• 제목/요약/키워드: Flow Impingement

검색결과 217건 처리시간 0.022초

고온제트에 의한 금형표면 가열기법에서의 유량, 온도, 가열시간의 결정 (Determination of mass flow rate, jet temperature and heating time in mold surface heating technology using hot jet impingement)

  • 최성주;유영은;김선경
    • 한국금형공학회:학술대회논문집
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    • 한국금형공학회 2008년도 하계 학술대회
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    • pp.135-139
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    • 2008
  • Development of surface heating technology using hot jet impingement onto mold inner surface for improvement of pattern transcription. This study is focused on how to control the parameters related to hot jet impingement. The mass flow rate, the jet temperature and the duration of the impingement are major parameters. The nozzle design and other geometric configurations also affect the heat transfer to the surface. In terms of heat transfer analysis, the most important number is the heat transfer coefficient, which is influenced by the mass flow rate, nozzle design, distance between the nozzle tip and the surface. In summary, several parametric studies using the developed model are conducted to investigate the effects of mass flow rate, jet temperature and Heating Time in Surface heating technology using hot jet impingement onto mold.

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경질양극산화된 5083-H321 알루미늄 합금의 해수 내 액적충격침식부식 손상 연구 (Investigation of Liquid Droplet Impingement Erosion Corrosion based on the Flow Rate of Anodized 5083-H321 Al Alloy in Seawater)

  • 신동호;김성종
    • Corrosion Science and Technology
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    • 제19권6호
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    • pp.310-317
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    • 2020
  • This study investigated the damage to the specimen due to liquid droplet impingement erosion corrosion, which improved the corrosion resistance and durability via hard anodization of 5083-H321 aluminum alloy, which is widely used for small ships and marine structures. The experiment combined liquid droplet impingement erosion and electrochemical equipment with the flow rates in natural seawater solution. Subsequently, Tafel extrapolation of polarization curves was performed to evaluate damage due to the liquid droplet impingement erosion corrosion. The damaged surface was observed using a 3D microscope and a scanning electron microscope. The degree of pitting damage was measured using the Image J program, and the surface hardness was measured using the micro-Vickers hardness tester. The corrosion current density, area, depth, and ratio of the damaged areas increased with the increase in flow rate. The grain size of the damaged area at a flow rate of 20 m s-1 showed fewer and minor differences in height, and a smooth curved shape. The hardness of the damaged surface tended to decrease with increase in flow rate.

이차원 다중젯트의 유동 및 열전달 특성의 수치적 해석(I) -돌출열원이 없는 경우의 유동특성- (A Numerical Analysis of Flow and Beat Transfer Characteristics of a Two-Dimensional Multi-Impingement Jet(I))

  • 장대철;이기명
    • Journal of Biosystems Engineering
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    • 제20권1호
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    • pp.58-65
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    • 1995
  • A numerical study for a two dimensional multi-jet with crossflow of the spent fluid has been carried out. Three different distributions of mass-flow rate at 5 jet exits were assumed to see their effects upon the flow characteristics, especially in the jet-flow region. For each distribution, various Reynolds numbers ranging from laminar to turbulent flows were considered. Calculations drew the following items as conclusion. 1) The development of the free jets issued from downstream jets was hindered by the crossflow formed due to jets. Consequently, the free jet was developed into the channel flow without any evident symptom of impingement jet flow characteristics 2) The crossflow induced the pressure gradient along the cross section of jet exits and the value of the pressure gradient increased as going downstream. The crossflow generated also the turbulent kinetic energy as it collied with the downstream jets. 3) The skin friction coefficient along the impingement plate was affected more by the distribution of mass flow rate at jet exits rather than by the Reynolds number. The skin friction coefficient was inversely proportional to the square root of the Reynolds number, regardless of flow regime when a fully developed flow was formed in the jet flow region. 4) The distribution of the skin friction coefficient along the impingement plate was found to be controlled by adjusting the distribution of mass flow rate at jet exits.

