• Journal of agriculture & life science
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• v.53 no.5
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• pp.137-143
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• 2019

To manufacturing of solid fuel by reuse of the wastes, the drying unit which have 500 kg/hr of drying capacity was developed and experimentally evaluate the performance. The spinach grown in Nam-hae island were used for the experiments and investigated of the heated-air drying characteristics as the inlet amount of raw materials, raw material stirring status, conveying type and drying time. The drying air heated by the energy derived from the steam which is supplied from the incineration plant. The moisture contents of raw materials were measured 85.65%. The inlet flow rate of drying air made a difference as the depth of the raw materials loaded on the drying unit and temperature has showed 108~144℃. The drying speed of the mixed drying more than doubled as that of non mixed drying under the same drying type, inlet amount, drying time and drying air temperature. In each experiment, the drying capacity have showed over 500 kg/hr. A drying efficiency of the ratio of drying consumption energy to input energy was 33.46%, lower than the average of 57.76% for the 157 conventional dryers. Because developed dryer must have a drying time of less than one hour, it is considered that the dry efficiency has been reduced due to the loss of wind volume during drying. If waste heat from incineration plant is used as a direct heat source, the dry air temperature is expected to be at least 160℃, greatly improving the drying capacity.

• The Journal of Engineering Geology
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• v.34 no.2
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• pp.229-248
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• 2024

This investigated the hydrogeochemical and isotopic characteristics of geothermal waters, groundwaters, and surface waters in Dongrae-gu, Busan, South Korea, in order to determine the origins of the salinity components in the geothermal waters, and their formation mechanisms and heat sources The geothermal waters are Na-Cl-type, distinct from surrounding groundwaters (Na-HCO₃^- and, Ca-HCO₃^- (SO₄, Cl)-type) and surface waters (Ca-HCO₃(SO₄, Cl)-type). This indicates the geothermal waters formed at depth as compared with the groundwaters. δ¹⁸O and δD values of the geothermal waters are relatively depleted as compared with the groundwaters, due to altitude effects and deep circulation of the geothermal waters. Helium and neon isotope ratios (³ He/⁴He and, ⁴He/²⁰Ne) of the geothermal waters plot on a single mixing line between mantle (³He = 3.76~4.01%) and crust (⁴He = 95.99~96.24 %), indirectly suggesting that the heat source is due to the decay of radioactive elements in rocks. The geothermal reservoir temperatures were calculated using the silica-enthalpy and Giggenbach models, yielding values of 82~130℃, and the depth of the geothermal reservoir is estimated to be 1.7~2.9 km below the surface. The correlation between Cl/Na and Cl/HCO₃ for the Dongrae geothermal waters requires the input of salty water. The supply of saline composition is interpreted due to the dissolution of residual paleo-seawater.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.3 no.2
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• pp.39-51
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• 2007

Unconsolidated and permeable alluvial deposit composed of sand and gravel is distributed along the fluvial plain at the Iryong study area. Previous studies on the area show that a single alluvial well can produce at least 1,650m3d-1 of bank infilterated shallow groundwater(BIGW) from the deposit. This study is aimed to evaluate and simulate the influence that seasonal variation of water levels and temperatures of the river have an effect on those of BIGW under the pumping condition and also to compare seasonal variation of COPs when indirectly pumped BIGW or directly pumped surface water are used for a water to water heat pump system as an heat source and sink using 3 D flow and heat transport model of Feflow. The result shows that the magnitude influenced to water level of BIGW by fluctuation of river water level in summer and winter is about 48% and 75% of Nakdong river water level separately. Seasonal change of river water temperature is about $23.7^{\circ}C$, on other hand that of BIGW is only $3.8^{\circ}C$. The seasonal temperatures of BIGW are ranged from minimum $14.5^{\circ}C$ in cold winter(January) and maximum $18.3^{\circ}C$ in hot summer(July). It stands for that BIGW is a good source of heat energy for heating and cooling system owing to maintaining quite similar temperature($16^{\circ}C$) of background shallow groundwater. Average COPh in winter time and COPc in summer time of BIGW and surface water are estimated about 3.95, 3.5, and about 6.16 and 4.81 respectively. It clearly indicates that coefficient of performance of heat pump system using BIGW are higher than 12.9% in winter time and 28.1% in summer time in comparision with those of surface water.

