• Nuclear Engineering and Technology
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• 제38권2호
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• pp.109-118
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• 2006

Various indirect power cycle options for a helium cooled gas cooled fast reactor (GFR) with particular focus on a supercritical $CO_2(SCO_2)$ indirect cycle are investigated as an alternative to a helium cooled direct cycle GFR. The balance of plant (BOP) options include helium-nitrogen Brayton cycle, supercritical water Rankine cycle, and $SCO_2$ recompression Brayton power cycle in three versions: (1) basic design with turbine inlet temperature of $550^{\circ}C$, (2) advanced design with turbine inlet temperature of $650^{\circ}C$ and (3) advanced design with the same turbine inlet temperature and reduced compressor inlet temperature. The indirect $SCO_2$ recompression cycle is found attractive since in addition to easier BOP maintenance it allows significant reduction of core outlet temperature, making design of the primary system easier while achieving very attractive efficiencies comparable to or slightly lower than, the efficiency of the reference GFR direct cycle design. In addition, the indirect cycle arrangement allows significant reduction of the GFR &proximate-containment& and the BOP for the $SCO_2$ cycle is very compact. Both these factors will lead to reduced capital cost.

• Journal of Power Electronics
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• 제15권3호
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• pp.702-711
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• 2015

In this paper, an effective carrier-based modulation (CBM) strategy to reduce the switching losses for indirect matrix converters (IMCs) is presented. The discontinuous pulse width modulation method is applied to decrease the switching numbers in one carrier cycle, and an optimum offset voltage is selected to avoid commutations of the high output phase currents. By decreasing the switching numbers along with avoiding commutation of the high currents, the proposed CBM strategy significantly reduces the switching losses in IMCs. In addition, the proposed CBM strategy is independent of load conditions, such as load power and power factor, and it has good performance in terms of the input/output waveforms. Simulation and experimental results are provided to verify the effectiveness of the proposed CBM strategy.

• Nuclear Engineering and Technology
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• 제39권2호
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• pp.95-102
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• 2007

The conceptual design of the MIT modular pebble bed reactor is described. This reactor plant is a 250 Mwth, 120 Mwe indirect cycle plant that is designed to be deployed in the near term using demonstrated helium system components. The primary system is a conventional pebble bed reactor with a dynamic central column with an outlet temperature of 900 C providing helium to an intermediate helium to helium heat exchanger (IHX). The outlet of the IHX is input to a three shaft horizontal Brayton Cycle power conversion system. The design constraint used in sizing the plant is based on a factory modularity principle which allows the plant to be assembled 'Lego' style instead of constructed piece by piece. This principle employs space frames which contain the power conversion system that permits the Lego-like modules to be shipped by truck or train to sites. This paper also describes the research that has been conducted at MIT since 1998 on fuel modeling, silver leakage from coated fuel particles, dynamic simulation, MCNP reactor physics modeling and air ingress analysis.

• 한국군사과학기술학회지
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• 제13권4호
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• pp.601-611
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• 2010

Currently, a life cycle cost estimates(LCCE) is the most important factor in weapon system acquisition process. However, operation and maintenance(O&M) cost related studies are insufficient from the previous literature survey. O&M cost consists of various cost factors such a man power, maintenance and direct & indirect support costs. We have known that spare-parts cost is a key factor in the O&M cost. In this paper, we developed the spare-parts cost estimating relationships(CERs) of fixed-wing aircraft and armored vehicle weapon systems which include 4 historical cost drivers ; system acquisition cost, deterioration rate, localization rate, mission characteristic. Furthermore, we proposed the application methodologies that O&M cost estimating, total life cycle cost estimating and determination of the economic life using the spare-parts CERs.

