• Title/Summary/Keyword: Jet impingement heat transfer

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Round Jet Impingement Heat Transfer on a Pedestal Encountered in Chip Cooling (원형 충돌제트를 이용한 Pedestal 형상의 핀이 부착된 Chip 냉각)

  • Chung, Young-Suk;Chung, Seung-Hoon;Lee, Dae-Hee;Lee, Joon-Sik
    • Proceedings of the KSME Conference
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    • 2001.06d
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    • pp.546-552
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    • 2001
  • The heat transfer and flow measurements on a pedestal encountered in chip cooling. A uniform wall temperature boundary condition at the plate surface and on a pedestal was created using shroud method. Liquid crystal was used to measure the plate surface temperature. The jet Reynolds number (Re) ranges from 11,000 to 50,000, the dimensionless nozzle-to-surface distance (L/d) from 2 to 10, and the dimensionless pedestal diameter-to-height (H/D) from 0 to 1.0. The results show that the Nusselt number distributions at the near the pedestal exhibit secondary maxima at $r/d{\cong}1.0\;and\;1.5$. The formation of the secondary maxima is attributed to an create in the vortex by the pedestal.

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A study on the boiling heat flux on high temperature surface by impinging water jet (衝突水噴流에 의한 高溫面의 沸騰熱流束에 관한 硏究)

  • Lee, Ki-Woo;Kim, Yoo
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.12 no.1
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    • pp.81-94
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    • 1988
  • A series of experiments was performed in this study to investigate the boiling heat flux between an impinging water jet and a hot surface. Test variables were surface roughness, jet velocity, saturation temperature excess of surface, nozzle diameter and the gap distance between nozzle plate and the hot surface. In order to make the impinged cooling water a forced flow streaming a long the hot surface immediately after the initial impingement, the flat nozzle tip was extended to a circular flat plate having the same diameter as the hot surface. Utilizing the dimensionless parameter study on continuity, momentum and energy equations, 5 groups of variables involved in the nucleate boiling heat transfer were derived so that it is possible to estimate the increased heat flux by impinging water jet in a similar experimental work. For the case of saturated water being impinging onto a high temperature surface, an applicable correlation among dimensionless parameters describing the heat flux was found to be as follow.

Comparison of Unconfined and Confined Micro-scale Impinging Jets

  • Choo, Kyo-Sung;Youn, Young-Jik;Kim, Sung-Jin
    • Proceedings of the KSME Conference
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    • 2008.11b
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    • pp.2210-2213
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    • 2008
  • In the present study, effects of degree of confinement on heat transfer characteristics of a micro-scale slot jet impinging on a heated flat plate are experimentally investigated. The effects of Reynolds numbers (Re = $1000{\sim}5000$), lateral distances (x/B = $1{\sim}10$), nozzle-to-plate spacings (Z/B = $1{\sim}20$), and degree of confinement ($B_c$/B = 3, 48) on the Nusselt number are considered. The results show that the effects of the degree of confinement on the cooling performance of the micro-scale impinging slot jet are significant at lower nozzle-to-plate spacings and higher Reynolds numbers. In addition, it is shown that the cooling performance of the micro-scale unconfined slot impinging jet is 200% higher than that of the micro-scale confined slot impinging jet.

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The Characteristics of Heat Transfer in a Channel with Wire-screen Baffles (와이어 스크린 배플이 설치된 채널에서의 열전달 특성)

  • Kim, W.C.;Ary, B.K.;Ahn, S.W.;Kang, H.K.
    • Journal of Power System Engineering
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    • v.13 no.2
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    • pp.11-17
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    • 2009
  • The heat transfer characteristics of flow through two inclined wire-mesh baffles in a rectangular channel were investigated experimentally with varying the mesh number of wire screens and inclination angle of the baffles. Two different types of wire meshes such as dutch and plain weaves, were used in this experiment. Three kinds of baffle plates with different mesh specifications in the dutch weave and four different kinds in the plain weave were manufactured. Baffles were mounted on bottom wall with varied angles of inclination. Reynolds number was varied from 23,000 to 57,000. It is found that the placement of inclined wire-mesh baffles in the channel affects the heat transfer characteristics by combining both jet impingement and flow disturbance. The wire screen modified the flow structure leading to a change in the heat transfer characteristics. The results show that the baffle plate with the most number of mesh (type SA) has the highest heat transfer rate.

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Jet Impingement Heat Transfer on a Cylindrical Pedestal Encountered in Chip Cooling (충돌제트를 이용한 Pedestal 형상의 칩 냉각연구)

  • Lee, Dae-Hee;Lee, Joon-Sik;Chung, Young-Suk;Chung, Seung-Hoon
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.27 no.1
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    • pp.1-8
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    • 2003
  • The heat transfer and flow measurements on a cylindrical pedestal mounted on a flat surface with a turbulent impinging jet were made. The experiments were made for the jet Reynolds number of Re = 23,000, the dimensionless nozzle-to-surface distance of L/d = 2~10, the dimensionless pedestal height of H/D = 0~1.5. Measurements of the surface temperature and the Nusselt number distributions on the plate surface were made using liquid crystal and shroud-transient technique. Flow measurements involve smoke flow visualization and the wall pressure coefficient. The results show that the wall pressure coefficient sharply decreases along the upper surface of the pedestal. However, the pressure increases when the fluid escapes from the pedestal and then collides on the plate surface. The secondary maxima in the Nusselt numbers occur in the region of 1.0 $\leq$ r/d $\leq$ 1.9. Their values for the case of H/D = 0.5 are maximum 80% higher than those for other cases. The formation of the secondary maxima may be attributed to the reattachment of flow on the plate surface which was separated at the edge of the pedestal.

