• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 하계학술발표대회 논문집
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• pp.1053-1058
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• 2008

Porous medium was considered in the present study for the heat transfer enhancement. This was attributed to its high surface area to volume ratio as well as intensive flow mixing by tortuous flow passages. But when the air or water flow through in the porous medium, it is occurred the pressure drop between inlet and outlet. So in the present study investigated simulation result about the pressure drop in the porous medium before apply to heat exchanger. In this simulation, the thickness of the solid inside the porous medium region was varied 0.2 mm to 0.4 mm. And then the simulation result were compared the pressure drop in the same unit cell ($0.5\;mm{\times}0.5\;mm{\times}0.5\;mm$). To make the analysis model, it was assumed the 14-sided tetrakaidecahedron cell which has long been considered the optimal packing cell first proposed by the Lord Kelvin in 1887. And then the simulation is carried out using by STAR-CCM+ which is commercial software. The simulation result can be showed quantified pressure drop by solid effect in the porous medium.

• 상하수도학회지
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• 제36권5호
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• pp.261-273
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• 2022

In this study, we collect water control valves that have had accidents due to existing cracks, etc. are collected, and propose investigation items for strengthening the valve structural safety evaluation through a series of analyzes from valve specifications to physicochemical properties are proposed. The results of this study are as follows. First, there was a large variation in the thickness of the body or flange of the valves to be investigated, which is considered to be very important factor, because it may affect the safety of the valve body against internal pressure and the flange connected with the bolt nut. Second, 60% of the valves under investigation had many voids in the valve body and flange, etc. and the decrease in thickness due to corrosion was relatively large on the inner surface in contact with water rather than the outer surface. It is judged that the investigation of depth included voids is very important factor. Third, all valves to be investigated are made of gray cast iron foam, and therefore it is judged that there is no major problem in chemical composition. It is judged that the chemical composition should be investigated. Fourth, as a physical investigation item, the analysis of metal morphology structure seems to be a very important factor for nodular cast iron from rather than a gray cast iron foam water valve with a flake structure. As it was found to be 46.7~68.8% of the standard recommended by KS, it could have a direct effect on damage such as cracks, and therefore it is judged that the evaluation of tensile strength is very important in evaluating the safety of the valve.

• 한국결정성장학회지
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• 제33권5호
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• pp.196-201
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• 2023

수소에너지 생산을 위한 물분해 시스템의 효율을 향상시키기 위해서는, 수소발생반응 (HER)과 산소발생반응(OER) 각각에서 촉매로 인한 전기화학적 반응에서의 높은 과전압의 감소가 수반되어야 한다. 그 중에서도 전이금속 기반의 화합물(수산화물, 황화물 등)은 현재 상용되고 있는 백금 등의 귀금속을 대체할 촉매 재료로써 주목받고 있다. 본 연구에서는, 저렴한 금속 다공성 소재인 Ni foam을 지지체로 사용하고, 수열합성 공정을 통해 β-Ni(OH)₂ 마이크로결정을 합성하고자 하였다. 또한 전기화학적 특성을 향상시키기 위하여 Fe을 도핑하여 합성된 β-Ni(OH)₂ 마이크로 결정의 형상, 결정구조 및 물분해 특성의 변화를 관찰하였으며, 상용 수전해 시스템의 촉매로서의 적용가능성을 검토하였다.

• 한국결정성장학회지
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• 제34권1호
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• pp.30-35
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• 2024

수소에너지 생산을 위한 물분해 시스템의 효율을 향상시키기 위해서는, 수소발생반응(HER)과 산소발생반응(OER) 각각에서 촉매로 인한 전기화학적 반응에서의 높은 과전압의 감소가 수반되어야 한다. 그 중에서도 전이금속 기반의 화합물들은 현재 상용되고 있는 백금 등의 귀금속을 대체할 촉매 재료로써 주목받고 있다. 본 연구에서는, 저렴한 금속 다공성 소재인 니켈폼(Ni foam)을 지지체로 사용하고, 수열합성 공정을 통해 Fe-doped β-Ni(OH)₂ 마이크로결정을 합성하였다. 또한 OER 특성을 향상시키기 위하여 Mo을 동시도핑하여 합성된 Fe-Mo co-doped β-Ni(OH)₂ 마이크로결정의 형상, 결정구조 및 수전해 특성의 변화를 관찰하였으며, 상용 수전해 시스템의 촉매로서의 적용가능성을 검토하였다.

• 한국분말재료학회지
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• 제29권5호
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• pp.411-417
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• 2022

Environmental issues such as global warming due to fossil fuel use are now major worldwide concerns, and interest in renewable and clean energy is growing. Of the various types of renewable energy, green hydrogen energy has recently attracted attention because of its eco-friendly and high-energy density. Electrochemical water splitting is considered a pollution-free means of producing clean hydrogen and oxygen and in large quantities. The development of non-noble electrocatalysts with low cost and high performance in water splitting has also attracted considerable attention. In this study, we successfully synthesized a NiCo₂O₄/NF electrode for an oxygen evolution reaction in alkaline water splitting using a hydrothermal method, which was followed by post-heat treatment. The effects of heat treatment on the electrochemical performance of the electrodes were evaluated under different heat-treatment conditions. The optimized NCO/NF-300 electrode showed an overpotential of 416 mV at a high current density of 50 mA/cm² and a low Tafel slope (49.06 mV dec^-1). It also showed excellent stability (due to the large surface area) and the lowest charge transfer resistance (12.59 Ω). The results suggested that our noble-metal free electrodes have great potential for use in developing alkaline electrolysis systems.

