• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.292-295
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• 2008

In a SCWR (SuperCritical pressure Water cooled Reactor), the coolant temperature initially at below the pseudo-critical temperature at the bottom of a reactor core increases as the coolant flows upward through the sub-channels of the fuel assemblies, and it finally becomes higher than the pseudo-critical temperature when it leaves the reactor core. At certain conditions, heat transfer deterioration occurs near the pseudo-critical temperature and it may cause a drastic rise of the fuel surface temperature resulting a fuel failure. Therefore, an accurate estimation of the heat transfer coefficient is very important for the thermal-hydraulic design of a reactor core. An experiment on heat transfer to the vertically upward flowing $CO_2$ at a supercritical pressure in a circular tube were performed at KAERI. The internal diameter of the test section is 6.32 mm, which corresponds to the hydraulic diameter of a sub-channel in the conceptional design proposed by KAERI. The test range of the mass flux is 285 to 1200 kg/m$^2$s and the maximum heat flux is 170 kW/m$^2$. The inlet pressure is maintained at 8.12 MPa, which is 1.1 times the critical pressure. A new correlation, which covers both the normal and deterioration heat transfer regimes was proposed and compared with the estimations by exiting correlations.

• 한국초전도ㆍ저온공학회논문지
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• 제8권4호
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• pp.22-25
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• 2006

This paper deals with the computation of the current limiting behavior of high-temperature superconducting (HTS) modules for the superconducting fault current limiter (SFCL). The SFCL module consists of a monofilar type BSCCO-2212 tube and a shunt coil made of copper or brass. The shunt coil is connected to the monofilar superconducting tube in parallel. Through analysis of the quench behavior of the monofilar component with shunt coils, it is achieved to drive an equivalent circuit equation from the experimental circuit structure. In order to analyze the quench behavior of the SFCL module, we derived a partial differential equation technique. Inductance of the monofilar component and the impedance of the shunt coil are calculated by Bio-Savart and Ohm's formula, respectively. We computed the quench behavior using the calculated values, and compared the results with experimental results for the quench characteristics of a component. The results of computation and test agreed well each other, and it was concluded that the analytic result could be applied effectively to design of the distribution-level SFCL system.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2000년도 추계학술발표대회 논문집
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• pp.84-87
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• 2000

Square tubes used for vehicle structure components have an important role on keeping its stiffness and preserving occupant safety in vehicle collision and rollover in which it experience axial collapse, bending collapse or both. Bending collapse, which absorbs kinetic energy of the impact and retains a survival space for the occupant, is a dominant failure mode in oblique collision and rollover. Thus, in this paper, the bending collapse characteristics such as the maximum bending moment and energy absorption capacity of the square tube replaced by light-weight material were evaluated and presented. The bending test of cantilever tubes which were fabricated with aluminum, GFRP and aluminum/ GFRP hybrid by co-curing process was performed. Then the maximum bending moment and the energy absorption capacity from the moment-angle curve were evaluated. Based on the test results, it was found that aluminum/ GFRP hybrid tube can show better specific energy absorption capacity compared to the pure aluminum or GFRP tube and can convert unstable collapse mode which may occur in pure GFRP tube to stable collapse mode like a aluminum tube in which plastic hinge is developed.

• 한국자동차공학회논문집
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• 제24권3호
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• pp.338-344
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• 2016

The study is actively being performed to increase fuel injection pressure of common rail system among countermeasures to meet the emission regulation strengthen of the Diesel engine. The common rail fuel injection tube in such ultra high pressure common rail system has the weakest structural characteristics against vibration that is generated by fuel injection pressure and pulsation during engine operation and driving. Thus the extreme durability is required for common rail fuel injection tube, and the drawing process is being magnified as the most important technical fact for strength of seamless pipe that is the raw material of common rail tube. In this respect, we analyzed the characteristic of dimension and stress variation of the ultra high pressure common rail fuel injection tube by variation of Die and Plug angle in drawing process. Based on the analysis, we tried to obtain the raw material strength of common rail fuel injection tube for applying to the ultra high pressure common rail system. As a result, Plug angle is more important than entry angle of Die and we could obtain the target dimension and strength of the ultra high pressure common rail fuel injection tube through optimization of Plug angle.

• 한국진공학회지
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• 제16권4호
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• pp.305-310
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• 2007

W-target 투과양극형 x-ray tube를 개발하고, 특성을 조사하였다. 관전압이 12kV이하에서는 연속 x-ray만 방출되었고, 12kV 이상에서부터 특성 x-ray가 관측되었다. 연속 x-ray와 특성 x-ray의 에너지 분포 및 선량 특성을 조사한 결과 알려진 결과와 잘 일치함을 알 수 있었다. 또한 상용화된 제품과의 비교에서, 기존 제품 이상의 성능을 가질 수 있음을 확인하였다. 따라서 본 연구에서 개발된 x-ray tube는 상용화할 수 있을 만큼 충분히 우수한 특성을 가지고 있음을 확인하였다.

