均匀加热全长棒束过冷沸腾工况子通道参数场计算分析

Parameter Analysis among Sub-channels of Subcooled Flow Boiling in Full Scale Bundle with Uniform-APD

采用壁面热分配模型对PSBT基准题中的5×5均匀加热全长棒束过冷沸腾传热进行了数值模拟研究,分析了均匀加热全长棒束通道中不同子通道和加热元件表面参数沿轴向的发展过程和径向的分布特性。研究发现,角通道和边通道是弱对流区域,其质量流速低于棒束平均值,但由于冷棒功率偏低,消除了流动不均衡性对传热效果的影响。在棒束径向方向,不同位置子通道间参数场存在差异,这是由于位于搅混格架横向导流对角方向的通道具有更有效的通道间对流效果,其传热效果更好。这种流动特性引起的参数差异在角通道中尤为显著。热棒表面过热度明显高于冷棒过热度,且位于非搅混格架横向导流方向的热棒具有更高的壁面过热度。

Subcooled boiling heat transfer simulation of PSBT full scale 5×5 rod bundle with uniform-axial power distribution(APD)was carried out with wall heat flux partition method.Axial sub-channel averaged parameter analysis along axial orientation among different sub-channels was studied.It is found that lower mixing effect,observed in corner and lateral sub-channels,makes negative contribution to heat transfer.But this effect is eliminated due to the lower power of cold rod(CR).The difference of parameter distribution is found among sub-channels.The mixing process among sub-channels in the central diagonal of mixing is strengthened due to the sustaining transverse flow induced by the vanes,which leads to an increasing heat transfer in these sub-channels.In the corner sub-channels,notable difference is observed.The wall superheat of hot-rod(HR)is higher than that of the CR.The HRs,which locate outside of the central diagonal of mixing,have a higher wall superheat than other HRs.