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描述了自然循环系统中所观察到的闪蒸现象及其对自然循环流动稳定性的影响。实验研究是在清华大学核能技术设计研究院的5MW低温供热堆热工水力学模拟实验回路(HRTL-5)上进行的。采用可视化观察与数据同步记录分析相结合的方法,研究了不同压力条件下自然循环系统上升段中的闪蒸现象及其对自然循环稳定性的作用。研究结果表明:系统压力愈低,闪蒸现象愈明显,对系统流动稳定性的影响也愈强烈。在低压下,即使加热段出 口过冷度相当大,也会因强烈的热力学不平衡过程导致上升段中能量的积累。而后出现闪蒸现象,并引起系统流动的大周期振荡,周期可长达40s。当系统压力升高达到1.5MPa时,上升段中的闪蒸现象消失。在实验研究的基础上,阐明了闪蒸及自然循环闪蒸不稳定性的机理。
The observed flash phenomenon in a natural circulation system and its effect on the stability of natural circulation flow are described. The experimental study was carried out on the thermal hydraulics simulation experiment loop (HRTL-5) of 5MW low temperature heating reactor of Tsinghua University Institute of Nuclear Energy Technology Design. By means of visual observation and simultaneous data recording and analysis, the phenomenon of flashover in the ascending section of natural circulation system and its effect on the stability of natural circulation under different pressure conditions were studied. The results show that the lower the system pressure, the more obvious the flash phenomenon and the stronger the influence on the system flow stability. At low pressures, even if the subcooling at the outlet of the heating section is rather large, the energy accumulation in the ascending section can be caused by a strong thermodynamic imbalance. Then the phenomenon of flash evaporation, and cause the system to flow large-cycle oscillation, the cycle can be as long as 40s. When the system pressure reaches 1.5MPa, the flash in the ascending section disappears. Based on the experimental study, the mechanism of flash and natural circulation flash instability is clarified.