Nuclear Engineering and Technology

Korean Nuclear Society (한국원자력학회)
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Experimental research on flow regime and transitional criterion of slug to churn-turbulent and churn-turbulent to annular flow in rectangular channels

  • Qingche He (Key Laboratory of Low-Grade Energy Utilization Technologies and Systems, Ministry of Education, Chongqing University) ;
  • Liang-ming Pan (Key Laboratory of Low-Grade Energy Utilization Technologies and Systems, Ministry of Education, Chongqing University) ;
  • Luteng Zhang (Key Laboratory of Low-Grade Energy Utilization Technologies and Systems, Ministry of Education, Chongqing University) ;
  • Wangtao Xu (Key Laboratory of Low-Grade Energy Utilization Technologies and Systems, Ministry of Education, Chongqing University) ;
  • Meiyue Yan (Key Laboratory of Low-Grade Energy Utilization Technologies and Systems, Ministry of Education, Chongqing University)
  • Received : 2023.02.08
  • Accepted : 2023.07.08
  • Published : 2023.11.25
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Abstract

As for two-phase flow in rectangular channels, the flow regimes especially like churn-turbulent and annular flow are significant for the physical problem like Countercurrent Flow Limitation (CCFL). In this study, the rectangular channels with cross-sections of 4 × 66 mm, 6 × 66 mm, 8 × 66 mm are adopted to investigate the flow regimes of air-water vertical upward two phase flow under adiabatic condition. The gas and liquid superficial velocities are 0 ≤ jg ≤ 20m/s and 0.25 ≤ jf ≤ 3m/s respectively which covering bubbly to annular flow. The flow regimes are identified by random forest algorithm and the flow regime maps are obtained. As the results, the transitional void fraction from slug to churn turbulent flow fluctuate from 0.47 to 0.58 which is significantly affected by the dimensional size of channel and flow rate. Besides, the void fraction at transitional points from churn-turbulent (slug) to annular flow are 0.66-0.67, which are independent with the gap size. Furthermore, a new criteria of slug to churn-turbulent flow is established in this study. In addition, by introducing the interfacial force model, the criteria of churn-turbulent (slug) flow to annular flow is verified.

Keywords

Acknowledgement

The authors appreciate the National Natural Science Foundation of China (Grant Code U21B2059) and (Grant Code U22B2090).

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