• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 추계학술대회 논문집
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• pp.600-605
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• 2009

A general purpose viscous flow solver Ansys CFX is used to study a Savonius type wave energy converter in a 3D numerical viscous wave tank. This paper presents the results of a computational fluid dynamics (CFD) analysis of the effect of blade configuration on the performance of 3 bladed Savonius rotors for wave energy extraction. A piston-type wave generator was incorporated in the computational domain to generate the desired incident waves. A complete OWC system with a 3-bladed Savonius rotor was modeled in a three dimensional numerical wave tank and the hydrodynamic conversion efficiency was estimated. The flow over the rotors is assumed to be two-dimensional (2D), viscous, turbulent and unsteady. The CFX code is used with a solver of the coupled conservation equations of mass, momentum and energy, with an implicit time scheme and with the adoption of the hexahedral mesh and the moving mesh techniques in areas of moving surfaces. Turbulence is modeled with the k.e model. Simulations were carried out simultaneously for the rotor angle and the helical twist. The results indicate that the developed models are suitable to analyze the water flows both in the chamber and in the turbine. For the turbine, the numerical results of torque were compared for all the cases.

• 태양에너지
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• 제16권2호
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• pp.39-47
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• 1996

본 연구에서는 실제 열 파이프용 수평 축열조에서 등간격인 heating pad 수와 위치 및 공급열량을 변화시키면서 축열조내의 순수 Plume 유동특성을 파악하였다. 동일한 heating pad수를 가지고 집중 배치 형태와 분산 배치 형태를 취하였을 때 집중 배치 형태로 취하는 것이 $5{\sim}6%$ 정도의 더 높은 효율을 얻었다. 따라서 열 파이프용 수평 축열조에서 heating pad를 장착할 때 동일한 heating pad의 수에서는 집중(concentration)배치형태로 설계하는 것이 효과적임을 알 수 있다.

• 한국태양에너지학회 논문집
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• 제28권4호
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• pp.50-55
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• 2008

The Storage efficiency of concentric evacuated tube solar collector is tested for one year from January 1st to December 31st under the real sun condition. The testing equipment is operated continuously for three days without cooling the storage tank. Daily storage efficiency is obtained from dividing stored energy in the storage tank by solar insolation on the solar collector for each day. Daily averaged temperature of the storage tank is lowest in January and highest in August. Monthly averaged storage efficiency is also lowest in November and highest in June. Therefore, it can be said that the storage temperature and the storage efficiency are roughly proportional to outdoor temperature. Furthermore, the daily storage efficiency is reversely proportional to $(T_s-T_a)/I_c$ where $T_s$ and $T_a$ are daily averaged storage temperature and outdoor temperature from sunrise to sunset, and $I_c$ is total insolation on the solar collector for a day.

• 한국수산과학회지
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• 제33권2호
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• pp.137-142
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• 2000

수산자원 증강을 위한 방류용 종묘로서 연안 정착성 어종인 조피볼락의 종묘성 강화와 우량종묘의 판정기법에 대한 기초적 연구를 위하여 서해안 윽상수조산, 축제식 양식산 및 자연산 조피볼락 치어에 대한 일반성분, 비만도, 간중량지수, 복강내지방, 장중량지수, 근육중량비, 일반 아미노산 함량 및 무기질 함량을 비교하였다. 수분 함량은 자연산이 양식산 (축제식 망식산과 육상수조산) 보다 높게 나타났지만 지질함량은 자연산이 가장 낮았다. 회분 함량은 자연산이 양식산(축제식 양식산과 육상수조산) 보다 높았다. 치어 전어체에서 단백질함량의 차이는 없었다. 비만도는 육상수조산이 자연산보다 높은 값을 보였지만 축제식 양식산과는 유사하였다. 간중량지수 (HSI), 복강내지방 (IPF) 및 장중량지수 (ISI)에서 육상수조산과 축제식 양식산은 차이가 없었으나 자연산보다 높은 값을 나타내었다. 근육중량비는 사육방법에 따라 차이가 없었다. 일반아미노산 총함유량은 자연산이 육상수조산보다 높았으나 축제식 양식산과는 차이가 없었다. 자연산은 asparatic acid, glutamic acid, isoleucine, leucine, Iysine, phenylalanine, threenine, valine에서 양식산 (축제식 양식산과 육상수조산) 보다 유의적으로 높았다. 무기질 함량 중 Ca, P 함량은 자연산과 육상수조 양식산은 유사하였으나, 축제식 양식산보다 유의적으로 높게 나타났다. Mg 함량은 자연산이 가장 높았으며, Mn 함량은 자연산, 육상수조산, 축제식 양식산의 순서로 나타났다. 자연산의 Zn 함량은 육상수조산과는 유사하였으나, 축제식 양식산 보다는 높게 나타났다. 전체적으로 수분과 회분 함량, asparatic acid, glutamic acid, isoleucine, leucine, lysine, phenylalanine, threonine, valine과 일반아미노산 총함유량 및 Mg 함량은 자연산이 양식산 (축제식 양식산과 육상수조산) 보다 높게 나타났으며, 지질함량, Mn 함량과 비만도, 간중량지수 (HSI), 복강내지방 (IPF) 및 장중량지수 (ISI)에 있어서는 양식산이 자연산보다 높은 값을 보였다. Ca, P 및 Zn함량은 축제식양식산에서 가장 낮게 나타났다. 그러므로 이러한 체성분 및 생물학적 특성은 조피볼락 방류용 우량종묘의 판정과 종묘성 강화의 지표로서 적용이 될 수 있을 것이다.

