• Journal of Biosystems Engineering
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• v.6 no.2
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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.

• Journal of Power System Engineering
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• v.14 no.4
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• pp.23-28
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• 2010

Of the roughly four million known substances, about 60,000 are processed and sold ; many of these must be dried. Many materials are processed in the liquid state - ideal for mixing and reacting - but most products are needed or wanted as dry, or relatively dry, solids. Usually operation is just below atmospheric pressure, as with direct dryers, but some are built for vacuum operation with pressures as low as 26.66kPa abs.. In spite of the global-class aquiculture agriculture and fisheries technology of our country, the processing technologies are lags behind the other nations relatively. These problems are considered to be caused directly by the lack of drying technologies. This paper is concerned to the experimental results of drying heat transfer characteristics for the green energy type vacuum dryer for the high quality agriculture and fisheries production.

• Journal of Biosystems Engineering
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• v.42 no.3
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• pp.190-198
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• 2017

Purpose: A thin-layer drying equation was developed to analyze the drying processes of soybeans (white and black beans) and investigate drying conditions by verifying the suitability of existing grain drying equations. Methods: The drying rates of domestic soybeans were measured in a drying experiment using air at a constant temperature and humidity. The drying rate of soybeans was measured at two temperatures, 50 and $60^{\circ}C$, and three relative humidities, 30, 40 and 50%. Experimental constants were determined for the selected thin layer drying models (Lewis, Page, Thompson, and moisture diffusion models), which are widely used for predicting the moisture contents of grains, and the suitability of these models was compared. The suitability of each of the four drying equations was verified using their predicted values for white beans as well as the determination coefficient ($R^2$) and the root mean square error (RMSE) of the experiment results. Results: It was found that the Thompson model was the most suitable for white beans with a $R^2$ of 0.97 or greater and RMSE of 0.0508 or less. The Thompson model was also found to be the most suitable for black beans, with a $R^2$ of 0.97 or greater and an RMSE of 0.0308 or less. Conclusions: The Thompson model was the most appropriate prediction drying model for white and black beans. Empirical constants for the Thompson model were developed in accordance with the conditions of drying temperature and relative humidity.

• Food Science of Animal Resources
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• v.18 no.2
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• pp.164-175
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• 1998

The objective of this study was to investigate the effects of freezing rate on ice crystal size and freeze-drying rate. Our experiments were carried out with self-manufactured freeze-dryer. Gelatin gels (2% w / w, 80$\times$20mm) were frozen unidirectionally (Neumann's model) from the bottom at -45, -30, -20, and -15$^{\circ}C$ and followed with freeze-drying. Under the upper conditions we measured freezing rate and the change of temperature and pressure during freeze drying. Freeze-dried gelatins were cut horizontally into 5 mm thickness from the bottom and measured their pore sizes. Also freeze-drying rate(primary drying) is estimated by measuring the temperature of sample and pressure of vacuum chamber. During freeze-drying, profiles of pressure and temperature were shown constant tendency regardless of freezing temperature and we could expect the end-point of freeze drying by considering pressure and temperature together. In temperature profiles, the point which temperature increased significantly was observed during freeze-drying. There is no relationship between freeze temperature and drying rate of primary drying in our model system. As freezing temperature increased, ice crystal size(X*) which correspond to 63.2% of cumulative frequency was increased and at the same freezing temperature ice crystal size(X*) was decreased with distance from the bottom of the sample. Freezing conditions have a strong influence on the quality of the final freeze-dried products in freeze-drying system.

• Food Science and Biotechnology
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• v.16 no.5
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• pp.771-777
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• 2007

Sliced and whole root of rehmannia were dehydrated in a laboratory dryer at 40, 60, 80, and $100^{\circ}C$ to evaluate the kinetic parameters for dehydration of rehmannia. The drying curves of both samples were characterized by a falling-rate drying period only. Sliced rehmannia dried 1.1 to 3.1 times faster than whole root of rehmannia depending on drying temperature. Equilibrium moisture content (EMC) of rehmannia samples at the drying temperature tested were 0.069-0.078 g water/g dry solid, which was coincided with the monolayer moisture content (0.06 and 0.07 g water/g dry solid) evaluated from desorption isotherms using GAB (Guggenheim-Anderson-de Boer) model. A logarithmic model for thin layer drying was applied to evaluate the drying time to reach EMC ($t_{EMC}$) and drying constant (k). The effect of temperature on $1/t_{EMC}$ and k was described by the Arrhenius model with activation energy values of 32.56 and 47.14 kJ/mol determined using the former parameter, and 34.27 and 38.26 kJ/mol determined using the latter parameter for sliced and whole root of rehmannia, respectively.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.15 no.3
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• pp.207-210
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• 1982

