• 대한기계학회논문집
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• 제14권3호
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• pp.676-684
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• 1990

본 연구에서는 다공성 매질을 이용하여 예혼합기체를 맥동연소시킬 때의 진동 특성, 열적특성 및 연소특성에 관한 것이다. 먼저, 맥동의 모우드형상 및 발생조건 을 열전달과 음향이론을 바탕으로하여 예측하고 실험을 통하여 검토하였다. 또한 맥 동에 의한 화염형상의 변화를 가시화하여 관측하고, 온도분포 및 배기가스의 조성등을 측정하여 맥동 연소와 비맥동 연소를 비교 고찰하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 하계학술대회 논문집 Vol.6
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• pp.548-549
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• 2005

본 논문에서는 인가 전극구조가 다른 두가지 형태의 아크성 스트리머 방전용 플라즈마 반응기를 설계 제작하였다. 제작된 반응기에 60 Hz상용전원과 펄스파워를 인가전원으로 사용하여 반응기 형태와 인가전원에 따른 수소발생 특성에 대하여 조사하였다. 또한 방전 전력에 따른 수소발생량을 비교 분석하였다. 수소 발생을 위한 효과적인 수표면 방전은 강한 전계 집중과 높은 에너지 밀도를 동반한 아크성 스트리머 방전 분위기 형성이 필요하다. 인가전원으로 상용전원을 이용한 경우보다 펄스파워를 사용한 경우와 강한 전계집중 증대를 위해 인가 전극이 석영관 내에 배치된 전극 구조에서 수소발생에 효과적이였다.

• Korean Chemical Engineering Research
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• 제44권3호
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• pp.277-283
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• 2006

화력발전소에서 배출되는 배연가스에서의 $CO_2$가스 흡수를 목적으로 sodium glycinate계 흡수제를 개발하기 위하여 sodium glycinate의 순수 및 수용액의 물성인 용해도, 증기압과 비점, 열전도 및 증발 잠열을 측정 또는 추산하였다. 용매인 $H_2O$ 25 g에 대한 sodium glycinate의 온도별 용해도는 y = 0.3471x + 20.993의 1차 함수 관계로 증가하였다. Sodium glycinate 10 wt％, 20 wt％, 30 wt％, 40 wt％, 50 wt％, 60 wt％ 수용액의 증기압과 비점을 측정하고, Antoine 상수를 구하였으며 Clausius- Clapeyron 식을 이용하여 증기압 측정값으로 증발 잠열을 구하였다. Sodium glycinate 분체의 열전도도 측정은 분체를 disk판으로 성형한 후, 고체 열전도도 측정 장치로 측정하였으며 그 값은 $1.0933kcal/m{\cdot}hr{\cdot}^{\circ}C$이었다.

• Current Optics and Photonics
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• 제6권6호
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• pp.521-549
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• 2022

Fiber lasers have made remarkable progress over the past three decades, and they now serve far-reaching applications and have even become indispensable in many technology sectors. As there is an insatiable appetite for improved performance, whether relating to enhanced spatio-temporal stability, spectral and noise characteristics, or ever-higher power and brightness, thermal management in these systems becomes increasingly critical. Active convective cooling, such as through flowing water, while highly effective, has its own set of drawbacks and limitations. To overcome them, other synergistic approaches are being adopted that mitigate the sources of heating at their roots, including the quantum defect, concentration quenching, and impurity absorption. Here, these optical methods for thermal management are briefly reviewed and discussed. Their main philosophy is to carefully select both the lasing and pumping wavelengths to moderate, and sometimes reverse, the amount of heat that is generated inside the laser gain medium. First, the sources of heating in fiber lasers are discussed and placed in the context of modern fiber fabrication methods. Next, common methods to measure the temperature of active fibers during laser operation are outlined. Approaches to reduce the quantum defect, including tandem-pumped and short-wavelength lasers, are then reviewed. Finally, newer approaches that annihilate phonons and actually cool the fiber laser below ambient, including radiation-balanced and excitation-balanced fiber lasers, are examined. These solutions, and others yet undetermined, especially the latter, may prove to be a driving force behind a next generation of ultra-high-power and/or ultra-stable laser systems.

• 설비공학논문집
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• 제22권4호
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• pp.248-257
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• 2010

An exhausted heat recovery system for a small gas engine cogeneration plant was investigated. The system was designed and built in a 300 kW class cogeneration demonstrative system. The basic performance was tested depending on load variation, and installed to a field site as a bottoming heat and power supply system. The exhaust gas heat exchangers (EGHXs) in shell-and-tube type and shell-and-plate type were tested. The entire efficiency of the cogeneration system was estimated between 85 to 90% under the 100% load condition, of which trend appears higher in summer due to the less thermal loss than in winter. Power generation efficiency and thermal efficiency was measured in a range of 31~33% and 54~57%, respectively.

