• 설비공학논문집
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• 제21권9호
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• pp.483-495
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• 2009

Feedwater heaters of many nuclear power plants have recently experienced severe wall thinning damange, which will increase as operating time progresses. Several nuclear power plants in Korea have experienced wall thinning damage in the area around the impingement baffle-installed downstream of the high pressure turbine extraction stream line-inside number 5A and 5B feedwater heaters. At that point, the extracted steam from the high pressure turbine is two phase fluid at high temperature, high pressure, and high speed. Since it flows in reverse direction after impinging the impingement baffle, the shell wall of the number 5 high pressure feedwater heater may be affected by flow-accelerated corrosion. This paper describes operation of experience and numerical analysis composed similar condition with real high pressure feedwater heater. This study applied squared, curved and new type impingement baffle plates to feedwater heater same as previous study. In addition, it shows difference of pressure distribution and value between single phase and two phase based on experience and numerical analysis.

• Journal of Electrical Engineering and Technology
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• 제5권2호
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• pp.307-318
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• 2010

In this work, an accurate analysis of low frequency current ripple in residential fuel cell power generation systems is performed based on the proposed residential load model and its unique operation algorithm. Rather than using a constant dc voltage source, a proton exchange membrane fuel cell (PEMFC) model is implemented in this research so that a system-level analysis considering the fuel cell stack, power conditioning system (PCS), and the actual load is possible. Using the attained results, a comparative study regarding the discrepancies of low frequency current ripple between a simple resistor load and a realistic residential load is performed. The data indicate that the low frequency current ripple of the proposed residential load model is increased by more than a factor of two when compared to the low frequency current ripple of a simple resistor load under identical conditions. Theoretical analysis, simulation data, and experimental results are provided, along with a model of the load usage pattern of low frequency current ripples.

• 설비공학논문집
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• 제21권9호
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• pp.505-512
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• 2009

A thermosiphon is utilized as a thermal shunt to reduce the cool-down time of a cryogenic system cooled by a two stage cryocooler. The cool-down time reduction by the thermosiphon is determined by the type of working fluid which is directly related to the operating temperature range of the thermosiphon. A mixed working fluid has a potential to widen the operation temperature range of the thermosipohon. In this study, the thermosiphon using N$_2$ and CF$_4$ mixture as the working fluid is fabricated and tested to verify its transient heat transfer performance. The thermosiphon with the mixed working fluid has no noticeable reduction of cool-down time compared with that of the thermosiphon with pure working fluid in this experiment. However, it seems that the thermosiphon with mixed working fluid may have an advantage according to the cooling capacity of a cryocooler, the cooling target temperature and the size of a cooling object.

• 전력전자학회논문지
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• 제12권5호
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• pp.400-408
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• 2007

본 논문에서의 병렬제어를 이용한 8kW급 대용량 영전압/영전류 풀 브릿지 DC-DC 컨버터의 개발 결과를 보인다. 본 논문에서는 효율적인 시스템 구성을 위해 4-병렬 단위 모듈 운전을 제안한다. 각 단위모듈은 위상 천이 풀 브릿지를 채택하고, ZVZCS 운전을 위해 간단한 보조 회로를 2차측에 추가하였다. ZCS를 위한 보조 회로 동작 로직은 환류 모드 구간에서 1차측 전류를 제거하도록 구현하였다. 또한 병렬 운전시의 출력 전류의 균등 제어를 위해 위상천이로직을 활용한 Charge Control 방식을 적용하였다. 전압 제어기는 DSP TMS320LF2406을 활용하여 4 모듈의 출력전류 및 출력전압을 A/D로 입력받아 구현하였다. 개발된 컨버터는 차량에 설치되는 고속 발전기용 전력 변환기에 장착되었으며, 구축된 모니터링 시스템으로 고속 발전기의 실제 운전 조건에서 데이터를 획득하여, 분석을 통해 그 성능을 입증하였다.

• 한국항행학회논문지
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• 제26권1호
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• pp.35-45
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• 2022

본 논문에서는 PV 시스템에서 태양광 발전 시스템의 완전한 동작을 위해 DC-DC 벅-부스트 컨버터와 MPPT (Maximum Power Point Tracking)제어 시스템에 대한 완전한 동작 시스템에 대해 모델링하고 시뮬레이션을 수행하여 양호한 동작을 확인하고자 한다. 이를 위해 이중층 커패시터(EDLC:Electric double-layer capacitors )를 사용한 순간전압강하 보상장치가 개발되어 적용되고 있다. 따라서 태양광 발전의 ESS(Energy Storage System)를 고려한 PCS(Power Conditioning System)를 제안하여 부하평준화를 통한 전력의 안정적인 공급을 확인한다. 본 논문에서는 순간전압강하 보상장치(DVR :Dynamic Voltage Restorer)에 사용되는 전기 이중층 커패시터에 비해 동일 사이즈 대비 에너지 밀도가 높은 하이브리드 커패시터(hybrid capacitor)를 적용하는 연구를 하였고, 단상 3[kW] 계통 연계형 태양광 전력변환기를 제안하였다.

