• Nuclear Engineering and Technology
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• 제33권2호
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• pp.145-155
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• 2001

This simulation first allows us to define a transition zone from a bubble to jet mode of the argon out-flow and hereinafter to define a similar area for water-steam leak in the KALIMER SG (Korea Advanced Liquid Metal Reactor Steam Generator) using a water mock-up system, taking into account the KALIMER leak classification and tube bundle design, as a simulation of a real water-steam into sodium leak. in accordance with leak conditions in the KALIMER SG, the transition from bubbling to jetting is studied by means of turbulence regime simulation for argon out-flow through a very small orifice, which has the equivalent diameter of about 0.253 mm. finally the noise generation mechanism is explained from the existing experimental data. We also confirmed the possibility of micro-leak detection from the information of the bubbling mode through simulations and the experiment in this study.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 춘계학술대회 초록집
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• pp.109.1-109.1
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• 2011

KEPCO was operating power plants with diesel generators in 49 islands including Baekryeong-Do, and the generation capacity was about 66 MW in 2008. The cost of fuel is increasing by the international oil price inflation and continuous rise of oil price is predicted. For the stabilizing of electric power supply to the separate islands, renewable energy and fuel cell systems were considered. Hydrogen is made using renewable energy such as wind power and solar energy, and then a fuel cell system generates electricity with the stored hydrogen. Though the system efficiency is low, it is treated as the only way to secure the stable electric supply using renewable energy at this present. The analytic hierarchy process was used to select suitable candidate island for the system installation and 5 islands including Ulleung-Do were selected. Economic evaluation for the system composed of a kerosene generator, a wind power, an electrolysis, and a fuel cell system was conducted with levelized generation cost based on present value methode. As the result, the necessity of renewable energy combined generation system and micro grid composition in the candidated islands was confirmed. Henceforth, the development of an integration technology which connects micro grid to the total power grid will be needed.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2007년도 춘계학술대회
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• pp.28-32
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• 2007

최근 대두되고 있는 에너지 문제와 더불어 대체에너지 개발 및 에너지의 이용효율을 높이려는 연구가 많이 이루어지고 있다. 수소에너지는 비 탄소계 연료로서 그 중요성에 대한 인식이 높아지고 있으며, 다양한 분야에서 수소에너지를 이용하기 위한 노력이 이루어지고 있다. 수소는 재순환이 가능하고, 환경에 미치는 영향이 적기 때문에 미래형 에너지원으로 각광을 받고 있다. 수소이용 기술 중 연료 전지는 에너지 변환효율이 높고 유해 배출물이 생성되지 않아 차세대 발전시스템으로 유망하지만 비용과 기술적 제약으로 단기간에 상용화하기에는 어려움이 있다. 따라서 저비용, 고효율의 수소에너지를 이용 할 수 있는 시스템 개발이 요구되고 있다. 리니어동력/발전시스템은 저비용으로 제작이 가능하고 기존 기술의 인프라를 활용할 수 있는 장정과, 크랭크 기구가 없기 때문에 얻어지는 변환손실, 열손실을 최소화 할 수 있는 효율의 장점 때문에 고효율의 수소 이용 기관으로 평가되고 있다. 본 연구에서는 수소이용 통력시스템의 직선운동을 전기적인 에너지로 변환 할 수 있는 고효율의 리니어 발전시스템 개발을 위해 Prototype의 평판형 및 원통형의 리니어발전기를 제작했고 각각의 성능에 대한 평가와 엔진과 발전기의 연계운전 결과를 비교하여 시스템 전체에 대한 성능예측을 했으며 연계운전을 통해 출력된 발전기의 출력파형을 PCS로 변환하여 정현파의 AC 출력을 얻었다.

• 한국수소및신에너지학회논문집
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• 제23권6호
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• pp.619-627
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• 2012

This study was experimentally investigated on the effects of spring stiffness applied to linear compressor chambers. The springs prevented piston head from colliding with engine cover, stored the kinetic energy and regenerated the kinetic energy. The linear engine has two combustion chambers and four compressor chamber. The combustion chamber bore size was 30 mm, maximum stroke was 31 mm and effective stroke volume was 25.45 cc respectively. The spring stiffness was varied such as 0, 0.5, 1.00, 2.9 and 14.7 N/mm. The linear engine was fueled with premixed LPG (propane 99%) and air by pre-mixture device. As an experimental result, The stroke, piston velocity and the piston frequency were increased by high spring stiffness. Also, thermal efficiency was grown. because the increased stroke made the higher compression ratio. In conclusion, electric power and efficiency were improved.

