• 제목/요약/키워드: jet impingement

검색결과 215건 처리시간 0.021초

충돌수분류계(衝突水噴流系)에서 와이어 메쉬를 사용(使用)한 열전달(熱傳達) 증진(增進)에 관(關)한 연구(硏究) (A Study on the Heat Transfer Augmentation by Using Wire-mesh Impinging Water Jet)

  • 나기대
    • 설비공학논문집
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    • 제6권3호
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    • pp.291-301
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    • 1994
  • This paper presents the promotion of heat transfer through the use of wire-mesh screens. To improve heat transfer in an impingement water system, the wire-mesh screens are installed between the nozzle-to-heater surfaces. When the wire-mesh screens are not employed, this report exhibits the maximum heat transfer and the secondary maximum value at the stagnation point. But in case of using the wire-mesh screens, the transfer coefficient value of maximum heat exists at the stagnation point, and the second maximum value doesn't occur. Therefore, the heat transfer is more improved than 4~6 times that of the mean Nusselt numbers of simple water jet system, Also, within the region presented in this study, the heat transfer was promoted by using the wire-mesh screens at the stagnation point ; thus, the heat transfer was more increased than 6-7. 5 times that of simple water jet system.

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이동하는 평판에서 충돌제트의 유동 및 냉각 특성에 대한 수치적 연구 (A Numerical Study on Flow and Cooling Characteristics of Impinging Jets on a Moving Plate)

  • 전진호;서영호;손기헌
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2008년도 추계학술대회B
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    • pp.2562-2567
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    • 2008
  • Jet impingement on a moving plate, which is applicable to cooling of hot metals in a steel-making process, is investigated numerically by solving the Navier-Stokes equations in the liquid and gas phases. The liquid-gas interface or free surface is tracked by a level-set method which is improved by incorporating the ghost fluid approach based on a sharp-interface representation. The computations are made for multiple jets as well as a single jet to compare their flow characteristics. Also, the effects of the nozzle pitch, moving velocity of plate and jet velocity on the interfacial motion and the associated flow and temperature fields.

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해상용 원심펌프 임펠러의 침식억제법으로 음극방식 및 재료개발에 관한 기초연구(2) (Fundamental Study on Cathodic Protection and Material Development as Erosion-Control Methods of Oceanic Centrifugal Pump(2))

  • 이진열;임우조;오인호
    • Journal of Advanced Marine Engineering and Technology
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    • 제20권2호
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    • pp.92-92
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    • 1996
  • Recently, with the rapid development in the oceanic systems such as the oceanic structures and vessel, there occurs much interest in the impingement erosion-corrosion. In this paper, Cu-metal was tested by using of erosion apparatus with water-jet type and was investigated under the behaviour of impingement erosion-corrosion according to various environmental conditions, and the properties of Cu-metal were evaluated through the measurement by weight loss, weight loss rate, protective efficiency. The results were compared with those obtained using Cu-metal applied to cathodic protection and Cu-alloys added to Zn or Al-metal. As a basis of those results, the best protective efficiencies could be taken as using cathodic protection method and Cu-alloy with Al & Zn material addings, and will be suggested as the fundamental data of the anti-impingement erosion-corrosion on Cu-metal of impeller material for oceanic centrifugal pump.

해상용 원심펌프 임펠러의 침식억제법으로 음극방식 및 재료개발에 관한 기초연구 (2) (Fundamental Study on Cathodic Protection and Material Development as Erosion - Control Methods of Oceanic Centrifugal Pump(2))

  • 이진열;임우조;오인호
    • Journal of Advanced Marine Engineering and Technology
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    • 제20권2호
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    • pp.24-31
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    • 1996
  • Recently, with the rapid development in the oceanic systems such as the oceanic structures and vessel, there occurs much interest in the impingement erosion-corrosion. In this paper, Cu-metal was tested by using of erosion apparatus with water-jet type and was investigated under the behaviour of impingement erosion-corrosion according to various environmental conditions, and the properties of Cu-metal were evaluated through the measurement by weight loss, weight loss rate, protective efficiency. The results were compared with those obtained using Cu-metal applied to cathodic protection and Cu-alloys added to Zn or Al-metal. As a basis of those results, the best protective efficiencies could be taken as using cathodic protection method and Cu-alloy with Al & Zn material addings, and will be suggested as the fundamental data of the anti-impingement erosion-corrosion on Cu-metal of impeller material for oceanic centrifugal pump.

