• Journal of Korean Society of Coastal and Ocean Engineers
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• v.26 no.5
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• pp.335-341
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• 2014

Physical experiments were carried out to measure the wave force on the vertical walls of perforated breakwater considering several phases of a wave acting on the breakwater. The maximum horizontal wave force acting on each vertical wall was compared between single and double chamber caisson breakwater. The experimental data in this study showed that the total horizontal wave force for double chamber caisson was 9.6% smaller on average than that for single chamber caisson when the total chamber width was the same for both caissons. Such reduction of the wave force is due to the dissipation of wave energy at the porous middle wall, which is located between the porous front wall and non-porous rear wall.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.201.2-201.2
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• 2015

현대 디지털 사회에서 고효율 에너지와 파워소스에 관한 요구가 커짐에 따라 차세대 에너지 저장 소자에 대한 연구가 계속되고 있다. 그 중 리튬이온 배터리, 슈퍼커패시터, 그리고 연료 전지들이 우리의 일상생활에서 점점 더 중요하게 자리잡아가고 있는데 이런 다양한 에너지 저장소자 중 슈퍼커패시터가 많은 관심을 받고 있다. 이는 긴 수명, 빠른 충-방전 속도, 높은 에너지 밀도, 그리고 안전함 때문이다. 슈퍼커패시터는 에너지 저장 메커니즘에 따라 두 가지로 분류될 수 있는데 전기이중층 커패시터(EDLC)와 슈도커패시터(pseudocapacitor)로 나누어질 수 있다. 슈도커패시터는 active 물질과 전해질 이온 간의 전기화학적 반응으로 인해 EDLC보다 더 많은 에너지를 저장할 수 있다. 그러므로 지금까지 새로운 형태의 슈도용량성 물질을 만들기 위한 노력이 집중되고 있다. 본 연구에서는 전기화학적증착 방법을 통해 graphene-like ${\beta}$-nickel hydroxide (${\beta}-Ni(OH)_2$) 나노판 구조를 전도성 직물에 합성하였다. ${\beta}-Ni(OH)_2$ 슈도커패시터의 유연하고 효율적인 비용의 전극으로서 높은 비정전용량, 우수한 전기화학 가역성, 그리고 뛰어난 사이클 안정성을 보였다. 이런 쉬운 방법으로 유연한 전도성 직물에 합성된 metal hydroxide/oxide 나노구조는 웨어러블 에너지 저장소자와 변환소자 분야에 사용될 것으로 기대된다.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.104.1-104.1
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• 2011

가볍고, 유연성(flexibility)을 갖는 박막(thin film)형 플랙서블 태양전지(flexible solar cell)는 상황에 따른 형태의 변형이 가능하여, 휴대가 간편하고, 기존 혹은 신규 구조물의 지붕(rooftop)등에 설치가 용이하여, 차세대 성장 동력 분야에서 각광받고 있다. 그러나 아직까지 플랙서블 태양전지는 제작시 열에 의한 기판의 변형, 기판 이송시 너울 현상, 대면적 패터닝(patterning) 기술 등 많은 어려움 등으로 웨이퍼나 글라스 기판에 제조된 태양전지 대비 낮은 광전환 효율을 갖는다. 따라서 본 연구에서는 플랙서플 태양전지 성능개선을 위해 3.5세대급 ($450{\times}450cm^2$) 스퍼터(sputter), 금속유기 화학기상장치 (MOCVD), 플라즈마 화학기상장치 (PECVD), 레이저 가공장치 (Laser scriber)를 이용하여 a-Si:H/a-SiGe:H 이중접합(tandem)을 갖는 태양전지를 제작하였고, 광 변환효율 특성을 평가하였다. 전도도(conductivity), 라만(Raman)분광 및 UV/Visible 분광 분석을 통하여 박막의 전기적, 구조적, 광학적 물성을 평가하여 단위박막의 물성을 최적화 했다. 또한 제작된 태양전지는 쏠라 시뮬레이터 (Solar Simulator)를 이용하여 성능 평가를 수행하였고, 상/하부층의 전류 정합 (current matching)을 위해 외부양자효율 (external quantum efficiency) 분석을 수행하였다. 제작된 이중접합 접이식 태양전지로 소면적($0.25cm^2$)에서 8.7%, 대면적($360cm^2$ 이상) 8.0% 이상의 효율을 확보하였으며, 성능 개선을 위해 대면적 패턴 기술 향상 및 공정 기술 개선을 수행 중이다.

