• 제목/요약/키워드: ribs

검색결과 814건 처리시간 0.027초

쐐기형 요철이 설치된 사각덕트에서의 열/물질전달 및 압력강하 특성 (Heat/Mass Transfer and Pressure Drop in A Square Duct with V-Shaped Ribs)

  • 최청;이동호;조형희
    • 대한기계학회논문집B
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    • 제26권11호
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    • pp.1542-1551
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    • 2002
  • The present study investigates the convective heat/mass transfer characteristics and pressure drop inside the rib-roughened cooling passage of gas turbine blades. The internal cooling passage is simulated using a square duct with h- and V-shaped rectangular ribs which have a 60。attack angle. A naphthalene sublimation technique is employed to determine the detailed local heat/mass transfer coefficients using the heat and mass transfer analogy. The ribs disturb the main flow resulting in the recirculation and secondary flows near the ribbed wail. The secondary flow patterns and the local heat transfer in the duct are changed significantly according to the rib orientation. A square duct with ∧ - and V-shaped ribs have two pairs of secondary flow due to the rib arrangement. Therefore, the average heat/mass transfer coefficients and pressure drop of ∧ - and V-shaped ribs are higher than those of the continuous ribs with 90$^{\circ}$ and 60$^{\circ}$attack angles. The ∧-shaped ribs have higher heat/mass transfer coefficients than the V-shaped ribs, and the uniformity of heat/mass transfer coefficient are increased with the discrete ribs due to the flow leakage and acceleration near the surface.

쐐기형 요철이 설치된 사각덕트에서의 열전달 및 압력강하 특성 (Heat/Mass Transfer and Pressure Drop of Square Duct with V-shape Ribs)

  • 최청;이동호;조형희
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2001년도 추계학술대회논문집B
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    • pp.280-287
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    • 2001
  • The present study investigates convective heat/mass transfer and flow characteristics inside the rib-roughened cooling passage of the gas turbine blades. A square duct with rectangular ribs is used and $\wedge-$ and V-shape ribs with $60^{\circ}$ attack angle are installed on the test plate surfaces. Naphthalene sublimation technique is employed to determine the detailed local heat transfer coefficients using the heat and mass transfer analogy. The ribs disturb the main flow resulting in the recirculation and secondary flows near the ribbed wall and the vortices near the side-wall. The local heat transfer and the secondary flow in the duct are changed largely according to the rib orientation. A square duct with $\wedge$ and V-shape ribs has two pairs of secondary flow because of the rib arrangement. So, the duct has complex heat/mass transfer distribution. The average heat/mass transfer coefficient and pressure drop of $\wedge-$ and V-shape ribs are higher than those with $90^{\circ}$ and $60^{\circ}$ attack angles. The average heat/mass transfer coefficient on the $\wedge-shape$ ribs is higher than that on the V-shape ribs. Also, the uniformity of heat/mass transfer coefficient on discrete ribs is higher than that on continuous rib.

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Sintering Distortion of Barrier Ribs Formed via Capillary Molding Route

  • Chang, Tae-Jung;Kim, Yong-Seog
    • 한국정보디스플레이학회:학술대회논문집
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    • 한국정보디스플레이학회 2003년도 International Meeting on Information Display
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    • pp.362-364
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    • 2003
  • In this study, sintering behavior of closed-cell type barrier ribs formed via capillary molding route was examined. Sintering of the molded barrier ribs revealed asymmetric shrinkage, leading to distortion of the cells. The effects of the parameters such as solid loading in the paste, presintering temperature, and morphology of the barrier ribs on the sintering shrinkage of the barrier ribs were investigated.

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Technique for evaluating the mechanical properties of barrier ribs in PDP

  • Hwang, Seong-jin;Kim, Hyung-Sun
    • 한국정보디스플레이학회:학술대회논문집
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    • 한국정보디스플레이학회 2005년도 International Meeting on Information Displayvol.II
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    • pp.1241-1244
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    • 2005
  • To prevent deformation and fracture of barrier ribs we suggest how to evaluate the mechanical properties of barrier ribs which depend on porosity and components by indentation technology. Our experimental results show that the mechanical properties of barrier ribs are strongly correlated to porosity and components.

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Effects of ceramic fillers on fracture resistance of barrier ribs of PDP

  • Baek, Se-Kyung;Kim, Yong-Seog
    • 한국정보디스플레이학회:학술대회논문집
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    • 한국정보디스플레이학회 2004년도 Asia Display / IMID 04
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    • pp.552-554
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    • 2004
  • Barrier ribs of plasma display panel (PDP) are glass matrix composite reinforced with alumina particles. Mechanical properties of the ribs are very crucial for the improvement in reliability of the panel as the ribs might fracture during transportation and service. In this study, therefore, the effects of filler type and content on the mechanical properties of the ribs were investigated. The fillers used include $Al_2O_3$, $TiO_2$, $ZrO_2$ and fused silica. The content of the filler was changed from 0 to 40 vol.%. The mechanical properties of the ribs measured were hardness, Young's modulus, fracture toughness, and 3-point bending modulus. The fracture toughness evaluated by micro-Vicker's indentation of the composites, in general, was measured to increase with the content of the filler until the sintered density does not decrease significantly. The improvement, however, was dependent on the type of filler employed.

