• Journal of Biosystems Engineering
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• v.38 no.1
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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 the Korean Wood Science and Technology
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• v.17 no.1
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• pp.22-54
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• 1989

Seasonal semi-greenhouse type solar-drying of 2.5cm-and 5.0cm-thick lumber of Quercus aliena Blume and Quercus variailis Blume was carried out to investigate the possibility of solar-drying of wood and to decide the active solar-drying period in Korea. In the active solar-drying period obtained solar-dehumidification, semi-greenhouse type solar-, air- and kiln-drying of 2.5cm -thick lumber of oaks were carried out to analyze drying-rates. -defects, and -yield in each drying-method and to calculate daily total absorbed solar-radiation the solar dryers. The energy balance equations were set up, considering all the energy requirements, to analyze the heat efficiencies of semi-greenhouse type solar and solar-dehumidification-dryer. In a seasonal drying the drying rate of semi-greenhouse type solar-dryer was highest in summer, and greater in fall, spring, and winter in order. Solar-drying time was 45% in summer to 50% in winter of the air-drying rime, and more serious drying-defects occurred in air-drying than in solar-drying. In the active solar-drying period. April, May, and June, the average drying rate in solar-dehumidification-drying was 1.0%/day and greater than 0.8%/day in semi-greenhouse type solar-drying. In solar-dehumidification-drying the time required to dry lumber to 10% moisture content was less than 60 days, and solar-dehumidification-drying showed the highest drying-yield, 65.01%, than the other drying methods. The daily total absorbed solar radiations were 8.51MJ on the roof collector and 6.22 MJ on the south wall collector. In the energy blance 69.48% of total energy input was lost by heat conduction through walls, roof. and floor 11.68% by heat leakage, 0.33% by heating the internal structures of the solar-dryer and 5.38% by air-venting. Therefore the heat efficiency of semi-greenhouse type solar-dryer 13.13%, was lower than that of solar-dehumidification-dryer, 14.04%. Solar-drying of lumber in Korea showed the possibility to reduce the air-drying-time in every season and the efficiency of solar-dehumidification drying was higher than that of semi-greenhouse type solar-drying.

• Journal of Biosystems Engineering
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• v.3 no.1
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• pp.64-76
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• 1978

A dimensional supply of petroleum fuels and increased competition for petroleum products has made the conservation of energy in grain drying an important cost and management factor. Research on solar grain drying is directed toward utilization of a renewable energy source as an alternative to petroleum fuels for drying. There are many technical and economic problems in accepting and adopting solor energy as a new energy source for grain drying. The purpose of this study are to assess the state of the art of solar grain drying and to find out the problems by reviewing literatures available. The results obtained may be summarized as follows; 1.It may be considered that the weather conditions in October of Korea was satisfactory for the forced natural air and solar heated air drying. 2. Solar energy is considered more applicable to low-temperature, In-storage drying systems than to high-temperature, high-speed drying systems. In-storage drying systems require low levels of heat input. The costs of collector systems to provide low temperature are considerably cheaper than for high-temperature systems. 3. Tubular type collector made of polyvinyle film seems to be the most practical at this stage of development and black-painted bare-plate collectors mounted on the outside of a typical, round, low-temperature drying bin can supply an appreciable amount of the energy efficiently needed for low-temperature grain drying at a lower cost. 4. All of the grains in solar drying tests was successfully dried up to safe storaged moisture levels without significant spoilage. Drying rates with solar system were faster than natural air drying systems, and usually a little slower than similar low-temperature electric drying systems. 5. Final grain moisture levels were lower in solar tests than in natural air tests, and generally higher than in tests with continuous heated air. 6. Savings of energy by use of solar collectors ranged from 23% to 55%, compared to the natural and electric ileated air drying systems. However, total drying cost effectiteness tvas not significant. Therefore, it is desirable that solar grain dry-ing sIFstems tvhich could be suitable for multiple heating purposes on farms shouldbe developed. 7. Supplemental heat with solar radiation did little to reduce air flow requirementsbut refuced drying time and increased the p\ulcornerobability of successful drying duringdrying poriod.

• Journal of the Korean Wood Science and Technology
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• v.20 no.2
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• pp.23-30
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• 1992

An experimental external external collector type, solar dehumidification dryer was retrofitted with a simple computer-based control system. Solar, solar-dehumidification, and air-drying of 3cm-thick douglas-fir were carried out to investigate the drying-conditions and characteristics of this system, and to analyze the energy efficiencies of each drying met hods in summer. The drying rate of solar-dehumidification was 12%/day, which was about 2 times and 3 times faster than that of solar-and air-drying, respectively. The amount of diurnal temperature fluctuation inside the solar-dryer was greatly reduced and the energy efficiency was enhanced from 25% to 60% by the dehumidifier.

• 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.

• Solar Energy
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• v.7 no.1
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• pp.14-22
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• 1987

This paper presents an experimental study of a solar drying system designed and installed by KIER. Experiments have been performed using the KIER system for the drying of marine products, such as squid. Presented in detail are the experimental observations of collector air temperature, solar intensity, absorber plate temperature, drying chamber temperature, humidity and other measures of drying chamber performance with variation of air mass flow rate. As a result, average temperature attained in the drying chamber during autumn weather has been adequated for drying of squids.

• Solar Energy
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• v.11 no.3
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• pp.9-20
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• 1991

Experiments for drying radish were carried out to analyze the drying characteristics and quality evaluation between solar heated-air drying and natural air drying system. Solar heated-air drying system consists of a small fan, a solar air heater and a tunnel dryer. Simulation model for thermal environments of solar collector was developed to investigate the effect of solar radiation and airflow rate on thermal performance.

• 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%.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1993.10a
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• pp.877-885
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• 1993

Three types of solar grain dryers, namely , the solar grain bin dryer, the solar greenhouse rotary drum dryer and small scale solar green house tray dryer, have been tested. The results showed that each type of solar grain dryer has its feature. These solar drying units have three main advantages : (1) Required commercial energy to remove 1Kg moist from rough rice is only 5.3% to 15.8% of the energy consumed by common heated dryer : 2) The area of solar drying system is only about 10% of the area of the sunny ground to give equal drying capacity ; (3) There are good drying quality in the moisture uniform , germination percentage, and grain color.

• Journal of the Korean Wood Science and Technology
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• v.20 no.1
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• pp.5-14
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• 1992

Experimental external collector type solar lumber dryer of $1m^3$ of maximum capacity with $1.6m^3$ of collector area was designed and constructed. The seasonal performance of solar dryer, including air-conditions, energy efficiency, and drying characteristics of 3cm-thick red pine and douglas-fir lumber was investigated. Also, the economic analysis was carried out. Annual average solar drying rate was about 2 times faster than air-drying rate with no significant difference in the amount of drying defects. But in initial drying stage air-drying rate in winter was much faster and those in spring and autumn were slightly slower than solar drying rate in each season. Annual average energy efficiency of solar-dryer and-collector was 25% and 57%, respectively. Fuel savings were over 50% at 15% of energy inflation rate and the payback period was estimated as 6.10 years at 30% of energy inflation rate.