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충돌로 인해 분산된 2상 제트스팀의 재부착 현상과 국부 감육 상관관계 규명 및 설계개선에 관한 연구 (Design Modification and Correlation Verification between Reattachment Flow of Dispersed Jet and Local Thinning of Feedwater Heater)

  • 김형준;김경훈;황경모
    • 설비공학논문집
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    • 제21권9호
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    • pp.483-495
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    • 2009
  • Feedwater heaters of many nuclear power plants have recently experienced severe wall thinning damange, which will increase as operating time progresses. Several nuclear power plants in Korea have experienced wall thinning damage in the area around the impingement baffle-installed downstream of the high pressure turbine extraction stream line-inside number 5A and 5B feedwater heaters. At that point, the extracted steam from the high pressure turbine is two phase fluid at high temperature, high pressure, and high speed. Since it flows in reverse direction after impinging the impingement baffle, the shell wall of the number 5 high pressure feedwater heater may be affected by flow-accelerated corrosion. This paper describes operation of experience and numerical analysis composed similar condition with real high pressure feedwater heater. This study applied squared, curved and new type impingement baffle plates to feedwater heater same as previous study. In addition, it shows difference of pressure distribution and value between single phase and two phase based on experience and numerical analysis.

충돌제트의 경사각도가 파형 구조의 열유동 특성에 미치는 영향 (Oblique Angle Effect of Impinging Jet on Heat Flow Characteristics of a Corrugated Structure)

  • 황병조;김선호;주원구;조형희
    • 한국추진공학회지
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    • 제21권2호
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    • pp.83-93
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    • 2017
  • 파형 구조는 배열 충돌제트 하류에서의 횡방향 유동 영향을 줄이기 위해 충돌제트 사이의 파형 속에 사용된 냉각 공기를 유입시키며, 이러한 파형 구조에서의 유동 및 열전달 특성에 대해 수치해석을 수행하였다. 모든 계산은 3차원, 정상상태, 비압축성 유동으로 고려하였으며 ANSYS-CFX 15.0 코드를 사용하였다. 제트 홀에서 평균 Reynolds 수는 10,000이며, Spanwise 단면에서 충돌제트의 경사각도는 $70^{\circ}$, $80^{\circ}$$90^{\circ}$ 이고, Streamwise 단면에서 충돌제트의 경사각도는 $70^{\circ}$, $90^{\circ}$$110^{\circ}$ 이다. 본 연구에서는 배열 충돌제트의 경사각도가 파형 구조의 유동 및 열전달 특성에 미치는 영향에 대해 고찰하였다.

형상 및 경사 각도에 따른 난류 충돌 제트에 의한 과도 액정 기법을 이용한 열전달 특성에 대한 연구 (A Study on Heat Transfer According to Inclined Angle and Surface Performance Using Turbulent Impingement Jet with a Liquid Crystal Transient Method)

