• 한국추진공학회지
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• 제15권5호
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• pp.72-81
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• 2011

이중연소 램제트 엔진의 작동특성 및 주요 설계인자를 파악하기 위하여 공기역학 및 열역학적 이론을 기반으로 한 기본적인 성능해석 모델을 수립하였다. 이중연소 램제트 엔진의 예비 성능해석을 수행하였고, 그 결과는 흡입구, 가스발생기, 초음속 연소기 사이의 상세한 관계를 설명하고 있다. 본 연구에서 제시된 방법은 가스발생기와 초음속 연소기의 기하학적 형상을 정량적으로 결정하고, 엔진 각 구성품의 성능에 대한 영향을 평가하기 위한 도구를 제공한다. 또한 예비 성능해석을 통해 이중연소 램제트 엔진의 기본 형상 설계 결과를 도출하였다.

• 한국환경과학회지
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• 제22권11호
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• pp.1433-1441
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• 2013

The adsorption ability of wood-based activated carbon to adsorb methylene blue (MB) and crystal violet (CV) from aqueous solution has been investigated. Adsorption studies were carried out on the batch experiment at different initial MB and CV concentrations (MB=150 mg/L~400 mg/L, CV=50 mg/L~350 mg/L), contact time, and temperature. The results showed that the MB and CV adsorption process followed the pseudo-second-order kinetic and intraparticle diffusion was the rate-limiting step. Adsorption equilibrium data of the adsorption process fitted very well to both Langmuir and Freundlich model. The maximum adsorption capacity ($q_m$) by Langmuir constant was 416.7 mg/g for MB and 462.4 mg/g for CV. The thermodynamic parameters such as ${\Delta}H^{\circ}$, ${\Delta}S^{\circ}$ and ${\Delta}G^{\circ}$ were evaluated. The MB and CV adsorption process was found to be endothermic for the two dyes.

• Bulletin of the Korean Chemical Society
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• 제34권9호
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• pp.2753-2759
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• 2013

The aim of the present study is to explore the possibility of utilizing fly ash and loess, as alternative to activated carbon, for the adsorption of diazinon in water. Batch adsorption experiment was performed to evaluate the influences of various factors like initial concentration, contact time and temperature on the adsorption of diazinon. The adsorption data shows that fly ash is not effective for the adsorption of diazinon. The equilibrium data for both activated carbon and loess were fitted well to the Freundlich isotherm model. The pseudo-second-order kinetic model appeared to be the better-fitting model because it has higher $R^2$ compared to the pseudo-first-order kinetic model. The thermodynamic parameters such as free energy (${\Delta}G$), the enthalpy (${\Delta}H$) and the entropy (${\Delta}S$) were calculated. Contrary to loess, the ${\Delta}G$ values of activated carbon were negative at the studied temperatures. It indicates that the adsorption of diazinon by activated carbon is a favorable and spontaneous process. The positive ${\Delta}H$ values of activated carbon and loess suggest that the diazinon adsorption process is endothermic in nature. In addition, the positive ${\Delta}S$ values show that increased randomness occurs at the solid/solution surface during the adsorption of diazinon.

• 한국수소및신에너지학회논문집
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• 제26권6호
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• pp.590-599
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• 2015

In this paper a performance analysis is carried out based on the first and second laws of thermodynamics for heat exchanger in organic Rankine cycle (ORC) for the recovery of low-temperature finite thermal energy source. In the analysis, effects of the selection of working fluid and pinch temperature difference are investigated on the performance of the heat exchanger including the effectiveness of the heat exchanger, exergy destruction, second-law efficiency, number of transfer unit (NTU), and pinch point. The temperature distribution are shown depending on the working fluids and the pinch temperature difference. The results show that the performance of the heat exchanger depends on the pinch temperature difference sensitively. As the pinch temperature increases, the exergy destruction in the evaporator increases but the effectiveness, second law efficiency and NTU decreases.

• 한국항공우주학회지
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• 제38권6호
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• pp.586-595
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• 2010

초음속에서 극초음속 영역까지 작동 가능한 이중램제트(이중연소/이중모드) 추진기관의 성능특성을 파악하고 설계인자를 도출하기 위하여 램제트/스크램제트 추진기관의 작동원리에 대한 물리적인 이해를 바탕으로 공기 및 열역학적 관점에서 각 추진기관의 성능특성에 대한 이론적인 연구를 수행하였다. 사이클 해석을 기반으로 하여 각 추진기관의 연소기 입구 마하수와 연소기 형상에 따른 성능특성 및 작동영역의 한계를 연구하였다. 이를 바탕으로 이중램제트의 작동천이 마하수를 파악하고 효율적인 작동영역분배특성을 살펴보았다.

