中文摘要：

本文对二氧化碳在矩形封闭回路中自然对流循环的流动特性进行了实验研究，研究了回路在临界点附近三种流动循环的稳定性。在所有的实验结果中，气-液两相循环是不稳定的，跨临界／超临界循环是稳定的，而单相的气态循环的稳定性还取决于循环所处的热力学状态。

英文摘要：

This study presents an experimental investigation on the flow characteristics of natural circulation in a rectangular closed loop. The flow stability of the three types of flow circulation near the critical point of CO2 is examined. For all the experimental flow circulation results, it＇s found that the two phase gas-liquid circulations are unstable, the transcritical/supercritical circulations are always stable; while the stability of the single phase circulations is depends on its thermodynamic state.