• Journal of Advanced Marine Engineering and Technology
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• 제38권3호
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• pp.276-284
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• 2014

본 연구의 목적은 ORC(Organic Rankine Cycle) 반경류터빈의 설계기법을 확립하는 것이다. 이를 위하여 반경류터빈의 예비설계프로그램인 RTDM(Radial Turbine Design Modeler) Ver.2.1를 개발하였다. RTDM Ver.2.1의 정확성을 검증하기 위해 R32를 이용한 200kW급 OTEC(Ocean Thermal Energy Conversion)용 반경류터빈을 설계하였고 이에 대해 CFD(Computational Fluid Dynamics) 수치해석을 수행하였다. 그 결과 RTDM Ver.2.1의 정확성은 설계한 반경류터빈의 전엔탈피 강하를 기준하여 약 94.6%로 나타났다. 본 연구에서는 반경류터빈의 설계요구조건인 출력조건과 로터출구조건을 충족시키기 위해 질량유량조정 방법을 도입하였다. 이에 따라 RTDM Ver.2.1을 이용하여 설계한 200kW급 OTEC용 반경류터빈의 질량유량은 21.2kg/s이며 이 때 Total to Total과 Total to Static 효율은 각각 89.8%, 85.3%이다.

• 대한기계학회논문집B
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• 제22권5호
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• pp.640-650
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• 1998

Pumping performances of a helical molecular drag dump(MDP) and of a radial MDPs are numerically analyzed by using the direct simulation Monte Carlo (DSMC) method. A helical- and radial-MDP have rotating pumping channels cut on a cylinder and on a disk, respectively. For a helical MDP, the present results agree quantitatively with the previously known numerical results. For radial MDPs, both of the Type 1 (having pumping channels cut on the stationary disk) and of the Type 2 (having pumping channels cut on the rotating disk) are analyzed to predict their performances for various parameters, i.e., the radius of curvature center of the channel wall, the depth of the channel, the clearance between housing and disk, and the rotating speed. The results show that the performance of the Type 2 is superior to that of the Type 1, and that for all types the pumping efficiency decreases as the clearance increases. Also, the radial type MDP has larger leakage losses in the direction of pumping channel than does the helical one.

• 한국지하수토양환경학회지:지하수토양환경
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• 제15권4호
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• pp.1-12
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• 2010

Well production by a riverbank filtration facility with multi-radial collector well systems in Jeungsan-ri, Changnyeong gun, Korea was evaluated. In this study, the drawdown at collector wells due to pumping and groundwater inflow rates along the horizontal arms of the collector wells were computed through numerical simulations. Sensitivities of the well production to hydraulic conductivity and well flow coefficient, which represents the resistance to the flow from the aquifer to the horizontal arms, were analyzed. Simulation results showed that, with given proposed pumping rate conditions, the drawdown in the caisson exceeded maximum drawdown constraints in the study site and the adjustment of the pumping rate at each well is needed. The drawdown is affected by the hydraulic conductivity of the main aquifer and the well flow coefficient, which means the profound field investigation of the study site is needed to accurately estimate the efficiency of riverbank filtration through radial collector wells.

• Journal of Electrical Engineering and Technology
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• 제9권6호
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• pp.2042-2048
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• 2014

In medium voltage electrical distribution networks, reforming the loss reduction is important, and in line with this, the issue of system engineering and use of proper equipment Expansion of distribution systems results in higher system losses and poor voltage regulation. Therefore, an efficient and effective distribution system has become more important. So, proper selection of conductors in the distribution system is crucial as it determines the current density and the resistance of the line. Evaluation of aging conductors for losses and costs imposed in addition to the careful planning of technical and economic networks can be identified in the network design. In this paper the use of imperialist competitive algorithm; genetic algorithm; is proposed to optimal branch conductor selection and reconstruction in radial distribution systems planning. The objective is to minimize the overall cost of annual energy losses and depreciation on the cost of conductors to improve productivity given the maximum current carrying capacity and acceptable voltage levels. Simulations are carried out on 69-bus radial distribution network using genetic algorithm approaches to show the accuracy as well as the efficiency of the proposed solution technique.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 춘계 학술발표회 초청강연 및 논문집
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• pp.905-913
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• 2008

The water resource depending on mostly surface water has many problems, such as contaminated and unpredicted contamination event. For this reason, it has been employed highly technical treatment method for them, such as ground water dam and river bank filtration. it has been developed the radial collector wells in kind of bank filtration to increase efficiency for in-taking the water resource insead of the vertical well needed many wells to take more resource. But it has many problems with the incumbent method to bore the horizontal hole for radial collector wells, such as filling with the filter material outside of a strainer by watering, jamming as retrieving the casing tube with the filter material, eccentric boring etc. To reduce the problems of incumbent equipment, it has been developed the horizontal boring equipment and performed the field trial tests several times, which have bits and water jetting system with rotating the cone-shaped front to be excavated easily. In this paper, it was compared the brand-new with the incumbent non-rotating pressing insertion method. Also it was shown the problems of the incumbent method was reduced effectively.

