• Journal of computational fluids engineering
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• v.7 no.3
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• pp.44-52
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• 2002

An analytic methodology was developed for free surface motions between liquid metal coolant and cover gas in order to calculate the phenomena of gas entrainment in hot pool surface through IHX EMP and reactor core. The methodology was setup by applying the first order VOF convection model to CFX4 general purpose fluid dynamics analysis code. The methodology was validated by applying it to an experimental apparatus designed for free surface motions of KALIMER reactor. The distributions of free surface calculated by the present methodology were almost coincident with the experimental data. The developed methodology was applied to the KALIMER reactor of full power operating condition. The shapes of the free surface were nearly uniform. From the results, it was found that the altitude of the free surface from the IHX inlet nozzle of KALIMER reactor is high enough not to affect to free surface motions of generating gas bubbles from the turbulent shear flows such as hydraulic jump and water falls.

• 한국전산유체공학회:학술대회논문집
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• 2010.05a
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• pp.562-566
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• 2010

Numerical analysis of 150kW Huels-type arc jet was performed using compressible Navier-Stokes CFD code. To consider chemical reaction by high temperature, the flow was assumed to be chemical equilibrium states. As a turbulence and a radiation model, the two-equation k-epsilon model and the 3-band radiation model were adopted, respectively. Mass flow rate and current density were given as conditions for calculations. In this study, two kinds of mechanisms for injection of air flow wire considered. One is that air is provided by left wall surface and the other is that air is injected from upper wall surface. The pressure, density and temperature contours of two cases were compared and heat transfer rates were estimated. The numerical results of two cases were not much different to each other. However, in real 150KW device, air is injected from upper wall surface with swirl. To calculate more accurately, swirl effect is must be considered.

• 한국전산유체공학회:학술대회논문집
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• 1998.05a
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• pp.110-115
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• 1998

An axisymmetric Navier-Stokes procedure has been developed to analyze the pulse jet flow in a ceramic filter unit for the dust dislodging process. Using Baldwin-Lomax turbulence model as a closure relationship, the SIAF(Scalar Implicit Approximate Factorization) algorithm together with the ${\delta}^k-Correction$ iterative time marching scheme is adopted to solve the unsteady compressible Navier-Stokes equations. After some validation tests, the code has been applied to solve the pulse jet flow and examine the effects of geometry and reservoir pressure condition on the pressure level inside the filter unit. To avoid dealing with the uncertainty of such factors as the cohesion of the collected dust and the adhesion of the dust to the medium and also to simplify the analysis, the filter wall is assumed to be impermeable. The results for various test cases are presented.

• Journal of ILASS-Korea
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• v.20 no.1
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• pp.7-13
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• 2015

In this study, the behavior of water or nanofluid droplets impacting upon a hot surface was investigated by visualization of impacting phenomena with time-delayed photographic technique. Changing the mass ratio of nanofluid and the temperature of the heated surface, the characteristics of the spreading behavior and the diameter of spreading liquid film was compared between water and nanofluid droplets. The impacting droplet spreaded as a liquid film after impact and nanofluid droplets spreaded more widely than water droplets. After reaching the maximum diameter, water droplets shrinked more than nanofluid droplets. Based on this, the heat transfer area from a hot surface to impacting nanofluid droplets would be wider than that of impacting water droplets. Considering individual impacting droplet only, spray cooling using nanofluid would be better than using water.

• 유체기계공업학회:학술대회논문집
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• 2004.12a
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• pp.104-108
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• 2004

Micro turbine is an electric power generating system using a gas turbine whose rated power is under 300kW, and it is featured as a small, efficient. maintenance free and environment-friendly system. Air foil bearing has several advantages over conventional bearings for micro turbine because it is oilless and non-contact. Recently, air foil bearings for high temperature over $500^{\circ}C$ has been developed for the application of 65kW micro turbine system. In this paper, the development and current status are summarized in detail.

