• Title/Summary/Keyword: Angled Rib

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Effects of Rib Angles on Heat Transfer in a Divergent Square Channel With Ribs on One Wall (한 면에 리브가 설치된 확대 정사각 채널에서 리브 각이 열전달에 미치는 효과)

  • Lee, Myung Sung;Ahn, Soo Whan
    • Journal of Advanced Marine Engineering and Technology
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    • v.39 no.6
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    • pp.609-613
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    • 2015
  • In this study, the experiments are performed to investigate the local heat transfer and pressure drops of developed turbulent flows in the diverging square channels along the axial distance. The square divergent channels are manufactured with a fixed rib height (e) = 10 mm. Four different parallel angled ribs ($a=30^{\circ}$, $45^{\circ}$, $60^{\circ}$, and $90^{\circ}$) are placed on the channel's one-sided wall only. TThe measurement are conducted within the range of Reynolds numbers from 22,000 to 79,000. The results show that a rib angle-of-attack of $45^{\circ}$ produces the best heat-transfer performance.

Effects of Rib Angles on Heat Transfer in a Square Convergent Channel with Ribs on One Wall (한면에 리브가 설치된 4면 수축 사각채널에서 리브의 각도가 열전달에 미치는 영향)

  • Lee, Myung-Sung;Kim, Beom-Soo;Ahn, Soo-Whan
    • Journal of Power System Engineering
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    • v.20 no.1
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    • pp.69-74
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    • 2016
  • The local heat transfer and pressure drops of developed turbulent flows in the convergent channels with square cross-sectional areas along the streamwise distance have been investigated experimentally. Four different parallel angled ribs (a = $30^{\circ}$, $45^{\circ}$, $60^{\circ}$, and $90^{\circ}$) are placed to the one sided wall only, respectively. The ribbed walls are manufactured with a fixed rib height (e)=10 mm and the ratio of rib spacing (p) to height (e) = 10. The measurement was run within the range of Reynolds numbers from 22,000 to 79,000. The result shows that the increases in the Nusselt numbers for the flow attack angles can be seen in the order of $30^{\circ}$, $45^{\circ}$, $60^{\circ}$ and $90^{\circ}$.

Rib-Dimple Compound Cooling Techniques in a Gas Turbine Blade Cooling Channels with an Aspect ratio (4:1) (4:1 종횡비를 갖는 가스터빈 블레이드 냉각 유로에서의 립-딤플 복합 냉각 특성 연구)

  • Choi, Yong-Duck;Kim, Seok-Beom;Lee, Yong-Jin;Kim, Jin-Kon;Kwak, Jae-Su
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2010.05a
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    • pp.304-310
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    • 2010
  • Heat transfer coefficients in a dimpled channel, a ribbed channel, and a rip-dimple compound channel were measured by the transient liquid crystal technique. The channel aspect ratio, the rib height, the rip pitch, and the rib angle were 4:1, 6 mm, 60 mm and $60^{\circ}$, respectively. The dimple diameter and the center-to-center distance were 6mm and 7.2 mm, respectively, and the Reynolds number range was 30,000-50,000. Results showed that the heat transfer coefficients were increased by the angled rib. For the dimple-rib compound cooling cases, the heat transfer coefficients were further augmented and the thermal performance factor for the case was the highest.

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Rib-Dimple Compound Cooling Techniques in a Gas Turbine Blade Cooling Channels with an Aspect ratio (4:1) (4:1 종횡비를 갖는 가스터빈 블레이드 냉각 유로에서의 립-딤플 복합 냉각 특성 연구)

  • Choi, Yong-Duck;Kim, Seok-Beom;Lee, Yong-Jin;Kim, Jin-Kon;Kwak, Jae-Su
    • Journal of the Korean Society of Propulsion Engineers
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    • v.14 no.4
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    • pp.32-38
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    • 2010
  • Heat transfer coefficients in a dimpled channel, a ribbed channel, and a rip-dimple compound channel were measured by the transient liquid crystal technique. The channel aspect ratio, the rib height, the rip pitch, and the rib angle were 4:1, 6 mm, 60 mm and $60^{\circ}$, respectively. The dimple diameter and the center-to-center distance were 6mm and 7.2 mm, respectively, and the Reynolds number range was 30,000-50,000. Results showed that the heat transfer coefficients were increased by the angled rib. For the dimple-rib compound cooling cases, the heat transfer coefficients were further augmented and the thermal performance factor for the case was the highest.