• Geomechanics and Engineering
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• 제5권2호
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• pp.165-185
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• 2013

In the present study, the numerical and experimental investigations were performed on the backfill- exterior wall-fluid interaction systems in case of empty and full tanks. For this, firstly, the non-linear three dimensional (3D) finite element models were developed considering both backfill-wall and fluid-wall interactions, and modal analyses for these systems were carried out in order to acquire modal frequencies and mode shapes by means of ANSYS finite element structural analysis program. Secondly, a series of field tests were fulfilled to define their modal characteristics and to compare the results from proposed approximation in the selected structures. Finally, comparing the theoretical predictions from the finite element models to results from experimental measurements, a close agreement was found between theory and experiment. Thus, it can be easily stated that experimental verifications provide strong support for the finite element models and the proposed procedures themselves are the meritorious approximations to the real problem, and this makes the models appealing for use in further investigations.

• Nuclear Engineering and Technology
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• 제20권1호
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• pp.1-8
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• 1988

상업용 발전소의 가동시, 출력 변화에 의해 1차 계통 보론 농도의 변화가 요구되었을 때 CVCS보충 시스템에서의 보충 유량이 연속 방정식과 질량 평형 방정식을 이용하여 측정된다. 이를 위하여, 1차 계통, 가압기, 그리고 volume control tank가 각각 질량과 보론 농도를 가진 control volume으로 그리고 1차측과 가압기, CVCS를 연결하는 파이프들이 시간 지연 요소로 모델화 되었다. 14-2-6-2 (출력변화 100-50-100) 부하 추종운전의 경우(7호기 EOL에서)를 이 모델을 이용하여 계산하였다.

• 한국자동차공학회논문집
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• 제9권4호
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• pp.10-17
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• 2001

The performance of a radiator is generally determined using a wind tunnel, in which the air velocity is uniform. However, when it is installed in a car, the distribution of the air velocity becomes nonuniform due to front-end openings, cross members, and horns etc., resulting in lower performance. In this study, several underhood flow simulations have been first performed to get flow rates and velocity distributions over the radiator. Secondly heat release rates are calculated by both a performance curve and a radiator model. Finally, using an engine cooling system simulator, radiator-top-tank temperature is predicted and the variations of heat release rate and radiator-top-tank temperature with nonuniformity of air velocity distributions are analyzed. The results show that the current engine cooling model successfully accounts for the nonuniformity effects that should be considered for higher accuracy in predicting engine cooling performance.

• Journal of Electrical Engineering and Technology
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• 제7권2호
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• pp.225-229
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• 2012

This paper proposes a reduced-scale simulator that can replace numerical analytic methods for the estimation of potential distribution caused by ground faults in various grounding systems. The simulator consists of a hemispherical electrolytic tank, a three-dimensional potential probe, a grounding electrode, and a data acquisition module. The potential distribution is measured using a potentiometer with a position-tracing function when a test current flows to the grounding electrode. Using the simulator, we could clearly analyze the potential distribution for a reduced- scale model by one-eightieth of the buried depth and length of the grounding rod and grounding grid. Once both the shape of the grounding electrode and the fault current are known, the actual potential distribution can be estimated.

• 전기학회논문지P
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• 제65권2호
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• pp.114-121
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• 2016

This paper is Instant space vector PWM(Pulse Width Modulation)power conversion devices in switching power semiconductors from my generation to losses and switching when the voltage surge and current surge of electronic noise(EMI: Electro Magnetic Interference / RFI: Radio Frequency Interference)to effectively minimize the power soft-switching power conversion circuit topologies of auxiliary resonant DC tank for the purpose of high performance realization of the electric power conversion system by the high-speed switching of a semiconductor device(AQRDCT simultaneously : an active auxiliary resonance using auxiliary Quasi-resonant DC tank)DC link snubber switch has adopted a three-phase voltage inverter. AQRDCL proposed in this paper can reduce the effective and current peak stress of the power semiconductors of the auxiliary resonant snubber circuit compared to the conventional active-resonant DC link snubber, it is not necessary to install the clamp switch of the auxiliary resonant DC link, DC the peak current and power loss of the bus line can be reduced.

• Structural Engineering and Mechanics
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• 제54권5호
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• pp.909-922
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• 2015

The dynamic response and the mooring line tension of a 1/75 scale model of spar-type platform for 2.5 MW floating offshore wind turbine subject to one-dimensional regular harmonic wave are investigated numerically and verified by experiment. The upper part of wind turbine which is composed of three rotor blades, hub and nacelle is modeled as a lumped mass the scale model and three mooring lines are pre-tensioned by means of linear springs. The coupled fluid-rigid body interaction is numerically simulated by a coupled FEM-cable dynamics code, while the experiment is performed in a wave tank with the specially-designed vision and data acquisition system. The time responses of surge, heave and pitch motions of the scale platform and the mooring line tensions are obtained numerically and the frequency domain-converted RAOs are compared with the experiment.