• Clinical and Experimental Pediatrics
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• v.48 no.3
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• pp.292-297
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• 2005

Purpose : It is known that 3-50 percent of type 1 diabetes mellitus(T1DM) patients develop autoimmune thyroid disease. We analyzed the clinical characteristics of autoimmune thyroid disease(AITD) developed in patients with T1DM in Korean. Methods : The medical records of 139 patients, who were followed up in Department of Pediatrics, Seoul National University Children's Hospital from Jan. 1981 to Jul. 2004, were analyzed retrospectively. Results : Forty-four males and 95 females were enrolled. At least one of the autoantibodies for thyroid was positive in 54 cases. The detection rate for AITD was not correlated with sex ratio, control of T1DM, body mass index, age at diagnosis of T1DM, and familial history of thyroid disease, between two groups. In the male group, AITD was more frequently found at a younger age than in the female group. The frequency of AITD was significantly higher in the goiter group without sex differences. In the thyroid disease group, 40 patients(74.0 percent) were euthyroid, seven patients(12.9 percent) were hypothyroid, and seven patients(12.9 percent) were hyperthyroid. Conclusion : We should monitor thyroid function and autoantibodies routinely in T1DM patients who develop goiters, or young boys with T1DM.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2004.11a
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• pp.175-181
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• 2004

A construction project of Incheon 2nd bridge, which is connected between the Incheon Song-Do New Town and the Incheon International Airport in Young-Jong-Do, have been proposed by the private capital in 1999. But the optimal span width in the bridge main span have not been decided in spite of the three investigations into the feasibility of ship's safe transit in this planned bridge. In this paper, we study the optimal main span width according to the traffic volume in the future traffic and the ship maneuverability of maximum size aspect. The result cf this study, Incheon 2nd bridge main span design is required to design two-way traffic scheme and 1,000m span width, which will satisfy the safe transit from the viewpoint of the traffic volume in the future traffic and the ship maneuverability maximum size.

• Horticultural Science & Technology
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• v.19 no.4
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• pp.591-595
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• 2001

This study was conducted to find out the proper chemicals and doses for controlling the bulb disease of Lilium Oriental hybrids 'Capablanca' and 'Marco Polo' cultivars during storage, and to ascertain any disadvantage of the treatment on shoot growth and flower development. Bulbs of 'Casablanca' and 'Marco Polo' cultivars were dipped in some fungicide solutions, including azoxystrobin, benomyl+thiram, and prochloraz, and culture broth of antagonistic bacteria for one hour. The rot was apparently inhibited by azoxystrobin and prochloraz solution dippings and it was not by benomyl+thiram in bulbs produced domestically. To improve physiological integrity, calcium chloride was treated. However, this treatment had no positive effects on bulb rot of lily. When bulbs were dipped in one-fifth of diluted broth. But the bulb rot was inhibited effectively as compared with untreated during storage. Benomyl+thiram and that with calcium inhibited the sprouting in 'Casablanca' and 'Marco Polo' cultivars during cultivation. Calcium and benomyl+thiram treatments decreased growth of leaf and flower but with no statistically significant difference. Other fungicidal materials treated to bulbs showed no effect on vegetative growth and flower quality.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.6
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• pp.475-482
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• 2014

