• Proceedings of the KIPE Conference
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• 2017.07a
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• pp.50-51
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• 2017

최근 전 세계적으로 차세대 초고속 교통수단의 연구, 개발에 박차를 가하고 있다. 대표적으로 미국에서 개발하고 있는 하이퍼루프는 승객을 태운 차체가 원통형인 튜브안에서 최대 1200 km/h로 이동하는 초고속 교통수단이다. 이렇게 빠른 속도에 도달하기 위해서 수십 MW 수준의 상당히 큰 전력이 필요하며, 이러한 큰 전력소모에 의한 전력망의 부담을 덜기 위해, 태양광 시스템을 튜브에 장착하여 추진에 필요한 일부 전력을 태양광 발전으로 대체하는 시스템이 연구되고 있다. 본 논문에서는 튜브의 방향, 태양전지의 배열에 따른 에너지 생산량, 전력발전량 및 비용 등의 다각적인 측면에서의 분석을 제시하였다. 원통형 튜브에 부착되는 태양전의 배열을 여섯 가지 경우로 나누었을 때, 삼각 지붕 모양으로 태양전지를 배열한 Case 2가 가장 높은 에너지 생산량을 보였다. 하지만 태양전지의 단위면적 당 에너지 생산량을 비용으로 계산하였을 경우, 튜브 위에 평평하게 태양전지를 배열한 Case 1이 가장 높은 가격 경쟁력을 가졌다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.11
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• pp.719-726
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• 2017

An experimental study was performed to investigate the combined effects of the pitch and heat flux of nearby tubes on boiling in a pool as well as the heat transfer from a horizontally-installed tube bundle. For this test, two smooth stainless steel tubes (19 mm outside diameter) were used, and the water was at atmospheric pressure. The pitch of these tubes was varied between 28.5 mm and 95 mm, and the heat flux of the nearby tube altered between 0 and $90kW/m^2$. Enhancements in heat transfer were clearly observed when the heat flux of the nearby tube increased while the heat flux of the test section remained below $40kW/m^2$. The tube pitch was found to have a negligible effect on heat transfer when the pitch was greater than four times larger than the tube diameter. The circulating flow, convective flow, and liquid agitation were all seen to enhance heat transfer; however, the interaction between the flow and coalescence of bubbles was detrimental to heat transfer.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.05a
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• pp.157-157
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• 2004

최근 탄소나노튜브는 역학적으로 견고하고 화학적 안정성이 뛰어나며 열전도도가 높고 속이 비어 있다는 특성 때문에 다양한 분야에 응용될 수 있을 뿐만 아니라 기능 또한 뛰어나다. 특히 구조적으로 매우 큰 aspect ratio를 가지고 있기 때문에 탄소나노튜브는 국소적으로 상당한 전계 증가를 보이고 비교적 낮은 전압에서도 다량의 전계방출 전류를 생성하는 특징을 가지고 있다 그래서, 탄소나노튜브를 전계 방출원으로 사용하기 위해서는 균일하게 수직 배열된 탄소나노튜브를 성장시키는 기술을 요구한다.(중략)

• Journal of Energy Engineering
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• v.15 no.1 s.45
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• pp.28-34
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• 2006

The convective heat transfer on the outer surface of tube arrays perpendicular to the flow direction was experimentally investigated. The test sections which include the aligned and staggered arrangements were made and the local heat transfer coefficients on the outer surface of the tube were measured after the Hour has been fully developed. The results showed that the local heat transfer coefficients of the staggered arrangement, which has transverse pitch of 0.075 m and longitudinal pitch of 0.08 m, were about 15% greater than that of the aligned arrangement. Also, the overall mom Nusselt number of the former was greater thu that of the latter.

• Elastomers and Composites
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• v.45 no.2
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• pp.80-86
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• 2010

Carbon nanotubes (CNTs) exhibit excellent mechanical, electrical, and magnetic properties as well as nanometer scale diameter and high aspect ratio, which make them an ideal reinforcing agent for high strength polymer composites. The functionalized CNTs are believed to be very promising in the fields such as preparation of functional and composite materials. CNT-Polymer composites are expected to have good processability characteristics of the polymer and excellent functional properties of the CNTs. However, since CNTs usually form stabilized bundles due to Van der Waals interactions, are extremely difficult to disperse and align in a polymer matrix. The biggest issues in the preparation of CNT-reinforced composites reside in efficient dispersion of CNTs into a polymer matrix, and the alignment and control of the CNTs in the matrix. There are several methods for the dispersion of nanotubes in the polymer matrix such as solution mixing, bulk mixing, melt mixing, in-situ polymerization and chemical functionalization of the carbon nanotubes, etc. These methods and preparation of high performance CNT-polymer composites are described in this review.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.05a
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• pp.268-268
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• 2004

머플러는 소음의 저감과 공기 정화의 특성으로 인해 자동차와 중장비에 적용되고 있다 최근에는 강화되고 있는 엄격한 환경규제를 만족하기 위해 그 설계와 제조에 있어 그 중요성이 높아지고 있으며, 머플러 튜브의 형태와 타공의 개수 및 배열은 다양한 형태로 연구가 이루어지고 있다. 이 중에서 튜브의 타공은 차량의 중량과 기능에 따라 다양한 형태를 가지며, 모델수의 증가와 출시기간의 단축으로 인해 튜브의 타공기술은 머플러 시장의 경쟁력을 좌우할 정도로 중요해 지고 있다.(중략)

