球床反应堆体心棱柱单元局部高温热点与涡特性分析

Local high-temperature hot spots and vortex characteristics of body centered prism in a pebble bed reactor

球床反应堆燃料球堆积会产生高温热点从而影响燃料球的完整性,高温热点的形成与复杂的氦气流动及产生的涡密切相关。为了确保数值模拟结果的准确性,对比了体心棱柱(BCP)面接触处理方式与人工间隙处理方式的差异,证明面接触结构更为合理。对研究对象构建结构化网格,采用大涡模拟(LES)方法分析不同接触位置处流场与温度的分布。采用Q准则确定局部位置的涡结构,分析涡对球床内流动换热的影响。结果表明,BCP结构的特殊接触面会产生高温热点从而影响整体温度分布,涡的存在能够增强流动换热。

Generation of high-temperature hot spots was closely related to the complex flow of helium gas and the formation of vortices in a pebble-bed reactor,which could influence the integrity of fuel ball.In this paper,differences between surface contact structure by body-centered prism(BCP)and artificial gap structure were compared,and it is proved that surface contact structure is more reasonable.Structured grid of BCP surface contact was constructed.Flow field and temperature distribution of different contact locations were analyzed by large eddy simulation(LES)method.The Q criterion method was used to determine local vortex structure.And influence of vorticity on heat transfer in the pebble-bed was analyzed.The results show that high-temperature hot spots are generated on the special contact surface by BCP,which can affect the overall temperature distribution.In addition,existence of vortexes can enhance the flow and heat transfer.