• Journal of Welding and Joining
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• 제30권6호
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• pp.10-14
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• 2012

Recently the low alloy steel plate made with manganese-molybdenum is used widely in steam drum and separator of the new coal-fired power plant boiler. This material is suitable for the vapor storage of high pressure and high temperature. The high temperature creep strength of Mn-Mo alloy is higher than the carbon plate(SA516) that used in the subcritical pressure boiler. It reduces the thickness of the pressure vessel and makes the lightweight possible. Recently in the power plant boiler operation and production process, the damage has happened frequently in the heat affected zone and base material according to the hydrogen crack and delayed crack. This paper describes the research result about the damage case experienced in the boiler steam drum production process and present the optimum manufacture method for the similar damage prevention of recurrence.

• 한국수소및신에너지학회논문집
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• 제31권6호
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• pp.530-545
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• 2020

This paper reviews and summarizes the fuel-cell-related studies those have been recently published in major Korean Citation Index journals, aiming at analyzing the research trend in fuel cell technologies. Six major journals are selected for the literature survey; 57 papers are chosen for the detailed analysis through a screening examination on the total 1,040 papers published during between 2018 and 2020. Papers are classified into six technical categories, such as i) electrode, ii) electrolyte, iii) bipolar plate and stack, iv) fuel cell system, v) balance of plant, and vi) diagnosis-related studies, and summarized by the experts in the relevant area. Through this paper, we provide a comprehensive review on the recent trends and progress in fuel-cell-related research work in Korea.

• 한국산학기술학회논문지
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• 제12권4호
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• pp.1999-2004
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• 2011

본 논문은 매트릭스 수지로 LCP(Liquid crystal polymer)를 사용하였으며, 기계적 특성 및 화학적 특성을 증대시키기 위해 주 첨가제로 synthetic graphite, expanded graphite와 보조 첨가제로는 carbon black을 사용하여, 함량 별로 복합소재를 제조하였다. 사출성형 전 CAE 프로그램으로 해석을 하였으며, 유동성과 섬유 배향을 예측 했다. 복합 소재는 전동식 사출기를 이용하여 ASTM 복합 시편으로 사출성형 하였으며, 시편을 four point probe 장치를 사용하여 전기전도도를 측정/비교 하였으며, 기계적 강도는 굴곡강도, 굴곡탄성률, 충격강도를 측정하였다. 첨가제가 증가할 수록 전기전도도는 증가하나 첨가제의 brittle한 특성으로 인해 기계적 강도는 감소하는 것을 확인 할 수 있었다.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2000년도 춘계학술대회 논문집(Proceeding of the KOSME 2000 Spring Annual Meeting)
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• pp.153-158
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• 2000

Flow visualization and PIV measurements were conducted to investigate the flow characteristics of multi-channel with inclination angle. The water flow seeded with tiny vegetable powder as tracers revealed details of flow field. The PIV measurement to acquire multi-point velocity data simulatneously was carried out at three space of plates for 5, 10, and 15mm with variation of inlet flow rates of $0.25m^3/h$ and <$0.5m^3/h.$ Experiment results show that space of plates acts a significant role in separating process.

• 한국생산제조학회지
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• 제5권1호
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• pp.27-32
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• 1996

This paper deals with the distributions of magnetic flux of an electro-magnetic chuck which is one of the most commonly used chucking attachments in a surface grinding machine. The measured results showed good correspondence with the theoretical results which were previously presented by the same author. The normal and tangential components of the magnetic flux density were measured using the gauss meter. The measured results indicated that the magnetic flux density was periodically changing over the transverse position to the magnetic pole. The normal component of magnetic flux decreases very rapidly for the increased z position.

• Elastomers and Composites
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• 제43권4호
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• pp.253-258
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• 2008

본 연구에서는 열가소성 고분자인 폴리아미드 6,6, 전도성 충전제인 흑연과 카본블랙을 이용하여 높은 기계적 물성 및 전기적 특성, 우수한 기체 내투과성을 동시에 갖는 연료전지 분리판용 복합체에 대하여 연구하였다. 성형압력과 충전제의 함량이 복합체의 물성에 미치는 영향을 굴곡강도, 전기전도도, 기체투과도 등을 측정하여 살펴보았다. 복합체 내의 흑연함량이 증가함에 따라 전기전도도는 증가하였으며, 굴곡강도는 80 wt% 일때 최대 값을 나타내었다. 굴곡강도는 $400\;kgf/cm^2$의 성형압력에서부터 일정한 값을 나타냈으며, 전기전도도는 압력에 큰 영향을 받지 않음을 알 수 있었다. 또한 흑연에 카본블랙이 첨가된 경우 전기적 특성이 크게 향상됨을 확인할 수 있었다. 산에 침전된 복합체의 기계적 성질은 감소함을 알 수 있었다.

