• Journal of Biosystems Engineering
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• 제39권2호
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• pp.101-110
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• 2014

Purpose: The purpose of this study is to develop a system to optimize drying potential energy of the exhausted hot air by changing relative humidity of the air. This study modified the conventional drying method into a drying method changing exhaust cycle and time in order to control the relative humidity of the exhausted hot air during drying process. Method: A valve on the vent was controlled according to a preset time to change the exhaust cycle and time. This study analyzed the influence of the two different types of drying method on the drying characteristics, required energy, and quality of the dried peppers: conventional drying method exhausting hot air continuously and new drying method controlling exhaust cycle and time. Results: Drying characteristics based on exhaust time showed that drying time increased with exhaust time, and specific energy consumption was reduced by 28% from 18.39 MJ/kg (conventional method) to 13.24 MJ/kg when exhaust time was set to one minute. Drying characteristics based on heating time showed that drying time increased with heating time and specific energy consumption was reduced by 30% from 18.39 MJ/kg (conventional method) to 12.87 MJ/kg when exhaust time was set to 22 minutes. Drying characteristics based on exhaust cycle showed that drying time increased with exhaust cycle, and specific energy consumption was reduced by 31% from 18.39 MJ/kg (conventional method) to 12.69 MJ/kg when exhaust time was set to one minute and exhaust cycle was set to 22 minutes before drying and 40 minutes after drying. The quality of the dried red peppers showed that capsaicin, color, and sugar content were high as 34.87 mg/100g, 66.33, and 11.87%, respectively, when exhaust time was set to one minute and exhaust cycle was set to 22 minutes before drying and 40 minutes after drying. Conclusions: In order to utilize the drying potential energy of the exhausted air during drying process, the conventional drying method was modified into the drying method controlling exhaust cycle and time. The results showed that drying with exhaust cycle of one minute was more efficient in terms of drying time, required energy, and quality of the dried peppers than the one with exhaust cycle of 20~40 minutes.

• 설비공학논문집
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• 제27권10호
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• pp.544-551
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• 2015

This study was conducted to determine the LCC of apartment complexes with district heating and a cogeneration system. For the purpose of analyzing LCC according to the size of the apartment complex, 500, 1,500, and 4,000-unit model apartments were selected. Analysis was performed on the design of the heating system and the life cycle cost including total construction cost, maintenance and operation cost for the duration of the project period (15 years). According to the calculated results, 1) The initial cost of the cogeneration system for 500, 1,500, and 4,000-unit apartments is higher than that of the district heating system by 20%, 13%, and 12%, respectively. 2) In the case of the cogeneration system, the payback period by electric generation was found to be 5.21, 4.92 and 4.47 years, and saving cost was calculated to be 29 billion won, 94 billion won and 262 billion won after the payback period for 500, 1,500, and 4,000-unit apartments, respectively. 3) The LCC values of the cogeneration system were 1.12, 1.07 and 1.06 times larger than those of the district system according to the size of the apartment complex. In this study, the district heating system was found to be more efficient than the cogeneration system in terms of LCC reduction. 4) District heating is affected by fuel bills, so energy efficiency should be improved through recovering waste heat (incineration heat, etc.). Also, district cooling should be provided according to heat use to keep the temperature high in winter and low in summer.

• 생명과학회지
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• 제14권1호
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• pp.110-114
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• 2004

본 연구는 뽕나무 품종간의 유전적 특성 분석을 위한 기초 자료로서 최적의 RAPD-PCR 조건을 확립하기 위하여 수행하였다. 본 연구를 위해 '밀성뽕', '청일뽕', '수일뽕' 그리고 한성뽕'등의 4품종을 이용하여 Operon사의 OPY15 (5'-AG-TCGCCCTT-3') primer를 사용, 여러 가지 PCR 조건하에서 실험하였다. DNA 농도, primer농도, $MgCl_2$ 농도, PCR 횟수, annealing temperature, pre-heating time의 조작유무 등 여러 가지 요인들을 대상으로 시험을 수행한 결과, $25 \mu$ 반응용액을 기준으로 50 ng의 template DNA, $1 \muM$의 random primer, 1.5 mM의$MgCl_2$45회의 PCR cycle, 45$^{\circ}C$의 annealing temperature 그리고 pre-heating time이 없는 조건이 최적으로 나타났다. 이러한 RAPD-PCR법의 안정적인 조건의 확립은 후차적인 뽕나무 품종간의 유전적 특성의 규명, 계통간의 관련, 신품종 육성 등을 위한 중요한 기초 자료로 활용될 것으로 생각된다.