• 한국산학기술학회논문지
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• 제15권7호
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• pp.4177-4183
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• 2014

본 연구는 지역전략산업인 광산업을 중심으로 생산성 변화를 추정하고 이러한 변화를 기술변화 요인과 효율성변화 요인으로 분해함으로써 광산업의 생산효율성 향상 방안을 모색한다. 특히 기존의 연구들과 달리 투입최소화와 산출최대화를 동시에 고려하고 아울러 투입요소와 산출물의 잔여를 모두 반영할 수 있는 비방사적 비지향적 맘퀴스트 생산성지수를 분석에 활용한다. 실증분석 결과, 광산업의 생산성은 증가한 것으로 나타났으며, 이러한 생산성 증가는 주로 기술적 효율성 증가에 기인한 것으로 분석되었다. 또한 정부지원사업 수혜 여부와 지리적 입지에 따라 생산성 변화에 통계적으로 유의미한 차이가 있음을 확인하였다. 이와 같은 결과는 정부의 지역전략산업 육성정책이 광산업의 생산효율성 향상에 기여하고 있음을 시사하는 것으로 향후 광산업의 경쟁력 제고에 도움이 되는 실질적인 참고자료로 활용될 것으로 기대된다.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제4B권1호
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• pp.20-23
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• 2004

BLDCMs are widely used in many industries. In certain specialized areas, they need to have high efficiency, high power rate and produce a low volume of noise, etc. In this study, a new type of slotless BLDCM is proposed that has no cogging torque, low iron loss and low volume as compared to commonly used BLDCMs. With a high performance magnet and coreless compact winding structure similar to those employed in linear synchronous motors, motor volume is reduced. The proposed motor has been put been through various experiments arid has demonstrated acceptable results for industry applications.

• 전자공학회논문지A
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• 제28A권10호
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• pp.799-805
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• 1991

In this paper, the analysis and design of a spirally slotted array antenna with high efficiency are presented. Electric fields in the slots are calculated by electromagnetic fields in the upper waveguide and radiation field equations are derived. Slots are arrayed spirally on the upper circular plate of twofold radial waveguide. In order to suppress grating lobes from the array, a slow wave structure is inserted in the upper waveguide. This antenna is characterized by a good circular polarization, high efficiency of 75 percent and grating lobes below -34dB.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.86-86
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• 2012

The new approaches for silicon solar cell of new concept have been actively conducted. Especially, solar cells with wire array structured radial p-n junctions has attracted considerable attention due to the unique advantages of orthogonalizing the direction of light absorption and charge separation while allowing for improved light scattering and trapping. One-dimenstional semiconductor nano/micro structures should be fabricated for radial p-n junction solar cell. Most of silicon wire and/or pillar arrays have been fabricated by vapour-liquid-solid (VLS) growth because of its simple and cheap process. In the case of the VLS method has some weak points, that is, the incorporation of heavy metal catalysts into the growing silicon wire, the high temperature procedure. We have tried new approaches; one is electrochemical etching, the other is noble metal catalytic etching method to overcome those problems. In this talk, the silicon pillar formation will be characterized by investigating the parameters of the electrochemical etching process such as HF concentration ratio of electrolyte, current density, back contact material, temperature of the solution, and large pre-pattern size and pitch. In the noble metal catalytic etching processes, the effect of solution composition and thickness of metal catalyst on the etching rate and morphologies of silicon was investigated. Finally, radial p-n junction wire arrays were fabricated by spin on doping (phosphor), starting from chemical etched p-Si wire arrays. In/Ga eutectic metal was used for contact metal. The energy conversion efficiency of radial p-n junction solar cell is discussed.

• Journal of Advanced Marine Engineering and Technology
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• 제35권2호
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• pp.175-181
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• 2011

본 연구에서는 선박용 폐열회수 발전시스템에 적용 가능한 100kW급 구심터빈의 설계 및 CFD 해석기법을 이용하여 열사이클 시스템 및 구심터빈 최적화를 위한 설계자료를 확보하는 것이다. 구심터빈은 스크롤 케이싱, 18개의 베인노즐, 13개의 로터 블레이드로 구성되며, 해석격자는 격자테스트를 통해 약 230만개 정도의 최적격자를 구성하였다. 질량유량 0.5kg/s, 회전속도는 75,000rpm, 입구압력은 195~620kPa 범위 내에서 8가지 조건으로 설정하였다. 베인노즐 내부로 증기가 유입된 후 출구로 갈수록 노즐의 압력면과 흡입면의 압력이 비슷해지면서 마하수가 거의 같은 값을 보였다. 입구온도와 압력이 $250^{\circ}C$, 352kPa 일 때 등엔트로피 효율은 74%, 기계동력은 108kW의 해석결과를 보이고 있다.