• Journal of the KSME
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• v.30 no.6
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• pp.548-554
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• 1990

대체에너지 기관으로서 요구되는 조건을 갖춘 스터링엔진의 이해를 돕기 위하여 기본원리, 개 발현황, 개발상 문제점 등의 기본사항을 소개하였다. 내연기관과는 달리 외연기관인 스터링엔 진은 작동유체가 밀폐공간 내에서 고. 저온 양 영역을 이동하면서 압력차를 발생시켜 일을 형성 하는 과정을 밟기 때문에 고온. 고압일수록 높은 출력이 예상되며, 전열성능과 작동저항면에서 수소나 헬륨과 같은 저분자량의 가스가 작동체로 채택되기 때문에 작동유체의 누기(leakage) 및 크랑크실의 냉각 윤활유의 작동공간으로의 누유 등은 스터링엔진의 출력 저하에 가장 큰 요인 으로 작용한다. 마찰 등 기계적 손실의 저감기술, 속도제어기술, 용도에 따른 엔진 형식 설계 기술, 구성부품 성능향상을 위한 요소기술 등의 개발이 중요한 과제가 되고 있으며, 이상 소개한 내용이 관심있는 많은 분들의 스터링엔진 연구나 이해에 도움이 될 수 있기를 바란다.

• Journal of the KSME
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• v.35 no.1
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• pp.71-83
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• 1995

최근 충격파현상을 이용하여 고온 고압의 상태를 용이하게 발생시킬 수 있는 기술 및 장치들이 여러 분야에서 요구되고 있으며, 이들에 대한 연구의 필요성이 갈수록 증대되어 가고 있다. 그 러나 우리나라에서의 충격파현상에 대한 이해와 지식은 비압축성 유체공학에 대한 연구에 비해 매우 미비한 실정이며, 이에 대한 관ㅅ미과 체계적인 연구가 절실한 실정이다. 일반적으로 충 격파현상을 이해하는 데에는 압축성 비정상흐름, 혹은 정상적인 초음속흐름에 대한 지식이 필 요하지만, 이 글에서는 충격파현상에 대한 이론적 기술들을 생략하고, 충격파현상들을 소개하기 위한 목적으로 충격파현상에 대한 현재의 연구동향과 충격파현상을 응용하는 실례들에 관해 간략히 기술하고, 충격파현상의 연구를 위해 필요한 충격과 발생장치에 대해서 기술하였다.

• The KSFM Journal of Fluid Machinery
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• v.8 no.6 s.33
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• pp.40-46
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• 2005

Because of design and manufacturing costs, it is important to predict an expected life of bellows with component stresses of bellows as its design factors and material characteristics. In this study, numerical analyses are carried out to elucidate the thermal and flow characteristics of the bellows-seal gate and globe valves for high temperature (max. $600^{\circ}C$) and for high pressure (max. $104 kgf/cm^2$) conditions. Using commercial codes, FLUENT, which uses FVM and SIMPLE algorithm, and ANSYS, which uses FEM, the pressure and temperature fields are graphically depicted. In addition, when bellows have an axial displacement, thermal stress affecting bellows life is studied. The pressure and temperature values obtained from the flow analyses are adopted as the boundary conditions for thermal stress analyses. As the result of this study, we got the reasonable coefficients for valve and thermal stress for bellows, compared with existing coefficients and calculated values.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2003.05b
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• pp.397-398
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• 2003

대기 중 분진을 제거하는 방식으로 여과 이론을 적용할 수 있는 경우는 섬유 여과기, 입자상 여과기, 액적에 의한 습식 세정기 그리고 기포를 이용한 분진 제거 방법 등을 들 수 있다. 이러한 여과 원리를 이용한 집진 설비를 설계하는데 있어, 액적 또는 기포 주위의 유동장을 정확히 파악하는 것은 매우 중요하다. 특히, 포집구의 크기가 작아지고 화학적으로 반응성을 갖는 고온의 함진가스가 유입되는 경우 및 저압에서 운영되는 경우에 누드센수(Knudsen number)의 영향을 무시할 수 없는데 이러한 영역을 저 누드센 영역(low Kundsen number regime)이라고 한다(Lee et al., 1978). (중략)

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.4
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• pp.907-911
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• 1990

본 연구에서는 비열이 일정하고 초기온도가 주어진 열원으로부터, 일정한 열 전달 용량의 열교환기를 사용하여 최대의 에너지를 전달시키기 위한 조건을 구해 보기 로 한다. 즉, 저온유동은 고온의 열원유동과 대항류로서 열교환하며 위치에 따라 저 온유체의 온도가 가역 단열압축 또는 팽창에 의하여 임의로 조절될 수 있는 일반적인 경우에 대하여, 저온유체가 최대의 가용 에너지를 흡수하기 위한 온도분포를 변분법 문제로서 해석하고 그에 다른 부수조건들을 검토하고자 한다.