• 동력기계공학회지
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• 제16권5호
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• pp.32-39
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• 2012

The study experimented to understand ice-on-coil type ice making characteristics on to 3 kinds of circular tube, oval tube and small diameter tube using ice maker. The experiment were carried out under various conditions, that used brine temperature($-10^{\circ}C$, $-6^{\circ}C$), brine flow rate(1.0m/s, 1.8m/s) and inlet water temperature ($6^{\circ}C$, $12^{\circ}C$) etc. Mass of ice per ice making area increased according to the decrease of the brine temperature and inlet water temperature, but that was increased according to the increase of the brine flow rate. Oval ice making tube produced ice 1.11 to 2.46 times that of 9mm circular ice making tube, and 3mm small diameter ice making tube produced ice 1.06 to 1.51 times that of 9mm circular ice making tube.

• 한국기계가공학회지
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• 제18권6호
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• pp.39-44
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• 2019

The evaporator is a key driver of an air conditioning system's efficiency. In this study, we study methods of maximizing the efficiency of a Massey Ferguson (MF) evaporator by measuring how the cooling performance of different shapes vary with temperature. We varied the tube insertion depth as well as the shape of the evaporator's header and tube. When we compare header shapes of "D", "Ellipse", and "Quadrangle" types, we find that the elliptical header creates the smallest pressure loss and the highest temperature difference. Between tube shapes of "Rectangular", "Projection", and "Circular" types, the "Projection" type tube creates the most temperature difference. We also investigated the depth of tube insertion in the header and find that tube insertion of 5 - 10 mm is feasible; we selected the depths of 5, 7, and 10 mm since they corresponded to approximately 30%, 50%, and 70% of the total width of the header. The tube insertion test demonstrated that a tube insertion depth of 7 mm creates the least pressure loss and the highest temperature difference. In conclusion, the optimal evaporator design uses an "Ellipse" type header, "Projection" type tube, and a tube insertion depth between 30 and 50% of the header width.

• 한국진공학회지
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• 제17권3호
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• pp.247-252
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• 2008

휴대용 XRF(X-Ray Fluorescence) 장치에 적용하기 위하여 개발한 투과 양극형 x-ray tube를 이용하여 XRF 실험을 하고, x-ray tube가 XRF data에 미치는 영향을 조사하였다. W-target tube와 Rh-target tube를 이용하여 측정한 XRF data는 알려진 결과와 잘 일치하였다. 35 kV와 관전압과 $40{\mu}A$의 관전류에서 W-target tube로 측정한 Fe $K_{\alpha}$-line의 FWHM은 약 180 eV로써, 이 값은 물질의 성분분석을 하기에 충분한 것으로 확인하였다. XRF data와 x-ray tube의 적분강도 곡선을 비교 분석해 본 결과, 휴대용 XRF 장치에는 W-Target tube보다는 Rh-Target tube를 사용하는 것이 더 유리함을 밝혀내었다.

• 한국가스학회지
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• 제11권2호통권35호
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• pp.5-9
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• 2007

지구상에 역사가 시작된 이후로 에너지, 경제, 환경 등 3E 문제가 존재해 왔다. 특히 근대산업혁명 이후 에너지 및 환경에 대한 문제가 두각을 나타내게 되었다. 따라서 환경친화적인 에너지원으로서 가스의 수요가 날로 급증하고 있다. 가스의 수요와 더불어 가스보일러의 설치 및 사용이 늘어나면서 보일러 폐가스(CO)에 의한 인명피해가 해마다 증가하고 있다. 따라서 가스보일러 직관 배기통의 길이에 따른 CO농도의 고찰을 통하여 인체에 대한 위해성을 파악코자 함이다. CO의 허용농도인 50 ppm에 해당하는 길이는 1곡관 3 m에서는 5분이 경과할 경우이며, 4 m와 5 m에서는 3분 경과부터 CO 농도가 허용농도를 초과하는 것으로 나타났다.

• Journal of Mechanical Science and Technology
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• 제20권3호
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• pp.418-425
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• 2006

The present investigation deals with the study of the internal flow phenomena of the counterflow type vortex tube using experimental testing and numerical simulation. Visualization was carried out using the surface tracing method, injecting dye on the vortex tube wall using a needle. Vortex tube is made of acrylic to visualize the surface particle tracing and the input air pressure was varied from 0.1MPa to 0.3MPa. The experimentally visualized results on the tube show that there is an apparent sudden changing of the trajectory on the vortex tube wall which was observed in every experimental test case. This may indicate the stagnation position of the vortex flow. The visualized stagnation position moves towards the vortex generator with increase in cold flow ratio and input pressure. Three-dimensional computational study is also conducted to obtain more detailed flow information in the vortex tube. Calculated total pressure, static pressure and total temperature distributions in the vortex tube were in good agreement with the experimental data. The computational particle trace on the vortex tube wall is very similar to that observed in experiments.