  • 임경빈;이창희;이상훈
    • 대한기계학회논문집B
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    • 제30권12호
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    • pp.1164-1172
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    • 2006
  • Measurements of the local heat transfer coefficients on hemispherical convex and concave surfaces with a turbulent impinging jet were made. The Reynolds number used was 11000, 23000, 50000 and the nozzle- to- surface distance was L/d=2, 4, 6, 8, and 10 and the jet angle was a = $0^{\circ}$, $15^{\circ}$, $30^{\circ}$ and $40^{\circ}$. In case of concave surface, the Nusselt number at the stagnation point decreases as the jet angle increases and has the maximum value for L/d=6. The X-axis Nusselt number distributions exhibit secondary maxima at $0^{\circ}$ $\leq$ a $\leq$ $15^{\circ}$, L/d $\leq$ 4 for X/d<0(upstream) and at $0^{\circ}$ $\leq$ a $\leq$ $40^{\circ}$, L/d $\leq$ 4 and at $30^{\circ}$ $\leq$ a $\leq$ $40^{\circ}$, 4 < L/d $\leq$ 6 for X/d<0(downstream). The secondary maximum occurs at long distance from the stagnation point as the jet angle increases or the nozzle-to-surface distance decreases. In case of convex, correlations of the stagnation point Nusselt number according to Reynolds number, jet-to-surface distance ratio and dimensionless surface angle are presented. In the stagnation point, in term of Ren, n ranges from 0.43 in case of 2 $\leq$ L/d $\leq$ 6 to 0.45 in case of 6 < L/d $\leq$ 10, there agrees roughly appears to be laminar boundary layer result. The maximum Nusselt number, in this experiment, occurred in the direction of upstream. The displacement of the maximum Nusselt number from the stagnation point increases with increasing surface angle or decreasing nozzle-to-surface distance. On this condition about surface curvature D/d=10, the maximum displacement is about 0.7 times of the jet nozzle diameter. The ratio of the maximum Nusselt number to the stagnation Nusselt number increases as the jet angle increases.

마이크로 유동에서 PtOEP/PS 박막을 이용한 용존 산소 농도장의 정량적 가시화 (Quantitative Visualization of Dissolved Oxygen Concentration Field in Micro Flows using PtOEP/PS Membrane)

  • 송대헌;김현동;김경천
    • 한국가시화정보학회지
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    • 제9권1호
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    • pp.36-41
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    • 2011
  • It is highly needed to measure the dissolved oxygen (DO) concentration field in water for a variety of purposes such as biological, industrial, environmental monitoring and medical application. Application of PSP (Pressure Sensitive Paint) which is sensitive to oxygen concentration has been carried out to measure DO concentration field using PtOEP/PS film and intensity based method under the UV-LEDs illumination. A micro round water jet having 100% of DO was obliquely impinged on to a PtOEP/PS film coated plate placed in a 0% of DO water container. DO concentration fields on the impinging plate were quantitatively visualized with a $2.94\;{\mu}m$ of spatial resolution. Through pixel-by-pixel calibration, uncertainty of each pixel by different sensitivity, different dye concentration and non-uniformity of illumination was removed. It is demonstrated that the high DO concentration region was coincided with the impingement area. The DO concentration gradient due to DO diffusion was affected by Reynolds number.

삼각형 멀티 탭을 이용한 충돌제트 열전달 향상 연구 (Enhancement of Impinging Jet Heat Transfer Using Triangular Multi-Tabs)

  • 이정욱;이상준
    • 대한기계학회논문집B
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    • 제28권10호
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    • pp.1139-1146
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    • 2004
  • The effect of triangular tabs attached at the perimeter of jet nozzle on heat transfer enhancement was investigated experimentally. The modified flow structure was visualized using a smoke-wire method. Four different types of jet nozzle having 0, 4, 6 and 8 tabs were tested at jet Reynolds number Re=15,000 to investigate the effect of tabs on the variation of heat transfer rate. The local and average Nusselt numbers are increased with increasing the number of tabs. At nozzle-to-plate distance of L/D=4, the average Nusselt number was increased about 9.9% at Re=15,000 in the impingement region for the case of 8 tabs attachment. As the nozzle-to-plate distance increases, however, the heat transfer enhancement effect of triangular tabs is reduced. For the case of 4 tabs, the heat transfer enhancement is not so distinctive at L/D=8. As the protrusion depth of tabs into the jet flow increases, the heat transfer rate is also enhanced when the nozzle-to-plate distance is smaller than L/D=6.