• 지질공학
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• 제25권4호
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• pp.599-612
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• 2015

신재생에너지는 지금까지 화석연료의 잔량과 환경적인 면에서 그 중요성이 부각되었지만, 경제성에 대한 요구도 점차 커져가고 있다. 특히, 지열 냉난방시스템은 초기 투자비가 큰 점이 단점으로 부각되어 경제성 분석을 통한 결과 제시가 더욱 중요해지고 있다. 따라서 본 연구에서는 지열 냉난방시스템의 경제성과 이산화탄소 발생량을 경유보일러, 도시가스 보일러, 수직밀폐형 및 SCW형의 4가지 방식으로 비교하여 분석을 수행하였다. 생애주기비용분석 결과, 지열 냉난방시스템의 경제성이 높게 나타났으며, 이중 SCW형 지열 냉난방시스템을 이용하는 경우 절감액이 가장 높은 것으로 분석되었다. 또한 이산화탄소 발생량 분석 결과, SCW형 지열 냉난방시스템을 적용할 때 저감량이 가장 크게 나타났다. 따라서 본 연구결과에서 제시된 분석 결과를 대규모 시설농업단지나 간척지에 적용 시 많은 비용을 절감할 수 있을 것으로 판단된다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.3241-3246
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• 2007

Integrated Gasification Combined Cycle (IGCC) power plant converts coal to syngas, which is mainly composed with hydrogen and carbon monoxide, by the gasification process and produces electric power by the gas and steam turbine combined cycle power plant. The purpose of this study is to investigate the influence of the syngas to the performance of a gas turbine in a combined cycle power plant. For this purpose, a commercial gas turbine is selected and its performance characteristics are analyzed with three different fuels, i.e., natural gas ($CH_4$), syngas and hydrogen. It is found that different heating values of those fuels and chemical compositions in their combustion gases are the causes in the different performance characteristics.

• International Journal of Air-Conditioning and Refrigeration
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• 제8권1호
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• pp.29-39
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• 2000

A series of tests were performed to verify the transient characteristics of heat pump in heating and cooling mode when operating speed was varied over the 30 to 102Hz. One of the major issues that has not been addressed so far is transient characteristics during speed modulation. The model for cycle simulation has been developed to predict the cycle performance under conditions of decreasing drive frequency and the results of the theoretical study were compared with the results of the experimental study. The simulated results were in good agreement with the experimental result within 10%. The transient cycle migration of the liquid state refrigerant causes significant dynamic change in system. Thus, the migration of refrigerant was the most important factor whenever do experimental results analysis or develop simulation model.

• Journal of Power Electronics
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• 제7권2호
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• pp.118-123
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• 2007

This paper presents a new ZCS-PWM high frequency inverter. Zero current switching operation is achieved in the whole load range by using a simple auxiliary reverse blocking switch in parallel with series resonant capacitor. Dual duty cycle control scheme is used to provide a wide range of high frequency AC output power regulation that is important in many high frequency inverter applications. It found that a complete soft switching operation can be achieved even for low power setting ranges by introducing high-frequency dual duty cycle control scheme. The proposed high frequency inverter is more suitable for consumer induction heating(IH) applications. The operation and control principle of the proposed high frequency inverter are described and verified through simulated results.

• 한국수소및신에너지학회논문집
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• 제32권6호
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• pp.649-655
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• 2021

The recently proposed Kalina based power and cooling cogeneration cycles (KPCCCs) have shown improvement in the energy utilization of the system compared to the basic Kalina cycle. This paper suggests a combined tri-cogeneration system for power, heating and cooling based on the Kalina cycle. And thermodynamic performances of the suggested system based on the first and second thermodynamic laws are parametrically investigated with respect to the ammonia mass fraction and the boiler pressure. Results showed that the thermodynamic performance of the system could be greatly improved compared to the former KPCCCs.

• 대한기계학회논문집
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• 제13권3호
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• pp.490-499
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• 1989

본 연구에서의 CO$_{2}$ 프로세스는 1차 루프인 원자로에서 유도되는 나트륨 과 2차 루프인 CO$_{2}$ 가스터빈 사이클로 구성하였고, CO$_{2}$ 임계점 부근에서 압축을 행하였다. 또한 최적의 사이클을 결정하기 위해 h-s 선도와 이에 대한 열역 학적, 칼로리로 유도하였다. 그리고 최적화를 위해 출력을 각각 300,600, 1000MWe로 선택하였고, 터빈 입구압은 150-350bar의 범위로 선택하였으며 이들로부터 열효율에 영향을 주는 각 설계변수의 특성을 연구 분석하였다.

• 설비공학논문집
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• 제20권4호
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• pp.230-237
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• 2008

The objective of this paper is to investigate the performance characteristics of a $CO_2$ cooling and water heating system using a twin-rotary compressor with the compression volume ratio of 0.6. The cooling performances of the $CO_2$ heat pump were measured and analyzed with the variations of charge amount, EEV opening, and compressor frequency. In addition, the performance of the combined system including cooling and water heating was also measured and analyzed by varying inlet temperature of the EEV. As a result, the optimal normalized charge and cooling COP in the cooling mode were 0.307 and 2.06, respectively. The application of the water heating into the $CO_2$ heat pump improved the cooling performance over 78% and decreased the EEV inlet temperature by $8^{\circ}C$, which can increase system reliability.