Abstract The transient process of the gravity-driven draining in the core make-up tank (CMT) system will be affected by the wall-stored energy, which will lead to the deviation of experimental results based on scaled-down test facilities. In order to understand the corresponding mechanism, the Hierarchical Two-Tiered Scaling (H2TS) method was adopted to scaling effects. The Relap5 code was used to simulate the gravity-driven draining process of the models with different scaling sizes, and the transient scaling distortion were evaluated. It was found that all the dynamic distortions of the similarity criterion numbers increase with the decreasing of the scaling size. Among the two key criterion numbers that dominate the wall heat transfer, the distortion of the condensation number is very small while that of the heat conduction number is larger. Under all scaled-down cases, the water level in CMT drops slightly slower than that under the prototype case, and the smaller the length scale is, the slower the dropping speed is. Under all cases, the discharging mass flow rate decreases gradually with time, and the dynamic processes of fluid temperature and solid temperature between the model and the prototype are basically the same under the condition of equal physical properties.

中文翻译：

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岩心补水池重力驱动排水过程动态特性及结垢畸变

摘要 岩心补给罐（CMT）系统中重力驱动排水的瞬态过程会受到壁面储存能量的影响，这将导致基于按比例缩小测试设备的实验结果的偏差。为了理解相应的机制，采用分层两层缩放（H2TS）方法来缩放效果。使用Relap5代码模拟不同缩放大小模型的重力驱动排水过程，并评估瞬态缩放失真。发现所有相似准则数的动态失真都随着尺度大小的减小而增加。在主导壁面传热的两个关键准则数中，凝结数的畸变很小，而热传导数的畸变较大。在所有按比例缩小的情况下，CMT中的水位下降比原型情况下略慢，长度尺度越小，下降速度越慢。在所有情况下，排放质量流量随时间逐渐减小，在物理性质相同的条件下，模型与原型之间流体温度和固体温度的动态过程基本相同。