• 자원리싸이클링
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• 제12권1호
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• pp.41-47
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• 2003

대기에 방치된 생석회의 상온에서 내수화성을 향상시키기 위해 생석회의 탄산화반응과 수화반응실험을 수행하였다. 제강공정에서 사용시까지 수화반응을 억제시키기 위해서는 생석회 표면을 약 6%정도 탄산화시킬 필요가 있었다. 생석회의 탄산화를 위한 회전로 배가스 재순환이 평형연소온도 및 NOx농도에 미치는 영향을 열역학적으로 계산한 결과, 배가스 부피 백분율이 증가함에 따라 연소온도와 NOx농도는 감소하였다.

• 에너지공학
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• 제8권4호
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• pp.560-566
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• 1999

가압 조건하에서의 석탄가스화 특성을 규명하기위해 , 온도 압력 , 산소/석탄비, 수증기/석탄비 등을 변화시켜가며 로토탄(sub A)에 대하여 PDTF(Pressuized drop tube furnace)실험을 수행하였다. 실험결과, 상압 조건에서보다 가압조건에서의 가스화가 탄소전환율과 냉가스효율의 측면에서 더 유리한 것으로 측정되었다. 최대의 냉가스효율을 보이는 산소/석탄비의 증가가 냉가스효율의 증가를 가져왔다. 압력이 증가할수록 열분해에 의한 탄소전환의 비중은 감소하고 대신 기고반응에 의한 탄소전환의 비중이 증가하였다.

• 한국에너지공학회:학술대회논문집
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• 한국에너지공학회 1999년도 춘계 학술발표회 논문집
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• pp.23-31
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• 1999

가압 조건하에서의 석탄가스화 특성을 규명하기 위해, 온도, 압력, 산소/석탄비, 수증기/석탄비 등을 변화시켜가며 로토탄(Sub A)에 대하여 PDTF(Pressurized drop tube furnace) 실험을 수행하였다. 실험결과, 상압 조건에서보다 가압조건에서의 가스화가 탄소 전환율과 냉가스효율의 측면에서 더 유리한 것으로 측정되었다. 최대의 냉가스효율을 보이는 산소/석탄비(무게기준)는 0.5∼0.7(g/g)로 측정되었고, 온도가 충분히 높은 경우에만 수증기/석탄비의 증가가 냉가스효율의 증가를 가져왔다. 압력이 증가할수록 열분해에 의한 탄소전환의 비중은 감소하고 대신 기고반응(heterogeneous reaction)에 의한 탄소전환의 비중이 증가하였다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2005년도 제24회 춘계학술대회논문집
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• pp.168-175
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• 2005

액체로켓 추진시스템에서 가압시스템은 발사체 추진제 탱크의 얼리지 공간에 제어된 가스를 공급하는 것이다. 가압시스템에서 고온 가스 열교환기를 적용하는 데는 가압제의 비용적을 증가시켜 전체 발사체 시스템의 중량을 감소시키는 장점이 있다. 가압시스템 성능에 있어서 주목할 만한 개선점은 극저온 시스템에서 얻어질 수 있다. 이러한 경우 가스 공급은 극저온 탱크 내부에 저장되어 진다. 극저온 가압제의 온도 특성은 가압시스템에서 구성 단품을 개발하는데 있어서 매우 중요하다. 본 연구에서는 SINDA/FLUINT를 이용한 수치적 모델링과 PTF(Propellant-feeding Test Facility)에서 수행된 실험에 대하여 해석 및 시험이 수행되었다.

• 대한기계학회논문집B
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• 제22권4호
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• pp.542-550
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• 1998

A direct contact heat exchanger using particle-suspended gas as a heat transfer medium is analyzed with an extended emphasis on the radiation, i. e., considering the radiation by both gas and particles. While the Runge-Kutta method is used for a numerical analysis of the momentum and energy equations, the finite volume method is utilized to solve the radiative transfer equation. Present study shows a notable effect by the gas radiation in addition to the particle radiation, especially when changing the chamber length as well as the gas and particle mass flow rate. When the gas and particle mass flow rate is raised, the gas temperature in the particle heater still increases as the gas absorption coefficient increases, which is different from the results for the small scale heat exchanger.

