• Journal of Advanced Marine Engineering and Technology
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• 제24권3호
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• pp.79-87
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• 2000

This paper describes experimental investigations of helium-air exchange flow through openings with vertical partitions. Such exchange flows may occur following rupture accident of stand pipe in high temperature gas cooled reactor. Exchange flow rates are investigated experimentally by using partitioned opening and opening with extended partition to assess fluids interference of the exchange flow at the stand pipe rupture accident. A tests vessel with the two types of opening on top of test cylinder is used in the experiments. An estimation method of mass increment is developed and applied to measure the exchange flow rate. A technique of flow visualization by Mach-Zehnder interferometer is provided to recognize the exchange flows. Amplitude and progress of interference fringes of the flows are observed and used as a support in comparison with the exchange flow rates. Flow passages of upward flow of the helium and downward flow of the air for both two types of the opening are separated by inserted partition within the opening, but in the case of partitioned opening, unseparated flow is formed at the opening entrance and the two flows interface. The exchange flow rate for the partitioned opening is not greater than that of the opening with extended partition because of the fluids interference at the entrance of opening. Finally, the fluids interference at the opening entrance is found to be one of important factors on the helium-air exchange flow rate.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.207-210
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• 2005

In this paper, a two-dimensional cross-channel model was applied to investigate influence of the gas diffusion layer(GDL) property and flow field geometry in the anode side for proton exchange membrane fuel cell(PEMFC). The GDL is made of a porous material such as carbon cloth, carbon paper, or metal wire mesh. To the simplicity, the GDL is represented as a block of material containing numerous pathways through which gaseous reactants and liquid water can pass. The purpose of present work was to study the effect of the GDL thickness and the porosity, and flow field geometry by computational fluid dynamics(CFD)

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.553-554
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• 2006

This paper presents the effects of different operating parameters on the performance of a proton exchange membrane (PEM) fuel cell by a three-dimensional computational fluid dynamics (CFD) model. The effects of different operating parameters on the performance of PEM fuel cell studied using pure hydrogen on the anode side and air on the cathode side. The various parameters are temperatures, pressures, humidification of the gas steams and various combinations of these parameters. In addition, geometrical and material parameters such as the gas diffusion layer (GDL) thickness and porosity as well as the ratio between the channel width and the land area were investigated.

• 오토저널
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• 제8권1호
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• pp.62-74
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• 1986

The simulation of power cycle and unsteady gas exchange processes in the inlet and exhaust systems of the single-cylinder 2-stroke cycle compression ignition engine was studied in this paper. In power cycle process, the single-zone model proposed by Whitehouse and Way was used, and the convective and radiative heat transfer from cylinder contents to surroundings was considered. To solve the equations for gas exchange process, the generalized method of characteristics including area change, friction, heat transfer and entropy gradients was used. Also with the path line calculation, the entropy change along the path line and the variation of specific heat due to the change of temperature and the composition of cylinder gas were considered. As a result of the simulation, the change of pressure and temperature in the cylinder against the crank angle, the rate of net heat release, and the change of properties at each point in the inlet and exhaust pipe against the crank angle were obtained. The engine performances under various operating conditions were also calculated.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2017년도 제48회 춘계학술대회논문집
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• pp.1068-1071
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• 2017

3단 터빈배기부 구성은 터빈 플랜지, 열교환기, 배기덕트와 추력노즐로 이루어진다. 냉가스 가압 방식에 비하여 열교환기 가압 방식을 사용함으로서 추진제탱크 가압을 위한 헬륨가스 자체 무게와 저장 탱크 무게가 감소하는 장점이 있기 때문에 발사체에 열교환기를 사용한다. 가스발생기는 추진제 연료과농 조건에서 연소가 이루어지며, 연소가스 중에 그을음이 많이 포함되어 있기 때문에 열교환 효율이 감소하는 것을 고려하여 열교환기를 설계해야 한다. 본 논문에서는 터빈배기부 구성품 배치, 열교환기 내부 구조 및 제작성을 고려한 설계기법, 기 설계된 노즐 설계를 바탕으로 3단 터빈배기부 재 노즐 설계 형상에 대한 장점을 기술하였다.

• 한국수소및신에너지학회논문집
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• 제27권6호
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• pp.670-676
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• 2016

Hydrogen town in Republic of Korea was established in 2013. Hydrogen as a byproduct produced by various processes of factories is used in hydrogen town facilities. As cell performance is affected by contaminations in fuel gas, various standards about impurities of fuel have been determined by many countries. This study shows performance degradation of single cell with impurities concentrations. Traces of carbon monoxide (CO) and hydrogen sulfide ($H_2S$)can cause considerable cell performance losses. For comparing the performances by poisoning of CO, acceleration test, I-V curve, constant current are performed. Both the CO and $H_2S$ poisoning rate are a function of their concentration. With the higher concentrations the higher poisoning rates are observed. And, it was confirmed that, oxidation behavior and side reaction generation are not affected. Under the lower $H_2S$ concentration condition, the poisoning rate is much higher than that of CO because of its different adsorption intensity. It can be possible that the result of this study can be used for enacting regulation as a baseline data.

