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On the effects of centrifugal forces in air-water two-phase flow regime transitions in an adiabatic helical geometry.

机译：在空气-水两相流状态下的绝热螺旋几何形状中，离心力的影响。

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摘要

Two-phase flow in helical conduits is important in many industries where reaction between components, heat transfer, and mass transport are utilized as processes. The helical design is chosen for the effects of secondary flow patterns that reduce axial dispersion, increased heat transfer, and also their compact design. The first is a result of the secondary flow, which continually transports fluid from the near wall region to the bulk of the flow. In single-phase chemical reactor design this secondary flow increases radial mixing and reduces axial dispersion. In heat exchanger design it increases laminar heat transfer while extending the Reynolds number range of laminar flow.;A literature review of the work on helical pipe flow shows that the vast majority of the work is on toroidal single-phase flow, and analyses of two-phase flow are sparse. This dissertation addresses this void by presenting an analytical model of the stratified and annular flow regime transitions in helical conduits, by consideration of the governing equations and mechanisms for transition in the toroidal geometry including the major impact of pitch. Studies have taken a similar approach for straight inclined horizontal and vertical geometries, but none have been found which resolve two-phase flow in the curved geometry of a helix. The main issue in resolving the flow in this geometry is that of determining appropriate inter-phase momentum transfer, and the appropriate friction correlations for wall interaction. These issues are resolved to yield a novel attempt at modeling helical two-phase flow. Pitch is considered negligible in introduction of torsion, while the dominating influence of the centrifugal force is retained. The formulation of the governing equations are taken from a general vector form that is readily extended to a true helix that includes torsion. The predictive capability of the current model is compared to the data and observations of the two-phase helical flow studies available in the open literature. The new model is found to be accurate in the linear asymptote, and to correctly predict the trends of increased liquid hold-up, a shift in the transition boundary between non-stratified and stratified flows such that the non-stratified regimes are favored, and the new liquid equilibrium height calculations shift the transition between annular and intermittent flows such that the intermittent regime is favored. The current model is an improvement over the previous methods in that it has the same accuracy of prediction of linear flowing inclined flows as methods developed for the linear flow condition, and improves the prediction of curved flow regimes by correctly shifting the boundaries as described above.
机译：在许多行业中，螺旋管道中的两相流非常重要，在这些行业中，组件之间的反应，传热和传质被用作过程。选择螺旋设计是为了减小二次流动模式的影响，这些模式会减少轴向扩散，增加热量传递以及紧凑的设计。第一个是二次流的结果，二次流不断地将流体从近壁区域传输到大部分流中。在单相化学反应器设计中，该二次流增加了径向混合并减小了轴向分散。在换热器设计中，它增加了层流传热，同时扩展了层流的雷诺数范围。；对螺旋管流的工作进行的文献综述表明，绝大多数工作是在环形单相流上进行的，并分析了两者相流稀疏。本文通过介绍螺旋管道中分层和环形流动状态转变的分析模型，并考虑了包括螺距的主要影响在内的环形几何形状的控制方程和转变机理，从而解决了这一空白。对于直线倾斜的水平和垂直几何形状，已经采取了类似的方法，但是没有发现能够解决螺旋弯曲几何形状中的两相流的方法。解决这种几何形状中的流动的主要问题是确定合适的相间动量传递以及合适的壁相互作用的摩擦相关性。解决了这些问题，从而产生了对螺旋两相流建模的新颖尝试。在引入扭转时，螺距可以忽略不计，而离心力的主要影响却得以保留。控制方程的公式取自易于扩展为包含扭转的真实螺旋线的一般矢量形式。将当前模型的预测能力与公开文献中提供的两相螺旋流研究的数据和观察结果进行比较。发现该新模型在线性渐近线中是准确的，并且能够正确预测液体滞留量增加的趋势，非分层流和分层流之间的过渡边界发生变化，从而有利于非分层流态，并且新的液体平衡高度计算可移动环形流和间歇流之间的过渡，从而有利于间歇状态。当前模型是对先前方法的改进，因为它具有与针对线性流动条件开发的方法相同的线性流动倾斜流预测精度，并且通过如上所述正确地移动边界来改善了弯曲流动状态的预测。

著录项

  • 作者

    Young, Eric Paul.;

  • 作者单位

    Oregon State University.;

  • 授予单位 Oregon State University.;
  • 学科 Engineering Nuclear.
  • 学位 Ph.D.
  • 年度 2006
  • 页码 158 p.
  • 总页数 158
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 原子能技术;
  • 关键词

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