• Journal of Energy Engineering
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• v.25 no.1
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• pp.15-22
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• 2016

The heat transport system transients of Wolsong 2,3,4 nuclear power plants were analysed during abnormal operating conditions. The compliance with requirements of AECB Regulatory Document R-77 for CANDU reactor was estimated. The analysis results showed that for each postulated accident the peak pressure values in the reactor headers are within the acceptance criteria given in ASME code requirements. The effect of LRV that is one of the overpressure protection device was very minor.

• Journal of the KSME
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• v.30 no.4
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• pp.374-381
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• 1990

수격해석은 최근의 펌핑 설비의 중요한 선결 과제이고 산업계에서도 자주 문제시되고 있으므로 본 글은 직접 전원 차단으로 인한 수격현상 해석을 수행하는 데 도움이 되도록 여러 문헌을 분 석하여 간략히 정리하였고 그 분석으로부터 다음과 같은 결론을 얻었다. (1) 직경이 다른 관, 분기관 및 병열관 등의 경우는 2절에서와 같이 등가치를 계산함으로써 해석을 단순화한다. (2) 수주 분리시 유체 정지시간, 이동거리 및 보급수량은 3절에 따라 산출하며 이는 수격방지장치 용량 결정의 기초자료가 된다. (3) 실제 펌핑 설비에서 수격현상의 발생은 대부분이 예기치 않는 펌프 전원차단시에 기인된다. 이때의 수격현상 해석을 실용선도에 의해 4.1에 따라 관로내 각 지점의 최고 및 최저 압력을 산출한다. (4) 끝으로 기존 참고문헌에 의한 해석은 여러 가지의 어려운 한계가 존재하므로 추후 수격해석 방안으로서는 특정방정식을 이용한 컴퓨터 수치해석 수행되어야 될 것으로 사료된다.

• Journal of Energy Engineering
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• v.12 no.2
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• pp.124-130
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• 2003

In the present study, the combustion characteristics of methane and hydrogen-supplemented methane as alternative fuels for automotive vehicles were investigated at various hydrogen substitution rate, ignition position and ignition methods in a CVCC. As a result, it is possible to decrease the total burning time and to obtain the reduction of NO concentration by using MSCDI device under the lean mixture conditions without deteriorating combustion characteristics such as combustion efficiency, maximum combustion pressure etc.. And by mixing hydrogen into methane, it was found that the reduction of the total burning time was obtained, in comparison with the use of methane only ; and at the same time, the combustion promotion rate was improved remarkably in comparison with the use of methane only.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.6
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• pp.639-647
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• 2014

Due to global warming and depletion of fossil fuels, technologies reducing $CO_2$ emission and increasing fuel efficiency simultaneously are required. An exhaust gas heat recovery system is a technology to satisfy both issues. This study analyses three types of heat exchanger installed on an exhaust pipe. In case of plate type heat exchanger, back pressure rapidly increased and maximum cylinder pressure reduced in high speed and maximum load, and back pressure increased over twice and specific fuel consumption also increased up to 2% which were the highest increasing rate. In case of fin tube type, the amounts of exhaust emissions and specific fuel consumption rate were less than the other two types. The effect of shell and tube was in the middle. Making a decision by only the effect on engine performance, a fin tube type is the best for exhaust heat recovery systems.

• Nuclear Engineering and Technology
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• v.12 no.3
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• pp.163-170
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• 1980

A Mather type plasms gun is operated at below 1 torr with a energy storage system (4KJ, 16.5KV, 35nH) to study the conditions of the efficient plasma focus. When the $D_2$ gas filling pressure is 0.18 torr and the stored energy is 3.8KJ, the discharge current of max. 180KA is obtained and the average axial velocity of the plasma is about $7cm/\mu\textrm{s}$. This is lower than the calculated velocity with above conditions by the snow-plow model. The discrepancy is due to the currents flowing over the insulator surface. The plasma focus occurs at low pressure compared with the results obtained by Bruzzone. The reasons are such that the plasma gun employed in this experiment is large for tile stored energy and the concentration of the residual gas is comparatively high. It is confirmed by a Long counter that the neutrons are generated from the dense plasma focus.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.6
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• pp.403-410
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• 2020

