Abstract The study of the influence of different densities on the mixing behavior is very important in industries such as nuclear reactors. In this study a PLIF experiments and CFD simulation were performed to study the effect of slug densities on the mixing process in the vessel down-comer. Three different tests of different injected slug densities 1028, 1060 and 1090 kg/m3 were performed in HEU facility. Mixing of injected slug of 0.014 mg/L concentration of Rhodmine-B and ambient water in the vessel investigated by the Laser induced fluorescence technique. To provide a qualitative analysis of the results, the average values of the mass fraction at specified locations (y = 0 cm and y = 5 cm below the inlet part) were calculated for each experiment test and contour plots were created. These contours represent snapshots of the concentration field captured for the three tests. It is observed from the results, the mixing behavior in the vessel down-comer was strongly depend on the slug density. The mixing was slower when the density difference between the slug and ambient water was high and conversely the mixing behavior was higher when the density difference was low. A selected experimental result was used to validate CFD. The CFD simulations were carried out with FLUENT code and the turbulent model that used in this simulation was Reynolds stress model (RSM). A good agreement was achieved between experimental data and CFD-Fluent simulation.

中文翻译：

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利用PLIF实验和FLUENT模拟研究段塞密度对反应器容器混合性能的影响

摘要 研究不同密度对混合行为的影响在核反应堆等工业中非常重要。在这项研究中，进行了 PLIF 实验和 CFD 模拟，以研究段塞密度对容器下降管中混合过程的影响。在高浓铀设施中进行了三种不同注入段塞密度 1028、1060 和 1090 kg/m3 的不同测试。通过激光诱导荧光技术研究的容器中注射的 0.014 mg/L 浓度的罗丹明 B 和环境水的混合。为了对结果进行定性分析，计算了每个实验测试的指定位置（入口部分下方 y = 0 cm 和 y = 5 cm）的质量分数的平均值，并创建了等高线图。这些等高线代表为三个测试捕获的浓度场的快照。从结果可以看出，容器下降管中的混合行为强烈依赖于段塞密度。当段塞与环境水之间的密度差异大时，混合较慢，相反，当密度差异小时，混合行为较高。选定的实验结果用于验证 CFD。CFD 模拟使用 FLUENT 代码进行，该模拟中使用的湍流模型是雷诺应力模型 (RSM)。实验数据和 CFD-Fluent 模拟之间取得了很好的一致性。当段塞与环境水之间的密度差异大时，混合较慢，相反，当密度差异小时，混合行为较高。选定的实验结果用于验证 CFD。CFD 模拟使用 FLUENT 代码进行，该模拟中使用的湍流模型是雷诺应力模型 (RSM)。实验数据和 CFD-Fluent 模拟之间取得了很好的一致性。当段塞和环境水之间的密度差异大时，混合较慢，相反，当密度差异小时，混合行为较高。选定的实验结果用于验证 CFD。CFD 模拟使用 FLUENT 代码进行，该模拟中使用的湍流模型是雷诺应力模型 (RSM)。实验数据和 CFD-Fluent 模拟之间取得了很好的一致性。