• Food Science and Preservation
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• v.2 no.1
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• pp.155-161
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• 1995

We examined the drying characteristics and the drying rate model equation of garlic(allium sativum L.) using computer aided convective drying. The drying chanacteristic curve of garlic divided into constant rate drying period and 2 stage of falling rate drying period. The drying rate was fairly affected by hot air temperatures during the total drying period, but air flow rates has nearly no effect on the drying rate except initial drying period. Of the several model equation, r2 values of page model equation was the highest, and the estimated drying profiles were comparatively coincided with the observed drying profiles. Page model equation was suitable to predict the drying rate and moisture content during drying of sliced garlic.

• Journal of Environmental Science International
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• v.30 no.3
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• pp.245-255
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• 2021

In this study, we evaluated the effect of the type of sewage sludge (digested, non digested) on drying efficiency according to the polymer injection rate. The drying characteristics were shown using a near-infrared ray (NIR) and a microwave. As a result of the drying characteristics with NIR at a polymer dose ratio of 8%, the heating up period is up to 6 minutes after the start of the drying experiment. Afterwards, the constant rate drying period of the digested sludge (A, C and G sites) was 6 minute → 18 minute, showing a rapid decrease in moisture. On the other hand, non digested sludge (B, D, E, F, H, I, J and K sites) showed gradual drying characteristics compared to digested sludge until complete drying (10%). As the polymer dose ratio of 10% and 12%, the heating up period for digested sludge is up to 6 minute after the start of the experiment. Afterwards, the constant rate drying period of the digested sludge was 6 minute → 20 minute, showing a rapid decrease in moisture. On the other hand, the heating up period of non digested sludge was up to 10 minute after the start of the experiment, and the constant rate drying period was 10 minute → 22 minute, which was shorter than digested sludge. As a result of the drying characteristics with microwave at a polymer dose ratio of 8%, 10% and 12%, the constant rate drying period the digested sludge was 4 minute → 20~22 minute, showing a rapid decrease in moisture. On the other hand, non digested sludge of the constant rate drying period was 4 minute → 22~30 minute, which was longer than digested sludge.

• Journal of Biosystems Engineering
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• v.19 no.2
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• pp.112-123
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• 1994

At present, no appropriate drying conditions can be found for the heated-air drying of mushroom in Korea. Usually, mushroom is being dried at the temperature range of 40 to $50^{\circ}C$ until the moisture content reaches 10~13% (wb). However, drying characteristics of the mushroom should be investigated for quality improvement and efficient drying operation of the mushroom. The results of this study may be summarized as follows ; 1. The effect of air temperature on the rate of drying was greater than that of relative humidity for drying of mushroom, and the rate of drying was increased with increase in the air temperature. 2. Drying rate for Shiitake mushroom showed falling-rate period of drying without constant-rate period of drying. Drying rate for Oyster mushroom showed a short constant-rate period at the initial stage of drying process, and followed by falling-rate period of drying. 3. Exponential and App.-Diffusion models were found to describe well the drying process of Shiitake mushroom. Exponential and Thompson models for Oyster mushroom in which Thompson model was the most suitable for Oyster mushroom. 4. The equilibrium moisture content of the mushroom decreased with decrease in the air temperature and increase in the relative humidity. In room condition($20^{\circ}C$, 54% RH), the calculated values of the equilibrium moisture content showed 11.17% for Shiitake mushroom and 13.19% for Oyster mushroom, respectively.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.242-247
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• 2009

The present study has been conducted to reduce the cold air drying rate. According to the cold air drying method, the quality-excellent product could be made and there would be little change of color, taste and smell. As compared with the hot air drying, the cold air drying equipment has the superior dehumidification in a constant drying zone. However, in a falling drying zone that equipment is not energy-efficient because the drying period could be longer by the dehumidificated.

• Analytical Science and Technology
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• v.10 no.6
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• pp.418-426
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• 1997

Dewatered digested sewage sludge were heated with microwave and their drying characteristics were investigated on the effect of their surface area, shape, diameter and thickness. The drying characteristics of identical samples in a conventional drying oven were studied. In conventional drying, constant rate period was not found and moisture was evaporated with capillary action. Moisture in the sludge was a bound water and free water was not exist. In microwave drying, the falling rate period was divided into two zones. In falling rate drying period, moisture movement occured by diffusion. The evaporation surface area was a significant variable, the greater heating surface area promoted water removal rate over wide region of water content. Drying rate was slow and constant rate drying period was found in wide moisture content region with increasing diameter. Drying characteristics appeared differently in various shape. In microwave heating, first of all temperature of sludge center was increased and was the highest. Temperature in the constant rate drying period was remained constantly at $80{\sim}100^{\circ}C$.

