• Title/Summary/Keyword: 압력강하

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Design of Portable Welded-Nitrogen Vessel (11 kg, 10 L and 50 bar) for Shipbuilding (선박용 휴대형 질소용기(11 kg, 10 L 및 50 bar)의 두께 및 외형 설계)

  • Seong, Hansaem;Kim, Jaeyeol;Eom, Taejin;Kawk, Hyo Seo;Lee, Kwang O;Kim, Chul
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.41 no.4
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    • pp.263-270
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    • 2017
  • The shipbuilding industry uses large stationary tanks to store low-pressure air, which is used to open and close large shut-off valves. However, when supplying air from the tank to a distant valve, there are problems related to the need for supplementary pipes and the pressure drop during transportation. In this study, a portable welded vessel for storing high-pressure nitrogen (11 kg, 10 L, and 50 bar) was designed to prevent air leakage and improve the convenience of workers. This pressure vessel was elliptical to reduce the number of welded parts, which are structurally weak. The thickness and ratio of the major and minor axes of the pressure vessel were calculated to verify its structure stability at the working pressure (50 bar), and that the proposed weight and capacity were satisfactory. The residual stress caused by the welding process was calculated by performing a transient thermal-structural coupled field analysis using the ANSYS parametric design language (APDL), and the fatigue life of the vessel was verified based on the Goodman criterion.

Study on the Modeling Technique for Prediction about Pressure Drop of an Intravenous Lung Assist Device (혈관 내 폐 보조장치의 압력손실 예측을 위한 모델링기법에 관한 연구)

  • 김기범;권대규;정경락
    • Journal of Biomedical Engineering Research
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    • v.24 no.4
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    • pp.293-299
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    • 2003
  • In this paper, the correlation of Pressure drop about the Newtonian and non-Newtonian fluid was investigated experimentally for vibrating intravascular lung assist device (VIVLAD) and we determined correlation equation to make a prediction about Pressure drop for designing VIVLAD. Design conditions to predict the pressure drop of the modules were studied through an experimental modeling before inserting the artificial lung assist device into as venous. Experiments were performed by distilled water, glycerol/water mixed solution(40% glycerol) of Newtonian fluids. and the bovine blood of non-Newtonian fluids. These fluids were flowed outside and parallel of hollow fiber membranes. Also we measured pressure drop according to the number of the fiber membranes which ware inserted into the inside diameter of shell of 3 cm, and developed the prediction equations by curve fitting method based on correlation between the experimental pressure drop and the frontal area or the packing density of device. The result showed that the Pressure drop and the friction factor of the water/glycerol mixed solution were similar to that of bovine blood. It was showed that the water/glycerol mixed solution (40% glycerol) could be used for measuring the pressure drop and the friction factor instead of the bovine blood. Also, we could estimate the prediction equation of pressure drop and friction factor as the function of Packing density at the number of hollow fibers. We obtained the reliance of the prediction equations because the pressure drop and the friction factor measured from the experiments were similar to that from the prediction equation. These results may be used to further usefulness for the design of VIVLAD.

Reaction Characteristics of Combined Steam and Carbon Dioxide Reforming of Methane Reaction Using Pd-Ni-YSZ Catalyst (Pd-Ni-YSZ 촉매를 이용한 수증기-이산화탄소 복합개질 반응 특성)

  • Kim, Sung Su
    • Applied Chemistry for Engineering
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    • v.29 no.4
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    • pp.382-387
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    • 2018
  • In this study, the reaction characteristics of combined steam and carbon dioxide reforming of methane (CSCRM) reaction using Pd-Ni-YSZ catalyst were investigated according to types of catalysts and gas compositions. Catalysts were prepared in the form of powder and porous disk. The injected gases were supplied at different ratios of $CH_4/CO_2/H_2O$. As a result, the conversion of $CH_4$ and $CO_2$ was improved as a result of using the porous disc type catalyst as compared with that of the powder type catalyst. When the $CH_4/CO_2/H_2O$ ratio of the feed gas was 1 : 0.5 : 0.5, the $H_2/CO$ ratio was adjusted close to 2. However, after 6 hours of the reaction, $CH_4$ conversion was partially reduced by the carbon deposition and the pressure drop increased from 0.1 to 0.8. This issue was then solved by optimizing the water content. As a result, it was confirmed that the durability was secured by preventing the carbon deposition when the gas was supplied at a $CH_4/CO_2/H_2O$ ratio of 1 : 0.5 : 1, and the conversion rate was maintained at a relatively high level.

