The liquid-metal cooled fast reactor is known as one of the most promising Gen-IV nuclear power system due to its high safety and superior economy. However, the turbulent heat transfer behaviors of low-Prandtl-number liquid metal in fast reactors are quite different from that of ordinary fluids due to its violation in Reynolds analogy, and there is still lack of a unified turbulent-Prandtl-number (Pr_t) models in eddy viscous RANS models for liquid metals. In the present study, all existing Pr_t models were firstly collected and divided into two groups according to their dependent variables, then a comprehensively assessment on the applicability of both two types of Pr_t models in predicting turbulent heat transfer of liquid metal is conducted. The study found that an optimal Pr_t number exists in eddy viscous models under fixed Pe conditions, and Pr_t plays a significant role on heat transfer in the buffer zone and the fully-turbulent region, Under certain conditions, if the averaged second-type Pr_t in these two regions equals to the Pr_t in the first type of models, a similar heat transfer result with the same accuracy could be obtained. A big deviation (about 13%) is observed in Kays' model, even though Kays’ model in the second type of Pr_t models performs best at various Pe. To get more accurate predicting results, an improved Pr_t model has been proposed based on high fidelity DNS/LES profiles and experimental data, the deviation is less than 5%, which agreed well with the experimental data and correlations.

液态金属冷却快堆以其高安全性和优越的经济性被称为最有前途的第四代核电系统之一。然而，低普朗特数液态金属在快堆中的湍流传热行为由于违反雷诺类比而与普通流体的湍流传热行为大不相同，仍然缺乏统一的湍流普朗特数（Pr _t ) 液态金属涡粘性 RANS 模型中的模型。在本研究中，首先收集所有现有的Pr _t模型并根据其因变量将其分为两组，然后综合评估这两种Pr _t模型的适用性进行了预测液态金属湍流传热的模型。研究发现，在固定Pe条件下涡粘性模型中存在一个最优Pr _t数，Pr _t对缓冲区和全湍流区的传热作用显着，在一定条件下，如果平均第二型镨_吨在这两个区域等于镨_吨在第一类型的模型，可以得到具有相同精度的类似的热传递的结果。在 Kays 的模型中观察到一个很大的偏差（大约 13%），尽管第二类 Pr _t模型中的 Kays 模型在各种Pe 下表现最好. 为了得到更准确的预测结果，改进的镨_吨模型已经基于高精度DNS / LES型材和实验数据已经提出，其偏差小于5％，这与实验数据和相关性吻合。