Abstract

The sodium flow resistance in sodium-cooled fast reactor cores experiencing natural circulation conditions was measured for wire-wrapped 19- and 37-pin bundles using low-velocity water flows with Re <1000 and Re <750, respectively. The measurements were compared with predictions of existing wire-wrapped bundle friction factor correlations. The results show that the existing correlations usually underestimate the friction factors in the transition flow regime particularly for those with small transition Reynolds numbers from laminar to turbulent flow. The reason for the underestimation is that the transition Reynolds numbers observed in this study were much smaller than the predictions of all the existing correlations, and as a result, the transition flow at the small Reynolds number was treated as laminar or quasi-laminar flow by the correlations. In addition, the quasi turbulence in the early stage of transition flow should have a significant influence on flow resistance.

摘要

分别使用 Re < 1000 和 Re < 750 的低速水流，对绕线的 19 针和 37 针束测量钠冷快堆堆芯中的钠流动阻力。将测量结果与现有的绕线束摩擦系数相关性的预测进行了比较。结果表明，现有的相关性通常低估了过渡流态中的摩擦因子，特别是对于从层流到湍流的过渡雷诺数较小的那些。低估的原因是本研究中观察到的过渡雷诺数远小于所有现有相关性的预测，因此，通过相关性将小雷诺数处的过渡流视为层流或准层流。此外，过渡流早期的准湍流对流阻应该有显着影响。