• Title/Summary/Keyword: Diameter control

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CHARACTERISTIC OF BUTTERFLY VALVE FLOW WITH DIFFERENT DESIGN FACTORS (설계인자 변경에 따른 버터플라이 밸브 유동 특성에 관한 연구)

  • Lee, J.W.;Choi, H.K.;Yoo, G.J.
    • 한국전산유체공학회:학술대회논문집
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    • 2009.11a
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    • pp.170-176
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    • 2009
  • Flow control butterfly valve(FCBV) is known to have difficulty in controlling flow rate along valve opening due to its high flow rate. In low opening condition, the butterfly valve also has some shortcomings such as noise, vibration and erosion which are mostly caused by cavitation effects. Therefore, the FCBV requires proper remedies to reduce cavitation effects and to improve flow control performance. Numerical analysis is applied to FCBV flow to find effects of design factors such as seat diameter and valve opening rate. Cases with 3 different sizes of seat diameter and various valve opening rate are selected for the numerical analysis. From the analysis results, it is found that the FCBV with small seat diameter shows better pressure loss performance and reduced cavitation effects.

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CHARACTERISTIC OF BUTTERFLY VALVE FLOW WITH DIFFERENT DESIGN FACTORS (설계인자 변경에 따른 버터플라이 밸브 유동 특성에 관한 연구)

  • Lee, J.W.;Choi, H.K.;Yoo, G.J.
    • Journal of computational fluids engineering
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    • v.15 no.1
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    • pp.64-70
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    • 2010
  • Flow control butterfly valve(FCBV) is known to have difficulty in controlling flow rate along valve opening due to its high flow rate. In low opening condition, the butterfly valve also has some shortcomings such as noise, vibration and erosion which are mostly caused by cavitation effects. Therefore, the FCBV requires proper remedies to reduce cavitation effects and to improve flow control performance. Numerical analysis is applied to FCBV flow to find effects of design factors such as seat diameter and valve opening rate. Cases with 3 different sizes of seat diameter and various valve opening rate are selected for the numerical analysis. From the analysis results, it is found that the FCBV with small seat diameter shows better pressure loss performance and reduced cavitation effects.

Propulsion Force Coefficient of Injection Nozzle Size on Air Levitation Type Wafer Transfer System (공기부상방식 웨이퍼 이송시스템의 추진 노즐 크기에 따른 추진력계수에 관한 연구)

  • Moon, In-Ho;Cho, Sang-Joon;Hwang, Young-Kyu
    • Journal of the Semiconductor & Display Technology
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    • v.4 no.1 s.10
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    • pp.35-41
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    • 2005
  • An air levitation type wafer transfer system is composed of control and transfer track. Wafer transfer speed is mainly affected by air velocity of propulsion nozzle. In this study, the propulsion force coefficient was evaluated experimentally for the nozzle with 0.5mm, 0.8mm, and 1.0mm diameter. As a result, the propulsion force was largest in the smallest size of nozzle at same air velocity. The propulsion force coefficient of nozzle increases with reducing diameter of nozzle. This increment of propulsion force coefficient was enlarged remarkably at the 0.5mm diameter of nozzle.

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Case Studies of Several Load Tests for Large Diameter Battered Steel Pipe Piles Constructed on the Offshore Area. (대구경 해상 강관말뚝의 설계지지력 확인을 위한 여러 가지 재하시험의 적용)

  • 이정학;서덕동;정헌주
    • Proceedings of the Korean Geotechical Society Conference
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    • 2001.03a
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    • pp.291-298
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    • 2001
  • It is very difficult to accomplish load tests of piles with large diameter constructed on the offshore area, because of requirement for large scaled loading equipment and bad testing conditions. Therefore, so far in many cases pile driving dynamic formulas have applied to quality control, and recently dynamic load test method is widely used for confirming bearing capacities of such piles. However, in cases of piles with very large diameter about 2,500mm, it is nearly impossible for regular type load test methods of piles such as static and dynamic to apply owing to very large design load. This is case studies of load tests such as modified static and dynamic load tests of piles and point load tests of rock samples for estimating rational allowable bearing capacity of very large diameter piles constructed on the marine area.

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Effect of a Tube Diameter on Single Bubble Condensation in Subcooled Flow (튜브 직경에 따른 과냉각 유동 내 단일 기포 응축의 영향)

  • Sun Youb Lee;Cong-Tu Ha;Jae Hwa Le
    • Journal of the Korean Society of Visualization
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    • v.21 no.1
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    • pp.47-56
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    • 2023
  • Bubble condensation, which involves the interaction of bubbles within the subcooled liquid flow, plays an important role in the effective control of thermal devices. In this study, numerical simulations are performed using a VOF (Volume of Fluid) model to investigate the effect of tube diameter on bubble condensation. As the tube diameter decreases, condensation bubbles persist for a long time and disappear at a higher position. It is observed that for small tube diameters, the heat transfer coefficients of condensation bubbles, which is a quantitative parameter of condensation rate, are smaller than those for large tube diameters. When the tube diameter is small, the subcooled liquid around the condensing bubble is locally participated in the condensation of the bubble to fill the reduced volume of the bubble due to the generation of a backflow in the narrow space between the bubble and the wall, so that the heat transfer coefficient decreases.