• Journal of Power Electronics
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• 제19권2호
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• pp.529-539
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• 2019

The modular multilevel converter (MMC) has become a promising topology for high-voltage direct current (HVDC) transmission systems. To control a MMC system properly, the ac-side current, circulating current and submodule (SM) capacitor voltage are taken into consideration. This paper proposes a low-computation indirect model predictive control (IMPC) strategy that takes advantages of the conventional MPC and has no weighting factors. The cost function and duty cycle are introduced to minimize the tracking error of the ac-side current and to eliminate the circulating current. An optimized merge sort (OMS) algorithm is applied to keep the SM capacitor voltages balanced. The proposed IMPC strategy effectively reduces the controller complexity and computational burden. In this paper, a discrete-time mathematical model of a MMC system is developed and the duty ratio of switching state is designed. In addition, a simulation of an eleven-level MMC system based on MATLAB/Simulink and a five-level experimental setup are built to evaluate the feasibility and performance of the proposed low-computation IMPC strategy.

• 동력기계공학회지
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• 제15권5호
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• pp.37-42
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• 2011

The normal cooling system of a refrigerator is applied to indirect a cooling methods. But the Kimchi refrigerator is applied to direct the cooling method. Recently when the model was applied to both direct and indirect the cooling methods, the improvement was considerable. With the development of the living standards in Korea, there has been more sensitive dissatisfaction about the taste and the smell of Kimchi. In order to solve these kinds, there is a need to systematic and scientific approach. Based on these, the purpose of this study is to optimize design for improve the storage period of Kimchi refrigerator. In this research, we concentrate on the temperature change and heat transfer characteristics of interior parts of the Kimchi refrigerator due to control cycle of temperature and flow phenomenon of cooling air.

• KEPCO Journal on Electric Power and Energy
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• 제4권1호
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• pp.19-24
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• 2018

가스터빈 동익에 대한 지속적인 국산화 개발이 추진되어, 국내 정밀 주조 기술을 향상시키고, 동익의 유지 보수 비용을 낮추는 등의 직간접적인 긍정적 효과를 가져왔지만, 여전히 국산화 개발품이 발전소에서 안정적인 실사용이 가능한지에 대한 우려가 존재한다. 향상된 소재와 주조기술을 바탕으로 조직학적, 기계적 성질에서 충분한 품질을 확보하였더라도, 개발품을 대상으로 다양한 신뢰성 검증이 요구되는 이유이다. 고속회전시험기는 로터, 디스크 등의 회전체에 원심력을 가하여, 이에 따른 제품의 특성을 분석하기 위한 시험장비로 일반적으로 과속도시험을 통한 최종적인 품질검사에 주로 사용된다. 본 논문에서는 전력연구원에 구축된 고속회전시험기를 활용한 가스터빈 동익에 대한 과속도시험을 포함한 저주기피로시험 사례를 중심으로 신뢰성 시험 및 평가 결과를 기술하였다.

• KEPCO Journal on Electric Power and Energy
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• 제2권4호
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• pp.531-536
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• 2016

세계적으로 온실가스저감에 대한 요구가 높아지고 있는 가운데 고효율 발전 시스템의 개발에 대한 연구개발이 꾸준히 진행되고 있다. 초임계 $CO_2$ 발전기술은 효율 향상과 소형화, 다양성의 장점을 가지고 있어, 2000년대 이후 세계 여러 나라에서 연구개발에 박차를 가하고 있다. 초임계 $CO_2$ 발전 시스템은 $CO_2$를 작동유체로 하는 발전 시스템으로 크게 간접가열방식과 직접가열방식으로 구분될 수 있다. 현재, 대부분의 연구는 간접가열방식의 초임계 $CO_2$ 발전 시스템 개발에 집중되어 있고, 미국은 NREL을 중심으로 태양열 연계 초임계 $CO_2$ 발전 시스템을 개발 중이며, DOE는 올 해 화력 연계 초임계 $CO_2$ 발전 시스템 개발에 대한 투자도 시작할 계획이다. GE는 10MW급 초임계 $CO_2$ 발전 시스템 개발뿐만 아니라, 50MW급과 450MW급 초임계 $CO_2$ 발전시스템의 개념 설계도 진행 중에 있다. 우리 나라에서는 원자력연구원이 초임계 $CO_2$ 발전시험 설비를 구축해오고 있으며, 한국전력공사 전력연구원은 현대중공업과 함께 디젤 및 가스엔진 폐열을 이용하여 2MW급 초임계 $CO_2$ 발전시스템 개발을 진행 중에 있다.