• 한국자동차공학회논문집
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• 제11권6호
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• pp.51-58
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• 2003

A cycle simulation method is developed by coupling a commercial code, Ricardo's WAVE, with the SENKIN code from CHEMKIN packages to predict combustion characteristics of an HCCI engine. By solving detailed chemical kinetics the SENKIN code calculates the combustion products in the combustion chamber during the valve closing period, i.e. from IVC to EVO. Except the combustion chamber during the valve closing period the WAVE code solves thermodynamic status in the whole engine system. The cycle simulation of the complete engine system is made possible by exchanging the numerical solutions between the codes on the coupling positions of the intake port at IVC and of the exhaust port at EVO. This method is validated against the available experimental data from recent literatures. Auto ignition timing and cylinder pressure are well predicted for various engine operating conditions including a very high ECR rate although it shows a trend of sharp increase in cylinder pressure immediate after auto ignition. This trend is overpredicted especially for EGR cases, which may be due to the assumption of single-zone combustion model and the limit of the chemical kinetic model for the prediction of turbulent air-fuel mixing phenomena. A further work would be needed for the implementation of a multi-zone combustion model and the effect of turbulent mixing into the method.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2008년도 춘계학술대회 논문집
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• pp.169-173
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• 2008

Stirling engine is a promising heat engine with a high efficiency, muti-fuel capability, low emission, quiet operation, very low maintenance and long life. As one of the promising applications, solar power system based on the Stirling dish, providing net solar-to-electric conversion efficiencies reaching 30%, can operate as stand-alone units in remote locations or can be linked together in groups to provide utility-scale power. This paper introduced a new Scroll-type Stirling engine, being developed for solar power, superior to conventional Stirling engines. The Scroll-type Stirling engine is characterized as traits of continuous and wholly separated compression and expansion; one-way flow system; direct cooling and heating the fluid in the working spaces through the extensive inner surfaces of scroll wraps. All theses traits contribute to achieving thermodynamic cycle closer to the ideal Stirling cycle (exactly speaking, Ericsson cycle).

• 한국세라믹학회지
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• 제48권4호
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• pp.293-297
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• 2011

The thermodynamic behavior of phenolic resin was investigated to verify the relation between the properties of porous ceramics with $ZrO_2$-C system for submerged entry nozzle and the characteristics of phenolic resin with various relative humidity. The green and the sintered density were decreased between 25% and 50% relative humidity, whereas they were gradually enhanced above 50% relative humidity. The highest value of apparent porosity was 20.1% and the minimum compressive strength was 69MPa in the specimen using the powder exposed to 50% relative humidity. As a result of thermal analysis for phenolic resin, the shift of endothermic peak to low temperature and the reduction of exothermic peak were observed, and the peaks corresponded to melting and curing of phenolic resin, respectively. The melting and the curing of phenolic resin generate the change of green density, and it can affect the properties of submerged entry nozzle.

• Journal of Advanced Marine Engineering and Technology
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• 제35권4호
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• pp.388-396
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• 2011

온실가스 및 대기오염물질 배출 규제는 고효율 및 친환경에 적합한 새로운 선박용 동력장치의 필요성을 제기하고 있다. 최근 이와 같은 문제들을 근본적으로 해결하기 위한 지속가능한 방법으로서 연료전지를 선박의 동력발생장치로 도입하고자 하는 검토가 진행되고 있다. 본 논문은 선박용 연료전지시스템에 사용될 수 있는 최적의 연료를 파악하기 위하여 다양한 탄화수소계 및 알코올계 연료의 수증기 개질특성을 열역학적으로 검토하고 있다.

• Journal of Astronomy and Space Sciences
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• 제16권2호
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• pp.149-158
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• 1999

A Fourier Transform Spectrometer was used to study upper mesospheric thermodynamic by observing the hydroxyl(OH) emission. Rocket-born and satellited-born photometers place the peak emission near 87 km. The instrument was installed in February 1999 at King Sejong station ($62.22^{circ}S,301.25^{circ}E$), Antarctica and has been in routine operation since then. An intensive operational effort has resulted in a substantial data between April and June, 1999. A harmonic analysis was carried out to examine information on the tidal characteristics. The measured amplitudes of the 12-hour oscillation are in the range of 2.4-3.7 K, which are in resonable agreement with theoretical model outputs. The harmonic analysis also revealed 8-hour oscillation which is not expected from the traditional theoretical studies. In addition, the observed 8-hour oscillations are apparent and sometimes dominate the temperature variation in the upper mesosphere.