• 제목/요약/키워드: Layer transfer

검색결과 1,533건 처리시간 0.026초

Boundary layer measurements for validating CFD condensation model and analysis based on heat and mass transfer analogy in laminar flow condition

  • Shu Soma;Masahiro Ishigaki;Satoshi Abe;Yasuteru Sibamoto
    • Nuclear Engineering and Technology
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    • 제56권7호
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    • pp.2524-2533
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    • 2024
  • When analyzing containment thermal-hydraulics, computational fluid dynamics (CFD) is a powerful tool because multi-dimensional and local analysis is required for some accident scenarios. According to the previous study, neglecting steam bulk condensation in the CFD analysis leads to a significant error in boundary layer profiles. Validating the condensation model requires the experimental data near the condensing surface, however, available boundary layer data is quite limited. It is also important to confirm whether the heat and mass transfer analogy (HMTA) is still valid in the presence of bulk condensation. In this study, the boundary layer measurements on the vertical condensing surface in the presence of air were performed with the rectangular channel facility WINCS, which was designed to measure the velocity, temperature, and concentration boundary layers. We set the laminar flow condition and varied the Richardson number (1.0-23) and the steam volume fraction (0.35-0.57). The experimental results were used to validate CFD analysis and HMTA models. For the former, we implemented a bulk condensation model assuming local thermal equilibrium into the CFD code and confirmed its validity. For the latter, we validated the HMTA-based correlations, confirming that the mixed convection correlation reasonably predicted the sum of wall and bulk condensation rates.

복사가 수축 확대 노즐의 벽면에서 열전달과 벽마찰에 미치는 효과 (Effects of radiation on wall-friction and heat-transfer in a convergent- divergent nozzle)

  • 강신형;이준식;김성훈
    • 대한기계학회논문집
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    • 제14권6호
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    • pp.1639-1644
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    • 1990
  • 본 연구에서는 경계층 해석 방법의 범위 내에서 복사열전달의 영향을 고려하 는데 있어서 매질의 광학적 두끼ㅔ가 얇다고 가정하여 매질 내부에서의 자체적인 복사 열의 후ㅂ수는 무시하고, 가스의 방사 에너지가 모두 벽으로 전된다고 가정하였으며 복사 전달량은 평균광로(mean beam length)를 고려한 가스방사율을 도입하여 복사전달 량을 계산하였다.

Decal Method with High Catalyst Transfer Ratio and Its Performance in PEMFC

  • Park, Hyun-Seo;Cho, Yong-Hun;Cho, Yoon-Hwan;Sung, Yung-Eun
    • 한국신재생에너지학회:학술대회논문집
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    • 한국신재생에너지학회 2007년도 춘계학술대회
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    • pp.169-171
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    • 2007
  • A breaking layer was introduced to conventional decal transfer method in membrane electrolyte assembly fabrication for high catalyst transfer ratio. In this study, the modified decal transfer method with high catalyst transfer ratio was introduced and its performance is studied. The structural features of electrodes made by decal method were investigated using scanning electron microscopy and current-voltage polarization measurement.

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부직포내 공기함량이 열전달에 미치는 영향 (Effect of Air Content on the Heat Transfer Characteristics of Nonwoven Insulating Materials)

  • 김희숙;김은애
    • 한국의류학회지
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    • 제18권2호
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    • pp.244-251
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    • 1994
  • The purpose of this study was to analyze conductive convective and radiative heat transfer characteristic of the nonwovens were studied by measuring thermal conductance at atmospheric and low air pressure. The results obtained were as follows . 1) As thickness of air layer Increased, overall heat transfer was decreased by reducing conductive and radiative heat trasfer. 2) The conductive and convective heat trasfer by air were in the range of 79~8971 of overall heat transfer. 3) As thickness of nonwoven increased for a given solidity, overall heat trasfer was decresed by increasing total thickness of air layer and by reducing conductive and radiative heat transfer. 4) For a given weight, increasing thickness is more effective than increasing solidity.

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The Onset of Natural Convection and Heat Transfer Correlation in Horizontal Fluid Layer Heated Uniformly from Below

  • Kim, Min-Chan;Kim, Sin
    • Journal of Mechanical Science and Technology
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    • 제15권10호
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    • pp.1451-1460
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    • 2001
  • The critical condition of the onset of buoyancy-driven convective motion of uniformly heated horizontal fluid layer was analysed by the propagation theory which transforms the disturbance quantities similarly. The dimensionless critical time, $\tau$$\sub$c/, is obtained as a function of the Rayleigh number and the Prandtl number. Based on the stability criteria and the boundary-layer instability model, a new heat transfer correlation which can cover whole range of Rayleigh number was derived. Our theoretical results predict the experimental results quite reasonably.