Study on the Drying Characteristics of Band Dryer using Impingement Jet Stream (충돌제트기류를 이용한 밴드건조기의 건조특성에 관한 연구)

  • Kim, S.I.;Lee, W.H.;Chun, W.P.;Lee, K.W.;Lee, K.J.
    • Proceedings of the KSME Conference
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    • 2007.05b
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    • pp.1931-1936
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    • 2007
  • The application of high velocity air jets to heat transfer surface has tremendous engineering potential in various industries. The impinging jets are therefore widely used for their enhanced transport characteristics, especially for drying of continuous materials such as sheet, film, carpets, forming materials and pallets. This paper presents the drying characteristics of plate type material and performs the test with the change of operating conditions in conveyer band dryer using the impinging jet nozzles. The factors influencing drying rate were confirmed, also the design data of band dryer using the impinging jet was obtained.

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Cooling of a Rotating Heated Flat Plate by Water Jet Impingement (회전전열평판(回轉傳熱平板)의 충돌수분류(衝突水噴流)에 의한 냉각(冷却))

  • Jeon, Sung-Taek;Kim, Yeun-Young;Lee, Jong-Su;Park, Jong-Suen;Lee, Doug-Bong
    • Solar Energy
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    • v.15 no.2
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    • pp.47-64
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    • 1995
  • An experimental investigation is carried out to see the local heat transfer characteristics of a rotating heated flat plate surface with constant heat flux when a normal water jet is impinging on this surface. The effects of jet Reynolds number, rotating Reynolds number are investigated while the distance between the nozzle and the flat plate is set fixed. As a result, correlations to relate the local Nusselt number to the local rotational Reynolds number, jet Prandtl number and the dimensionless radial position are presented.

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Effects of Baffles on Heat Transfer and Friction Factors in a Rectangular Channel (사각채널에 설치된 배플이 열전달과 마찰계수에 미치는 효과)

  • Ahn, Soo-Whan;Kang, Ho-Keun;Bae, Sung-Taek;Song, Min-Ho
    • Journal of Advanced Marine Engineering and Technology
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    • v.30 no.6
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    • pp.693-701
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    • 2006
  • The present work investigates the local heat transfer characteristics and the associated frictional loss in a rectangular channel with inclined solid and perforated baffles to obtain the basic design data for gas turbine. Five different geometries of baffles such as 1) solid (without hole), 2) three holes, 3) six holes, 4) nine holes, 5) twelve holes were covered. A combination of two baffles of same overall size is used. The flow Reynolds number is ranged from 28,900 to 70,100. The placement of baffles augments the overall heat transfer greatly by combining both jet impingement and the boundary layer separation. The present results show that the average Nusselt number distribution is strongly dependent on number of holes in the baffle plates, i.e., the average Nusselt number increases with increasing number of holes. The friction factor decreases also with increasing the number of holes. however. its value increases with increasing the Reynolds number.

Conjugate Heat Transfer Analysis for High Pressure Cooled Turbine Vane in Aircraft Gas Turbine (항공기용 가스터빈의 고압 냉각터빈 노즐에 대한 복합열전달 해석)

  • Kim, Jinuk;Bak, Jeonggyu;Kang, Young-Seok;Cho, Jinsoo
    • The KSFM Journal of Fluid Machinery
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    • v.18 no.2
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    • pp.60-66
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    • 2015
  • Conjugate heat transfer analysis was performed to investigate the flow and cooling performance of the high pressure turbine nozzle of gas turbine engine. The CHT code was verified by comparison between CFD results and experimental results of C3X vane. The combination of k-${\omega}$ based SST turbulence model and transition model was used to solve the flow and thermal field of the fluid zone and the material property of CMSX-4 was applied to the solid zone. The turbine nozzle has two internal cooling channels and each channel has a complex cooling configurations, such as the film cooling, jet impingement, pedestal and rib turbulator. The parabolic temperature profile was given to the inlet condition of the nozzle to simulate the combustor exit condition. The flow characteristics were analyzed by comparing with uncooled nozzle vane. The Mach number around the vane increased due to the increase of coolant mass flow flowed in the main flow passage. The maximum cooling effectiveness (91 %) at the vane surface is located in the middle of pressure side which is effected by the film cooling and the rib turbulrator. The region of the minimum cooling effectiveness (44.8 %) was positioned at the leading edge. And the results show that the TBC layer increases the average cooling effectiveness up to 18 %.