Abstract In the present work, in order to investigate and solve the issue associated with the circulation ratio (CR) for naturally assisted utility boilers, analysis of the boiler riser downcomer circuit has been performed for the whole range of operating pressure that supports natural circulation. This is done by developing a two phase flow model suitable for thermosyphon circuit analysis. The model is well validated with available numerical and experimental data for thermosyphon loop and practical boiler. In compliance with the industrial need, the tubes of boiler system are chosen based on the ASME boiler code. A set of case study of practical boilers has been conducted to determine the minimum possible safe circulation ratio for each separate case. Finally the computed circulation ratios are plotted against the operating pressure ranging from 5 to 180 bar. The trend of variation is discussed along with the discussion of safe operating range, considering the issue of vulnerability of tube overheating. The overheating of tube wall is correlated with the critical circulation ratio. The range of minimum safe CR is identified for low, medium and high operating pressure natural circulation boilers.

中文翻译：

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一种确定大范围压力下自然循环锅炉最小循环比的多相模型

摘要 在目前的工作中，为了研究和解决与自然辅助电站锅炉的循环比 (CR) 相关的问题，对支持自然循环的整个工作压力范围内的锅炉立管降水管回路进行了分析。这是通过开发适用于热虹吸回路分析的两相流模型来完成的。该模型得到了热虹吸回路和实际锅炉的可用数值和实验数据的充分验证。根据工业需要，锅炉系统的管子是根据ASME锅炉规范选择的。已经进行了一组实际锅炉的案例研究，以确定每个单独案例的最小可能安全循环率。最后，根据 5 至 180 bar 的操作压力绘制计算出的循环比。考虑到管子过热的脆弱性问题，随着安全工作范围的讨论，讨论了变化趋势。管壁过热与临界循环比有关。最低安全 CR 范围是针对低、中和高工作压力自然循环锅炉确定的。