• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.8 no.2
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• pp.1-6
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• 2012

A PHE (Process Heat Exchanger) in a nuclear hydrogen system is a key component required to transfer heat energy of $950^{\circ}C$ generated in a VHTR (Very High Temperature gas cooled Reactor) to the chemical reaction that yields a large quantity of hydrogen. A small-scale PHE prototype made of Hastelloy-X is being tested in a small-scale gas loop at Korea Atomic Energy Research Institute. Previous research on the high-temperature structural analysis of the small-scale PHE prototype had been performed only using parent material properties. In this study, high-temperature structural analysis using weld properties in weld zone was performed and the analysis results compared with the previous research.

• International Journal of Automotive Technology
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• v.7 no.6
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• pp.659-666
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• 2006

EGR(Exhaust Gas Recirculation) systems are extensively used to reduce NOx emissions in light duty diesel engine but its application to heavy duty diesel engines is yet to be widely implemented. In this study, the simulation model for a EURO 3 engine was developed using WAVE and then its performance and emission levels were verified with experimental results. The possibility of operating a EURO 3 engine with LPL EGR system to satisfy the EURO 4 regulation was investigated. Each component of the engine was modeled using CATIA and WaveMesher. The engine test mode was ESC 13, and the injection timing and fuel quantity were changed to compensate for the reduction of engine power caused by applying EGR. As a result of the simulation, it was found that EURO 4 NOx regulation could be satisfied by applying an LPL EGR system to the current EURO 3 engine.

• Proceedings of the KIEE Conference
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• 1998.07b
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• pp.825-827
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• 1998

Air pollution is one of the most important global issues of the environmental concerns. Some advanced foreign countries have developed the air pollution control technology. KEPCO has been researching on the air pollution control technology and developed the FGD(Flue Gas Desulfurization) system for 200MW thermal power plant. In this paper, we describe the major control loops implemented to the domestic FGD system. The major control loops are to be classified into booster fan control, absorber PH control and limestone density control. The control loops were applied to the actual desulfurization processes and proved to their performance.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.34S no.3
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• pp.46-54
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• 1997

In this paper, we psropose the feedback linearization technique for a nonlinear system using genetic algorithms (GAs) and fuzzy logic system. The proposed control scheme approximates the nonlinear term of a nonlinear system using the fuzzy logic system and computes the control input for cancelling the nonlinear term. Then in the fuzzy logic system, the number and shape of membership function of the premise aprt will be tuned to minimize the control error boundary using GAs. And the parameters of the consequence of fuzzy rule will be tuned by the adaptive laws based on lyapunov stability theory in order to guarantee the closed loop stability of control system. The evolution of fuzzy logic system is processed during the on-line adaptive control. The effectiveness of proposed method will be demonstrated by computer simulation of simple nonlinear sytem.

• 한국가스학회:학술대회논문집
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• 2007.04a
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• pp.42-49
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• 2007

가스크로마토그래피 불꽃이온화검출기(FID)에서, 천연가스 표준물질만을 사용하여 분석할 때 발생할 수 있는 분석 불확도에 대하여 연구하였다. 일반적으로 $10^5$ 범위 농도까지 직선성이 확보된 것으로 알려진 FID 검출기에 대하여 실제 분석에서 동일한 직선성이 확보되는지를 확인하였다. 본 연구에서 7성분으로 조성된 천연가스용 표준가스를 샘프링 loop의 크기를 1.0mL, 0.50mL, 0.25mL로 변환시키면서 GC/FID를 사용하여 분석한 상대표준불확도 결과는 다음과 같다. 메탄은, 0.458 %, 에탄은 0.20247%, 프로판은 0.1497%, i-부탄은 0.1854 %, n-부탄은 0.2977%, i-펜탄은 0.263%, n-펜탄은 0.383%이었다. 각 경우에서 직선성 상대표준불확도값이 $0.15%{\sim}0.45 %$까지 이른다. 일반적으로 농도가 높은 메탄의 경우에 직선성 불확도값이 큰 값을 보여 주었고 농도범위가 1-5%인 $C2{\sim}C5$의 경우는 작은 직선성 표준불확도를 나타내었다.