Estimating Tree Shape Ratio by Region for Pinus Densiflora and Larix Kaempferi in Korea (우리나라 소나무 및 일본잎갈나무의 지역별 형상비 추정)

  • Kang, Jin-Taek;Ko, Chi-Ung;Yim, Jong-Su;Lee, Sun-Jeoung;Moon, Ga-Hyun
    • Journal of Korean Society of Forest Science
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    • v.108 no.4
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    • pp.600-609
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    • 2019
  • This study was conducted to highlight the necessity for a stand density control management plan in consideration of the shape ratio of Pinus densiflora and Larix kaempferi in Korea. A total of 2,112 Pinus densiflora samples and 2,030 Larix kaempferi samples were cut, and their diameter at breast height (DBH), height, and clear length were measured for regional shape ratio (height/DBH) comparison and analysis.The shape ratio of Pinus densiflora was 72.3% in the Gangwon district, 64.0% in the central district, and 70.8% on average, indicating a higher percentage of Pinus densiflora in Gangwon than in the central area. Regionally, Yeongju had the highest percentage at 78.4%, with Yeongwol indicating 77.5%. Measured by diameter, results showed a presence of 90.4% for small diameter trees (6-16 cm), 71.7% for medium diameter trees (18-28 cm), and 56.1% for large diameter trees (30 cm). As density increased, the shape ratio of height to tree trunk diameter also increased; below 70% indicated a more stable trunk, while a result above 80% indicated trunks prone to wind hazards and snowstorms, and, therefore, the need for density control in partial areas. The overall shape ratio of Larix kaempferi was 90.6%. Pyeongchang indicated a 108.5% ratio, Yeongju 105.4%, and Danyang 100.5%, respectively.According to diameter class, small diameter trees showed 104.9% occurrence, medium diameter trees 92.7%, and large diameter trees 73.4%. The shape ratio of Larix kaempferi was higher than 80% overall, indicating vulnerability to wind hazards and snowstorms. Therefore, appropriate stand density management is required.

Effect of Irrigation Automation Using Stem Diameter Variation as an Indicator of Irrigation Timing in Greenhouse Tomato (온실재배 토마토에서 관개시기 진단지표로 경직경 변화를 이용한 관개 자동화 효과)

  • 이변우;신재훈
    • Journal of Bio-Environment Control
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    • v.8 no.4
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    • pp.232-241
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    • 1999
  • The automatic irrigation system using the stem diameter monitoring and the transpiration model for the determination, respectively, of irrigation timing and amount was designed and evaluated for its applicability in pot and field culture of greenhouse tomato. In the pot culture condition, the yield and quality of greenhouse tomato were improved when irrigation was practiced based on the stem diameter monitoring and the transpiration model as compared to the irrigation practice based on soil moisture monitoring. However, the effects were not significant in the field culture condition.

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Flow control downstream of a circular cylinder by a permeable cylinder in deep water

  • Gozmen, Bengi;Akilli, Huseyin
    • Wind and Structures
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    • v.19 no.4
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    • pp.389-404
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    • 2014
  • The flow characteristics of a circular cylinder surrounded by an outer permeable cylinder were experimentally investigated using Particle Image Velocimetry Technique in deep water flow. In order to consider the effects of diameter and porosity of the outer cylinder on flow structures of the inner cylinder, five different outer cylinder diameters (D=37.5, 52.5, 60, 75 and 90 mm) and eight different porosities (${\beta}$=0.4, 0.5, 0.6, 0.65, 0.7, 0.75, 0.8 and 0.85) were selected. During the experiments, the diameter of inner cylinder was kept constant as d=30 mm. The depth-averaged free-stream velocity was adjusted as U=0.156 m/s, which corresponds to the Reynolds number of Re=5000 based on the inner cylinder diameter. It has been concluded that both the outer permeable cylinder diameter and the porosity have important influences on the attenuation of vortex shedding in the wake region. The presence of outer permeable cylinder decreases the magnitude of Reynolds shear stress and turbulent kinetic energy compared to the bare cylinder case. Moreover, the spectral analysis of vortex shedding frequency has revealed that the dominant frequency of vortex shedding downstream of the cylinder arrangement also reduces substantially due to the weakened Karman shear layer instability.

A Fuzzy Controller for Warp Tension Control in The Weaving Process (퍼지제어기를 이용한 제작공정에서의 경사장력제어)

  • 류도훈;이연정
    • Proceedings of the Korean Institute of Intelligent Systems Conference
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    • 2000.11a
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    • pp.335-339
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    • 2000
  • In the weaving process, tension control of the warp is important. The variation of the warp tension cause irregularities of the weft density and low quality of the woven fabrics. Due to the fact that the warp tension varies in depending on the difference between take-up velocity and let-off velocity, it is necessary to regulate the velocity of let-off in relation to that of take-up for keeping the warp tension. Futhermore, the diameter of warp beam changes in the weaving process. The changing diameter of warp beam cause changing inertia of warp beam and the velocity of the let-off. It makes the control of such a system more complex. In this paper, we propose a fuzzy controller for the warp tension control. From the computer simulation, it was observed that a developed fuzzy controller has a better performance than that of conventional PI controller.

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Surface Temperature Control of an Insulated Horizontal Pipe under Thermal Radiation Environment (복사효과를 포함하는 수평관 표면의 온도제어)

  • Kang, Byung-Ha;Pi, Chang-Hun;Kim, Suk-Hyun
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.23 no.1
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    • pp.54-60
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    • 2011
  • Procedures for estimation of insulation thickness for a horizontal pipe for condensation control or personnel protection has been investigated, parallel to the previous work of a vertical wall case. Parameters include pipe diameter, emissivity, thermal conductivity, and operating temperatures. The results indicated that the surface emissivity plays a very important role in the design of insulation, specially for the case of high temperature application with low Bi. The effect of surface radiation in such case could be up to 65% of the total. Required insulation thickness for the surface temperature control increases as pipe diameter increases and as surface emissivity decreases. Adequate revision of specifications or standards to include newly invented insulation materials with high emissivity has been also suggested.