• 한국결정성장학회:학술대회논문집
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• 한국결정성장학회 1998년도 PROCEEDINGS OF THE 14TH KACG TECHNICAL MEETING AND THE 5TH KOREA-JAPAN EMGS (ELECTRONIC MATERIALS GROWTH SYMPOSIUM)
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• pp.49-54
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• 1998

The growth of diamond films in plasma enhanced chemical vapor deposition(PECVD) processes requires high substrate temperatures and gas pressures, as well as high-power excitation of the gas source. Thus determining the substrate temperature in this severe environment is a challenge. The issue is a critical one since substrate temperature is a key parameter for understanding and optimizing diamond film growth. The precise Si substrate temperature calibration based on rapid-scanning spectroscopic ellipsometry have been developed and utilized. Using the true temperature of the top 200 ${\AA}$ of the Si substrate under diamond growth conditions, real time spectroellipsometry (RTSE) has been performed during the nucleation and growth of nanocrystallind thin films prepared by PECVD. RTSE shows that a significant volume fraction of nondiamond(or{{{{ {sp }^{2 } -bonded}}}}) carbon forms during thin film coalescence and is trapped near the substrate interface between ∼300 ${\AA}$ diamond nuclei.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
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• pp.731-734
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• 2009

KIER has been developed a compact and highly efficient fuel processor which is one of the key component of the residential PEM fuel cells system. The fuel processor uses methane steam reforming to convert natural gas to a mixture of water, hydrogen, carbon dioxide, carbon monoxide and unreacted methane. Then carbon monoxide is converted to carbon dioxide in water-gas-shift reactor and preferential oxidation reactor. A start-up time of the fuel processor is about 1h and CO concentration among the final product is maintained less than 5 vol. ppm. To achieve high thermal efficiency of 80% on a LHV basis, an optimal thermal network was designed. Internal heat exchange of the fuel processor is so efficient that the temperature of the reformed gas and the flue gas at the exit of the fuel processor remains less than $100^{\circ}C$. A compact design considering a mixing and distribution of the feed was applied to reduce the reactor volume. The current volume of the fuel processor is 17L with insulation.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.393-396
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• 2002

Submerged gas-injected system can be applied to various industrial field such as metallurgical and chemical processes, So this study aims at presenting the relevant relationship between gas phase and liquid phase in a gas-injected bath. In a cylinderical bath, local gas volume fraction and bubble frequency were measured by electroconductivity probe and oscilloscope. The temperature of each phase was measured using thermocouple and data acquisition system. In vertical gas injection system, gas-liquid two phase plume was formed, being symmetry to the axial direction of injection nozzle and in a shape of con. Lacal gas-liquid flow becomes irregular around the injection nozzle due to kinetic energy of gas and the flow variables show radical change at the vicinity of gas(air) injection nozzle As most of the kinetic energy of gas was transferred to liquid in this region, liquid started to circulate. In this reason, this region was defined as 'developing flow region' The Bubble was taking a form of churn flow at the vicinity of nozzle. Sometimes smaller bubbles formed by the collapse of bubbles were observed. The gas injected into liquid bath lost its kinetic energy and then was governed by the effect of buoyancy. In this region the bubbles which lost their kinetic energy move upward with relatively uniform velocity and separate. Near the gas nozzle, gas concentration was the highest. But it started to decrease as the axial distance increased, showing a Gaussian distribution.

• 대한기계학회논문집B
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• 제25권6호
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• pp.837-844
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• 2001

Jet cutting technology currently makes use of a generic supersonic gas jet to improve the cutting speed and performance. In order to get a better understanding of the flow characteristics involved in the supersonic jet cutting technology, the axisymmetric Navier-Stokes equations have been solved using a fully implicit finite volume method. Computations have been conducted to investigate some major characteristics of supersonic coaxial turbulent jets. An assistant gas jet has been imposed on the primary gas jet to simulate realistic jet cutting circumstance. The pressure and the temperature ratios of the primary and assistant gas jets are altered to investigate the major characteristics of the coaxial jets. The total pressure and Mach number distributions, shock wave systems, and the jet core length which characterize the coaxial jet flows are strongly affected by the pressure ratio, but not significantly dependent on the total temperature ratio. The assistant gas jet greatly affects the basic flow characteristics of the shock system and the core length of under and over-expanded jets.

• 한국환경과학회지
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• 제4권1호
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• pp.41-52
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• 1995

The effects of reaction temperature, SO2 and CO2 concentration in an air gas stream, particle sizes of limestone on the reactivity and capacity of SO2 removal have been determined in a thermogravimetric analyser(TGA). The apparent reaction order of sulfation reaction of pre-calcined lime(CaO) with respect to SO2 is found to be close to unity. The apparent activation energies are found to be 17,000 kcal/kmol for sulfation of pre-calcined lime and 19,500 kcal/kmol for direct sulfation of limestone(CaCO3). The initial sulfation reaction rate of pre-calcined lime increases with increasing temperature, whereas the sulfur capture capacity exhibits a maximum value at 90$0^{\circ}C$. In direct sulfation of limestone, sulfation reactivity and sulfur capature capacity of sorbent increase with increasing temperature and decreasing CO2 concentration in a gas bulk stream. The main pare of pre-calcined lime is shifted to the larger pore sizes and pore volume decreases with increasing sulfation time and temperature. The surface area of lime decreases with increasing calcination temperature under an air atmosphere, whereas is yearly constant under a CO2(5, 10%) atmosphere in a gas stream.