yam chips using microwave vacuum drying, freeze drying and hot air drying, then to coat the dried yam chips with ascorbic acid cocrystallized sucrose, and finally to compare the quality of yam chip snack foods with respect to drying and coating characteristics. The microwave vacuum dried sample showed the highest drying rates and much less surface damage than the hot air dried one did. The shape and color of the microwave vacuum dried/coated sample were allocated between those of the freeze dried/coated sample and the hot air dried/coated sample. The freeze dried/coated sample scored excessively low in organoleptic hardness and chewiness to be suitable as a snack. The hot air dried/coated sample was too deep in color, wrinkled, excessively high in organoleptic hardness and chewiness, and excessively low in mouthfeeling. Therefore, the microwave vacuum dried/coated sample presented the best overall attributes as a snack, with respect to organoleptic characteristics, shape, color, and drying rates.

• 태양에너지
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• 제11권3호
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• pp.9-20
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• 1991

무우절편의 태양열건조 및 천일건조 실험을 수행하여 건조 특성 및 품질 변화 특성을 비교하여 분석하였다. 무우절편의 태양열 건조 시스템은 공기 가열식 태양열 집열기와 터널 건조실로 구성된다. 태양열 집열기의 구성 요소에 에너지 평형식을 적용하여 일사량과 송풍량의 변화에 따른 집열기의 집열성능을 분석할 수 있는 시뮬레이션 모형을 개발하였다.

• 설비공학논문집
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• 제18권8호
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• pp.678-685
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• 2006

Analysis of drying characteristics has been carried out with one-dimensional model in the dryer using the principle of the refraction of radiation. The dryer is composed of hot water tank, plastic film conveyer belt, drying material, etc. The model considers the con-duction and radiation within the plastic film and drying material. The film is semitransparent to radiation and the drying material is assumed to be semitransparent or opaque to radiation. The results show that the effect of radiative transfer on the drying rate is relatively large when the thickness of drying material is small and the water temperature is high. When the material is thin, the drying rate due to conduction is also enhanced and the drying time can considerably be reduced.

• 한국식품과학회지
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• 제21권2호
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• pp.203-211
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• 1989

근채류를 열풍건조할 경우 수축변형 및 표면 경화현상을 일으켜 품질변화를 수반하게 되므로 본 연구에서는 온도, 상대습도 및 풍속을 조절할 수 있고 건조중의 시료크기 변화를 측정할 수 있는 실험실 규모의 건조장치를 제작하여 무우 및 고구마의 건조특성과 수축특성에 영향을 미치는 외부 요인들에 대해 조사하였다. 건조속도는 무우 및 고구마 모두 항률건조기, 감률건조기, 감률건조 2단계 a 및 b의 4단계로 구분되어 나타났다. 수축속도 곡선은 각각 건조속도에 대응하여 기울기가 다른 4단계로 나타났으며 항률건조 기간에서는 수축속도가 서서히 증가하다가 감률건조 1단계에서 급격히 증가하였고 감률건조 2단계의 초기에 상당하는 점에서 최대에 달하였다. 또한 시료의 두께. 상대습도 및 초기 함수율 등은 표면적 수축에 큰 영향을 미쳤고 시료의 두께가 얇을수록, 그리고 상대습도 및 초기 함수율이 높을수록 평형 상태에서의 수축율은 증가하였다.

• 한국식품영양학회지
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• 제22권2호
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• pp.192-198
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• 2009

Cheongkukjang is a traditional fermented soybean food in Korea that is used in the manufacture of functional foods. This study was conducted to assess vitamin contents and sensory qualities of powdered Cheongkukjang dried by oven drying, far-infrared drying and freeze drying. Vitamins $B_1$, $B_2$, $B_6$, E, niacin and pantothenic acid were detected using all drying methods. However, vitamin D was not detected in the oven drying samples, and was most prevalent($82.47{\mu}g$/100 g) in the far-infrared drying samples. The sensory characteristics included color, off flavor, salty taste, bitter taste, sweet taste, roasted taste and after-taste. Oven drying and freeze drying samples exhibited highest and lowest color scores(5.62 and 2.0, respectively). Oven drying samples also exhibited the highest roasted taste score(4.76), although not significantly different from far-infrared drying samples(4.0, p<0.05), while the score of freeze drying samples(2.38) was significantly different from the other methods(p<0.05). It is concluded that freeze drying is most suitable.

• 농업과학연구
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• 제45권4호
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• pp.847-857
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• 2018

Recently, customers' demand and attention to dried agricultural products or foods have increased due to their convenience and nutritional values. Conventional drying methods such as solar drying and hot air drying have been most widely used for producing a large amount of dried agricultural products; however, those methods require quite a long time and high energy consumption. To compensate for these issues associated with conventional methods, dielectric heating such as microwave and radio frequency heating has been used as a supplemental method in the drying procedure. This study investigated the microwave drying characteristics of squash slices with different thicknesses under different microwave power intensities and determined the best drying model that could precisely describe the experimental drying curves of the squash slices. The squash was cut into slices with two different thicknesses (5 and 10 mm), and then, they were dried under different microwave power intensity ranges between 90 and 900 W with an increase interval of 90 W. Six drying models were tested to evaluate the fit to the experimental drying data, and the effective moisture diffusivity ($D_{eff}$) values of the squash slices under microwave drying were determined. The results clearly show that as the microwave power was increased, the drying time of both squash slices was significantly decreased, and the slope of the drying rate increased. The effective moisture diffusivity was also significantly related with the microwave power intensities and thicknesses of the slices. In addition, the Page model was most suitable to delineate the drying curves of both squash slices under different microwave power intensities.

• 동력기계공학회지
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• 제15권4호
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• pp.5-10
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• 2011

In case of using rapid vacuum-freeze drying for high quality dry flower of flowering plant, the morphological and physiological characteristics of dry rose showed as the following. The dry ratio of about 82% presented after 1 day in case of using rapid vacuum-freeze drying and it was reached that the optimum storage water content of general dry products was 18%. The dry ratio of about 89% presented after 4 days. This result indicates very short dry time comparing with natural dry time of 12 days. Also, the morphological characteristics of flowering plant in case of vacuum-freeze drying showed similar shape with real flower. The contraction decreased about 9% comparing with real flower under dry time of 72 hours. But the contraction in case of natural dry decreased 36% and showed noticeable difference. The brightness which affects physiological characteristics of dry flowering plant showed lower values according to the dry process and chromaticity was thick. After 4 days, natural dry was thick with about 2 times comparing with vacuum-freeze drying. In case of vacuum-freeze drying, the quantity of anthocyanin and chlorophyl which affect discoloration and bleaching of dry flowering plant showed the clear difference comparing with natural dry method due to the sublimation by vacuum after rapid freeze with short initial time.