• 한국수소및신에너지학회논문집
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• 제19권4호
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• pp.313-321
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• 2008

Dynamics of the proton exchange membrane fuel cell is specially important when the system is frequently working on transient conditions. Even though the dynamics of proton exchange membrane fuel cell for residential power generation is less critical than that of PEMFC for transportation application, the system dynamics of PEMFC for RPG can be very important for daily start-up and stop. In particular, thermal management of the PEMFC for RPG is very important because the heat generation from electrochemical reaction is delivered to the home for hot water usages. Additionally, the thermal management is also very important for heat balance of the system and temperature control of the fuel cell. The objective of this study is to develop a dynamic system model for the study of PEMFC performance over various BOP options. Basic simulation results will be presented.

• 한국수소및신에너지학회논문집
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• 제32권1호
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• pp.68-76
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• 2021

Climate change problems occur during the use of fossil fuel and the process of biogas production. Research continues to convert carbon dioxide and methane, the major causes of climate change, into high-quality energy sources. in order to present the performance potential for the novel plasma-recuperative burner reformer, the reforming characteristics for each variable were indentified. The optimal operating condition of was an O2/C ratio of 1.0 and a total gas supply of 20 L/min. At this time, CH4 conversion was 64%, H2 selectivity was 39%, and H2/CO ratio was 1.13, which were the results applicable to the solid oxide fuel cell fuel stack for RPG, or Residential Power Generator. Recirculation of reformed gas increases the amount of H2 and CO, which are combustible gases, especially the amount of H2. As a result, the H2 selectivity is improved, and high-quality gas can be produced.

• Advances in aircraft and spacecraft science
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• 제10권3호
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• pp.203-222
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• 2023

The detonation combustion is a supersonic combustion process follows on shock wave oscillations in detonation tube. In this paper numerical studies are carried out combined effect of blockage ratio and spacing of obstacle on detonation wave propagation of hydrogen-air mixture in pulse detonation combustor. The deflagration to detonation transition of stoichiometric (ϕ=1)fuel-air mixture in channel has been analyzed for effect of blockage ratio (BR)=0.39, 0.51, 0.59, 0.71 with spacing of 2D and 3D. The reactive Navier-Stokes equation is used to solve the detonation wave propagation mechanism in Ansys Fluent platform. The result shows that fully developed detonation wave initiation regime is observed near smaller vortex generator ratio of BR=0.39 inside the combustor. The turbulent rate of reaction has also a great significance role for shock wave structure. However, vortices of rapid detonation wave are appears near thin boundary layer of each obstacle. Finally, detonation combustor demonstrates the superiority of pressure gain combustor with turbulent rate of reaction of 0.6 kg mol/m3 -s inside the detonation tube with obstacle spacing of 12 cm, this blockage enhanced the turbulence intensity and propulsive thrust. The successful detonation wave propagation speed is achieved in shortest possible time of 0.031s with a significance magnitude of 2349 m/s, which is higher than Chapman-Jouguet (C-J) velocity of 1848 m/s. Furthermore, stronger propulsive thrust force of 36.82 N is generated in pulse time of 0.031s.

• Corrosion Science and Technology
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• 제5권5호
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• pp.168-172
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• 2006