• Journal of Energy Engineering
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• v.21 no.4
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• pp.402-410
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• 2012

A two-loop Rankine cycle for engine waste heat recovery of gasoline vehicle has been investigated. Water-steam cycle as a high-temperature (HT) loop for exhaust gas heat recovery and R-134a cycle as a low-temperature (LT) loop for both heat recovery of the engine coolant and the residual heat from the HT loop were considered. Energy and exergy analysis was performed to investigate the performance of the system. Because two volumetric expanders are used for the HT and LT loop, the sizes of two expanders are very important for the optimization of the system. The effects of pressure ratio of the HT loop, considering the size of the HT expander, and the condensation temperature of LT loop on the performance of the system at a target engine condition were investigated. This study shows that about 20% of additional power from the engine waste heat recovery can be obtained at the target engine condition.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.111.2-111.2
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• 2010

One-dimensional nanostructures such as carbon nanotubes could be ideal templates for formation of metallic nanoparticles. Furthermore, bimetallic component nanoparticles have recently been interesting issues for having high catalytic activity. This work provides both a facile method to synthesize bimetallic catalysts via N atoms of carbon nanotubes and also a picture about how to design the optimal bimetallic catalyst for hydrogen generation from the hydrogen storage material. In principle, the ratio of one component to another component could be generically extended to fabricate the high-performance bimetallic catalysts on host nanostructures. Indeed, we demonstrate that the bimetallic catalyst composed of the optimum composition results in the excellent hydrogen generation property from an aqueous borane ammonia solution, thus being capable of satisfying the Depart of Energy in USA target required for many advanced applications even with the small amount of our bimetallic catalysts attached onto the N-doped carbon nanotubes. This high hydrogen generation rate is found to be attributed to the optimal distance between active Pt and cheap Ni atoms for effective hydrogen generation.

• Transactions of the Korean hydrogen and new energy society
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• v.12 no.4
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• pp.267-275
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• 2001

To clear the differences of heat transfer coefficient of in-cylinder gas with fuel properties, the transient heat transfer coefficient of hydrogen gas is investigated by using the hydrogen fueled engine. The measured results were also compared with those of gasoline engine and several empirical equations. Transient heat transfer coefficients were determined by measurements of unsteady heat flux and instantaneous wall temperature in the cylinder head. As the main results, it is shown that transient heat transfer coefficients have remarkable differences according to fuel properties, and it's value for hydrogen engine is twice higher than that of gasoline engine. It means that equation of heat transfer coefficient that the effect of fuel properties is considered sufficiently, is needed to analyze or simulate the gas engine performance.

• Journal of Energy Engineering
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• v.10 no.4
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• pp.379-386
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• 2001

This experimental study deals with on Nitric Oxide Formation & Reduction in Industrial Bunner. In this study, Laser-induced fluorescence (LIF) techniques have been used for quantitative measurements of Nitric Oxide. The NO A-X (0, 0) Vibrational band around 226 nm was excited using a XeCl excimer-pumped dye laser. And on-line excitation used $P_{21}+Q_1(14.5)/R_{12}+Q_2(20.5)/P_1(23.5)$ transition, for minimizing the other interferential effect. The measurements were taken NO concentration distribution in double swirling diffusion flame. In this swirl burner, NO concentration in downstream fo the flame decrease as primary/secondary air ratio increases.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.7 no.2
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• pp.51-59
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• 2011

Storage and transfer heat in soils are governed by the soil thermal properties and these properties are therefore needed in many engineering applications, including horizontal ground heat exchanger for ground-coupled heat pumps. This paper presents the measured results of the thermal diffusivity of soils(silica, quartzite, limestone, sandstone, and masonry soils) used for the trench backfilling materials of the horizontal ground heat exchanger. To assess this thermal property, we (i) measure the soil thermal conductivities and volumetric heat capacities using dual-probe method and (ii) compare the estimates from the de Vries method of summing the heat capacities of the soil constituents. The results show that the thermal diffusivity tends to increase as dry soil begins to wet, but it approaches a constant value or even decreases as the soil continues to wet. Measurements made by using the dual-probe method agreed well with independent estimates obtained using the single-probe method.

• Journal of the Korean Solar Energy Society
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• v.22 no.2
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• pp.27-32
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• 2002

The Characteristics of heat transport in the heat pipe with a double vapor path and different kinds of the working fluid were investigated experimentally. The Experiment was carried out with acetone/ethanol. ethanol/ethanol. and in the aluminium container of the double vapor path. Performance measurements can be operated at the high level by 24000 w/m2 heat flux in the 1000mm evaporator. They are each estimated at the high temperature and experimentally reviewed the characteric of the heat rejection. The results shew that they are stably operated under each condition and the fluid was complemented each other at the fluid's experiment and brought about the extention of operating temperature. In this study, The reliable basic data obtained by the teste in the heat pipe with a double vapor path can be used for thermal design, manufacture, and production etc.

• Journal of the Korean Society for Marine Environment & Energy
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• v.10 no.1
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• pp.53-58
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• 2007

In an estuary, mixing and transport of contaminant sometimes occurs in the salt finger favorable condition (Hwang ang Rehmann, 2004). Linearized theory is applied to predict flow dynamics in salt finger favorable condition. The simulated results match well with previous laboratory experiments. When the density ratio is larger than 2, the heat and salt system shows $0.55{\sim}0.57$ as Turner (1967) found, and the salt and sugar system produces 0.87 of Griffiths (1980). As the ratio of molecular diffusivities of two scalars increases, the flux ratio increases. The flux and eddy diffusivity ratios decrease with increase of density ratio, and it takes longer time for flux ratio to be steady state at the higher density ratios.