This paper focuses on the design of a 12-kW small-scale supercritical CO₂ test loop. A theoretical study, stabilization, and optimization of carbon dioxide were carried out with the application of a solar heat source based on solar thermal data in Pohang. The thermodynamic cycle of the test facility is a Rankine cycle (transcritical cycle), which contains liquid, gas, and supercritical CO₂. The system is designed to achieve 6.98% efficiency at a maximum pressure of 12 MPa and a maximum temperature of 70℃. In addition, the optimum turbine inlet temperature and pressure were calculated to increase the cycle efficiency, and the application of an internal heat exchanger (IHX) was simulated. It was found that the maximum efficiency increases to 18.75%. The simulation confirmed that the efficiency of the cycle is 6.7% in May and 6.26% in June.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.820-824
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• 2010

The purpose of this study is to develop basic technology of hybrid rocket vehicle by constructed and launched. This small hybrid rocket using HDPE/LN2O and Aluminium steel for its body (weight : 12.5 kg, diameter : 114 mm, height : 1.8 m) was designed. The fuel grain and injector were designed for 50 kgf thrust and burning time 2.5 sec. This rocket was loaded the data acquisition device for obtaining data of pressure and velocity during its flying and equiped an automatic ejector system using spring/motor and timer to collect the rocket more safely after launching. It was launched successfully, but found some problem that the rocket's weight was heavier than expected and the thrust was not enough to reach the designed altitude and analyzed its flight path way.

• Journal of the Mineralogical Society of Korea
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• v.5 no.2
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• pp.72-78
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• 1992

The Earth outer core accomodates moderately considerable amount of lighter elements than pure iron itself. Hydrogen is one of the possible candidates of minor constituents in the outer core. It would be worth while to extend for the pressure effect on the solubility of hydrogen in the metal-hydrides including iron hydride. In view of hydrogen being one of the potential substitutes for petroleum, searching a more efficient way for storing hydrogen in the form of hydrides is of considerable value. For two purposes, $TiH_2$was selected among lot of hydrides for its characteristics under pressure and temperature. There have been two kinds of experiment carried out on $TiH_2$ under different experimental conditions. As one of these attempts, polycrystalline $TiH_2$ was loaded up to 15 GPa stepwise at the constant temperature 500${\circ}$ using a piston-cylinder diamond anvil cell equipped with a miniature furnace of an electric power supply. The X-ra diffraction technique was employed on the quenched samples after the simultaneous high pressure and temperature treatments. During these high pressure-temperature runs, and irreversible phase of $TiH_2$ has been observed at the pressures higher than 11.3 GPa, which would be assigned to the orthorhombic crystal system as one of the new phase(s) of $TiH_2$. Molar volume change on this phase transition is ∼10%.

• Korean Chemical Engineering Research
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• v.57 no.5
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• pp.628-636
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• 2019

In various industrial processes, piping serves as a link between unit processes and is an essential installation for internal flow. Therefore, the optimum design of the piping system is very important in terms of safety and cost, which requires the estimation of the pressure drop, flow rate, pipe size, etc. in the piping system. In this study, we developed a software that determines pressure drop, flow rate, and pipe size when any two of these design variables are known. We categorized the flows into single phase, homogeneous two phase, and separated two phase flows, and applied suitable calculation models accordingly. We also constructed a system library for the calculation of the pipe material, relative roughness, fluid property, and friction coefficients to minimize user input. We further created a costing library according to the piping material for the calculation of the investment cost of the pipe per unit length. We implemented all these functions in an integrated environment using a graphical user interface for user convenience, and C # programming language. Finally, we verified the accuracy of the software using literature data and examples from an industrial process with obtained deviations of 1% and 8.8% for the single phase and two-phase models.

• Fire Science and Engineering
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• v.16 no.3
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• pp.26-31
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• 2002

Bromotrifluoromethane(halon-1301) and bromochlorodifluoromethane(halon-1211) have been widely used as a clean fire extinguishing agents due to their outstanding properties. However, production and use of halon are currently being phased out under an international agreements Montreal Protocol because of global environmental concerns and HFCs have been considered as promising alter-natives for the replacement of halon since their ozone depletion potentials are low. The vapor-liquid equilibrium data are required as important basic information in evaluating the solubility of clean fire extinguishing agents and determining their optimal compositions. In this work, we chose HFCs such as HFC-22 HFC-125, and HFC-l34a for gaseous fire extinguishing agents and nitrogen as a pressurization gas for a proper jet velocity of these agents. Phase equilibria for binary mixtures of nitrogen/HFC-22, nitrogen/HFC-125, and nitrogen/HFC-l34a were measured in the temperature range from 283.15K to 303.15K. For equilibrium measurement, we used a circulation type apparatus in which both vapor and liquid phases were continuously recirculated. The experimental data were relatively well correlated with the Peng-Robinson equation of state with Wong-Sandier mixing rules.