Void drift between subchannels in a rod bundle is a crucial phenomenon affecting the calculation accuracy of thermal-hydraulic parameters in SMRs. It holds significant importance in enhancing the precision of safety analysis for SMRs. Existing research on experiment and model of void drift between rod bundle subchannels is relatively rare, and the accuracy of model calculations requires improvement. In this study, experiments on gas-liquid two-phase non-equilibrium flow were conducted to measure the redistribution of two-phase flow induced by void drift in a 1 × 2 rod bundle. The experiment results indicated that in bubby flow regime with void fraction less than 0.3, the void diffusion coefficient showed little variation with changes in void fraction. However, in slug flow and annular flow regimes with void fraction exceeding 0.3, the void diffusion coefficient significantly increased with an increase in void fraction. Furthermore, a new void drift model was developed and validated based on a subchannel code. The overall predicted uncertainty for the outlet void fraction in the rod bundle benchmark was less than 13%.

中文翻译：

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杆束子通道间的空洞漂移研究

棒束子通道之间的空洞漂移是影响SMR热工水力参数计算精度的关键现象。它对于提高中小型反应堆安全分析的精度具有重要意义。现有关于棒束子通道间空洞漂移的实验和模型研究还比较少，模型计算的精度有待提高。本研究通过气液两相非平衡流实验来测量1×2棒束中由空隙漂移引起的两相流的重新分布。实验结果表明，在空隙率小于0.3的气泡流态中，空隙扩散系数随空隙率的变化变化不大。然而，在空隙率超过0.3的段塞流和环流流态中，空隙扩散系数随着空隙率的增加而显着增加。此外，基于子通道代码开发并验证了新的空洞漂移模型。棒束基准中出口空隙率的总体预测不确定性小于 13%。