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首页> 外文期刊>International Journal of Heat and Mass Transfer >Turbulent convective heat transfer of CO_2 in a helical tube at near-critical pressure
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Turbulent convective heat transfer of CO_2 in a helical tube at near-critical pressure

机译：临界压力下螺旋管中CO_2的湍流对流换热

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摘要

Experiments of carbon dioxide flowing in a helical pipe at near-critical pressure were performed at constant heat flux boundary condition. The helical curvature diameter, helical pitch and tube diameter were 283.0 mm, 32.0 mm and 9.0 mm, respectively. The inlet Reynolds number was larger than 10~4 to ensure the turbulent flow. The renormalization group RNG k-ε model simulated the three-dimensional turbulent heat transfer of CO_2 in the helical pipe. Much attention was paid to the combined effects of the centrifugal force and buoyancy force on the heat transfer. The RNG k-ε model reasonably simulates the complicated heat transfer. The wall temperatures near the tube exit were slightly over-predicted, due to the suppression of the increased wall temperatures near the tube exit by axial thermal conduction in the experiment. Before and near the pseudocritical temperature region, the varied physical properties caused significantly non-uniform velocity and temperature distributions over the tube cross section. The larger axial velocities appear at the outer-bottom location, and the higher wall temperatures appear at the inner-top location. Thus, the outer-bottom locations hold larger heat transfer coefficients. The turbulent kinetic energies are increased along the axial angles and larger in the inner-top region of the tube cross section. The effective viscosities are decreased along the axial angles, and the larger effective viscosities are shifted to the tube center with the axial flow development. Beyond the pseudocritical temperature region, the decreased buoyancy force suppressed the non-uniformity of the heat transfer coefficients over the tube circumference.
机译：在恒定热通量边界条件下进行了在接近临界压力的条件下在螺旋管中流动的二氧化碳的实验。螺旋曲率直径，螺旋节距和管直径分别为283.0mm，32.0mm和9.0mm。进口雷诺数大于10〜4，以确保湍流。重归一化组RNGk-ε模型模拟了螺旋管中CO_2的三维湍流传热。离心力和浮力对传热的综合影响引起了很多关注。 RNGk-ε模型合理地模拟了复杂的传热。由于在实验中通过轴向热传导抑制了管出口附近壁温度的升高，因此管出口附近的壁温度略有过高的预测。在伪临界温度区域之前和附近，变化的物理特性会导致整个管横截面上的速度和温度分布明显不均匀。更大的轴向速度出现在外底位置，而更高的壁温出现在内顶位置。因此，底部外位置保持较大的传热系数。湍动能沿轴向角增加，并且在管横截面的内顶部区域更大。有效粘度沿轴向角度减小，并且随着轴向流动的发展，较大的有效粘度移至管中心。超出伪临界温度区域，减小的浮力抑制了管圆周上传热系数的不均匀性。

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  • 来源
  • 作者

    Jinliang Xu; Chuanyong Yang; Wei Zhang; Dongliang Sun;

  • 作者单位

    The Beijing Key Laboratory of Multiphase Flow and Heat Transfer, North China Electric Power University, Beijing 102206, PR China;

    Electric Power Department, Beijing Zhongan Quality Assessment Center, Central Technology, Beijing 100022, PR China;

    The Beijing Key Laboratory of Multiphase Flow and Heat Transfer, North China Electric Power University, Beijing 102206, PR China;

    The Beijing Key Laboratory of Multiphase Flow and Heat Transfer, North China Electric Power University, Beijing 102206, PR China;

  • 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

    Helical tube; Centrifugal force; Buoyancy force; Heat transfer coefficient;

    机译：螺旋管离心力浮力;传热系数;

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