Synthesis of Nanostructured Si Coatings by Hybrid Plasma-Particle Accelerating Impact Deposition (HP-PAID) and their Characterization (하이브리드 플라즈마 입자가속 충격퇴적(Hybrid Plasma - Particle Accelerating Impact Deposition, HP-PAID) 프로세스에 의한 Si 나노구조 코팅층의 제조 및 특성평가)

  • 이형직;권혁병;정해경;장성식;윤상옥;이형복;이홍림
    • Journal of the Korean Ceramic Society
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    • v.40 no.12
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    • pp.1202-1207
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    • 2003
  • Using a recently developed Hybric Plasma-Particle Accelerating Impact Deposition (HP-PAID) process, synthesis of nanostructured silicon coatings has been investigated by injecting vapor-phase TEOS (tetraethosysilane, (C$_2$H$\_$5/O)$_4$Si) into an Ar hybrid plasma. The plasma jet with reactants was expanded through nozzle into a deposition chamber, with the pressure dropping from 700 to 10 torr. Ultrafine particles accelerated in the free jet downstream of the nozzle, deposited by an inertial impaction onto a temperature controlled substrate. By using this process, nanostructured amorphous silicon coatings with grain size smaller than 10 nm could be synthesized. These samples were annealed in an Ar and crystallized at 900$^{\circ}C$ for 30 min. TEM analysis showed that the annealed coatings were also composed of nanoparticles smaller than 10 nm, which showed a good consistency that the average grain size of 7 nm was also estimated from a peak shift of 2.39 cm$\^$-1/ and Full Width at Half Maximum (FWHM) 5.92 cm$\^$-1/ of Raman analysis. The noteworthy is that a strong PL peak at 398 nm was also obtained for this sample, which indicates that the deposited coatings also contained 3∼4 nm nanostructured grains.

Numerical Study of Turbulent Heat Transfer in Helically Coiled Tubes (나선형 튜브내의 난류 열전달에 대한 수치적 연구)

  • Yoon, Dong-Hyeog;Park, Ju-Yeop;Seul, Kwang-Won
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.36 no.8
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    • pp.783-789
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    • 2012
  • In this study, turbulent flow and heat transfer characteristics in a helically coiled tube have been numerically investigated. Helically coiled tubes are commonly used in heat exchange systems to enhance the heat transfer rate. Accordingly, they have been widely studied experimentally; however, most studies have focused on the pressure drop and heat transfer correlations. The centrifugal force caused by a helical tube increases the wall shear stress and heat transfer rate on the outer side of the helical tube while decreasing those on the inner side of the tube. Therefore, this study quantitatively shows the variation of the local Nusselt number and friction factor along the circumference at the wall of a helical tube by varying the coil diameter and Reynolds number. It is seen that the local heat transfer rate and wall shear stress greatly decrease near the inner side of the tube, which can affect the safety of the tube materials. Moreover, this study verifies the previous experimental correlations for the friction factor and Nusselt number, and it shows that the correlation between the two in a straight tube can be applied to a helical tube. It is expected that the results of this study can be used as important data for the safety evaluation of heat exchangers and steam generators.

Numerical Study based on Three-Dimensional Potential Flow in Time-Domain for Effect of Wave Field Change due to Coastal Structure on Hydrodynamic Performance of OWC Wave Energy Converter (연안 구조물로 인한 파동장의 변화가 진동수주 파력발전장치 유체성능에 미치는 영향에 관한 3차원 시간영역 포텐셜 유동 기반의 수치 연구)

  • Kim, J.S.;Nam, B.W.;Park, S.;Kim, K.H.;Shin, S.H.;Hong, K.
    • Proceedings of the Korean Institute of Navigation and Port Research Conference
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    • 2019.11a
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    • pp.150-152
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    • 2019
  • In this study, the effects of the wave field changes due to the coastal structure on the hydrodynamic performance of the OWC wave energy, converter are analyzed using a three-dimensional numerical wave tank technique (NWT). The OWC device is simulated numerically by introducing a linear pressure drop model, considering the coupling effect between the turbine and the OWC chamber in the time domain. The flow distribution around the chamber is different due to the change of reflection characteristics depending on the consideration of the breakwater model. The wave energy captured from the breakwater is spatially distributed on the plane of the front of the breakwater, and the converted pneumatic power increased when concentrated in front of the chamber. The change of the standing wave distribution is repeated according to the relationship between the incident wavelength and the length of the breakwater, and the difference in energy conversion performance of the OWC was confirmed.