• Macromolecular Research
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• 제11권6호
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• pp.481-487
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• 2003

Polypyrrole (PPy) was coated sequentially by chemical and electrochemical methods on a woven fabric, giving rise to a fabric having high electrical conductivity. We investigated the effects of the preparation conditions on the various properties of the resulting fabric. The PPy-coated fabric with optimum properties was obtained when it was prepared sequentially by chemical polymerization at the elevated temperature of 100$^{\circ}C$ under a pressure of 0.9 kgf/$\textrm{cm}^2$ and then electrochemical polymerization with a 3.06 mA/$\textrm{cm}^2$ current density at 25 $^{\circ}C$ for 2 hrs with the separator plate. The surface resistivity of the resulting fabric was as low as 5 Ω/$\square$ .The PPy-coated fabric prepared under the optimum conditions showed practically applicable heat generating property. When electrical power was supplied to the fabric using a commercial battery for a mobile phone (3.6 V, LGLl-AHM), the temperature of the fabric increased very quickly from room temperature to ca. 55 $^{\circ}C$ within 2 min and was maintained for ca. 80 min at that temperature. The heat generating property of the fabric was extremely stable, exhibiting similar behavior over 10 repeated cycles. Therefore, we suggest that the PPy-coated fabric in this study may be practically useful for many applications, including flexible, portable surface-heating elements for medical or other applications.

• 한국압력기기공학회 논문집
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• 제4권2호
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• pp.50-56
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• 2008

The tubes in heat exchanger are typically made of copper alloy, stainless steel, carbon steel, titanium alloy material. Type-439 ferritic stainless steel is ferromagnetic material, and furnish higher heat transfer rates than austenitic stainless steels and higher resistance to corrosion-induced flaws. Ferritic stainless steel can be found in low-pressure(LP) feedwater heaters and moisture separator reheaters(MSRs) in turbine system. LP feedwater heaters generally utilize thin wall Type-439 stainless steel tubing, whereas MSRs typically employ a heavier wall tubing with integral fins. Service-induced damage can occur on the O.D(outside diameter) surface of Type-439 ferritic stainless steel tubing which is employed for MSRs tubing, and the most typical damage mechanism is vibration-induced tube-to-TSP(tube support plate) wear and fatigue cracking. The wear has been reported that occurs mainly on the OD surface. Accordingly, in this study, we have evaluated the flaw sizing capability of magnetic saturation eddy current technique using magnetic saturation probe and flawed specimen.

• 설비공학논문집
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• 제11권5호
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• pp.658-668
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• 1999

The objective of the present study is to investigate the effect of experimental parameters on the hydrodynamic characteristics in a horizontal tee-type evaporator using R-22. The experimental apparatus consisted of an unheated tee-type test section, a liquid-vapor separator, a preheated, mass flow meters, a plate heat exchanger, pump, and other measurement devices. The experimental parameters were mass flux(500 and 600kg/$m^2$s), inlet quality(0.1~0.3) and separation ratio(0.3~0.7). Absolute pressure at the inlet of the test section was 0.652 MPa. The branch-to-inlet inner diameter ratio was 0.61. Pressure gradient at the branch section was larger than that at the run section at the same separation ratio. Pressure drop per unit length increased at the run section and decreased at the branch section as the separation ratio increased. Pressure drop predicted by the separated flow model agreed with experimental data within -35 to +16%. Generally, predicted values showed similar trend with the data. Mass flow ratio of vapor refrigerant was affected by the inlet quality more than the mass flux.

• 자원리싸이클링
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• 제15권6호
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• pp.48-55
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• 2006

가정용 폐건전지의 재활용 상용화를 위하여 물리적 처리방안에 대한 재활용 기술을 확립하기 위한 형상선별, 파쇄, 자력선별, 입도분리 그리고 와전류 정전선별을 통한 물리적 처리연구를 수행하였다. 그 결과 형상선별기를 이용하여 폐망간전지를 형상별 중량별로 시간당 $400{\sim}600$개의 속도로 분리하는 기술을 확립하였다. 파쇄, 자력선별 그리고 입도분리를 통해 망간, 아연, 철의 함량을 조사해본 결과, 자성체에는 망간과 아연 둥의 불순물 함량이 각각 0.1%이하였으며 99%이상이 Fe임을 알 수 있었다. 또한 비자성체의 경우에는 폐망간전지 종류에 따라 Zn이 $22{\sim}30%$, Mn이 $16{\sim}22%$ 그리고 Fe는 $1{\sim}3%$정도였고 기타 탄소봉과 플라스틱, 종이 등이 대략 $37{\sim}50%$정도였다. 와류 정전선별기로 Zn 판상을 회수한 결과, 최적실험 조건인 선속 $2,250m/min{\sim}2,750m/min$ 사이에서 96%이상의 회수가 이루어졌다.