• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 추계학술대회논문집
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• pp.389-395
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• 2000

It is usually the contractual responsibility of HRSG(Heat Recovery Steam Generator) supplier to limit combustion turbine exhaust noise at cogeneration sites. Thus, it is necessary to predict the noise level from HRSG at the stage of preliminary design. HRSG is usually composed of inlet duct, main casing, outlet duct, stack. To satisfy the noise limit level, additional equipments are sometimes required - duct shroud, silencer. We develop algorithms for predicting the noise emission from all these equipments of HRSG units. For the convenience of user, we develop the GUI window version program, named NP-HRSG program. To evaluate the accuracy of this program, predicted noise levels from a real HRSG model are compared with measured data. Through this comparison, we observe that the maximum error is just about 3dB.

• 한국막학회:학술대회논문집
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• 한국막학회 1997년도 제5회 하계 Workshop (97 한,카 국제공동 Workshop, 고도 수처리를 위한 막분리 공정)
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• pp.143-158
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• 1997

Electrochemical deionization (EDI) offers continuous demineralization at higher water recovery rates (>90%), compared with mixed bed ion exchange, and without the use of chemical regenerants and the associated production of saline waste water. Although EDI technology has been used in some power generation applications, its wider application requires the satisfactory resolution of outstanding capital cost and performance issues. This paper reports on the field evaluation of a new cost-effective EDI technology in a power generation application. The E-Cell System$^{TM}$, which became commercially available in the fourth quarter of 1996, consists of a rugged, modular system, based on a new high-performance EDI stack. Starting in May 1996, a 100 gpm modular EDI pilot system, rated for operation at 100 psi, was evaluated at the TVA Brown's Ferry Nuclear Plant. The feed consisted of Reverse Osmosis (RO) permeate with a conductivity of 4-7 $\mu$S/cm. The pilot system reliably produced 17.8-18.0 M$\Omega$.cm water under design operating conditions, independent. Silica levels were reduced from ca. 50 ppb to 4 ppb, while TOC levels were reduced from ca. 120 ppb to 30 ppb.

• 공업화학
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• 제28권1호
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• pp.118-124
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• 2017

공랭식 고분자전해질 연료전지는 개방된 cathode구조로 인하여 시스템의 단순화와 부품 수 저감의 장점이 있다. 공랭식 연료전지는 최근에 많이 연구되고 있지만, 성능이 외부 환경에 영향을 받으며, 공기의 상대습도가 낮은 경우 전해질막의 건조로 인한 성능 감소가 발생할 수 있다. 본 연구에서는 공랭식 연료전지의 성능에 영향을 주는 요인인 cathode 측 공기 유량과 anode 측 purge interval영향에 대해 분석하였으며, 스택을 운전하지 않는 상태로 장기간 보관하는 것이 성능에 미치는 영향에 대하여 실험을 수행하였다. 연료전지 외부에 설치한 fan의 전압을 조절하면 cathode 측 공기의 공급유량을 변화시킬 수 있고 스택의 온도도 제어할 수 있으므로, fan전압은 공랭식 연료전지의 성능에 영향을 주는 중요한 인자이다. 연료전지 시스템을 단순화하고 수소의 사용률을 높이기 위하여 anode 측은 dead ended anode (DEA) 기법을 사용하였다. 주기적인 purge를 실행하여 생성된 물과 가스를 배출하였으며, purge 주기를 변경하면서 스택의 성능에 미치는 영향에 대하여 실험을 수행하였다. 스택의 보관기간이 길어질수록 membrane dehydration으로 인해 성능이 감소하는 것을 실험을 통해 파악하였고, 단시간에 성능을 회복할 수 있는 기법을 제시하였다.

• 환경영향평가
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• 제32권6호
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• pp.463-472
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• 2023

산불에 대한 피해액과 피해 면적은 전 세계적으로 커지고 있지만 피해 후 복원 방법에 따른 효과연구는 부족한 현실이다. 본 연구는 Sentinel-2B 위성 영상과 임상도를 활용하여 산불 피해 면적을 산출하고, 임상에 따른 산불 피해 강도를 분석하였다. 또한, 다양한 파장대를 활용하여 식생지수를 계산하고, 이를 토대로 복원 방법에 따른 식생 회복력을 -1.0에서 1.0 범위 내에서 정량적으로 분석하였다. 그 결과 침엽수림 비율이 높은 지역에서 높은 강도의 산불 피해가 발생하였고, 상대적으로 혼효림과 활엽수림의 비율이 높은 지역에서 낮은 강도의 산불 피해 경향을 보였다. 산불 발생 이후 인공림과 천연림에서의 식생 회복률을 분석한 결과, 인공림은 산불 발생 이전 대비 약 92%, 천연림은 약 101% 식생을 회복하였으며 인공림보다 천연림에서 식생 회복력이 우수한 것을 확인할 수 있었다. 본 연구는 임상에 따른 산불 피해 강도를 분석하고 복원 방법에 따른 식생 회복력을 평가함으로써 산불 피해를 줄이기 위한 수목 선정에 기초자료를 제공하고 복원방법에 따른 식생회복력을 비교하는데 의의가 있다.

• Journal of Mechanical Science and Technology
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• 제20권9호
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• pp.1502-1513
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• 2006

This study analyzes the design and part load performance of a power generation system combining a micro gas turbine (MGT) and an organic Rankine cycle (ORC). Design performances of cycles adopting several different organic fluids are analyzed and compared with performance of the steam based cycle. All of the organic fluids recover greater MGT exhaust heat than the steam cycle (much lower stack temperature), but their bottoming cycle efficiencies are lower. R123 provides higher combined cycle efficiency than steam does. The efficiencies of the combined cycle with organic fluids are maximized when the turbine exhaust heat of the MGT is fully recovered at the MGT recuperator, whereas the efficiency of the combined cycle with steam shows an almost reverse trend. Since organic fluids have much higher density than steam, they allow more compact systems. The efficiency of the combined cycle, based on a MGT with 30 percent efficiency, can reach almost 40 percent. hlso, the part load operation of the combined system is analyzed. Two representative power control methods are considered and their performances are compared. The variable speed control of the MGT exhibits far better combined cycle part load efficiency than the fuel only control despite slightly lower bottoming cycle performance.