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수정된 화학증착과정에서 토치이송과 고체층이 열전달과 입자부착에 미치는 영향 (Effect of Torch Speed and Solid Layer Thickness on Heat Transfer and Particle Deposition During modified Chemical Vapor Deposition Process)

  • 박경순;최만수
    • 대한기계학회논문집
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    • 제18권5호
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    • pp.1301-1309
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    • 1994
  • A study of heat transfer and thermophoretic particle deposition has been carried out for the Modified Chemical Vapor Deposition(MCVD) process. A new concept utilizing two torches is suggested to simulate the heating effects from repeated traversing torches. Calculation results for the wall temperatures and deposition efficiency are in good agreement with experimental data. The effects of variable properties are included and heat flux boundary condition is used to simulate the moving torch heating. A conjugate heat transfer which includes heat conduction through solid layer and heat teansfer in a gas in a tube is analyzed. Of particular interests are the effects of torch speeds and solid layer thicknesses on the deposition efficiency, rate and the tapered entry length.

다공성 흡음재가 조합된 다중 다공판 시스템의 흡음성능에 관한 연구 (A Study on the Sound Absorption of Multiple Layer Perforated Plate Systems Combined with Porous Absorbing Materials)

  • 허성욱;김욱;이동훈;권영필
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 2002년도 추계학술대회논문집
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    • pp.896-901
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    • 2002
  • The sound absorption coefficients for multiple layer perforated plate systems containing several compartments with airspaces and porous absorbing materials are estimated using the transfer matrix method developed in the previous paper. The absorption coefficients from transfer matrix method agree well with the values measured by the two-microphone impedance tube method for various combinations of perforated plates, airspaces or porous materials. Based on these results, a guidance for the design of multiple layer perforated plate systems combined with airspaces and porous absorbing materials is discussed in detail.

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착상시 핀-관 열교환기의 열적 성능 예측을 위한 해석 (An Analysis for Predicting the Thermal Performance of Fin-Tube Heat Exchanger under Frosting Condition)

  • 이태희;이관수;김우승
    • 설비공학논문집
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    • 제8권2호
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    • pp.299-306
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    • 1996
  • This work presents an analytical model, so called modified LMTD method, to predict the thermal performance of finned-tube heat exchanger under frosting conditions. In this model, the total heat transfer coefficient and effective thermal conductivity of the frost layer were defined as a function of frost surface temperature. The surface temperature of the frost layer formed on the heat exchanger was calculated through the analysis of the heat and mass transfer process in the air and frost layer. To examine the validity of this analytical model, the computed results from the present model, such as heat transfer rate, frost mass and thickness of frost, were compared with the ones of the expermental work and LMED method.

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모세관 모델에 의한 다공층내의 증발 열전달 해석 (Analysis of Evaporative Heat Transfer in a Porous Layer by Capillary Model)

  • 김홍제;이진호
    • 대한기계학회논문집
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    • 제16권2호
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    • pp.391-399
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    • 1992
  • The analysis of the evaporative heat transfer in the inclined porous layer (0.deg.<.theta.<90.deg.) is made by using capillary model. The length of the evaporation zone is obtained numerically by integrating the differential equation using a Runge-Kutta algorithm. As a result, the length of the evaporation zone is inverse proportional to the dimensionless number, E(=Re*.phi./cos.theta.) representing the evaporation intensity, and the relationship of these parameters shows linear in the log graph.

Boundary layer analysis of persistent moving horizontal needle in Blasius and Sakiadis magnetohydrodynamic radiative nanofluid flows

  • Krishna, Penem Mohan;Sharma, Ram Prakash;Sandeep, Naramgari
    • Nuclear Engineering and Technology
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    • 제49권8호
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    • pp.1654-1659
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    • 2017
  • The boundary layer of a two-dimensional forced convective flow along a persistent moving horizontal needle in an electrically conducting magnetohydrodynamic dissipative nanofluid was numerically investigated. The energy equation was constructed with Joule heating, viscous dissipation, uneven heat source/sink, and thermal radiation effects. We analyzed the boundary layer behavior of a continuously moving needle in Blasius (moving fluid) and Sakiadis (quiescent fluid) flows. We considered Cu nanoparticles embedded in methanol. The reduced system of governing Partial differential equations (PDEs) was solved by employing the Runge-Kutta-based shooting process. Computational outcomes of the rate of heat transfer and friction factors were tabulated and discussed. Velocity and temperature descriptions were examined with the assistance of graphical illustrations. Increasing the needle size did not have a significant influence on the Blasius flow. The heat transfer rate in the Sakiadis flow was high compared with that in the Blasius flow.