• Tribology and Lubricants
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• v.29 no.5
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• pp.318-323
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• 2013

Overheating in electrical motors results in detrimental effects such as degradation of the insulation materials, demagnetization of magnets, increases in Joule losses, and decreases in motor efficiency and lifetime. Thus, it is important to find ways to dissipate heat from the motor and to keep the motor operating at its most efficient temperature. In this study, a new design to guide air flow through a given brushless direct current (BLDC) motor is developed and the design is analyzed, specifically by using computational fluid dynamics (CFD) simulations. The results showed that the temperature distribution in the three proposed models is lower than that in the original model, although the speed of the cooling fan in the original model reaches a very high value of $15{\times}10^3$ rpm. The results also showed that CFD can be effectively used to simulate the heat transfer of BLDC motors.

• Journal of Power System Engineering
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• v.16 no.1
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• pp.30-37
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• 2012

공기 양수 펌프는 재생 에너지 분야, 부식 및 마모 특성의 유체의 활용 등 높은 신뢰성과 낮은 유지보수 비용을 필요로 하는 분야에서 그 사용이 증대되고 있다. 본 연구에서는 소형 공기 양수 펌프의 성능 평가 및 기초 데이터를 얻기 위한 연구로, D=0.012~0.019m, L=0.933m인 배관의 침수 깊이(${\beta}$=0.55,0.60,0.65,0.70)에 따른 수치해석을 수행하였다. 수치 해석 및 실험 결과는 유사성을 뛰었으며, 펌프의 사양과 효율은 공기의 질량 유속 비, 침수 깊이 비와 양수 배관의 길이에 관한 함수로 나타났다. 그리고 최대 물과 공기 질량 유속의 비는 각 배관에서 서로 다른 침수 깊이의 비로 나타났으며, 공기 양수 펌프의 최대 효율이 발생되는 운전조건은 슬러그(slug)와 슬러그 교반 정도(slug-churn flow regime)에 따라 나타남을 알 수 있었다.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.58 no.4
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• pp.609-614
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• 2009

A fuel-cell power system among various alternative power sources has many advantages such as comparatively independable circumstances, high-efficient, and heat-recyclable, thus it is now able to be up to hundreds MWh-scaled through improving feasibility and longevity of it. During the last few decades, numerous research results has been investigated to expand interest in fuel-cell technology. This study presents pressure distribution on the geometrical manifold structures, which are U-type and Z-type, of a planar-type fuel-cell stack by simulated with computational fluid dynamics(CFD). Then, electrical performance of a 200W fuel-cell stack, which is U-type, was diagnosed after pre-conditioning operation. The stack has electrical characteristics ; 22V, 10A, 220W, and current density $200mA/cm^2$.

• 한국전산유체공학회:학술대회논문집
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• 1995.10a
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• pp.90-103
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• 1995

The field of computational fluid dynamics(CFD) is rapidly approaching the stage where viscous flows over complex configurations are solved. However, the situation is not as promising when one considers a more complete configuration. CFD is not a banana, but a onion. The difficulties arise mainly because the task of generating the grids for modeling such complex geometries is tedious. The primary interest of the author is in the area of grid generation, in particular, duct flow calculations typically encountered in the internal flow. Pertinent examples will be cited to demonstrate the feasibility of solving viscous flow over practical duct configurations of current interest on grid topologies.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2002.11a
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• pp.358-374
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• 2002

최근 빈번하게 발생하고 있는 사우나 등의 열을 방사하는 도크내에서 발생하는 화재사고는 다중이용업소를 이용하는 불특정한 사람들의 생명을 위협하고 있는 수준에 도달하고 있다. 특히 이런 시설의 화재는 화재발생 후에 소방대에 의한 진압에만 치중하고 있어 향후 계속하여 화재가 발생할 우려가 큼에도 불구하고 착화원인을 규명하는데 소홀히 하고있다. 특히 현장감식에 의한 육안조사만을 실시하여 화재원인을 추정하거나 설정하는 경우가 대부분이라 근본적인 대책을 세우지 못하고 있다. 따라서 본 연구에서는 육안조사 등에 의하여 설정한 착화원인을 과학적인 분석법 즉, EU국가에서 널리 사용하는 CFD(컴퓨터수치해석)시뮬레이션 S/W를 사용하여 연소모델링에 의한 검증조사기법을 적용하여 원인을 검증하는데 사용하여 국내화재조사기술의 과학화를 시도하였다.

