• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.1158-1161
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• 2003

For underwater milling of parts of nuclear reactor, a waterproof main spindle system was developed. which used a servo meter. Particularly, a waterproof system is available to cope with emergencies such as an electricity failure so that it prevents hazards from cutting radioactive materials. A developed spindle was designed to be capable of horizontal and vertical cutting and structural analysis was conducted with a FEM tool(Design Space) when the forces were loaded in each axis-direction.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1993년도 가을 학술발표회논문집
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• pp.186-192
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• 1993

Proto-type seismic isolation rubber bearings are investigated through nonlinear hyperelasticity finite elements using the ANSYS general purpose structural analysis code. The purpose of the analysis was to determine the maximum horizontal strain range which can be obtained with a 250KN hydraulic actuator. A Mooney-Rivlin strain energy density function was used as a constitutive law for rubber. The results are compared with the test data available in the literature and found to in good agreement only in the higy strain range. The analysis results can be used with conservatism to predict the necessary force required to a specified displacement such as the purpose of this analysis. However, more precise constitutive model will be required to simulate the bearing behavior with accuracy in the mid-range strain.

• Nuclear Engineering and Technology
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• 제38권2호
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• pp.119-128
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• 2006

We start to develop a predictable technology for thermal-hydraulic performance of the RMWR core using an advanced numerical simulation technology. As a part of this technology development, we are developing the advanced interface tracking method to improve the conservation of volume of fluid. The present paper describes a part of the development of the twophase flow simulation code TPFIT with the advanced interface tracking method. The numerical results applied to large-scale water-vapor two-phase flow in tight lattice rod bundles are shown and compared with experimental results. In the results of numerical simulation, a tendency of the predicted void fraction distribution in horizontal plane agreed with the measured values obtained by the advanced neutron radiography technique including the bridge formation of the liquid at the position of adjacent fuel rods where an interval is the narrowest.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.73-78
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• 2003

The InP thin films grown by metalorganic chemical vapor deposition (MOCVD) are widely used to optoelectronic devices such as laser diodes, wave-guides and optical modulators. Effects of various parameters controlling film growth rate such as gas-phase reaction rate constant, surface reaction rate constant and mass diffusivity are numerically investigated. Results show that at the upstream region where film growth rate increases with the flow direction, diffusion including thermal diffusion plays an important role. At the downstream region where the growth rate decreases with flow direction, film deposition mechanism is revealed as a mass-transport limited. Mass transport characteristics are also studied using systematic analyses.

• 한국자동차공학회논문집
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• 제4권3호
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• pp.176-186
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• 1996

The phenomena of drag reduction using small quantities of a liner macromolecules has attracted the attention of many experimental investigations. On the other hand drag reduction in two phase flow can be applied to the transport of crude oil, phase change system such as chemical reactor, pool and boiling flow, and to flow with cavitation which occurs pump impellers. But the research on dragreduction in two phase flow is not sufficient. The purpose of the present work is to evaluate the drag reduction by measuring pressure drop, void fraction, mean liquid velocity and turbulent intensity whether polymer additives a horizontal single and two phase system or not. Flow pattern of air-water two phase flow was classified by electrical conductivity probe signal. Velocities and turbulent intensities of signal were measured simultaneously with a Hot-film anemometer.

• Carbon letters
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• 제6권2호
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• pp.79-85
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• 2005

The work reported in this paper relates to preparation and characterization of carbon nanomaterials by CVD method on different substrates by decomposition of certain hydrocarbons at 550-$800^{\circ}C$ using a horizontal quartz tube reactor. Monometallic and bimetallic catalyst system of iron and nickel were used for the preparation of different carbon nanomaterials. The influence of various parameters such as substrate/catalyst preparation parameters, the nature of substrate, catalyst concentration, reaction time and temperature on the growth, yield and alignment of carbon nanotubes has been studied. The characterization of carbon nanomaterials has been carried out using SEM, TEM and TGA. The carbon nanomaterials developed were vertically aligned on a large area of flat quartz substrate.

• 한국표면공학회지
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• 제56권6호
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• pp.341-352
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• 2023

This paper reviews the potentials of a rotary chemical vapor deposition (RCVD) process for nanomaterial synthesis and coating on powder-based materials. The rotary reactor offers a significant improvement over traditional CVD methods having horizontal and fixed reaction chambers. The RCVD system yields enhanced productivity and surface coating uniformity of nanoparticles applied in various purposes, such as efficient heat dissipation, surface hardness enhancement, and enhanced energy storage performances. The effectiveness of the RCVD system would open up new possibilities in various applications because uniform coating on powder-based materials with massive productivity is inevitable to develop multi-functional materials with high reliability.