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Performance of High Temperature Filter System for Radioactive Waste Vitrification Plant (방사성폐기물 유리화 플랜트 고온여과시스템의 성능 특성)

  • Seung-Chul, Park;Tae-Won, Hwang;Sang-Woon, Shin;Jong-Hyun, Ha;Hey-Suk, Kim;So-Jin, Park
    • Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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    • v.2 no.3
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    • pp.201-209
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    • 2004
  • Important operation parameters and performance of a high temperature ceramic candle filter system were evaluated through a series of demonstration tests at a pilot-scale vitrification plant. At the initial period of each test, due to the growth of dust cake on the surface of ceramic candles, the pressure drop across the filter media increased sharply. After that it became stable to a certain range and varied continuously proportion to the face velocity of off-gas. On the contrary, at the initial period of each test, the permeability of filter element decreased rapidly and then it became stable. Back flushing of the filter system was effective under the back flushing air pressure range of 3∼5 bar. Based on the dust concentrations measured by iso-kinetic dust sampling at the inlet and outlet point of HTF, the dust collection efficiency of HTF evaluated. The result met the designed performance value of 99.9%. During the demonstration tests including a hundred hour long test, no specific failure or problem affecting the performance of HTF system were observed.

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Secondary Flow Patterns of Liquid Ejector with Computational Analysis (액체상 이젝터의 2차측 액체 송출량 특성 전산해석)

  • Kwon, Kwisung;Yun, Jinwon;Sohn, Inseok;Seo, Yongkyo;Yu, Sangseok
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.39 no.2
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    • pp.183-190
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    • 2015
  • An ejector is a type of non-powered pump that is used to supply a secondary flow via the ejection of a primary flow. It is utilized in many industrial fields, and is used for fueling the vehicle because of less failures and simple structure. Since most of ejectors in industry are gas-to-gas and liquid to gas ejector, many research activities have been reported in optimization of gas ejector. On the other hand, the liquid ejector is also applied in many industry but few research has been reported. The liquid ejector occurs cavitation, and it causes damage of parts. Cavitation has bees observed at the nozzle throat at the specified pressure. In this study, a two-dimensional axisymmetric simulation of a liquid-liquid ejector was carried out using five different parameters. The angle of the nozzle plays an important role in the cavitation of a liquid ejector, and the performance characteristics of the flow ratio showed that an angle of $35^{\circ}$ was the most advantageous. The simulation results showed that the performance of the liquid ejector and the cavitation effect have to be considered simultaneously.

Study on Cavitation Noise Predictions for an Elliptic Wing (타원형 날개에 대한 공동소음 예측 연구)

  • Jeong, Seung-Jin;Hong, Suk-Yoon;Song, Jee-Hun;Kwon, Hyun-Wung;Park, Il-Ryong;Seol, Han-Shin;Kim, Min-Jae
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.25 no.6
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    • pp.757-764
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    • 2019
  • Depressurization occurs around underwater objects moving at high speeds. This causes cavitation nuclei to expand, resulting in cavitation. Cavitation is accompanied by an increase in noise and vibration at the site, particularly in the case of thrusters, and this has a detrimental ef ect on propulsion performance. Therefore, predicting cavitation is necessary. In this study, an analytical method for cavitation noise is developed and applied to an elliptic wing. First, computational fluid dynamics are performed to obtain information about the flow fields around the wing. Then, through the cavitation nuclei density function, number of cavitation nuclei is calculated using the initial radius of the nuclei and nuclei are randomly placed in the upstream with large pressure drop around the wing tip. Bubble dynamics are then applied to each nucleus using a Lagrangian approach for noise analysis and to determine cavitation behavior. Cavitation noise is identified as having the characteristics of broadband noise. Verification of analytical method is performed by comparing experimental results derived from the large cavitation tunnel at the Korea Research Institute of Ships & Ocean Engineering.