• Title/Summary/Keyword: Angled Rib

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An Investigation of Angled Discrete Rib-Turbulators for Cooling Enhancement of Gas Turbine Blades (가스 터빈 블레이드 냉각 성능 향상을 위한 경사요철의 단락 효과)

  • Wu, Seong-Je;Lee, Sei-Young;Cho, Hyung-Hee
    • Proceedings of the KSME Conference
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    • 2001.06d
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    • pp.782-789
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    • 2001
  • Local heat/mass transfer and friction loss in a square duct roughened with various types of continuous and discrete rib turbulators are investigated. The combined effects of the gap flows of the discrete ribs and the secondary flows are examined for the purpose of the reduction of thermally weak regions and the promotion of the uniformity of heat/mass transfer distributions as well as the augmentation of average heat/mass transfer. The rib-to-rib pitch to the rib height ratio (p/e) of 8 and the rib angles of 90 and 60 deg are selected with $e/D_{h}=0.08$. The vortical structure of the secondary flows induced by the parallel angled arrays are quite distinct from that induced by the cross angled arrays. This distinction influences on heat/mass transfer and friction loss in all the tested cases. The gap flows of the discrete ribs reduce the strength of the secondary flows but promote local turbulence and flow mixing. As a result, the fairly uniform heat/mass transfer distributions are obtained with two row gaps.

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Heat/Mass Transfer Augmentation in a Square Duct . Roughened with Angled Discrete Ribs Having Narrow Gaps (정사각 덕트 내에서 열/물질전달 촉진을 위한 경사진 단락 요철의 좁은 틈새 효과)

  • Wu, Seong-Je;Lee, Sei-Young;Choi, Chung;Cho, Hyung-Hee
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.26 no.1
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    • pp.150-158
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    • 2002
  • Local heat/mass transfer and friction loss in a square duct roughened with various types of continuous and discrete rib turbulators are investigated. The combined effects of the gap flows of the discrete ribs and the secondary flows are examined for the purpose of the reduction of thermally weak regions and the promotion of the uniformity of heat/mass transfer distributions as well as the ;augmentation of average heat/mass transfer. The rib-to-rib pitch to the rib height ratio (p/e) of 8 and the rib angles of 90° and 60° are selected with e/D$\_$h/=0.08. The vortical structure of the secondary flows induced by the parallel angled arrays are quite distinct from that induced by the cross angled arrays. This distinction influences on heat/mass transfer and friction loss in all the tested cases. The gap flows of the discrete ribs reduce the strength of the secondary flows but promote local turbulence and flow mixing. Consequently, the angled discrete ribs with the small gaps provide a more uniform heat/mass transfer distribution sustaining high average heat/mass transfer.

Characteristics of Heat/Mass Transfer and Pressure Drop in a Square Duct with Compound-Angled Rib Turbulaters (복합각도 요철을 가지는 사각 덕트 내의 열전달 및 압력강하 특성)

  • Choi, Chung;Rhee, Dong Ho;Cho, Hyung Hee
    • 유체기계공업학회:학술대회논문집
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    • 2001.11a
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    • pp.325-333
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    • 2001
  • The present study investigates convective heat/mass transfer and flow characteristics inside the cooling passage of the gas-turbine blades. It is important to increase not only the heat transfer rates but also the uniformity of heat transfer in the cooling passage. The square duct has compound-angled ribs with $60^{\circ},\;70^{\circ}$ and $90^{\circ}$ attack angles, which are installed on the test plate surfaces. a 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 vertices near the side-wall. The local heat transfer and the secondary flow in the duct are changed largely according to the rib orientation. Therefore, geometry and arrangement of the ribs are important fur the advantageous cooling performance. The angled ribs increase the heat transfer discrepancy between the wall and center regions because of the interaction of the secondary flows. The average heat/mass transfer coefficient and pressure drop of the ribs with the $60^{\circ}$ $-90^{\circ}$ compound-angle are higher than those with the $60^{\circ}$ attack angle. Also, the thermal efficiency of the compound-angled rib is higher than that with the $60^{\circ}$ attack angle. The uniformity of heat/mass transfer coefficient on the cross ribs may is higher than that on the parallel ribs array.