• 한국축산시설환경학회지
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• 제13권2호
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• pp.121-128
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• 2007

축산분뇨와 톱밥을 혼합하여 수분조절을 한 후 발효조에 투입하는 방식이 아닌 발효상에 미리 투입된 톱밥위에 축산분뇨를 살포하면서 교반처리하여 발효증발 처리하는 시스템을 이용하여 퇴비 발효층의 온도, 수분함량, 수분수지, 퇴비의 비료성분을 연구하였다. 1. 본 처리공정은 과다한 수분을 신속하게 침출수 강제배출 방식으로 배출하여 슬러리 투입분뇨의 함수율이 높더라도 수분증발이 이루어지고 발효상 함수율은 $65{\sim}73%$ 전후로 유지되었다. 2. 연속퇴비화 과정에서 시험기간 중에 10.6% 정도의 침출수가 발생되었다. 또한 5개월 가동 기간 동안 톱밥 $1m^3$ 투입 당 $3.16m^3$의 돈분슬러리 처리가 가능하였다. 3. 침출여과액은 오염물질농도가 낮아져 투입분뇨 대비 BOD는 86.5%, SS은 96.2% 저감되었다. 4. 퇴비사의 미기상 분석결과 상대습도는 낮 시간을 제외한 야간시간에는 $80{\sim}100%$로서 높았다. 퇴비사의 습도가 높아지면 퇴비화 과정 중 수분증발 효율이 저하의 원인이 될 것으로 사료된다.

• Nuclear Engineering and Technology
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• 제44권6호
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• pp.597-610
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• 2012

The passive auxiliary feedwater system (PAFS) is one of the advanced safety features adopted in the APR+, which is intended to completely replace the conventional active auxiliary feedwater system. With an aim of validating the cooling and operational performance of PAFS, an experimental program is in progress at KAERI, which is composed of two kinds of tests; the separate effect test and the integral effect test. The separate effect test, PASCAL ($\underline{P}$AF$\underline{S}$ $\underline{C}$ondensing Heat Removal $\underline{A}$ssessment $\underline{L}$oop), is being performed to experimentally investigate the condensation heat transfer and natural convection phenomena in PAFS. A single, nearly-horizontal U-tube, whose dimensions are the same as the prototypic U-tube of the APR+ PAFS, is simulated in the PASCAL test. The PASCAL experimental result showed that the present design of PAFS satisfied the heat removal requirement for cooling down the reactor core during the anticipated accident transients. The integral effect test is in progress to confirm the operational performance of PAFS, coupled with the reactor coolant systems using the ATLAS facility. As the first integral effect test, an FLB (feedwater line break) accident was simulated for the APR+. From the integral effect test result, it could be concluded that the APR+ has the capability of coping with the hypothetical FLB accident by adopting PAFS and proper set-points of its operation.

• Nuclear Engineering and Technology
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• 제53권11호
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• pp.3635-3642
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• 2021

Natural circulation systems (NCSs) are extensively applied in nuclear power plants because of their simplicity and inherent safety features. For some passive natural circulation systems in floating nuclear power plants (FNPPs), the ocean is commonly used as the heat sink. Condensation induced water hammer (CIWH) events may appear as the steam directly contacts the subcooled seawater, which seriously threatens the safe operation and integrity of the NCSs. Nevertheless, the research on the formation mechanisms of CIWH is insufficient, especially in NCSs. In this paper, the characteristics of flow rate and fluid temperature are emphatically analyzed. Then the formation types of CIWH are identified by visualization method. The experimental results reveal that due to the different size and formation periods of steam slugs, the flow rate presents continuous and irregular oscillation. The fluid in the horizontal hot pipe section near the water tank is always subcooled due to the reverse flow phenomenon. Moreover, the transition from stratified flow to slug flow can cause CIWH and enhance flow instability. Three types of formation mechanisms of CIWH, including the Kelvin-Helmholtz instability, the interaction of solitary wave and interface wave, and the pressure wave induced by CIWH, are obtained by identifying 67 CIWH events.