• 한국신재생에너지학회:학술대회논문집
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• 2005.06a
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• pp.630-633
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• 2005

Some gases can be formed into hydrate by physical combination with water under appropriate temperature and pressure condition. Besides them, it was found that the pore size of the sediments can affect the formation and dissociation of hydrate. In this study, formation temperatures of carbon dioxide and methane hydrate have been measured using isobaric method to investigate the effects of flow rates of gases on formation condition of hydrate in porous rock samples. The flow rates of gases were controlled using a mass flow controller. To minimize Memory effect, system temperature increased for the dissociation of gas hydrates and re-established the initial saturation. The results show that the formation temperature of hydrate decreases with increasing the injection flow rate of gas. This indicates that the velocity of gas in porous media may act as kinds of inhibitor for the formation of hydrate.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.422-428
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• 2011

금속을 청정 에너지원으로 이용하기 위해 분말형 금속연료 연소시스템이 필요하고, 이에 대한 선행연구로 분말을 정량 공급할 수 있는 공급기를 설계 제작하였다. 유동층 방식의 분말 공급에 영향을 미칠 수 있는 변수들을 피스톤 및 벤츄리관이 적용된 공급 방법을 사용하여 통제한 후, 조절 가능한 공급기 내부 압력만을 변수로 하여 중요 성능인 분말 공급량을 직접적인 중량 측정 방법으로 측정하였다. 측정 실험의 결과로부터 연소시스템에 적용할 공급기의 작동 조건을 도출할 수 있었고, 작동 조건에서 벗어난 영역에서 분말 공급기가 가지고 있는 문제점을 확인하였다.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.4
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• pp.459-465
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• 2009

This paper considers the influence of internal heat exchangers to the efficiency of a refrigerating system. These internal heat exchangers(liquid-suction or suction-line heat exchangers) can, in some cases, yield improved system performance while in other cases they degrade system performance. A steady state mathematical model is used to analysis the performance characteristics of refrigeration system with internal heat exchanger. The influence of operating conditions, such as gas cooler pressure and evaporation temperatures, superheat in the evaporator and temperature of gas cooler outlet, to optimal dimensions of the heat exchanger is also analyzed in the paper. The main results were summarized as follows : the mass flowrate of R744, inner diameter tube and length of internal heat exchanger, and effectiveness have an effect on the cooling capacity, compressor work and RCI(Relative capacity index) of this system. With a thorough grasp of these effect, it is necessary to design the R744 compression refrigeration cycle using internal heat exchanger.

• 한국연소학회:학술대회논문집
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• 2012.04a
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• pp.241-243
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• 2012

Experiments were conducted to get the design concepts for the continuous aluminum particle feeding system. Two opposed cylinders were used. Aluminum particles in one cylinder were ejected to the air by the supplying gas and the pressure of the other cylinder. It was not possible to eject more aluminum mass flowrate than that of gas if particles were just thrust by the pressure difference between two cylinders. Aluminum particle/air mixture in the flow system was successfully ignited by the electric spark.

• The KSFM Journal of Fluid Machinery
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• v.18 no.4
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• pp.13-21
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• 2015

The system design of the Organic Rankine Cycle(ORC) is greatly influenced by the thermal properties such as the temperature or the thermal capacity of heat source. Typically waste heat, solar energy, geothermal energy, and so on are used as the heat source for the ORC. However, thermal energy supplying from these kinds of heat sources cannot be provided constantly. Hence, an experimental study was conducted to utilize fluctuating thermal energy efficiently. For this experiment, an impulse turbine and supersonic nozzles were applied and the supersonic nozzle was used to increase the velocity at the nozzle exit. In addition, these nozzles were used to adjust the mass flowrate depending on the amount of the supplied thermal energy. The experiment was conducted with maximum three nozzles due to the capacity of thermal energy. The experimented results were compared with the predicted results. The experiment showed that the useful output power could be producted from low-grade thermal energy as well as fluctuating thermal energy.

• The KSFM Journal of Fluid Machinery
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• v.16 no.3
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• pp.10-17
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• 2013

The organic Rankine cycle has been widely used to convert the renewable energy such as the solar energy, the geothermal energy, or the waste energy etc., to the electric power. Some previous studies focused to find what kind of refrigerant would be a best working fluid for the organic Rankine cycle. In this study, R245fa was chosen to the working fluid, and the cycle analysis was conducted for the output power of 30kW or less. In addition, properties (temperature, pressure, entropy, and enthalpy etc.) of the working fluid on the cycle were predicted when the turbine output power was controlled by adjusting the mass flowrate. The configuration of the turbine was a radial-type and the supersonic nozzles were applied as the stator. So, the turbine was operated in partial admission. The turbine efficiency and the optimum velocity ratio were considered in the cycle analysis for the low partial admission rate. The computed results show that the system efficiency is affected by the partial admission rate more than the temperature of the evaporator.

• Journal of the Korean Society of Propulsion Engineers
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• v.7 no.1
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• pp.57-65
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• 2003

As a compressed water is rapidly expanded through a nozzle, two-phase flow of vapor and liquid is formed in the nozzle due to the flash evaporation. In the present study, critical flow of two-phase fluids is analysized using an Isentropic-Homogeneous-Equilibrium model and a Leung model. Calculation results show that the choke of the two-phase flow can be two different types of continuous and discontinuous chokings. For the stagnation pressure below 10 Mpa it is found that the continuous choking, which is similar to the choking phenomenon of single-phase gas flow, is possible only when the degree of subcooling is less than 10K.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.05a
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• pp.61-64
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• 2008

For the performance evaluation of liquid mono-propellant thruster, Vacuum Hot-fire test is necessarily required. An accurate flow measurement is one of the key parameters to the successful T&E program. This paper describes the characteristics of the coriolis flowmeter, explains the cold-flow test using simulant propellant (DIW), and presents the test results. Finally, the cold test results have been verified in comparison with the hot-fire test data.

• Journal of Hydrogen and New Energy
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• v.16 no.2
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• pp.180-190
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• 2005

The PSA cycle was performed for the separation of binary gas mixture $H_2/Ar$ (80%/20%) using the six-step two-bed process. Adsorption equilibrium contains a LRC model for equilibrium adsorption isotherms and a LDF model for mass transfer. Aspen ADSIM, simulator was applied to predict the separation performance. The effect of cycle parameters such as feed rate, adsorption pressure and P/F ratio on the separation of hydrogen has been studied in experiment and simulation. In the results, maximize the recovery of hydrogen as a high purity was 13LPM feed flowrate, 120sec adsorption time, 11atm adsorption pressure and 0.1 P/F ratio in a cyclic steady-state come out since 10th cycle.

• The KSFM Journal of Fluid Machinery
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• v.17 no.6
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• pp.5-12
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• 2014

Organic Rankine Cycle is widely used to convert the low-grade thermal energy to the electrical energy. However, usually available thermal energy is not supplied constantly. This makes hard to use positive displacement expanders. Hence, turbo-expander has merits to apply as an expander in ORC because it can operate well off-design points even though the mass flowrate is fluctuated. The thermal energy fluctuation causes the turbo-expander to operate in partial admission. In addition, supersonic nozzles are required so that the partially admitted turbine operates efficiently. In this study, R245fa was chosen as a working fluid of ORC. A design method and an analysis technique of supersonic nozzle based on R245fa were developed. The shape of the nozzle was designed by the characteristic method. The thermal properties within the nozzle were estimated and the predicted results were agreed well with the computed results.