• 한국화재소방학회논문지
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• 제26권1호
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• pp.1-9
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• 2012

특수선(FPSO, Drillship)의 거주구역이나, 대형 여객선(크루즈선) 공간의 70% 이상을 차지하는 수용시설(accommodation), 공공장소, 서비스 구역 등은 24시간 사람이 상주하는 구역임으로 화재로부터 안전하게 보호되어야 한다. 이를 위해 국제해사기구(IMO)에서는 SOLAS II-2 Reg. 10.6과 FSS code Ch. 7에 적합한 미분무 소화설비를 설치할 것을 강제화하고 있다. 이러한 미분무 소화설비는 미분무 노즐, 압력용기, 섹션밸브, 펌프유닛 등으로 구성되는데 특히 핵심부품인 미분무 노즐은 최근에 개정된 IMO Res. MSC 265(84)에 따라 노즐성능시험 및 화재진압성능시험을 통해 선급인증을 득해야 한다. 본 연구에서는 이러한 기준을 만족하는 폐쇄형 미분무 노즐을 개발하고 선실 및 복도, 공공장소, 창고에 대한 화재시험을 통해 각 장소에 적용 가능한 총 5종의 미분무노즐의 성능평가를 실시하였다.

• Nuclear Engineering and Technology
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• 제52권9호
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• pp.1955-1962
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• 2020

In a sudden shutdown of primary pump or coolant loss accident in a marine nuclear power plant, the primary flow decreases rapidly in a transition process from forced circulation (FC) to natural circulation (NC), and the lower flow enters the steam generator (SG) causing reverse flow in the U-tube. This can significantly compromise the safety of nuclear power plants. Based on the marine natural circulation steam generator (NCSG), an experimental loop is constructed to study the characteristics of reverse flow under middle-temperature and middle-pressure conditions. The transition from FC to NC is simulated experimentally, and the characteristics of SG reverse flow are studied. On this basis, the experimental loop is numerically modeled using RELAP5/MOD3.3 code for system analysis, and the accuracy of the model is verified according to the experimental data. The influence of the flow variation rate on the reverse flow phenomenon and flow distribution is investigated. The experimental and numerical results show that in comparison with the case of adjusting the mass flow discontinuously, the number of reverse flow tubes increases significantly during the transition from FC to NC, and the reverse flow has a more severe impact on the operating characteristics of the SG. With the increase of flow variation rate, the reverse flow is less likely to occur. The mass flow in the reverse flow U-tubes increases at first and then decreases. When the system is approximately stable, the reverse flow is slightly lower than obverse flow in the same U-tube, while the flow in the obverse flow U-tube increases.

• 한국군사과학기술학회지
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• 제18권3호
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• pp.213-219
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• 2015

Piezoelectric-based hydraulic actuator is a hybrid device consisting of a hydraulic pump driven by piezoelectric stacks that is coupled to a conventional hydraulic cylinder via a set of fast-acting valves. Nowadays, such hybrid actuators are being researched and developed actively in many developed countries by requirement of high performance and compact flight system. In this research, a piezoelectric hybrid actuator has been designed and tested. To achieve bi-directional capabilities in the actuator, solenoid valves were used to control the direction of output fluid. The experimental testing of the actuator in uni-directional and bi-directional modes was performed to examine performance issues related to the solenoid valves. The results showed that the bi-directional performance was slightly lower than uni-directional performance due to air bubble developed in the valve system. A new design to solve the vacuum problem has been proposed to improve the performance of the hybrid actuator.

• Journal of Advanced Marine Engineering and Technology
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• 제37권6호
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• pp.638-643
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• 2013

유압시스템의 출력밀도를 높이기 위해 고압화, 대형화 되고 있으나, 유압동력 발생장치(HPU)를 구동할 때 110 dB(A) 정도의 높은 소음이 발생한다. 최근 산업안전규제 강화와 작업장 환경개선 요구 등으로 인하여 HPU의 소음저감을 위한 방안으로 실외나, 지하에 별도의 설치공간을 만들어 HPU를 이용하는 경우가 있었으나, 배관에서의 작동유 유동마찰로 인한 동력손실과 고장 났을 때 신속하게 대응하는데 문제가 있었다. 본 연구에서는 HPU의 동력변환 과정에서 필수적으로 발생되는 소음을 효과적으로 차폐시키면서 동력손실을 저감시키는 방음챔버(chamber)를 채용하여 소음특성을 개선하는 연구를 실험적으로 하였다.