For the removal of initial water content in cuttlefish, the effects of fixed-bed drying condition on the drying rate were investigated, with following results. 1. The drying rate of cuttlefish dried at fixed-bed condition was also faster than that at natural convection type or hot air dryer.2. By controlling air temperature and its direction to cut-and-peeled sample the drying time can be reduced to 2 hrs. 3. Shirai's equation and Arrhenius' law were applicable to fixed-bed dried cuttlefish. Drying rate constant (k) by Shirai's equation, and Arrhenius' plot were as shown in Table 3, 4 and Fig.3, respectively.

• Journal of Biosystems Engineering
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• v.25 no.2
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• pp.115-122
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• 2000

This study was performed to develop a prototype continuous flow ginseng dryer with which better product quality and lower drying energy consumption could be achieved compared with conventional ginseng dryers. A dryer having both far infrared ray (IR) and heated-air as the drying energy sources was designed and fabricated . Dryer performance was studied by examining energy efficiencies and dryer performance evaluation indices (DPEI) during the drying tests of medium-sized four year ginseng roots with IR radiating plate temperature and drying air temperature in the range of 80-12$0^{\circ}C$ and 22-5$0^{\circ}C$, respectively. The DPEI of IR /heated -air combined drying was 1/3 of that of the conventional heated-air drying when ginseng were dried to the same final moisture ratio. When ginsengs were dried for 12 hours in the prototype IR/heated-air combination dryer, a linear relationship was found to exist between final moisture ratio and ginseng temperature. As the drying progressed, drying air temperature inside the dryer was nearly constant but ginseng temperature was drastically increased during the first two hours and gradually increased thereafter until the end of drying. With the prototype Ir/heated-air combination dryer, the drying rate changed little but the energy efficiency increased proportionally when the amount of ginseng to be dried increased. Drying capacity, energy efficiency, and DPEI of the prototype IR/heated-air combination ginseng dryer were estimated to 1.500 roots, 65% and 3.800kJ/kg-water , respectively.

• Journal of The Korean Society of Grassland and Forage Science
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• v.33 no.4
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• pp.234-239
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• 2013

This study investigated the effects of drying methods and drying time on the changes in anthocyanin content in colored barley. Colored barley cultivar Boanchalbori was harvested at a time when the anthocyanin content was the most and dried in afield. The harvested barley was then treated by two methods, sun drying and shade drying, for 4, 8, 24, and 32 h. The moisture content of the sun-dried barley decreased slightly faster than shade-dried samples, but the difference was not statistically significant. Chemical analysis indicated that the samples dried under shaded conditions had slightly higher crude fiber and lower nitrogen free extract, but the difference was not statistically significant. There was no difference in the total digestible nutrients between the two methods. In the case of sun-dried barley, the anthocyanin content decreased compared to the control and shade-dried samples after drying for 4 h (p < 0.05), was maintained at a constant level at 24 h, and then decreased at 32 h. In case of shade-dried barley, the anthocyanin content decreased gradually with the drying time, and a significant decrease was found at 24 h of drying (p<0.05) as compared to the control. The shade-dried method was more successful in reducing anthocyanin loss than the sun-dried method (p<0.05). There was a slight decrease in 1,1-Diphenyl-2-Picrylhydrazyl radical scavenging with drying time in the shade-dried method, and a significant decrease after 4 h with the sun-dried method. These results showed that covering with a two-layer awning was advantageous to dry colored barley in the field conditions.

• Journal of Biosystems Engineering
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• v.41 no.4
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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.

• Applied Biological Chemistry
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• v.28 no.3
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• pp.167-173
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• 1985

Hot air drying characteristics of six year old cooked ginseng root at temperature ranges of $55{\sim}75^{\circ}C$ under 1.8m/sec air velocity and shrinkages accompained were investigated. Drying time to reach equilibrium moisture content of the root takes from 20 to 30 hours, depending on the subjected drying temperatures and root sizes. Drying curve shows that it has two or three falling stages and drying constant are continuously changed. Higher drying constant was observed both at early and late stages of drying. Shrinkage ratio of length, diameters, surface area and volume of the root were 13.0, 39.8, 47.7 and 68.5%, respectively, after 40 hours dry at $55^{\circ}C$. The most of shrinkage was observed at early drying stage.