• Journal of the Korean institute of surface engineering
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• v.48 no.4
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• pp.179-184
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• 2015

Quadrupole Mass Spectrometers (QMS) is a very useful tool in vacuum process diagnosis. Tungsten filament based ion sources are vulnerable to contamination from process gas monitoring. Common symptoms of quadrupole mass spectrometer malfunction is appearance of unwanted contaminant mass peaks or no detection of any ion peaks. We disassembled used quadrupole mass spectrometer and found out black insulating deposits on inside of ion source parts. Five steps of cleaning procedure were applied and almost full restoration of functions were confirmed in two types of closed ion source quadrupole mass spectrometer. By using a numerical modeling (CFD-ACE+) technique, the electric potential profile of ion source with/without insulating deposit was calculated and showed the possibility of quadrupole mass spectrometer malfunction by the deterioration of designed potential profile inside the ion source.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2011.11a
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• pp.163-166
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• 2011

본 연구는 Zone Model을 활용하여 장대도로터널의 화재성상 예측방법의 고찰을 목적으로 1/5 Scale 모형실험 및 MLZSUZUKI 결과 분석과 CFD와 MLZ의 비교 분석을 실시하였다. Modeling한 모형터널의 해석시간이 MLZ 1분, FDS 약 6시간으로 CFD에 비하여 360배의 시간 감소와 다층으로 구분하여 구간의 온도변화 및 환기풍에 의한 열기류의 움직임 등의 상황이 해석됨으로 향후 MLZ을 활용하여 터널화재의 위험성 예측에 용이할 것으로 판단된다.

• International Journal of Fluid Machinery and Systems
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• v.8 no.4
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• pp.240-253
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• 2015

The objective of this paper is to evaluate the applicability of mass transfer cavitation models and determine appropriate numerical parameters for cavitating flow simulations. CFD simulations were performed for a NACA66 hydrofoil at cavitation numbers of 1.49 and 1.00, corresponding to steady sheet and unsteady sheet/cloud cavitating regimes using the Kubota and Merkle cavitation models. The Merkle model was implemented into CFX by User Fortran code. The Merkle cavitation model is found to give some improvements for cavitating flow simulation results for these cases. Turbulence modeling is also found to have an important contribution to the prediction quality of the simulations. The relationship between the turbulence viscosity modification, in order to take into account the local compressibility at the vapor/liquid interfaces, and the predicted numerical results is clarified. The limitations of current cavitating flow simulation techniques are discussed throughout the paper.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.04a
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• pp.30-33
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• 2007

DSMC method is now widely accepted CFD approach to compute and simulate the nozzle plume in rarefied regimes. In this study, using SMILE(Statistical Modeling in Low-density Environment) code which was developed in ITAM, Russia and coded using DSMC method, the internal flow of the Rothe micronozzle was simulated. Moreover, to show the validity of the SMILE code, the centerline temperatures according to the Reynold's number were compared with the ones obtained by the Rothe's experiment.

• Journal of the Society of Naval Architects of Korea
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• v.40 no.2
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• pp.1-10
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• 2003

It is important to understand the flow characteristics such as wave and wake development around a ship for the design of the hull forms with better resistance and propulsive performance. The experimental results explicating the local flow characteristics are also invaluable for validation of the physical and numerical modeling of CFD codes, which are recently gaining acknowledgements as efficient tools for hull form evaluation This paper describes velocity and wave profiles measured in the towing tank for the KRISO 138K LNG Carrier (KLNG) model with propeller and rudder. The results contained in this paper can provide the valuable information on the effect of propeller and rudder on stern flow characteristics of the modern commercial hull form, furthermore, the present experimental data will provide important database for CFO validation.