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오목한 반구면의 Jet Impingement/Effusion Hole 주변 유동 특성에 대한 실험과 시뮬레이션의 비교 (Comparison of Experimental and Simulation Results for Flow Characteristics around Jet Impingement/Effusion Hole in Concave Hemispherical Surface)

  • 윤성지;서희림;염은섭
    • 한국가시화정보학회지
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    • 제20권2호
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    • pp.28-37
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    • 2022
  • Flow characteristics of jet impingement over concave hemispherical surface with effusion cooling holes is relatively more complex than that of a flat surface, so the experimental validation for computational fluid dynamics (CFD) results is important. In this study, experimental results were compared with simulation results obtained by assuming different turbulence models. The vortex was observed in the region between the central jets where the recirculation structure appeared. The different patterns of vorticity distributions were observed for each turbulence models due to different interaction of the injected jet flow. Among them, the transition k-kl-ω model predicted similarly not only the jet potential core region with higher velocity, but also the recirculation region between the central jets. From the validation, it may be helpful to accurately predict heat and mass transfer in jet impingement/effusion hole system.

제한면을 가지는 이차원 층류 충돌젯의 수치적 연구 (A Numerical Study of Planar Laminar Impingement Jet with a Confinement Plate)

  • 강동진;오원태
    • 대한기계학회논문집
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    • 제18권2호
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    • pp.414-423
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    • 1994
  • The planar laminar impingement jet with a confinement plate has been studied numerically. Discretzing the convection term with the QUICKER scheme, the full Navier-Stokes equations for fluid flow were solved using the well known SIMPLER algorithm. The flow characteristics with Reynolds number and jet exit velocity profile effects on it were considered for H=3, Re=200 - 2000. Results show that vortical flow forms in turn along the confinement and impingement plates as the Reynolds number increases and such a complicated flow pattern has never been reported prior. The jet exit velocity profile is shown to do an important role in determining the position of vortex flow and its size as well as in stagnation and wall jet flow region. Parabolic jet exit profile results in peak of skin friction 1.4-1.6 times greater than that of uniform profile. The channel height effects are also studied and shown to have an effect on flow pattern similar to that of Reynolds number. Also shown is that effects of the jet exit velocity profile becomes less significant over a certain channel height.

평면제트를 이용한 충돌면에서의 난류유동 특성 (Turbulent Flow Characteristics using Plane Jet on Impingement Surface)

  • 윤순현
    • Journal of Advanced Marine Engineering and Technology
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    • 제22권4호
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    • pp.429-435
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    • 1998
  • Experiments were conducted to investigate the turbulent flow characteristics from on oblique impingement surface to an plane jet at the jet Reynolds number(Re based on the nozzle width) $3{\times}10^4$ The jet mean velocity and turbulent intensity profiles have been measured along the impingement surface by hot-wire anemometer. The nozzle-to-plate distance(H/B) ranged from 2 to 10 and the oblique angle (a) from 45 to 90 degree. Also the secondary peak of the turbulent intensity was observed at H/B=4 S/B 5 and a=90 degree. It has been found that the stagnation point shifted toward the minor flow region as the oblique angle decreased and the position of the stagnation point nearly coincided with that of the maximum turbulent intensity.

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움직이는 평면으로의 충돌 제트에 대한 수치해석 (NUMERICAL ANALYSIS OF JET IMPINGING ON A MOVING PLATE)

  • 강수진;서석원;이관수
    • 한국전산유체공학회:학술대회논문집
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    • 한국전산유체공학회 2011년 춘계학술대회논문집
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    • pp.129-134
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    • 2011
  • In this paper, the confined single slot jet impingement is investigated numerically. Although the geometry of the jet impingement is simple, the flow pattern of the jet impingement is complex and the numerical results of the jet impingement is affected much by numerical methods. The first goal of this study is to analyze the effects of Reynolds models and numerical spatial discretization schemes on the results of heat transfer performance and the flaw characteristics and to select the best method. Various versions of the low Reynolds number k-epsilon turbulence models are compared. Using the selected numerical method, the flow field and heat transfer characteristics of confined single slot jet impingement on a moving plate are analyzed.