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Shape optimization of angled ribs to enhance cooling efficiency (냉각효율 향상을 위한 경사진 리브의 형상최적설계)

  • Kim, Hong-Min;Kim, Kwang-Yong
    • 유체기계공업학회:학술대회논문집
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    • 2003.12a
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    • pp.627-630
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    • 2003
  • This work presents a numerical procedure to optimize the shape of three-dimensional channel with angled ribs mounted on one of the walls to enhance turbulent heat transfer. The response surface method is used as an optimization technique with Reynolds-averaged Navier-Stokes analysis of flow and heat transfer. SST turbulence model is used as a turbulence closure. The width-to-height ratio of the rib, rib height-to-channel height ratio, pitch-to-rib height ratio and attack angle of the rib are chosen as design variables. The objective function is defined as a linear combination of heat-transfer and friction-loss related terms with weighting factor. D-optimal experimental design method is used to determine the data points. Optimum shapes of the channel have been obtained for the weighting factors in the range from 0.0 to 1.0.

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DESIGN OPTIMIZATION AND PERFORMANCE ANALYSIS OF INTERNAL COOLING PASSAGE WITH VARIOUS TYPE OF RIB TURBULATOR FOR HIGH PRESSURE TURBINE NOZZLE (전산유체해석을 이용한 다양한 요철 형상에 대한 고압터빈 노즐 냉각유로 최적화 및 냉각 성능 비교)

  • Lee, S.A.;Rhee, D.H.;Kang, Y.S.;Yee, K.J.;Kim, K.H.
    • Journal of computational fluids engineering
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    • v.19 no.4
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    • pp.14-19
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    • 2014
  • This study conducts shape optimization of rib turbulator on the internal cooling passage that has triangular cross-section of high pressure turbine nozzle. During optimization, various types of rib turbulator including angled, V-shaped, A-shaped and angled rib with intersecting rib are considered. Each type of rib turbulator is parameterized with attack angle(s), rib height, spacing ratio and bending/intersecting location. For optimization, Design of Experiment (DOE) and Kriging surrogate model are used to utilize computational resource more efficiently and Genetic Algorithm (GA) is used to search the optimum points. As a result, Pareto front of each type of rib turbulator with friction factor that relates to pressure drop in cooling passage and spatially averaged Nusselt number that relates to heat transfer on the wall is drawn and optimum points on the Pareto front are suggested.

Heat Transfer Characteristics in a Leading Edge Cooling Channel of a Turbine Blade with Various Rib Arrangements (터빈 기익 선단부에 설치된 냉각유로에서의 요철 배열에 따른 열전달 특성)

  • Lee, Dong-Hyun;Kim, Kyung-Min;Rhee, Dong-Ho;Cho, Hyung-Hee
    • 유체기계공업학회:학술대회논문집
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    • 2005.12a
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    • pp.459-466
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    • 2005
  • The present study investigates the heat transfer characteristics of a triangular channel. Three different rib configurations are tested. The ribs are installed on two sides of the channel. The rib height (e) to channel hydraulic diameter is 0.079 and the rib-to-rib pitch (p) is 8 times of the rib height. The rotation number ranges from 0.0 to 0.1 while the Reynolds number is fixed at 10,000. The copper blocks with heaters are installed on the channel walls to measure the regionally averaged heat transfer coefficients. For the stationary $45^{\circ}$ and $135^{\circ}$ ribbed channels, a pair of counter rotating vortices is induced by the angled rib arrangements, and high heat transfer coefficients are obtained on the regions near the inner wall for the $45^{\circ}$ ribbed channel and near the leading edge for the $90^{\circ}$ ribbed channel. The heat transfer coefficients of angled ribbed channels are changed little with rotation, whereas those of the transverse ribbed channel are changed significantly with rotation.