• 전기학회논문지
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• 제60권1호
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• pp.85-92
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• 2011

Main characteristic in railroad is the guided movement of the wheel by the track through a metal-to-metal contact, conferring to the rail vehicle a single degree of freedom. There are defects such as head check, shelling, corrugation, squats etc in surface of the rail by interface between the wheel and rail. These defects bring about reducing the life-cycle of rails and track components and increasing noises. In case of bad conditions, it is possible to happen to full-scale accident such as derailment. Recently, the track capacity has been increased for increasing speed and operation efficiency. So, maintenance and indirect cost have been increased. Currently, a coating method of rail construction is proposed by using the ceramics in Korea. Rails are used as the earth in electrical railroad systems. Currently traction return current is flowed through wheels of trains. In case of rails coated, problems are caused in the contact power between wheel and coating material of spray. In this paper, electric model is presented in the AT feeding method. In case of rails coated, electric model is presented. Also, standard resistance of the ceramic is demonstrated by contact power between wheel and coating material of spray.

• 에너지공학
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• 제28권3호
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• pp.65-79
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• 2019

본 연구는 산업단지 내 Gas Combined Cycle CHP와 연계 가능한 신재생에너지원을 조합하여 최적의 설비용량을 산정하고자 하였다. 특히 2013~2016년도 에너지사용계획 협의 대상 산업단지 중 집단에너지 공급대상 지역지정 연료사용량 요건은 연간 3.8만 TOE로 미달되지만, 열밀도가 $92.6Gcal/km^2{\cdot}h$로 높은 세종첨단일반산업단지를 연구 대상으로 하였다. 그리고 신재생에너지 Hybrid System 경제성 분석 프로그램인 HOMER Pro를 이용하여 연료전지와 태양광발전을 연계한 FC-PV Hybrid CHP System의 최적화 운영 모델에 대해 분석하였다. 또 CHP의 주 공급 에너지원인 열에너지에 있어, 열수요량 뿐만 아니라 우점 업종에 대한 열수요 패턴을 분석하여 연구의 신뢰도를 높이고자 하였으며, 경제성 분석을 추가하여 상대적 편익을 비교하고자 하였다. 연구 결과, 신규 조성 중인 세종첨단일반산업단지의 전체 간접열 수요는 연간 378,282 Gcal이며, 이중 제지업종이 연간 293,754 Gcal인 약 77.7%를 우점하고 있었다. 산업단지 전체 간접열 수요에 대해 단일 Combined Cycle CHP의 최적 설비용량은 30,000 kW로, 이때 열생산은 CHP가 275,707 Gcal, 72.8 %를 분담하고, 첨두부하보일러 PLB가 103,240 Gcal, 27.2 %를 분담하는 것으로 분석되었다. 그리고 CHP와 연료전지, 태양광 조합에서는 최적 설비용량이 각 30,000 kW, 5,000 kW, 1,980 kW이며, 이때 열생산은 Combined Cycle CHP가 275,940 Gcal, 72.8%, 연료전지가 12,390 Gcal, 3.3%, PLB가 90,620 Gcal, 23.9%를 분담하였다. 여기서 CHP 용량이 감소하지 않은 것은, CHP 용량 감소에 따른 부족한 열 생산량에 대해 PLB의 과다한 운전이 요구되는 경제적이지 못한 대안이 도출되었기 때문이었다. 한편 우점 업종인 제지업종의 간접열 수요에 대해서는 Combined Cycle CHP, 연료전지, 태양광 조합의 최적 설비용량은 25,000 kW, 5,000 kW, 2,000 kW로, 이때 열생산은 CHP 225,053 Gcal, 76.5%, 연료전지 11,215 Gcal, 3.8%, PLB가 58,012 Gcal, 19.7%를 분담하는 것으로 분석되었다. 그러나, 현행 전력시장 및 가스시장에서의 경제성 분석결과는 모두 투자비 회수가 불가능한 것으로 확인 되었다. 다만, 우점 업종인 제지 업종만을 대상으로 CHP와 연료전지, 태양광을 조합한 CHP Hybrid System이 단일 CHP System에 대해 연간 약 93억원의 경영여건을 개선시킬 수 있음을 확인하였다.