自然循环过冷沸腾流动不稳定性的实验研究

Experimental study of flow instability in a natural circulation system with subcooled boiling

以氟里昂作工质，对自然循环过冷沸腾流动不稳定性进行了实验研究，重点研究了加热段几何结构和系统操作参数对流动不稳定性的影响规律。实验过程中使用了三种不同结构的加热段。结果表明，流动不稳定性的发生不仅与加热段的加热功率有关，还与加热段的结构有关；自然循环过冷沸腾系统可能发生高频脉动和低频脉动二类流动不稳定性，系统操作参数对二类不同频率的流量脉动的发生有重要影响；流动不稳定性的发生主要取决于加热段的总加热功率，而与加热段内局部热流密度的大小关系不大。得出了判断系统稳定性的界限，并使用积分方程无因次分析方法得出了预测流动不稳定性的经验公式。

Experimental study has been performed to investigate flow instability in a natural circulation system with subcooled boiling by using Freon12 as the working medium. In the experiments three kinds of the heated sections are used. The effects of the construction of the heated section and the parameters of the working medium on the onset of flow instability were studied. Through the experiments two kinds of flow instabilities, high frequency oscillations and low frequency oscillations, have been found. The parameters of the working medium have great influence on the occurrence of the two kinds flow oscillations. The experimental results show that the occurrence of the flow instability mainly depends on the total heat input power to the heated section but is not essentially affected by the local heat flux of the heated section. The stability boundaries were determined through the experiments. By means of dimensional analysis of integral equations, a common correlation describing the threshold condition of onset of the flow instability was obtained.