• 에너지공학
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• 제6권2호
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• pp.129-136
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• 1997

본 연구는 전력계통의 화력발전소로부터 배출되는 NOx및 SO$_2$같은 대기환경오염물질을 고려한 새로운 경제부하배분법을 제시한다. 제안된 방법은 총배출량 제약, 지역별 배출랑 제약 그리고 이들의 동시제약을 만족하면서 화력발전기의 출력을 계획하는 것에 대해 설명되어진다. 또한, 모든 부하배분의 대체안이며 배출량과 총연료비 사이의 상호상충관계를 나타내는 Trade-Off곡선에 의해 배출량과 총연료비 사이의 감도해석이 이 알고리즘에 적용된다. 한편, 이 제안된 방법은 개별적 환경피해(NOx, SO$_2$등)의 상대적 가중치와 총환경비용의 함수로써 경제부하배분이 이것에 의해 어떻게 변화되는지를 해석한다. 본 연구에서 제안된 방법을 시험계통에 적용하여 그 유용성을 검증하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.776-781
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• 2001

To enhance thermal efficiency of thermal facility through recovery of low and medium temperature waste heat, 1MW organic Rankine cycle system was designed and developed. The exhaust gases of $175^{\circ}C$ at two 100MW power plants in pohang steel works were selected as the representative of low and medium temperature waste heat in industrial process for the heat source of the organic Rankine cycle system. HCFC-123, a kind of harmless refrigerant, was chosen as the working fluid for Rankine cycle. The organic Rankine cycle system with selected exhaust gases and working fluid was designed and constructed. From the operation, it was confirmed that the organic Rankine cycle system is available for low and medium temperature waste heat recovery in industrial process. The optimum operating manuals, such as heat-up of hot water, turbine start-up, and the process of electric power generation, were derived. However, electric power generated was not 1MW as designed but only 670kW. It is due to deficiency of pump capacity for supply of HCFC-123. So it is necessary to increase the pump capacity or to decrease the pressure loss in pipe for more improved HCFC-123 supply.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.292-292
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• 2014

Wide band gap semiconductors, such as III-nitrides (GaN, AlN, InN, and their alloys), SiC, and diamond are expected to play an important role in the next-generation electronic devices. Specifically, GaN-based high electron mobility transistors (HEMTs) have been targeted for high power, high frequency, and high temperature operation electronic devices for mobile communication systems, radars, and power electronics because of their high critical breakdown fields, high saturation velocities, and high thermal conductivities. For the stable operation, high power, high frequency and high breakdown voltage and high current density, the fabrication methods have to be optimized with considerable attention. In this study, low ohmic contact resistance and smooth surface morphology to AlGaN/GaN on 2 inch c-plane sapphire substrate has been obtained with stepwise annealing at three different temperatures. The metallization was performed under deposition of a composite metal layer of Ti/Al/Ni/Au with thickness. After multi-layer metal stacking, rapid thermal annealing (RTA) process was applied with stepwise annealing temperature program profile. As results, we obtained a minimum specific contact resistance of $1.6{\times}10^{-7}{\Omega}cm2$.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.2017-2022
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• 2004

There are multistage preheaters in the power generation plan to improve the thermal efficiency of the plant and to prevent the components from the thermal shock. The energy source of these heaters comes from the extracted two phase fluid of working system. These two-phase fluid can cause the so-called Flow Accelerated Corrosion(FAC) in the extracting piping and the bubble plate of the heater for example, in case of point Beach Nuclear Power Plant and in the Wolsung Nuclear Power Plant. The FAC is due to the mass transport of the thin oxide layer by the convection. FAC is dependent on many parameters such as the operation temperature, void fraction, the fluid velocity and pH of fluid and so on. Therefore, in this paper velocity was calculated by FLUENT code in order to find out the root cause of the wall thinning of the feedwater heaters. It also includeed in the fluid mixing analysis model are around the number 5A feedwater heater shell including the extraction pipeline. To identify the relation between the local velocities and wall thinning, the local velocities according to the analysis results were compared with distribution of the shell wall thicknes by ultrasonic test.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2002년도 학술대회 논문집
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• pp.318-321
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• 2002

Superconductivity has various applications in the whole industry such as the generation of high magnetic field for medical care and diagnosis, the lossless power transmission, environment-friendly vehicles and clean energy storage systems. This paper deals with the High-Tc superconducting(HTS) power supply using heater-triggered switch for the charging of the superconducting magnets. HTS superconducting power supply consists of two heaters, an electromagnet, and Bi-2223 solenoid and Bi-2223 pancake is used as a superconducting load, similar to real HTS magnet. The timing sequential control of two heaters and an electromagnet is an important factor to generate pumping- current in the Bi-2223 load. The thermal analysis of switching parts of the Bi-2223 solenoid according to the heater input was carried out. Based upon the analysis, the 0.8A of heater current were optimally derived. The maximum pumping current reached 1.7A.