• Design & Manufacturing
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• 제13권4호
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• pp.23-27
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• 2019

People's interest in the environmental problems of the Earth is growing as they come to the modern world, and research is being actively conducted on how to protect the environment. As a result, the automobile industry, one of the causes of environmental pollution, is also affected. Therefore, research is being conducted to improve the fuel economy and light weight of cars, development of pollution-free cars such as electric cars, and aluminium materials that are lighter than ordinary steel sheets and easier to recycle are gaining attention. In this experiment, the material was formed to form a form of aluminium and the material reduction rate of the side wall of the foam was tested according to the amount of side wall. The material used in the experiment was A3003-O, which is less plastic than normal steel plates, but has excellent corrosion resistance, plasticity and weldability compared to aluminium materials, but has poor tensile strength. For tensile testing, a certain array of Forming Shapes was molded and the height of the Forming was set to 5mm, and the height of the Forming was 4.7mm, indicating that the difference between the first 5mm Forming and the height was not large. In addition, the material reduction rate was tested by giving 15, 0, and -0.15 teas, respectively, and was found to be valuable as a product only for -0.15.

• Composites Research
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• 제23권6호
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• pp.19-25
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• 2010

본 논문은 유리섬유/에폭시 4-매 주자직 적층 복합재와 PVC 폼 코어로 제작된 철도차량용 복합재 대차프레임의 금속재 체결부 볼트 위치 최적화 연구에 대해 서술했다. 최적화 해석은 APDL(Ansys Parameter Design Language)을 이용한 서브모델링 기법을 적용하였으며 부분문제 근사방법에 의한 최적화를 수행하였다. 이때, 최적화 해석에 적용된 서브모델링 기법은 관심영역을 포함한 부분모델에 대한 계산을 재수행 함으로써 해석에 소요되는 시간을 절약하고 상세한 결과를 도출 할 수 있다. 복합재 대차프레임의 구조해석은 JIS E 4207에 의거하여 수행하였다. 서브모델링 기법을 적용한 복합재 대차프레임의 최적화 해석은 전체모델에 대한 결과에 비해 요소망 밀도의 조절을 통한 해석시간 절약과 상세한 결과를 얻을 수 있으며, 또한 볼트위치의 최적화로 인해 보다 낮은 Von-Mises 응력값이 나타남을 확인하였다.

• Elastomers and Composites
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• 제39권2호
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• pp.105-120
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• 2004

본 연구에서는 금속수산화물과 다양한 인계 난연제를 포함한 난연 acrylonitrile-butadiene rubber (NBR) 발포체를 제조하고, 이때 인 함유량에 따른 열적특성. 난연특성, 발포특성 등의 변화 및 이들의 상관관계를 조사하였다. NBR 발포체의 발포특성 및 모폴로지 분석 결과 인/질소계 난연제 10 phr 범위 내에서 대체적으로 인/질소계 난연제를 투입하지 않은 금속수산화물만을 사용한 경우와 유사한 발포특성 및 모폴로지를 가짐을 알 수 있었다. 열 분석에서는 인 함유량이 많은 인/질소계 난연제를 사용할 경우 화염분위기 하에서의 char 형성과 관련한 잔류량이 많아짐으로써 난연성이 향상됨을, LOI 분석에서도 인 함유량이 증가함에 따라 LOI가 증가함을 알 수 있었다. cone-calorimeter 분석 결과 열 및 LOI 분석 결과와 유사한 경향성을, 인 함유량이 증가함에 따라 HRR, THR, EHC 등이 감소하는 반면에 COY는 증가함을, 즉 난연성이 상승함을 확인할 수 있었다. 연기밀도 분석 결과 cone-calorimeter 분석에서의 (A)-COY와 같은 경향성을 보여주었다.

• 공업화학
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• 제30권5호
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• pp.633-638
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• 2019

실내공기질 중 지하시설은 휘발성유기화합물(VOC, volatile organic compound)의 처리가 미흡한 실정이며, 이를 환기와 같은 확산법이 아닌 오염물질 저감하기 위하여 다양한 제조, 활성화법을 이용해 메탈 필터에 흡착성을 부여한 제올라이트 코팅 흡착 필터소재를 제조하였다. 그 결과, 메탈폼 지지체 대비 약 2~20배 이상 흡착 성능의 증진을 확인하였으며 이는 기공의 증진에 기반함을 SEM 분석으로 확인하였다. 또한 리그닌을 첨가함에 따라 13.95 mg/g의 흡착 성능을 확보하였으며, 세척 후에도 평균 13.25 mg/g의 유사한 흡착 성능을 확보하여 높은 내구성을 가진 흡착 필터소재를 제조하였음을 확인하였다. 개발된 흡착 필터소재는 지하시설 내 기계적 환기로의 농도 저감이 아닌 근본적으로 VOCs를 제어할 수 있는 해결방법으로 제시할 수 있을 것으로 판단하였다.

• 한국정밀공학회지
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• 제19권6호
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• pp.136-144
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• 2002

Melting method has long been considered difficult to realize because of problems such as the low foamability of molten metal, the varying size of cellular structures and solidification shrinkage. The parameters to solve the problem in electric furnace were stirring temperature, stirring velocity, heating velocity and foaming temperature It is important to consider the effects of induction heating, because it brings about the inner flow by the temperature gradient. Aspect ratio also depends on the induction heating. Mechanical properties are dependent on cell sizes and aspect rations. Therefore, this paper presents the effects of these parameters on the cell sizes. For the sake of this, combined stirring process was used to fabricate aluminum foam materials by the above mentioned parameters. Image analysis was performed to calculate the cell sizes, distributions, and aspect ratioes at the cross section of feared aluminum in the direction of height.