• 대한기계학회논문집B
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• 제39권1호
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• pp.37-43
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• 2015

현열 뿐만 아니라 잠열을 이용하는 증발냉각은 배기열 회수에 매우 유용하게 사용될 수 있다. 본 연구의 목적은 증발냉각을 이용한 배기열 회수장치의 성능을 실험적으로 규명하는 것이다. 성능실험장치는 플라스틱 열교환기, 물 분무 노즐, 공기유동용 홴, 물 순환용 펌프, 수조, 온도 습도 유량 측정 센서 등으로 구성되었다. 증발이 없는 현열 회수에서의 유용도와 증발을 수반하는 전열 회수에서의 유용도를 여러가지 작동조건에서 측정하여 비교하였다. 현열냉각과 증발냉각의 유용도는 공기의 유량이 증가함에 따라 감소하고, 대향류에서의 유용도가 평행류에서의 유용도 보다 휠씬 높다. 증발냉각의 경우 물 유량이 증가함에 따라 유용도는 증가하고, 평행류가 대향류보다 물 유량에 더 민감함을 알 수 있다.

• 한국산학기술학회논문지
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• 제21권11호
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• pp.892-897
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• 2020

본 연구에서는 간접식 증발냉각 장치의 냉각 성능을 예측하고 다양한 공기 유량 및 물 분무 유량 조건을 만족하는 성능 상관식을 제안한다. 기존의 플라스틱 열교환기는 공조 공간의 크기에 따라 금형을 새로 제작해야 하기 때문에 높은 효율에도 불구하고 잘 사용하지 않았다. 한편 단프라시트는 일반적으로 두께가 얇아 열교환이 우수하고, 특히 제작이 매우 용이하다. 따라서 열교환기를 단프라시트로 제작할 경우 금형이 별도로 필요하지 않아 열교환기 제작 비용을 크게 절감할 수 있다. 이에 본 연구에서는 단프라시트로 다채널 열교환기를 제작하여 간접식 증발냉각 장치를 제작하였다. 성능 실험장치는 열교환기, 물 분사 노즐, 터보홴, 항온조, 순환 펌프, 온도 센서, 습도 센서, 차압식 유량계 및 자료획득 장치로 구성하였다. 증발냉각 시 공기 유량이 증가하면 유용도가 감소하였고, 수공비에 따라 유용도 최적점이 존재하였다. 등온 조건에서 냉각 성능을 예측하는 상관식과 실내 환기 온도와 외기 상태를 반영하는 성능 상관식을 제안하였다. 상관식들의 냉각 성능 오차는 4 % 이내였다.

• 한국정밀공학회지
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• 제23권10호
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• pp.103-112
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• 2006

This paper describes a theoretical analysis and experimental verification on the performances of a vacuum-compatible air bearing, which is designed with a cascaded exhaust scheme to minimize the air leakage in a vacuum environment. The design of the vacuum-compatible air bearing equipped with the differential exhaust system requires great care because several design parameters, such as the number of exhaust stages, diameter of exhaust tube, pumping speed of a vacuum pump, and bearing clearance greatly influence the air leakage and thus degree of vacuum. In this study, a performance analysis method was proposed to estimate the performances of the air bearing, such as load capacity, stiffness, and air leakage. Results indicate that the load capacity and stiffness of the air bearing was improved as its boundary pressure, which was determined by the $1^{st}$ exhaust method, was lowered, and the dominant factors on the chamber's degree of vacuum were the number of exhaust stages, exhaust tube diameter and bearing clearance. A vacuum chamber and air bearing stage using porous pad were fabricated to verify the theoretical analysis. The results demonstrate that chamber pressure up to an order of $10^{-3}$ Pa was achieved with the air bearing stage operating inside the chamber, and this analysis method was valid by comparing predicted values with experimental data, for the mass flow rates from the porous pad, and pressures at each exhaust port and chamber, respectively.