• Clean Technology
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• v.29 no.3
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• pp.217-226
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• 2023

The amount of hydrogen adsorbed in arrays of single walled carbon nanotubes (SWNTs) was studied as a function of nanotube diameter and distance between the nearest-neighbor nanotubes on square arrangements using a grand canonical Monte Carlo simulation. The influence of the geometry of a triangle array with the same diameters and distances was also studied. Hydrogen-carbon and hydrogen-hydrogen interactions were modeled with Lennard-Jones potentials for short range interactions and electrostatic interactions were added for hydrogen-hydrogen pairs to consider quantum contributions at low temperatures. At 194.5 K, Type I isotherms for large-diameter SWNTs and Type IV isotherms without hysteresis between adsorption and desorption processes for wider tube separations were observed. At 200 bars, the gravimetric hydrogen storage capacity of the SWNTs was reached or exceeded the US Department of Energy (DOE) target, but the volumetric capacity was about 70% of the DOE target. At 77 K, a two-step adsorption was observed, corresponding to a monolayer formation step followed by a condensation step. Hydrogen was adsorbed first to the inner surface of the nanotubes, then to the outer surface, intratubular space and the interstitial channels between the nanotube bundles. The simulation indicated that SWNTs of various diameters and distances in a wide range of configurations exceeded the DOE gravimetric and volumetric targets at under 1 bar.

• Journal of Energy Engineering
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• v.24 no.4
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• pp.211-216
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• 2015

Heat exchanger tube array in a heat recovery steam generator is exposed to the hot exhaust gas flow and it could cause the flow induced vibration, which could damage the heat exchanger tube array. It is needed for the structural safe operation of the heat exchanger to establish the characteristics of flow induced vibration in the tube array. The researches for the flow induced vibration of typical heat exchangers have been conducted by using single cicular tube or circular tube array and the nondimensional PSD(Power Spectral Density) function with the Strouhal number, fD/U, had been derived by experimental method. From the present study, the basis for the application of flow induced vibration to the heat recovery steam generator tube array would be prepared. For the previous mentioned purpose, the present CFD analysis introduced a single fin tube and calculated with the unsteady laminar flow over the single fin tube. The characteristics of vortex shedding and lift fluctuation over the fin tube was investigated. The derived nondimensional PSD was compared with the results of the previous experimental researches and the characteristics of lift PSD over a single fin tube was established from the present CFD study.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.10a
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• pp.37-41
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• 2003

열화학 기상합성법을 이용한 탄소나노튜브의 성장에서 촉매 금속 층의 형성 공정은 탄소나노튜브의 직경 및 길이를 제어해주는 가장 중요한 요소이다. 탄소나노튜브의 대량합성을 위해 자성유체를 이용한 촉매 금속 층의 손쉬운 형성공정을 개발하였다. 수용성 폴리비닐알코올과 마그네타이트 나노 입자들이 혼합된 자성유체를 다양한 기판에 스핀 코팅하여 촉매 금속 층을 간편하게 형성할 수 있었다. 자성유체 제조 시 혼합된 수용성 폴리비닐알코올은 자성유체용액의 점성을 증가 시켜 주었으며, 이러한 점성의 증가는 스핀 코팅 시 용액과 기판간의 접착력을 증대시켜 주었다. 또한 건조 과정 이후에도 잔류되어 탄소나노튜브 합성 공정 중에 촉매금속이 응집되는 현상을 방지 차여 균일한 입자 크기를 유지하도록 하였다. 이는 고밀도의 수직 배열된 탄소나노튜브의 성장의 직접적인 원인으로 생각된다. 또한 탄소나노 튜브의 대량 합성을 위해서 Si 기판 치에 알루미나와 금속 기판에서도 탄소나노튜브의 성장을 시도하였다.

• Journal of the Korean Institute of Gas
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• v.20 no.2
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• pp.23-29
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• 2016

Heat exchanger tube array in a heat recovery steam generator is exposed to the hot exhaust gas flow and it could cause the flow induced vibration, which could damage the heat exchanger tube array. It is needed for the structural safe operation of the heat exchanger to establish the characteristics of flow induced vibration in the tube array. The researches for the flow induced vibration of typical heat exchangers have been conducted by using single cicular tube or circular tube array and the nondimensional PSD(Power Spectral Density) function with the Strouhal number, fD/U, had been derived by experimental method. From the present study, the basis for the application of flow induced vibration to the heat recovery steam generator tube array would be prepared. For the previous mentioned purpose, the present CFD analysis introduced a single fin tube and calculated with the unsteady laminar flow over the single fin tube. The characteristics of vortex shedding and lift and drag fluctuation over the fin tube was investigated. The derived nondimensional lift PSD was compared with the results of the previous experimental studies and the characteristics of lift and drag PSD over a single fin tube was established from the present CFD study.