• 한국자동차공학회논문집
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• 제21권2호
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• pp.17-25
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• 2013

Performance of DI diesel engine with high fuel injection method is directly related to the emission characteristics and fuel consumption. At present, diesel injection system with piezo element is replacing conventional solenoid type due to their faster electro-mechanical properties. In this study, it was investigated the sensitivity characteristics regarding internal hydraulic modeling based on the AMESim environment of piezo-driven injector The analytic parameter for this study defined such as In/Out orifice, injection hole's diameter and driven voltage on piezo stack. As the results, it was shown that these parameter influence on a fast response characteristics of piezo-driven injector. Also we found fuel pressure recovery time is faster about 0.1 ms due to larger IN orifice diameter. And larger OUT orifice diameter occurs maximum pressure drop with faster its timing of about 0.2 ms.

• 설비공학논문집
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• 제17권6호
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• pp.536-543
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• 2005

This study analyzes the design performance of a combined system of a recuperated cycle micro gas turbine (MGT) and a bottoming organic Rankine cycle (ORC) adopting refrigerant (R123) as a working fluid. In contrast to the steam bottoming Rankine cycle, the ORC optimizes the combined system efficiency at a higher evaporating pressure. The ORC recovers much greater MGT exhaust heat than the steam Rankine cycle (much lower stack temperature), resulting in a greater bottoming cycle power and thus a higher combined system efficiency. The optimum MGT pressure ratio of the combined system is very close to the optimum pressure ratio of the MGT itself. The ORC's power amounts to about $25\%$ of MGT power. For the MGT turbine inlet temperature of $950^{\circ}C$ or higher, the combined system efficiency, based on shaft power, can be higher than $45\%$.

• Journal of Power Electronics
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• 제19권1호
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• pp.68-78
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• 2019

The emergence of high voltage conversion applications has resulted in a trend of using semiconductor device series associations. Series associations allow for operation at blocking voltages, which are higher than the nominal voltage for each of the semiconductor devices. The main challenge with these topologies is finding a way to guarantee the voltage balance between devices in both blocking and switching transients. Most of the methods that have been proposed to mitigate static and dynamic voltage unbalances result in increased losses within the device. This paper introduces a new series stack topology, where the voltage unbalances are reduced. This in turn, mitigates the switching losses. The proposed topology consists of a circuit that ensures the soft switching of each device, and one auxiliary circuit that allows for switching energy recovery. The principle for the topology operation is presented and experimental tests are performed for two modules. The topology performs excellently for switching transients on each of the devices. The voltage static unbalances were limited to 10%, while the activation/deactivation delay introduced by the lower module IGBT driver takes place in the dynamic unbalances. Thus, the switching losses are reduced by 40%, when compared to hard switching configurations.

• 한국수소및신에너지학회논문집
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• 제30권1호
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• pp.21-28
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• 2019

Reversible solid oxide fuel cell (ReSOC) system was integrated with waste steam for electrical energy storage in distributed energy storage application. Waste steam was utilized as external heat in SOEC mode for higher hydrogen production efficiency. Three system configurations were analyzed to evaluate techno-economic performance. The first system is a simple configuration to minimize the cost of balance of plant. The second system is the more complicated configuration with heat recovery steam generator (HRSG). The third system is featured with HRSG and fuel recirculation by blower. Lumped models were used for system performance analyses. The ReSOC stack was characterized by applying area specific resistance value at fixed operating pressure and temperature. In economical assessment, the levelized costs of energy storage (LCOS) were calculated for three system configurations based on capital investment. The system lifetime was assumed 20 years with ReSOC stack replaced every 5 years, inflation rate of 2%, and capacity factor of 80%. The results showed that the exergy round-trip efficiency of system 1, 2, 3 were 47.9%, 48.8%, and 52.8% respectively. The high round-trip efficiency of third system compared to others is attributed to the remarkable reduction in steam requirement and hydrogen compression power owning to fuel recirculation. The result from economic calculation showed that the LCOS values of system 1, 2, 3 were 3.46 ¢/kWh, 3.43 ¢/kWh, and 3.14 ¢/kWh, respectively. Even though the systems 2 and 3 have expensive HRSG, they showed higher round-trip efficiencies and significant reduction in boiler and hydrogen compressor cost.

• 청정기술
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• 제3권2호
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• pp.74-86
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• 1997

최근 청정기술의 필요성이 증가하면서 막분리 공정에 의한 산업폐수 처리기술에 대한 관심이 높아가고 있다. 이 연구는 중화법과 water-splitting electrodialysis (WSED)를 이용하여 금속을 포함하고 있는 폐수에서 유용한 물질을 회수하고 무방류계를 실현하기 위한 것이다. 본 연구에서는 산폐수와 혼합폐수 처리의 공정 설계를 위한 공정의 흐름를 확립하였고, 이 공정에 따른 물질수지를 계산하였다. 또한 주요 단위공정인 침전조와 산회수공정의 운전인자에 대한 실험을 수행하였다. 침전공정에서는 KOH와 NaOH를 중화제로 이용하여 pH에 따른 침전효율과 슬러지양을 비교하였으며 산회수 공정에서는 KCl과 NaCl을 합성원료로 이용하여 WSED의 막구조에 따른 회수효율을 조사하였다.