• 설비공학논문집
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• 제19권2호
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• pp.162-168
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• 2007

This paper presents the effects of thermoelectric module arrangement on the cooling performance of an air conditioner using thermoelectric module. A prototype of air cooling system, employing several thermoelectric modules, has been designed and built. The evaporative cooling technique is adopted for hot side of the module. The number of thermoelectric module in the system has been varied in the range of $2{\sim}8$. The optimal operation conditions, such as input power to the thermoelectric module, fans and pump, have been determined for each arrangement of the system and the cooling performance has been compared under the optimal operation. It is found that both cooling capacity and COP are increased as the number of thermoelectric module increased. It is also found that cooling capacity can be improved by connecting the thermoelectric modules in series than in parallel, while the COP is little affected.

• 설비공학논문집
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• 제18권11호
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• pp.874-880
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• 2006

The power density and heat dissipation rate per unit area of the telecommunication equipment have been increased with the technology development in the footprint of telecommunication hardware. A proper heat dissipation method from the PCB module is very important to allow reliable operation of its electronic component. In this study, a hybrid air-conditioner for the telecommunication equipment room was designed to save energy and obtain system reliability. For high outdoor temperatures, the hybrid system operates in the vapor compression cycle, while, for low outdoor temperatures, the hybrid system works in the secondary fluid cooling cycle with no operation of the compressor. The performance of the hybrid air-conditioner was measured by varying outdoor and indoor temperatures. The hybrid air-conditioner yielded 50% energy saving compared with the conventional refrigeration system when the mode switch temperature was $8.3^{\circ}C$.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2003년도 하계종합학술대회 논문집 V
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• pp.2769-2772
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• 2003

This paper presents results of the development of the Turbo-generator system with structure which is HSG(High Speed Generator) installed to high speed gas-turbine engine directly. Turbo-generator with high speed motor-generator directly has many advantages aspects of weight, size, lubrication system and complexity of the system compared of conventional turbo-generator system with gear-box. But because of direct high speed operation of the high speed generator, we have to need stable high speed motor driving algorithm for perfect engine ignition when gas turbine starting. Also we have to need design of the PCU(Power Conditioning Unit) for converting high speed AC output power to conventional AC power or needed DC power.

• 한국가스학회지
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• 제22권5호
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• pp.124-132
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• 2018

파리협정의 체결로 신 재생에너지 보급이 활발해지고 있다. 국내의 경우 공공건물 중심으로 신 재재생에너지 보급 정책이 진행되고 있으며, 건물 내에 설치가 비교적 수월한 연료전지 시스템의 보급이 확대될 전망이여서 계통연계형 연료전지 전력변환장치의 단독운전방지 평가 연구가 중요하다. 본 연구에서는 연료전지 전력변환장치의 국내 인증기준 KGS AB934 PC53이 해외 규격과 부합하는지 검토해보고 계통연계 시 중요한 안전성능인 단독운전방지 평가에 대해 분석하였다. 또한, 병렬로 연결된 두 대의 전력변환장치의 단독운전방지 평가를 위한 시작품을 제작하고 실증 평가를 통해 여러 대의 연료전지 시스템이 설치되고 있는 상황에 맞는 안전성능 확보 방안을 연구하였다.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 하계학술발표대회 논문집
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• pp.1099-1104
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• 2008

Recent year, mean energy consumptions of a people are higher than other country. And international oil price became over 120 dollar. This energy environment as well as energy war. Maybe, the Meteorological Administration is going to enforce scorching heatwave special report system from that come summer. Besides, 2008 summer, maximum demand power is expected by 64,240,000kW. The electric power equipment reserve rate appeared in to keep 12.5% level. Chilled water storage system witch is one of electric load administration system. Heat pump system used cooling tower heat recovery is advantage that use is possible to summer in small a public bath building. In this paper, we suggest that heat pump system by heat recovery using cooling tower when it is heating operation of ambient air temperature. To apply cooling tower heat recovery heat pump to chilled water heat storage type and achieved performance evaluation about operation. As a result, performance of heat pump system that about 121% in cooling mode, 138% in heating mode higher than KEPCO standard. And heating operation possible to ambient air temperature about $23^{\circ}C$, which of appear cooling tower outlet temperature about $13^{\circ}C$.