• 소음진동
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• 제9권4호
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• pp.720-729
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• 1999

Coventional methods for reducing vibration in engineering designs (i.e. by stifferning or detuning) may be undesirable in conditions where size or weight must be minimized, or where complex vibration spectra exist. Some alloys with a combination of high damping capacity and good mechanical properties can provide attractive techanical and economical solutions to problems involving seismic, shock and vibration isolation. Although several non ferrous damping alloys have been developed, none of those materials are applied in any industrial factor due largely to high production cost. To meet these requirement, we have developed a new Fe-Mn high damping alloy. In previous studies, we have reported that an Fe-17%Mn alloy exhibits the highest damping capacity(Specific Damping Capacity:SDC, 30%) among Fe-Mn binary system, and proposed that the boundaries of various types such as $\varepsilon$-martensite variant boundaries, stacking faults in $\varepsilon$-martensite, stacking faults in austenitic and ${\gamma}$$\gamma /\varepsilon$ interfaces give rise to a high damping capacity. The Fe-17%Mn alloy also has advantages of good mechanical properties(T.S. 70 kg/nm$^2$ and low cost over other damping alloys(1/4 times the cost of non-ferrous damping alloy). Thus, the Fe-17%Mn high damping alloy can be widely applied to household appliances, automobiles, industrial facilities and power plant components. In this paper, the overall properties of the Fe-17%Mn high damping alloy is introduced, and its applicability to containment spray pump in the power plant is discussed.

• 한국가스학회지
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• 제15권3호
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• pp.19-25
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• 2011

냉방용 에너지는 크게 전력과 가스로 대별할 수 있는데, 전기냉방 시스템은 하절기 최대전력을 상승시키는 요인이 되고 있다. 전기에너지는 수요 공급 특성상 저장이 불가능하기 때문에 예상되는 최대전력을 상회하는 공급능력을 보유해야 하며 매년 하절기의 사회문제로 대두되어 왔다. 한편 가스냉방의 경우 흡수식 시스템과 GHP 시스템이 있다. 그러나 가스냉방 보급용량은 전기 냉방에 비해 매우 적으며 소형시장은 대부분 전기냉방에 의존하고 있는 상황이다. 본 논문에서는 국내 냉방에너지 현황을 살펴보고 에너지원간의 부하분담 비중을 분석하여 냉방에너지의 합리적인 방향을 제시하고자 2024년까지 장기적인 가스냉방 보급 규모를 전망하였으며, 이를 바탕으로 가스냉방 보급효과를 분석하여 가스냉방의 확대 필요성을 뒷받침 하고자 하였다.

• The Korean Journal of Pain
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• 제22권3호
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• pp.199-205
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• 2009

Background: A major ingredient of green tea is epigallocatechin-3-gallate (EGCG), and this is known to have many beneficial effects for cancer prevention and also on the cardiovascular system and neurodegenerative diseases through its anti-oxidant, anti-angiogenic, anti-inflammatory, lipid-lowering and neuroprotective properties. Its actions on nociception and the spinal nervous system have been examined in only a few studies, and in these studies EGCG showed an antinociceptive effect on inflammatory and neuropathic pain, and a neuroprotective effect in motor neuron disease. This study was performed to investigate the effect of EGCG on acute thermal pain and the development of morphine tolerance at the spinal level. Methods: The experimental subjects were male Sprague-Dawley rats and the Hot-Box test was employed. A single or double-lumen intrathecal catheter was implanted at the lumbar enlargement for drug administration. An osmotic pump was used to infuse morphine for 7 days for induction of morphine tolerance. EGCG was injected repeatedly for 7 days at twice a day through the intrathecal catheter. Results: Intrathecal EGCG increased the paw withdrawal latency (PWL) after repeated administration for 7 days at twice a day, but this did not happen with administering on single bolus injection of EGCG. In addition, the antinociceptive effect of intrathecal morphine was not affected by co-administration with EGCG. A continuous 7-day infusion of morphine caused a significant decrease of the PWL in the control group (M + S, morphine plus saline). In contrast, intrathecal EGCG injection over 7 days blocked the decrease of the PWL in the experiment group (M + E, morphine plus EGCG). Conclusions: Intrathecal ECGC produced a weak antinociceptive effect for acute thermal pain, but it did not change the morphine's analgesic effect. However, the development of antinociceptive tolerance to morphine was attenuated by administering intrathecal EGCG.