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给出自然循环系统中欠热沸腾及闪蒸的分析及实验研究结果。实验在５ＭＷ核供热堆的模拟实验回路上完成。分析采用了四方程一维两相流漂移模型。用Ｃｌａｕｓｉｕｓ－Ｃｌａｐｅｙｒｏｎ方程计算上升段中汽泡闪蒸起始点。进口欠热度及系统压力作为变化参数。为了便于比较，也给出了仅采用饱和沸腾模型的结果。研究表明欠热沸腾及空泡的闪蒸对空泡分布及系统循环流量有很大影响，且系统压力越低，欠热沸腾及闪蒸的影响越大，在很宽的进口欠热度条件下加热段中只发生欠热沸腾。计算结果与实验值吻合得很好。此研究结果对于丰富和发展两相流理论，对自然循环两相流系统，特别是对以自然循环方式运行的低温核供热反应堆有重大意义。
The analysis and experimental results of underheated boiling and flashing in natural circulation system are given. The experiment is completed on the simulation experiment loop of 5MW nuclear heating reactor. Four-equation one-dimensional two-phase flow drift model was adopted. The Clausius-Clapeyron equation was used to calculate the bubble flash onset in the ascending section. Import under-heating and system pressure as a change in parameters. For the sake of comparison, the results of using only the saturated boiling model are also given. The results show that underheated boiling and vacuolating flash have a great influence on the distribution of vacuoles and the circulating flow of the system. The lower the system pressure, the greater the effect of underheated boiling and flashing. Under a wide range of under-heating conditions Only underheating boiling occurs in the heating section. The calculated results are in good agreement with the experimental data. The results of this study are of great significance for the enrichment and development of the theory of two-phase flow and for natural circulation two-phase flow systems, especially for low-temperature nuclear heating reactors operating in a natural circulation.