This paper presents the results of an experimental feasibility study on low-temperature differential Stirling engines with water spray heat transfer. The water spray enhances the efficiency of the heat transfer from heat sources to the engine and reduces the performance degeneration due to the dead volumes of conventional heat exchangers. A test Stirling engine was developed and an experiment was conducted to determine the characteristics for the initial start-up, steady-state operation, and power output for various flow rates and temperatures of hot supply water. The test results showed that larger flow rates led to reductions in the minimum working temperature of the hot water at start-up. During a series of steady-state operations, higher flow rates and temperatures increased the working speed. Furthermore, the work per cycle and power output were also increased. Eventually, the test Stirling engine had a power level of 0.05 W. Based on this, further research will be conducted to obtain a higher power output and investigate various applications.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.2
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• pp.926-933
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• 2012

Phosphoric acid used for the production of phosphate fertilizers is synthesized by the reaction of phosphate rock and sulfuric acid. As the reaction is exothermic, yield of phosphoric acid is poor at elevated temperature. Therefore, enhancement in its yield requires the process temperature be maintained by releasing the vapor ($80^{\circ}C$) containing HF and SiF4 through a vacuum cooler. However, these valuable resources; Fand Si, which can be utilized for the manufacture of refrigerant and polysilicon, respectively, are being wasted in the treatment process. We performed lab-scale experiments to estimate the amount of recoverable H2SiF6, a by-product of phosphoric acid manufacturing process. The experimental results showed a decrease of fluorine concentration by 0.12wt% in the liquid phase. Preliminary estimation showed a possible recovery of 5,509 ton/yr of fluorine considering the scale of the fertilizer manufacturing plant. Furthermore, field-scale experiment showed that H2SiF6 could be enriched in liquid phase from 0.35wt% to 7.33wt% and the vapor flow-rate from vacuum cooler was estimated at $51,000m^3/hr$. Anew, the efficiency of fluorine recovery in the pilot-scale experiment was found to be 76.74% and the production of H2SiF6 was estimated at 5,340 ton/yr.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.62.2-62.2
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• 2010

박막 실리콘 태양 전지는 저가격화 및 대량생산, 대면적화에 유리하다는 장점을 가지고 있다. 단점으로 지적되는 낮은 효율을 극복하기 위해 광흡수층의 밴드갭이 서로 다른 두 개 이상의 박막을 적층하여, 넓은 파장 대역의 빛을 효과적으로 흡수함으로써 광변환 효율을 올리기 위한 많은 연구가 이루어지고 있다. 서로 다른 밴드갭의 광흡수층을 가진 p-i-n 구조를 다중 적층하여 고효율의 태양 전지를 제작하기 위해서는 n-도핑층과, p-도핑층 간에 전자와 정공이 빠르게 재결합할 수 있는 터널 접합(Tunnel Recombination Junction)의 형성이 필수적이며, 이때 광손실이 최소화되도록 해야한다. 만약 터널 접합이 적절하게 형성되지 않으면 결합되지 않은 전자와 정공이 도핑층 사이에 쌓이게 되고, 도핑층 사이의 저항 증가로 태양 전지의 광변환 효율은 크게 하락한다. 이번 연구에서는 터널 접합이 잘 이루어지게 하기 위한 n-도핑층 및 p-도핑층 박막의 특성과, 터널 접합의 특성에 따른 적층형 태양 전지의 광효율 변화를 확인하였다. 광흡수층 및 도핑층은 TCO($SnO_2:F$, Asahi) 유리 기판 위에 PECVD를 사용하여 p-i-n 구조로 RF Power 조건에서 증착되었고, ${\mu}c$-Si 광흡수층의 경우에는 VHF Power 조건에서 증착되었다. 광흡수층이 a-Si/${\mu}c$-Si의 구조를 가지는 이중 접합 태양 전지에서 ${\mu}c$-Si n-도핑층/${\mu}c$-Si p-도핑층 사이의 터널 접합 실험 결과 n-도핑층 및 p-도핑층의 결정화도와 도핑 농도를 조절하여 터널 접합의 저항을 최소화했고, 터널 접합 특성이 이중 접합 셀의 광효율 특성과 유사한 경향을 보임을 확인하였다. 광흡수층이 a-Si/a-SiGe/${\mu}c$-Si의 구조를 가지는 삼중 접합 태양 전지 실험의 경우 a-Si과 a-SiGe 광흡수층 사이에 ${\mu}c$-Si n-도핑층/${\mu}c$-Si p-도핑층/a-SiC p-도핑층의 구조를 적용하여 터널 접합을 형성하였으며, ${\mu}c$-Si p-도핑층의 두께 및 박막 특성을 개선하여 광손실이 최소화된 터널 접합을 구현하였고, 삼중 접합 태양 전지에 적용되었다.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.120-120
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• 2010