• 한국자동차공학회논문집
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• 제18권2호
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• pp.135-140
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• 2010

An important goal in diesel engine research is the development of a means to reduce the emissions of nitrogen oxides (NOX). The use of a cooled exhaust gas recirculation (EGR) system is one of the most effective techniques currently available for reducing nitrogen oxides. Since Particular Matter (PM) fouling reduces the efficiency of an EGR cooler, a trade-off exists between the amount of NOX and PM emissions, especially at high engine loads. In the present study, engine dynamometer experiments have been performed to investigate the heat exchange characteristics of the stack-type EGR coolers with wave fin pitches of 3.6 and 4.6 mm. The results show that the heat exchange effectiveness is decreased as surface area decrease with pitch of 4.6 mm due to PM fouling. As surface area increase at pitch of 3.6 mm, super-cooling happens in the recirculated exhaust gas.

• 식물병연구
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• 제17권2호
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• pp.177-183
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• 2011

해송에서 분리한 Fusarium circinatum(FT-7)을 2009년 7월 21일에 4년생 해송, 소나무 및 리기다소나무 묘목에 인공접종한 후 병 진전 및 가스교환 특성을 조사하였다. 접종 18일 후 해송 10본 중 2본에서, 그리고 접종 21일후에는 리기다소나무 10본 중 2본에서 각각 침엽탈수 증상이 나타났으나 소나무는 실험기간동안 아무런 증상이 나타나지 않았다. 해송의 경우 가스교환율 모니터링을 실시한 5본 중 4본이 접종 25일 후 가스교환이 완전히 멈추었으나 리기다소나무는 5본 중 2본이 25일 이내, 나머지 3본은 39일 후 완전히 정지하는 것으로 나타나 해송의 병 진전도가 리기다소나무에 비해 더 빠른 것으로 나타났다. 실험기간인 78일 동안 리기다소나무 10본 중 9본, 해송 10본 중 8본이 거의 고사하였으나 소나무는 아무런 피해 증상이 나타나지 않았다. 본 연구 결과, 소나무는 F. circinatum(FT-7)에 저항성이 있는 수종으로 나타났으며 인공접종 후 가스교환율은 대조구와 유사한 양상을 보였다.

• 자원ㆍ환경경제연구
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• 제23권1호
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• pp.133-156
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• 2014

경제구조를 표현하는 식들로 구성된 모형을 이용하여 도출되는 정량적 분석결과는 성과의 크기를 제시하므로 정책을 평가할 때에 유용하다. 이에 본 논문에서는 해외석유 가스개발사업의 국민경제에 대한 효과를 정량적으로 측정하기 위하여 해외석유 가스개발사업을 반영한 거시경제모형을 구축하고, 이를 이용하여 해외석유 가스개발사업으로부터의 회수액이 GDP, 경상수지, 실업률, 소비자물가, 환율 등에 미치는 효과를 분석하였다. 해외석유 가스개발 사업의 회수액은 우리나라 기업이 해외석유 가스개발사업에 참여하여 획득한 석유 또는 가스를 달러 형태로 금액화한 것이다. 해외석유 가스개발사업을 반영한 거시경제모형은 한국은행의 모형(1997, 2004, 2012)을 이용하여 구축하였으며, 개별 행태방정식의 통계적 적합성과 historical simulation을 통해 모형 전체의 안정성을 확인하였다. 분석결과에 따르면 시간이 경과하면서 해외석유 가스개발사업 회수액의 규모가 커지면서 우리 나라의 거시경제 변수에 미치는 효과의 크기도 커졌다. 변수별로 보면 해외석유 가스개발사업은 경상수지, 실질 GDP, 실업률에 대해서 긍정적인 효과를 유도하였다. 이에 비해서 소비자물가에 대해서는 상승하는, 그리고 환율에 대해서는 하락(원화가치의 평가절상)하는 효과를 보였다. 매해마다 효과의 크기는 다르지만, 2011년 기준으로 해외석유 가스개발사업 회수액은 경상수지를 2.226%, 실질 GDP를 0.401% 증가시키고, 실업률을 0.489%p 감소시켰다. 소비자물가는 0.101% 증가시키고, 원/달러환율은 0.379% 낮추었다.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 2000년도 THE THIRD INTERNATIONAL CONFERENCE ON AGRICULTURAL MACHINERY ENGINEERING. V.III
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• pp.639-646
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• 2000

Hot air heater with light oil combustion is the most common heater for greenhouse heating in the winter season in Korea. However, since the heat efficiency of the heater is about 80%, considerable unused heat in the form of exhaust gas heat discharges to atmosphere. In order to capture this exhaust gas heat a heat recovery system for plant bed heating in the greenhouse was built and tested in the hot air heating system of greenhouse. The system consists of a heat exchanger made of copper pipes, ${\phi}\;12.7{\times}0.7t$ located inside the rectangular column of $330{\times}330{\times}900mm$, a water circulation pump, circulation plastic pipe and a water tame The total heat exchanger area is $1.5m^2$, calculated considering the heat exchange amount between flue gas and water circulated in the copper pipes. The system was attached to the exhaust gas path. The heat recovery system was designed as to even recapture the latent heat of flue gas when exposing to low temperature water in the heat exchanger. According to performance test it can recover 45,200 to 51,000kJ/hr depending on the water circulation rates of 330 to $690{\ell}$/hr from the waste heat discharged. The exhaust gas temperature left from the heat exchanger dropped to $100^{circ}C$ from $270^{circ}C$ by the heat exchange between the water and the flue gas, while water gained the difference and temperature increased to $38^{circ}C$ from $21^{circ}C$ at the water flow rate of $690{\ell}$/hr. And, the condensed water amount varies from 16 to $43m{\ell}$ at the same water circulation rates. This condensing heat recovery system can reduce boiler fuel consumption amount in a day by 34% according to the feasibility study of the actual mimitomato greenhouse. No combustion load was observed in the hot air heater.