Flow regime and void fraction predictions in vertical rod bundle flow channels
Flow regime and void fraction predictions in vertical rod bundle flow channels
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DOI：
10.1016/j.ijheatmasstransfer.2021.121637
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发表时间：
2021-10
影响因子：
5.2
通讯作者：
Xu Han;Xiuzhong Shen;Toshihiro Yamamoto;K. Nakajima;Haomin Sun;T. Hibiki
中科院分区：
文献类型：
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作者：
Xu Han;Xiuzhong Shen;Toshihiro Yamamoto;K. Nakajima;Haomin Sun;T. Hibiki
本文研究了垂直棒束流通道内上升气液两相流的流型及其转变。过去的流动状态的实验观察进行了广泛的审查和分析。根据垂直棒束流通道中不同流型的流动特性，将其分为泡状流、细分散泡状流、帽状流、搅动流和环状流5种流型。针对现有流型转变判据和漂移通量关联式存在的问题，提出了泡状流向帽状流、帽状流向搅动流、环状流和细分散泡状流转变的机理，并基于这些机理建立了相应的流型转变判据，预测了5种流型。本文进一步改进了Han等.在垂直棒束流通道中，利用分布参数和漂移速度的漂移通量参数关联式，结合新发展的过渡准则，预测了5种流型下的空泡率。新发展的流态转换准则和改进的Han等。用实验数据检验了分布参数和漂移速度的漂移通量参数的相关性。通过对451个垂直棒束流通道和改进的Han等人的漂移通量模型的流态观测数据的检验，表明新开发的流态转换判据能正确预测82.9%的流态。关联式和新发展的流型转换准则对959个含气率实验数据的预测结果令人满意，平均相对误差为0.0766。
This paper has studied the flow regimes and their transitions in upward gas-liquid two-phase flows in vertical rod bundle flow channels. The past experimental observations on the flow regimes have been extensively reviewed and analyzed. Various flow regimes with the observer-dependent names are re-classified into 5 flow regimes, namely, bubbly, finely dispersed bubbly, cap-bubbly, churn and annular flows according to their different flow characteristics in the vertical rod bundle flow channels. In view of the problems in the available flow regime transition criteria and the drift-flux correlations, this paper has proposed the mechanisms for the bubbly to cap-bubbly flow transition, the cap-bubbly to churn flow transition, the transition to annular flow and the transition to the finely dispersed bubbly flow and developed the corresponding flow regime transition criteria to predict the five flow regimes based on these mechanisms. This paper has further improved Han et al. correlations for the drift-flux parameters of the distribution parameter and the drift velocity to predict the void fractions in the 5 flow regimes, together the newly-developed transition criteria, in the vertical rod bundle flow channels. The newly-developed flow regime transition criteria and the improved Han et al. correlation for the drift-flux parameters of the distribution parameter and the drift velocity have been examined with the experimental data. The examination has concluded that the newly-developed flow regime transition criteria can correctly predict 82.9% of the 451 observed flow regime data in the vertical rod bundle flow channels and the drift-flux model using the improved Han et al. correlation and the newly-developed flow regime transition criteria can give satisfactory prediction for the 959 experimental data of the void fraction with the mean relative error of 0.0766.