• Journal of Advanced Marine Engineering and Technology
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• v.31 no.6
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• pp.707-714
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• 2007

The heat transfer coefficient and Pressure drop during gas cooling process of $CO_2$ (R-744) in inclined helical coil copper tubes were investigated experimentally. The main components of the refrigerant loop are a receiver. a variable-speed pump. a mass flow meter, a pre-heater and a inclined helical coil type gas cooler (test section). The test section consists of a smooth copper tube of 2.45mm inner diameter. The refrigerant mass fluxes were varied from 200 to $600[kg/m^2s]$ and the inlet Pressures of gas cooler were 7.5 to 10.0 [MPa]. The heat transfer coefficients of $CO_2$ in the inclined helical coil tubes increases with the increase of mass flux and gas cooling pressure of $CO_2$. The pressure drop of $CO_2$ in the gas cooler shows a relatively good agreement with those Predicted by Ito's correlation developed for single-phase in a helical coil tube. The local heat transfer coefficient of $CO_2$ agrees well with the correlation by Pitla et al. However, at the region near pseudo-critical temperature. the experiments indicate higher values than the Pitla et al. correlation. Therefore. various experiments in the inclined helical coil tubes have to be conducted and it is necessary to develop the reliable and accurate prediction determining the heat transfer and pressure drop of $CO_2$ in the inclined helical coil tubes.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.19 no.9
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• pp.640-646
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• 2007

The cooling heat transfer coefficient of $CO_2$ (R-744) for tube and coil diameter (CD), inclined angle of tube and coil pitch of inclined helical coil type copper tubes were investigated experimentally. The main components of the refrigerant loop are a receiver, a variable-speed pump, a mass flow meter, a pre-heater and a inclined helical coil type gas cooler (test section). The test section consists of a smooth copper tube of 2.45 and 4.55 mm inner diameter (ID). The refrigerant mass flukes were varied from 200 to 800 [$kg/m^2s$] and the inlet pressures of gas cooler were 7.5 to 10.0 [MPa]. The heat transfer coefficients of $CO_2$ in inclined helical coil tube with 2.45 mm ID are $5{\sim}10.3%$ higher than those of 4.55 mm. The heat transfer coefficients of 41.35 mm CD are $8{\sim}32.4%$ higher than those of 26.75 mm CD. Comparison between $45^{\circ}\;and\;90^{\circ}$ of coil angle, the heat transfer coefficients of $45^{\circ}$ are higher than those of $90^{\circ}$. For coil pitch of gas cooler, the heat transfer coefficients of inclined helical coil gas cooler with coil pitch of 5 mm are similar to those of 10 and 15 mm.

• Journal of the Korean Society of Propulsion Engineers
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• v.16 no.3
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• pp.34-40
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• 2012

A pressure control law to regulate pressure of gas generator is suggested. To design a model based control law, the governing equation which consists of Robert and conservation equation is built and verified through the ground burning test. PID and nonlinear adaptive control laws are designed to analyze the loop response characteristics under the system which has varying eigen properties arisen from combustion volume change. It is suggested that new approach, gain scheduling design, is required to overcome the defects identified from numerical simulation results of the two control laws. The newly suggested scheme shows good control performance even under disturbances and measurement noise.

• Korean Chemical Engineering Research
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• v.50 no.5
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• pp.825-829
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• 2012

In this study, we investigated NO oxidation characteristic that depends on available chlorine concentration and temperature of seawater which is treated by un-divided electrolysis. Reactant gas passed through bubbling reactors which is filled with electrolyzed water and then NO concentration change was analyzed. In the closed-loop electrolysis system, concentration of available chlorine increased with electrolysis time. The higher oxidation rate of NO to $NO_2$ was obtained with the higher concentration of available chlorine. Oxidation of NO was fast when temperature of electrolyzed water was high, in the case of same concentration of available chlorine.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.618-623
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• 2011

A pressure control law to regulate pressure of gas generator is suggested. To design a model based control law, the governing equation which is consisted of Robert and conservation equation is built and verified through the ground burning test. PID and nonlinear adaptive control laws are designed to evaluate the loop response characteristics under the system which has varying eigen properties as combustor volume is increased. It is suggested that new approach, gain scheduling design, is required to overcome the defects identified from numerical simulation results of the two control laws. The newly suggested scheme showed good control performance even under disturbances and measurement noise.