TY - JOUR
TI - Research on the effects of local throttling on thermal-induced two-phase flow instabilities in the typical coolant open-channel system in the nuclear reactor core
AU - Long Jianping
AU - Yang Bao-Wen
AU - Zhang Bin
AU - Wang Sipeng
JN - Thermal Science
PY - 2022
VL - 26
IS - 5
SP - 4095
EP - 4105
PT - Article
AB - Thermal-induced two-phase flow instabilities could badly slow the runtime  performance of two-phase systems, such as boiling water reactor core, and  even endanger the safe operation. Hence, many researchers have carried out  numerous researches on flow instability characteristics, but few  publications cover the effects of local throttling on two-phase flow  instabilities in open-channel systems such as coolant rod bundle subchannel  with spacer grids in the nuclear reactor core. This paper provides a  numerical study on the effects of local throttling on two-phase flow  instabilities in a simplified typical coolant open-channel system in a  nuclear reactor core by using the NUSOL-SYS code. The effects of local  throttling ratio, throttling position, and other throttling parameters on  the stability of the boiling channel system were carried out. The results  show that usually in uniformly distributed throttling conditions, the  stability of the system and high throttling ratio are positively correlated.  In fixed throttle ratio conditions, the stability of the system is  positively correlated with the distance from the throttling region to the  entrance and local void fraction. If throttling regions are uniformly  arranged along the heating channel with a certain value, the number of  throttle regions will enhance the instability of the system. Besides, this  paper preliminarily proposed a criterion function f(n, RT, α) to study the  complicated throttling effects on flow instability which could provide  technical reference for the safe design and operation of two-phase systems,  especially, the reactor core.