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터빈 기익 내부관 열전달 증대를 위해 설치된 요철의 형상 효과 (Effects of Rib Cross Section Shapes on Heat Transfer of a Rib-Roughened Duct)

  • 우성제;권혁진;조형희
    • 대한기계학회논문집B
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    • 제23권1호
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    • pp.149-157
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    • 1999
  • Heat transfer in a duct is augmented remarkably by rib turbulators. However, increasing friction loss is accompanied due to ribs disturbing flows. Hence, pressure drops and heat transfer are considered simultaneously to decide heat/mass transfer performance in a rib-roughened duct. In the present study, the effects of rib cross section shape on pressure drop through a duct are investigated as well as those on heat transfer characteristics. The results show that the characteristics of heat/mass transfer and friction loss in the duct roughened with triangular ribs are similar to those with square ribs, while significantly different from those with semicircular ribs. The best performance in the duct is obtained by using semicircular shaped ribs among three types of ribs for the large rib angles of ${\alpha}{\geq}63^{\circ}$.

Barriers Ribs using Molds Prepared by Inclined UV Lithography

  • Kim, Ki-In;Kim, Yong-Seog
    • 한국정보디스플레이학회:학술대회논문집
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    • 한국정보디스플레이학회 2003년도 International Meeting on Information Display
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    • pp.788-790
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    • 2003
  • Closed-cell type barrier ribs of PDP were formed by capillary molding process using molds prepared by inclined UV lithography process. Various types of molds with different inclined angles were prepared by patterning SU-8 thick photoresist film and casting with PDMS. The ribs with various type cells were successfully formed by the process. The effects of inclined angle on the distortion of barrier ribs during sintering were investigated. The results indicated that the barrier ribs with a draft angle and dimensional change does not affect the distortion of the barrier ribs during sintering, suggesting that the closed-cell must be isotropic in sintering shrinkage.

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사각 또는 반원 형상의 요철이 설치된 채널 내부의 유동 및 열전달의 큰에디모사 (Large Eddy Simulation of Flow and Heat Transfer in a Channel Roughened by Square or Semicircle Ribs)

  • 안준;최해천;이준식
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2004년도 춘계학술대회
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    • pp.1436-1441
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    • 2004
  • The internal cooling passage of a gas turbine blade can be modeled as a ribbed channel. Most studies have considered square ribs. However, the ribs can be rounded due to improper manufacturing or wear during the operation. Hence, we have studied two different rib geometries in this study, i.e. square and semicircle ribs. We have performed large eddy simulations (LES) and experiments to validate the results from the simulations. LES predicts the detailed flow and thermal features, which have not been captured by simulations using turbulence models. By investigating the instantaneous flow and thermal fields, we propose the mechanisms for the local heat transfer distribution between ribs. For both the geometries, heat transfer is enhanced by the entrainment of the cold fluid by the vortical motions and impingement of the entrained cold fluid on the ribs.

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테이프와 거칠기가 설치된 사각 채널의 압력강하 특성 (Characteristics of Pressure Drops in Square Channels with Twisted Tape Inserts plus Axial Interrupted Ribs)

  • 안수환;배성택;강호근
    • 동력기계공학회지
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    • 제10권4호
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    • pp.38-42
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    • 2006
  • Pressure drops and friction factors in square channels with twisted tape inserts plus axial interrupted ribs are investigated. Tests are performed for Reynolds numbers ranging from 8,900 to 29,000. The rib height-to-channel hydraulic diameter, $e/D_h$, is kept at 0.057 and test section length-to-hydraulic diameter, $L/D_h$ is 30. The pressure drops and friction factor values are enhanced with axial interrupted ribs and twisted tape inserts. Square channels with twisted tape inserts plus axial interrupted ribs show the greatest pressure loss penalty in the present work. Friction factor data obtained for the square channel with twisted tape inserts plus axial interrupted ribs are less than those in the past publications for circular tubes with axial interrupted ribs and twisted tape inserts.

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부분 등분포 하중을 받는 원형아치 리브의 면내 좌굴 거동특성 (Characteristic Behavior of In-plane Buckling of Circular Arch Ribs Subjected to Partial Distributed Loading)

  • 김성훈;문지호;윤기용;이학은
    • 한국방재학회 논문집
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    • 제5권3호
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    • pp.57-65
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    • 2005
  • 아치 리브가 비대칭 하중을 받는 경우 아치 리브의 면내 좌굴 강도는 대칭 하중이 작용하는 경우 보다 저하된다. 하지만 비대칭 하중을 받는 아치 리브에 관한 연구는 대칭 하중이 작용하는 아치 리브에 관한 연구에 비하여 적은 실정이다. 비대칭 하중을 받는 아치 리브에 관한 연구는 Deutch(1940), Chang(1973)과 Harrison(1982)에 의하여 수행되었으며, 비대칭 하중이 대칭하중보다 좌굴하중을 감소시킨다는 것을 밝혔다. 그러나 이러한 연구는 포물선아치에 국한되었다. 본 논문은 원형아치 리브에 비대칭하중이 작용하는 경우 아치 리브의 면내 거동을 연구하였다. 본 연구에 의하면 기하비선형이 고려된 임계좌굴하중은 활하중과 고정하중의 길이의 비가 $0.6{\sim}0.7$일 때 가장 작고, 기하 재료비선형이 고려된 경우에는 $0.5{\sim}0.6$에서 가장 작은 결과를 보인다.