Alloy 600 having a superior resistance to a corrosion is used as a steam generator tubing in nuclear power plants. In spite of its high corrosion resistance, there are many tubings which experience corrosion problems such as a SCC under the high temperature and high pressure environments of nuclear power plants. The Alloy 600 tubing can be repaired by using a Ni electroplating having an excellent SCC resistance. In order to carry out a successful Ni electrodeposition inside a steam generator tubing, the effects of various parameters on the material properties of the electrodeposit should be elucidated. Hence this work deals with the effects of an applied current density, duty cycle($T_{on}/(T_{on}+T_{off})$) of a pulse current, bath temperature and solution pH on the material properties of Ni electrodeposit obtained from a Ni sulphamate bath by analyzing the current efficiency, potentiodynamic curve, hardness and stress-strain curve. Hardness, YS(yield strength) and TS(tensile strength) decreased whereas the elongation increased as the applied current density increased. This was thought to be by a concentration depletion at the interface of the electrodeposit/solution, and a fractional decrease of the hydrogen reduction reaction. As the duty cycle increased, the hardness, YS and TS decreased while the elongation increased. During an off time at a high duty cycle, the concentration depletion could not be recovered sufficiently enough to induce a coarse grain sized electrodeposit. With an increase of the solution temperature and pH, the YS and TS increased while the elongation decreased. The experimental results of the hardness and the stress-strain curves can be supplemented by the results of the potentiodynamic curve.

• 한국수소및신에너지학회논문집
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• 제30권1호
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• pp.21-28
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• 2019

Reversible solid oxide fuel cell (ReSOC) system was integrated with waste steam for electrical energy storage in distributed energy storage application. Waste steam was utilized as external heat in SOEC mode for higher hydrogen production efficiency. Three system configurations were analyzed to evaluate techno-economic performance. The first system is a simple configuration to minimize the cost of balance of plant. The second system is the more complicated configuration with heat recovery steam generator (HRSG). The third system is featured with HRSG and fuel recirculation by blower. Lumped models were used for system performance analyses. The ReSOC stack was characterized by applying area specific resistance value at fixed operating pressure and temperature. In economical assessment, the levelized costs of energy storage (LCOS) were calculated for three system configurations based on capital investment. The system lifetime was assumed 20 years with ReSOC stack replaced every 5 years, inflation rate of 2%, and capacity factor of 80%. The results showed that the exergy round-trip efficiency of system 1, 2, 3 were 47.9%, 48.8%, and 52.8% respectively. The high round-trip efficiency of third system compared to others is attributed to the remarkable reduction in steam requirement and hydrogen compression power owning to fuel recirculation. The result from economic calculation showed that the LCOS values of system 1, 2, 3 were 3.46 ¢/kWh, 3.43 ¢/kWh, and 3.14 ¢/kWh, respectively. Even though the systems 2 and 3 have expensive HRSG, they showed higher round-trip efficiencies and significant reduction in boiler and hydrogen compressor cost.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.550-551
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• 2013

Large-area RF-driven ion source is being developed at Germany for the heating and current drive of ITER plasmas. Negative hydrogen (deuterium) ion sources are major components of neutral beam injection systems in future large-scale fusion experiments such as ITER and DEMO. RF ion sources for the production of positive hydrogen ions have been successfully developed at IPP (Max-Planck- Institute for Plasma Physics, Garching) for ASDEX-U and W7-AS neutral beam injection (NBI) systems. In recent, the first NBI system (NBI-1) has been developed successfully for the KSTAR. The first and second long-pulse ion sources (LPIS-1 and LPIS-2) of NBI-1 system consist of a magnetic bucket plasma generator with multi-pole cusp fields, filament heating structure, and a set of tetrode accelerators with circular apertures. There is a development plan of large-area RF ion source at KAERI to extract the positive ions, which can be used for the second NBI (NBI-2) system of KSTAR, and to extract the negative ions for future fusion devices such as ITER and K-DEMO. The large-area RF ion source consists of a driver region, including a helical antenna (6-turn copper tube with an outer diameter of 6 mm) and a discharge chamber (ceramic and/or quartz tubes with an inner diameter of 200 mm, a height of 150 mm, and a thickness of 8 mm), and an expansion region (magnetic bucket of prototype LPIS in the KAERI). RF power can be transferred up to 10 kW with a fixed frequency of 2 MHz through a matching circuit (auto- and manual-matching apparatus). Argon gas is commonly injected to the initial ignition of RF plasma discharge, and then hydrogen gas instead of argon gas is finally injected for the RF plasma sustainment. The uniformities of plasma density and electron temperature at the lowest area of expansion region (a distance of 300 mm from the driver region) are measured by using two electrostatic probes in the directions of short- and long-dimension of expansion region.