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유동가속부식으로 인한 급수가열기 동체 감육현상 규명과 완화 방안 및 충격판 설계개선에 관한 연구 (A Study on the Shell Wall Thinning by Flow Acceleration Corrosion and Mitigation Plan and Design Modification of a Feedwater Heater Impingement Baffle)

  • 김경훈;황경모;김인태
    • 한국분무공학회지
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    • 제15권2호
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    • pp.83-93
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    • 2010
  • Feedwater heaters of many nuclear power plants have recently experienced severe wall thinning damage, 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 inside feedwater heater installed downstream of the turbine extraction stream line. At that point, the extract steam from the turbine is two phase fluid at high temperature, high pressure, and high speed. Since it flows to reverse direction after impinging the impingement baffle, the shell wall of feedwater heaters may be affected by flow-accelerated corrosion. In this paper, to compare degree of shell wall thinning mitigation rate to squared type with mitigation rate of other type baffle plate, four different types of impingement baffle plate-squared, curved, mitigating type and multi-hole type-applied inside the shell. With these comparison data, this paper describes operation of experiments and numerical analysis which is composed similar condition with real feed water heater. And flow visualization is operated for verification of experiments and numerical analysis. In conclusion, this study shows that mitigating type and multi-hole type baffle plate are more effective than other baffle plate about prevention of pressure concentration and pressure value decrease.

초음속 충돌제트에 대한 수치적 연구와 응용 (Prediction of Supersonic Jet Impingement on Flat Plate and Its Application)

  • 이광섭;홍승규;박승오;배연숙
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2002년도 학술대회지
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    • pp.225-228
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    • 2002
  • Supersonic jet impingement on a flat plate has been investigated to show the flow physics for different jet heights and to demonstrate the adequacy of the characteristics-based flux-difference Wavier-Stokes code Current study also compares the steady-state solutions obtained with variable CFL number for different grid spacing with the time-accurate unsteady solutions using the inner iterations, displaying a good agreement between the two sets of numerical solutions. The unsteady nature of wall fluctuations due to bouncing of the plate shock is also uncovered for high pressure ratios. The methodology is then applied to a complex vertical launcher system where the jet plume hits the bottom wail, deflects into the plenum and eventually exits through the vertical uptake. Flow structures within vertical launcher system are captured and solutions are partially verified against the flight test data. Present jet impingement study thus shows the usefulness of CFD in designing a complex structure and predicting flow behavior within such a system.

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충돌제트에서의 횡방향 유동 감소를 위한 파형 구조의 유동 및 열전달에 관한 연구 (A Study on Fluid Flow and Heat Transfer of a Corrugated Structure for Crossflow Reduction of Impingement Jet)

  • 황병조;김선호;주원구;조형희
    • 대한기계학회논문집B
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    • 제41권5호
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    • pp.329-339
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    • 2017
  • 충돌제트는 제트가 충돌하는 정체 영역에 매우 높은 열전달을 제공하기 때문에 다양한 분야에서 적용되고 있다. 그러나 제트가 벽면에 부딪친 후 벽면 제트에 의해 야기되는 충돌 챔버 내의 횡방향 유동은 여러 개의 제트로 구성된 배열제트인 경우 하류에 있는 제트 유동을 방해하거나 휘게 할 수 있으며, 이로 인해 배열 충돌제트의 냉각 성능은 감소하게 된다. 파형 구조는 하류 제트에서의 횡방향 유동영향을 줄이기 위해 인접한 충돌 제트 사이에 있는 파형 속에 사용된 냉각 공기를 유입시키는 역할을 하며, 이러한 파형 구조에서의 유동 및 열전달 특성에 대해 수치해석을 수행하였다. 3차원, 정상상태, 비압축성 유동으로 고려하고 해석하였으며 ANSYS-CFX 15.0 코드를 사용하였다. 파형 구조의 형상 변수가 배열 충돌제트의 횡방향 유동 억제에 미치는 영향을 제시하고 분석하였다.