• Journal of Biosystems Engineering
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• v.11 no.1
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• pp.52-63
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• 1986

This study was performed to find out drying characteristics and develop drying model for the design of an efficient dryer or drying system of red peper. The basic model which describes drying phenomenon of red pepper was firstly established, and drying tests were conducted at 14-different drying conditions. In this test, the effects of drying air temperature and relative humidity on the rate of drying were undertaken. Finally, a new drying model based on these experimental results was developed to describe the drying characteristics of red pepper. The results from this study may be summarized as follows. 1. Drying constant of the basic model established from Lewis' experimental model and diffusion equation was theoretically deduced as a function of moisture content and inner-temperature of red pepper. 2. From the results of drying tests, drying air temperature was found to have the greatest effect on the rate of drying. However, the effect of temperature was small for the condition of high relative humidity, and for low temperature, the effect of relative humidity was found to be large even though the range of relative humidity was low. 3. Modified Henderson equation was found to be better than Chung equation as the EMC model for the estimation of the equilibrium moisture content of red Pepper. 4. Constant-rate drying period did not exist in the red pepper drying test. And falling-rate drying period was divided into three distinct phases. Drying rate was dependent on the moisture content, the inner-temperature of red pepper and the change of physical property due to drying. 5. Drying constant increased with decrease of free moisture content, but it decreased at the end of the drying period. Also, drying constant was dependent on the drying air temperature and relative humidity. 6. The new drying model developed in this study was found to be most suitable in describing the drying characteristics of red pepper. Therefore, it may be concluded that drying time could be accurately estimated by the new drying model.

• Journal of the Korean Society of Food Science and Nutrition
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• v.25 no.3
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• pp.453-459
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• 1996

This study was carried out to determine the changes in quality during the drying process and the optimum drying condition for utilizing soybean curd residue. The quality criteria for soybean curd residue were acid value, peroxide value, fatty acid composition and microbial concentration. The acid values of soybean curd residue were 7.5, 4.5 and 5.9 KOH mg/g upon 12 hour drying with open-air sun, ambient-air blast and warm-air blast, respectively. The numbers of total aerobic bacteria and molds increased remarkably during drying with open-air sunlight, ambient-air blast and warm-air blast except for hot air blast. Among different drying methods, the hot air blast drying(1kg of sample) was the most effective methods, which completed in three hours. Also, the drying method demonstrated a typical drying curve ; settling down, constant rate drying and falling rate drying period were shown within one hour, from one and three hours and after three hours, respectively. Moreover, there was significant variation in the constant drying period for the quality of soybean curd residue.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2001.10a
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• pp.256-260
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• 2001

This study was initially performed to investigate current red-pepper drying methods commonly being adopted on red-pepper cultivation farm area. Based on the informations obtained from the field survey, an experiment of red-pepper drying was carried out to verify the actual drying potential of plastic covered solar house similar to the conventional pipe frame greenhouses covered with one or two layer of plastic film. Some results obtained from field survey and drying experiment for red-pepper are summarized as follows; 1. Various patterns of red-pepper drying process were found; 1) complete natural drying with red-pepper exposed in outdoor air, 2) hot air drying by dry chamber only, 3) combination drying by hot air dryer together with plastic covered passive solar house, 4) drying with plastic covered solar house unit. 2. The average air temperatures of outdoor and solar house during drying experiment period were $26.9-30.8\;and\;28.6-33.8^{\circ}C$, respectively, and the maximum air temperatures of those two were $34.2-36.4\;and\;39.8\;-52.3^{\circ}C$, respectively. Horizontal solar intensity during experiment period was $18.49-23.96\;MJ/m^{2}$, and relative humidity of outdoor and experimental solar house were 56 - 66% and 64 - 70%, respectively. 3. The weight of red-pepper during drying experiment period was decreased almost linearly from initial moisture content of 85% to final moisture content of 14%.

• Journal of Animal Environmental Science
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• v.8 no.3
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• pp.177-182
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• 2002

Drying process is very important for commercialization of velvet antlers. So far, artificial drying has mostly depended on experience of farmers resulting in low efficiency of drying, deterioration during drying, and contamination by dust and bacteria. Various drying techniques for high-quality production have currently been commercialized in some developed countries, and one of them is a drying technique using microwave. In this study, application of the technique using an electronic (microwave) oven for drying of velvet antler was investigated. The results of this study are as follows. 1. It was found that the drying period was significantly affected by cornification of velvet antlers. Accordingly, it can be assumed that the velvet antlers should partly be sliced to save drying period and required drying energy. 2. It was also found that the drying speed was changeable according to tempering period and even with same drying period. The tempering period should be controlled according to processing rate. 3. The results indicated that a repeated drying of 2-min drying and 3-min tempering is the most effective when a microwave oven was used. 4. The results also showed that the drying technique using microwave of electronic oven can be effectively used for drying of velvet antlers. 5. Only drying and tempering periods were examined in this study, however, ingredient change of deer antler after drying is necessary to be investigated in the future.

• Korean Journal of Food Science and Technology
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• v.21 no.2
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• pp.203-211
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• 1989

During hot air drying of root vegetables such as radish and sweet potatoes, shrinkage and casehardening occurred, and thereby the quality change appeared. Therfore the hot air drying apparatus in which air temperature, relative humidity and air velocity could be controlled was designed, and the drying and shrinking characteristics of radish and sweet potatoes were studied. Also the external factors that affected these characteristics were investigated. The whole drying process of radish and sweet potatoes could be divided into four different drying rate periods, namely constant rate period, first falling rate period, second falling rate period (a) and (b). The shrinking rate curve consisted of four periods nearly corresponding to drying rate periods. The shrinking rate slowly increased in the constant rate period, rapidly increased in the first falling rate period, and reached the highest value in the early period of the second falling rate period. The surface shrinkage was greatly affected by the thickness of sample, relative humidity and initial moisture content. The shrinking ratio was increased with decreasing thickness and increasing relative humidity and initial moisture content.