Heat Transfer in Rotating Duct with $70^{\circ}$ Angled Ribs (회전하는 덕트내 설치된 $70^{\circ}$ 경사요철의 열전달 특성)

  • Choi, Chung;Lee, Sei Young;Won, Jung Ho;Cho, Hyung Hee;Park, Byung kyu
    • The KSFM Journal of Fluid Machinery
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    • v.4 no.3 s.12
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    • pp.7-13
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    • 2001
  • The present study investigates convective heat/mass transfer and flow characteristics inside a cooling passage of rotating gas-turbine blades. The rotating duct has staggered ribs with $70^{\circ}$ attack angle, which are attached on leading and trailing surfaces. Naphthalene sublimation technique is employed to determine detailed local heat transfer coefficients using the heat and mass transfer analogy. Additional numerical calculations are conducted to analyze the flow patterns in the cooling passage. The present experiments employ two-surface heating conditions in the rotating duct because the exposed surfaces to hot gas stream are pressure and suction side surfaces in the middle passages of an actual gas-turbine blade. Secondary flows are generated by Coriolis and centrifugal forces in the spanwise and streamwise directions. The ribs attached on the walls disturb the mainflow resulting in recirculation and secondary flows near the ribbed wall. The local heat transfer and flow patterns in the passage are changed significantly according to rib configurations and duct rotation speeds. Therefore, the geometry and arrangement of the ribs are important for the advantageous cooling performance. The experimental results show that the ribs enhance the heat transfer more than $70\%$ from that of the smooth duct. The duct rotation generates the heat transfer discrepancy between the leading and trailing walls due to the secondary flows induced by the Coriolis force. The overal heat transfer pattern on the leading and trailing walls for the first and second passes are depended on the rotating speed, but the local heat transfer trend is affected mainly by the rib arrangements.

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Enhanced heat transfer in the convergent rectangular channels with ∧/∨-shaped ribs on one wall (한 면에 ∧/∨형 리브가 있는 2벽면 수축 사각채널의 열전달 증가)

  • Lee, Myung-Sung;Yu, Ji-Ui;Jeong, Hee-Jae;Choi, Dong-Geun;Ha, Dong-Jun;Go, Jin-Su;Ahn, Soo-Whan
    • Journal of Advanced Marine Engineering and Technology
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    • v.40 no.4
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    • pp.270-274
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    • 2016
  • The effect of the rib angle-of-attack on heat transfer in the convergent channel with ${\vee}/{\wedge}$-shaped ribs was examined experimentally. Four differently angled ribs (a = $30^{\circ}$, $45^{\circ}$, $60^{\circ}$, and $90^{\circ}$) were placed to only the one sided wall. The ribbed wall was manufactured with a fixed rib height (e) of 10 mm and rib spacing (p)-to-height (e) ratio of 10. The convergent channel had a length of 1,000 mm and a cross-sectional areas of $100mm{\times}100mm$ at inlet and $50mm{\times}100mm$ at exit. The measurement was conducted for the Reynolds numbers ranging from 22,000 to 75,000. The results show that the Nusselt number is generally higher at higher Reynolds number and that an angle-of-attack of $45^{\circ}$ at the ${\wedge}$-shaped rib produces the greatest Nusselt number.

Heat Transfer and Total Friction Factors in the Convergent Channels with V/⋀-shaped Ribs on Two Opposite Walls (양 벽면에 V/⋀형 리브가 있는 수축 채널의 열전달과 전 마찰계수)

  • Lee, Myung-Sung;Heo, Meo-Seong;Jeong, Ui-Jae;Park, Young-Joon;Yoo, Jung-Hyun;Im, Gun-Woo;Ahn, Soo-Whan
    • Journal of Power System Engineering
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    • v.20 no.5
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    • pp.66-71
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    • 2016
  • The measurements of heat transfer and total friction factors for turbulent flows in the convergent rectangular channels with two opposite in-line ribbed walls are reported. The study has covered three different angled ribs ($30^{\circ}$, $45^{\circ}$ and $60^{\circ}$) and Reynolds number in the range of 22,000 to 75,000. The channel, composing of ten isolated copper sections in the length of test section of 1 m, has the channel convergence ratio of $D_{ho}/D_{hi}=0.67$. The results show that the ribs pointing downstream (${\wedge}-shaped$) is somewhat greater than the ribs pointing upstream (V-shaped) in the dimensionless Nusselt number and total friction factors.

Optimization of target, moderator, and collimator in the accelerator-based boron neutron capture therapy system: A Monte Carlo study

  • Cheon, Bo-Wi;Yoo, Dohyeon;Park, Hyojun;Lee, Hyun Cheol;Shin, Wook-Geun;Choi, Hyun Joon;Hong, Bong Hwan;Chung, Heejun;Min, Chul Hee
    • Nuclear Engineering and Technology
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    • v.53 no.6
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    • pp.1970-1978
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    • 2021
  • The aim of this study was to optimize the target, moderator, and collimator (TMC) in a neutron beam generator for the accelerator-based BNCT (A-BNCT) system. The optimization employed the Monte Carlo Neutron and Photon (MCNP) simulation. The optimal geometry for the target was decided as the one with the highest neutron flux among nominates, which were called as angled, rib, and tube in this study. The moderator was optimized in terms of consisting material to produce appropriate neutron energy distribution for the treatment. The optimization of the collimator, which wrapped around the target, was carried out by deciding the material to effectively prevent the leakage radiations. As results, characteristic of the neutron beam from the optimized TMC was compared to the recommendation by the International Atomic Energy Agent (IAEA). The tube type target showed the highest neutron flux among nominates. The optimal material for the moderator and collimator were combination of Fluental (Al203+AlF3) with 60Ni filter and lead, respectively. The optimized TMC satisfied the IAEA recommendations such as the minimum production rate of epithermal neutrons from thermal neutrons: that was 2.5 times higher. The results can be used as source terms for shielding designs of treatment rooms.