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Optimization of Angled Ribs for Heat Transfer Enhancement in a Square Channel with Bleed Flow (유출유동을 가진 정사각유로 내 열전달 향상을 위한 경사진 요철 최적설계)

  • Lee, Hyun;Kim, Kyung-Min;Lee, Dong-Hyun;Cho, Hyung-Hee
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.32 no.4
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    • pp.300-306
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    • 2008
  • In the present study, the second order response surface method (RSM) is carried out to get optimum thermal design for enhancing heat transfer in a square channel with bleed flow. The RSM is used as an optimization technique. To calculate the heat transfer, RNG k-epsilon model and enhanced wall function are used. To design optimum rib turbulators, two design variables such as attack angle of rib $({\alpha})$ and rib pitch-to-rib height ratio (p/e) are optimized. In these analyses, the channel inlet Reynolds number was fixed at 10,000 in both non-bleeding and bleeding cases. The response surfaces of two design variables are constructed in cases with and without bleed flow. As a result, the optimum (or highest) heat transfer values are almost the same in ranges of two cases with and without bleed flow. However, the friction losses in the case with bleed flow are lower than those without bleed flow.

Optimization of Angled Ribs for Heat Transfer Enhancement in Square Channel with Bleed Flow (유출홀이 설치된 정사각유로 내 열전달 향상을 위한 경사진 요철 최적설계)

  • Lee, Hyun;Kim, Kyung-Min;Lee, Dong-Hyun;Cho, Hyung-Hee
    • Proceedings of the KSME Conference
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    • 2007.05b
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    • pp.2384-2389
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    • 2007
  • The 2nd order response surface method (RSM) has been carried out to get optimum thermal design for enhanced heat transfer on square channel with bleed holes. The RSM was used as an optimization technique with Reynolds-averaged navier-stokes equation. Turbulence model for heat transfer analysis used RNG k-epsilon model. The wall function used enhanced wall function. Numerical local heat transfer coefficients were similar to the experimental tendency. Two design variables such as attack angle of rib (${\alpha}$), rib pitch-to-rib height ratio (p/e) were chosen. Operation condition considered bleeding ratio per bleed hole ($BR_{hole}$). A response surface were constructed by the design variables and operation condition. As a result, adjusted $R^2$ was more than 0.9. Optimization results of various objective function were similar to heat transfer in channel with and without bleed flow. But friction factor was lower than channel without bleed flow.

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Heat Transfer in a Two Wall Divergent Rectangular Channel with V-Shaped Ribs on One Wall (한 벽면에 V형 리브가 있는 2면 확대 사각채널의 열전달)

  • Lee, Myung-Sung;Ahn, Soo-Whan
    • Journal of Power System Engineering
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    • v.19 no.5
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    • pp.32-37
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    • 2015
  • The present study is to investigates the convective heat transfer characteristics and pressure drop inside the rib-roughened cooling passage of gas turbine blades. The divergent rectangular channel is fabricated with V-shaped ribs on one wall only and the inlet hydraulic diameter to outlet hydraulic diameter ratio($D_{ho}/D_{hi}$) of 1.49 is used. The current investigation has covered a Reynolds number (Re) range of 22,000~75,000, relative roughness height ($e/D_h$) of 0.1~0.2, and rib angle of attack (a) of $30^{\circ}$, $45^{\circ}$, and $60^{\circ}$ for a fixed relative pitch of 10. Results show that the Nusselt numbers are the greatest in the $60^{\circ}$-angled ribs; however, the total friction factors are the highest in the $30^{\circ}$-angled ribs.

Shape Design of Heat Transfer Surfaces with Angled Ribs Using Numerical Optimization Techniques (경사진 사각리브가 부착된 열전달면의 수치최적화기법을 이용한 형상설계)

  • Kim, Hong-Min;Kim, Kwang-Yong
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.28 no.9
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    • pp.1051-1057
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    • 2004
  • A numerical optimization procedure for the shape of three-dimensional channel with angled ribs mounted on one of the walls to enhance turbulent heat transfer is presented. The response surface method is used as an optimization technique with Reynolds-averaged Wavier-Stokes analyses of flow and heat transfer. SST turbulence model is used as a turbulence closure. Computational results for local heat transfer rate show reasonable agreements with experimental data. The pitch-to-height ratio of the rib and rib height-to-channel height ratio are set to be 9.0 and 0.1, respectively, and width-to-rib height ratio and attack angle of the rib are chosen as design variables. The objective function is defined as a linear combination of heat-transfer and friction-loss related terms with weighting factor. Full-factorial experimental design method is used to determine the data points. Optimum shapes of the channel have been obtained in the range from 0.0 to 0.1 of weighting factor.