Abstract Slip ratio can be readily measured in an adiabatic two-phase flow experiment. However, in the flow boiling experiments, as the phase velocities keep varying, the estimation of slip ratio becomes difficult. In the absence of reliable methodology, the slip ratio for boiling flows is either taken simply as unity or deduced from void fraction experiments. It is noticed in literature that the experimental results reveal the effects of pressure and mass flux on void fraction and hence slip ratio. In the present work, numerical simulations to estimate slip ratio are carried out based on a well established wall boiling model. The computationally obtained void fraction values for subcooled boiling conditions in the vertical tube are verified with the available experimental data. The effect of operating variables, such as the tube diameter, the inlet mass flux and the degree of subcooling, on the variation of slip ratio is presented. The results show that the values of slip ratio vary along the length of the tube. A new correlation is proposed relating slip ratio with the thermodynamic quality, implicitly taking into account the effect of length and the operating conditions.

中文翻译：

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立管中过冷流动沸腾过程中滑移率的行为：CFD 方法

摘要 在绝热两相流实验中可以很容易地测量滑移率。然而，在流动沸腾实验中，随着相速度的不断变化，滑移率的估计变得困难。在缺乏可靠方法的情况下，沸腾流的滑移率要么被简单地视为统一，要么从空隙率实验中推导出来。在文献中注意到，实验结果揭示了压力和质量通量对空隙率和滑移率的影响。在目前的工作中，估计滑移率的数值模拟是基于一个完善的壁面沸腾模型进行的。垂直管中过冷沸腾条件的计算获得的空隙率值已用可用的实验数据验证。操作变量的影响，例如管径、给出了入口质量通量和过冷度对滑移率变化的影响。结果表明滑移率值随管的长度而变化。提出了一种新的相关性，将滑移率与热力学质量联系起来，隐含地考虑了长度和操作条件的影响。