锆-4在冷却水中的骤冷沸腾传热实验研究

为了研究锆-4在冷却水中的骤冷行为与沸腾传热特性，本文采用可视化方法，并测量了锆-4在骤冷过程中的温度变化。基于一维导热反问题求解，计算得到锆-4表面的热流密度和温度。在骤冷过程中锆-4会依次经历膜态沸腾、过渡沸腾、核态沸腾以及单相对流换热4个阶段，并且分析了轴向高度和冷却水过冷度对骤冷行为以及沸腾传热的影响。结果表明，随着过冷度的增大，骤冷时间减小，最小膜态沸腾温度增大，并且核态沸腾与过渡沸腾传热受加热表面局部特性影响显著，并建立了锆-4表面最小膜态沸腾温度的关系式，对反应堆的安全分析具有重要的意义。 

Experimental Study on Boiling Heat Transfer of Zr-4 Quenched in Water

In order to study the quenching behavior and heat transfer performance of Zr-4 rodlet in water, the visualization method is employed, and the temperature history of Zr-4 rodlet is measured during the quenching process in the present study. Based on one-dimensional inverse heat conduction code, the surface heat flux and the temperature of Zr-4 rodlet are calculated, and hence the boiling curve is determined. Zr-4 experienced the following 4 stages, including film boiling, transition boiling, nucleate boiling and natural convective boiling. The effect of axial distance and liquid subcooling on the quenching behavior and the boiling heat transfer is analyzed. It is found that as the liquid subcooling increases, the quenching time is decreased, and the minimum film boiling temperature is increased. Noticeably, the transition boiling and the nucleate boiling are sensitive to the local surface conditions. A correlation for minimum film boiling temperature is developed, which is significant for reactor safety.