에너지 절약적 차원에서 한 대의 실외기에 다수의 실내기가 접속되는 개별공조형 멀티 열펌프에 관한 연구 및 개발과 보급이 증대되고 있다. 본 연구에서는 복수의 실내기를 갖고 가변속 압축기를 채용한 지열원 물대공기 멀티열펌프시스템을 학교 현장에 설치하여 제조사의 운전 제어 알고리즘에 따라 일일 냉난방 실증 성능 특성을 분석하였다. 2008년 9월 30일의 냉방부하가 낮은 일자에 대하여 시간에 따른 부하 변동에 따라 압축기의 용량가변으로 실내기 냉방용량은 정격용량 대비 17.1%에서 111.3%의 범위에서 변이되었으나, 열펌프 유닛의 일일 최대 COP는 6.2를 나타냈으며, 일일 평균 열펌프 유닛 COP는 4.5로 열펌프 유닛 인증 기준 이상의 성능을 나타냈다. 2008년 11월 10일 대비 2008년 12월 15일에는 시스템 가동 중의 평균 외기온도가 $9.6^{\circ}C$ 감소하였으나, 각 재실공간의 용도별 부분 부하특성으로 11월 10일 보다 난방 부하량이 작게 나타났다. 하지만, 12월 15일에는 부하량이 매우 작아서 11월 10일보다 잦은 압축기 가변에 따른 손실로 일일 평균 COP가 낮게 나타났다. 2009년 1월 12일에는 정격 용량대비 94%의 부하율로 11월 10일과 12월 15일 대비 4배 이상의 부하량으로 압축기 용량 가변율이 작아서 난방용량과 COP 변화율이 작게 나타났다. 2009년 1월 12일에는 지중순환수의 실외열교환기 유입온도가 2008년 12월 15일보다 감소하고, 시스템의 난방용량 증가로 상대적으로 응축기와 증발기 크기가 감소한 효과로 히트펌프 유닛 COP가 감소하였으나, 본 지열원 열펌프 제조사에서 생산하고 있는 본 지열원 시스템과 동일한 압축기 등을 채용한 동일 용량의 공기열원 열펌프의 1월 12일 외기온도 $-10^{\circ}C$에서의 열펌프 유닛 COP 대비 70% 우수한 성능을 나타냈다. 본 지열원 히트펌프의 2008년 11월 10일의 일일 평균 히트펌프 유닛 COP는 외기온도가 낮고 일일 부하량이 크게 나타난 1월 12일의 일일 평균 히트펌프 유닛 COP 대비 37% 높게 나타났으나, 지중순환펌프의 정속운전으로 시스템 요구 지중순환수 유량 증가에 따른 성능 향상보다 소비전력 증가 영향이 커서 1월 12일의 시스템 COP 보다 33.3% 작은 값을 나타냈다. 본 연구의 용량 가변형 압축기를 채용한 지열원 멀티 히트펌프 유닛을 지열원 냉난방 시스템의 히트펌프 유닛으로 사용할 경우 시스템 최적화를 통한 시스템 COP 향상과 연간에너지 절감을 이루기 위해서는 히트펌프의 용량 변화 시에 지중순환펌프의 순환 유량 최적화를 위한 효율적 운전 제어 알고리즘 개발이 요구된다.