自然循环工况下倒U型管蒸汽发生器的一次侧流量反转机理

Abstract

在自然循环工况下,倒U型管蒸汽发生器(UTSG)的进出口存在负压降,使得UTSG内的部分倒U型管易发生倒流现象.针对特定的UTSG,定量地建立倒; U型管进出口压差随一次侧质量流量变化的水动力曲线,并采用最佳估算程序Relap5对UTSG进行建模分析.针对同一给定的自然循环工况,分别采用UT; SG入口总质量流量从高到低和从低到高两种质量流量加载方式趋近.研究发现,自然循环工况的质量流量加载方式对UTSG倒流的发生有显著影响;从低到高的; 质量流量加载方式会导致更多倒U型管发生倒流,产生更大的流动阻力;在其他运行参数相同的情况下,UTSG倒流反转为正流的临界质量流量远高于正流反转为; 倒流的临界质量流量;采用从高到低的质量流量加载方式到达自然循环工况更有利于避免UTSG倒流的发生.

For natural circulation,it is shown that the negative drop of pressure; in the primary side of a inverted U-tube steam generator(UTSG)caused by; the density difference of the fluid inside may result in reverse flows; within some inverted U-tubes.A model of a given UTSG with nine parallel; U-tubes is established using the best estimate code Relap5.Two; conditions with different UTSG inlet mass flow rate loading methods are; compared.Results show that mass flow rate loading methods significantly; affect UTSG reverse flow phenomenon.Approaching the natural circulation; by decreasing the inlet mass flow rate leads to less reverse flow; U-tubes and flow resistance than increasing the inlet mass flow rate; from zero.And the critical mass flow rate of flow inversion for the; former condition is smaller than that for the later.In; conclusion,reaching natural circulation by decreasing inlet mass flow; rate of UTSG may avoid reverse flow.