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Numerical Research of Film Boiling Heat Transfer Around a Vertical Short Cylinder With Flat or Hemispherical Ends

机译:带有平面或半球形端部的垂直短圆柱体周围薄膜沸腾传热的数值研究

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摘要

Film boiling is a heat transfer mechanism that might appear in different processes, such as cryogenics, metallurgical, and nuclear reactors during abnormal operating conditions, as happens during a loss of coolant accident. In this research, film boiling around a finite vertical cylinder was studied by means of computational fluid dynamics (CFD) simulations, considering six cases that include three different levels of surface temperature and two different shapes of the cylinder ends: flat and hemispherical ends. Volume of fluid (VOF) method for the treatment of multiphase flow was used, and a user-defined function was programed to consider the exchange of mass and energy between the phases. The simulations were performed with a vertical cylinder of 32 mm in diameter and 32 or 64 mm in high for flat ends or hemispherical ends, respectively, placed in a two-dimensional axisymmetric domain of 0.125 m × 0.25 m. Results obtained for the heat flux show a periodic fluctuating behavior in time as a consequence of periodical variations in the thickness of the vapor film around the cylinder. A wavy liquid-vapor interface is observed as is reported in the experimental works. The simulations results are compared with the experimental values reported in literature as well as with values obtained from correlations. The results show that the computational code used captures reasonably well the physics involved in the film boiling, being obtained that average heat flux to the case of hemispherical ends is 15.6% higher than for the case of flat ends, versus 15.2% showing experiments and 1.6% calculated combining correlations for the individual surfaces. It shows that use of correlations in this way is not appropriate in film boiling because it does not take into account the interactions between the different surfaces.
机译:薄膜沸腾是一种传热机制,可能会在异常运行条件下(例如冷却剂损失事故期间)在不同的过程中出现,例如低温,冶金和核反应堆。在这项研究中,通过计算流体动力学(CFD)模拟研究了有限垂直圆柱周围的薄膜沸腾问题,其中考虑了六种情况,其中包括三种不同的表面温度水平和两种不同的圆柱端形状:平坦端和半球形端。使用了用于处理多相流的流体体积(VOF)方法,并对用户定义的函数进行了编程,以考虑各相之间质量和能量的交换。使用直径分别为32 mm和高32或64 mm的垂直圆柱体(分别用于扁平端或半球形端)进行仿真,该圆柱体放置在0.125 m×0.25 m的二维轴对称域中。对于热通量获得的结果表明,由于圆柱周围蒸气膜厚度的周期性变化,导致了时间上的周期性波动行为。如实验工作中所报道的,观察到波浪状的液体-蒸汽界面。将仿真结果与文献中报道的实验值以及从相关性获得的值进行比较。结果表明,所使用的计算代码可以很好地捕获膜沸腾过程中涉及的物理过程,从而得出半球形端的平均热通量比扁平端的平均热通量高出15.6%,而实验中的平均热通量为15.2%,而平端为1.6计算单个表面的组合相关性的%。它表明以这种方式使用相关性不适用于薄膜沸腾,因为它没有考虑不同表面之间的相互作用。

著录项

  • 来源
    《Journal of Heat Transfer》 |2016年第7期|074502.1-074502.7|共7页
  • 作者单位

    Mechanical Engineering Department, UNET, San Cristobal 5001, Venezuela;

    ETSII/Universidad Politecnica de Madrid, J. Gutierrez Abascal, Madrid 2-28006, Spain;

    ETSII/Universidad Politecnica de Madrid, J. Gutierrez Abascal, Madrid 2-28006, Spain;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

    vertical cylinder; film boiling; CFD; end surfaces configuration;

    机译:立式气缸薄膜沸腾;差价合约端面配置;
  • 入库时间 2022-08-18 00:22:18

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