棒束通道内自然循环流动阻力特性

Flow resistance characteristics in rod bundle channel under natural circulation condition

在自然循环条件下,进行了棒束通道内的流动阻力特性实验研究。结果表明,棒束通道内的流动摩擦阻力系数小于Cheng&Todreas关系式的预测值,且转捩现象不如圆管明显,转捩点Reynolds数为800左右。根据实验结果拟合了层流区的摩擦阻力系数计算关系式,该关系式仍然符合圆管中层流摩擦阻力系数的计算形式。另外,棒束通道的流动在自然循环条件下仍具有宽广的过渡区。通过实验还发现,加热段的热通量会影响棒束通道的摩擦阻力,摩擦阻力系数随热通量的增大而减小,并根据实验结果提出了不同热通量下摩擦阻力系数的黏度修正计算式。棒束定位格架的局部阻力没有明显的转捩现象,并根据局部阻力系数的变化规律拟合了Re<1500和Re>2000时的局部阻力系数计算关系式。

Rod bundle channel is widely applied as reactor core coolant passage,in which the flow characteristic is of great significance for safe operation of the reactor,it is necessary to do some experimental investigations on it.The flow resistance characteristics experiments were performed under natural circulation condition.It was found that the friction factor is less than predicted value by Cheng&Todreas correlation and has no obvious rise when the flow transition happens,which is different from the results in regular channel.A correlation to calculate the friction factor in laminar regime was proposed and it also has the same form with the correlation in regular channel.In addition,there is still a large transition region for friction factor in rod bundle channel under natural circulation condition.Based on the experimental results with different heat flux,it was found that the friction factor decreased with the rise of heat flux and viscosity revision was considered.As for local resistance at the spacer grid,no obvious flow transition occurred and correlations for local resistance calculation were fitted in different range of Reynolds number.