蒸汽发生器U型管低含气率两相倒流现象研究

Investigation of Two-phase Reverse Flow in U-tube under Low Mass Quality Condition

针对立式倒U型管自然循环蒸汽发生器传热管内的两相倒流现象,基于均相流模型,建立了U型管内低含气率两相流动传热理论模型,给出了U型管的进出口压降-质量流量曲线,分析了U型管内出现两相倒流现象的机理,研究了二次侧流体温度和入口含气率对倒流现象的影响规律,并与单相倒流进行了对比。利用RELAP5/MOD 3.3程序对相同条件下的倒流问题进行了计算。研究表明,提高蒸汽发生器二次侧工作压力可减少倒流,两相流入口含气率越高,倒流越易发生,两相流较单相流在U型管内更易倒流。

The two-phase reverse flow phenomenon may occur in the inverted U-tubes of steam generator（SG）for natural circulation.A theoretical model of flow and heat transfer for two-phase flow in U-tubes based on the homogenous flow model was established in this paper.A pressure drop-mass flow curve was derived to investigate the mechanisms of two-phase reverse flow in U-tubes.The effects of inlet mass quality and fluid temperature in secondary side on the reverse flow were also analyzed.Then the theoretical results were verified by the RELAP5/MOD 3.3 codes.The research shows that increasing the SG secondary side pressure may reduce reverse flow phenomenon in U-tubes,and the phenomenon more likely occurs when the inlet mass quality increases.