Research on Thermal Diffusion Performance of Fuel Assembly Spacer Grid Based on Numerical Methodology
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摘要: 作为堆芯热工设计中子通道分析程序的关键输入参数，热扩散系数（TDC）一般通过单相热工试验获得，时间和经济代价较高。本文从湍流交混的机理和模型出发，深入阐述了TDC在子通道程序中的模拟方法，纠正了以往只能温度场计算获得TDC的问题，提出了表征冷热通道温度交换效果的热扩散特性因子，基于计算流体动力学（CFD）技术形成了一整套热扩散特性评价方法，并和试验结果进行了对比验证。对比分析结果表明，数值方法的结果与试验结果相对偏差不超过10%，符合效果良好，在考虑一定保守惩罚的情况下基本上可替代相关试验，极大地提高了设计研发效率。此外，对热工水力参数、定位格架结构、轴向格架数量、格架跨距等因素对燃料组件热扩散特性的影响进行了深入分析，结果表明组件的热扩散特性与格架等结构密切相关，受热工参数的影响不大。
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关键词:
- 热扩散系数 /
- 子通道 /
- 计算流体动力学（CFD） /
- 定位格架 /
- 温度场
Abstract: As one of the most important parameters in subchannel analysis codes used in core thermal-hydraulic design, Thermal Diffusion Coefficient (TDC) is generally acquired by single phase thermal-hydraulic tests, which are costly in time and economy. Based on the mechanism and model of the turbulent mixing, this paper expounds the simulation method of TDC in subchannel code, corrects the problem that TDC was obtained only by temperature field calculation in the past, and puts forward the thermal diffusion factor that characterize the temperature exchange between hot and cold channels. As a result, the whole TDC evaluation method based on CFD technology is formed, and the simulation results are compared to the test results. The results of comparative analysis show that the relative deviation between the results of numerical method and the experimental results is less than 10%, which are in good agreement. Considering certain conservative punishment, it can basically replace the related experiments and greatly improve the efficiency of design and development. Besides, the influences on the TDC of relative parameters, such as thermal hydraulic conditions, grid structure, number of grids, grid spacing, are analyzed. The results demonstrate that the TDC characteristics of fuel assemblies are largely related to the grid structure, and are less affected by thermal parameters.-
Key words:
- Thermal Diffusion Coefficient /
- Sub-channels /
- CFD /
- Spacer grid /
- Temperature field
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图 1 TDC对于典型事故最小DNBR结果的影响
Figure 1. Impact of TDC on the Typical Accidents’ Minimum DNBR
图 2 相邻通道间热扩散原理示意图
Figure 2. Schematic Diagram of Thermal Diffusion Mechanism between Sub-channels
图 4 CFD与CORTH计算得到的各子通道出口温度对比
Figure 4. Comparison of Sub-channel Outlet Temperatures Calculated by CFD and CORTH
图 10 CFD 计算得到组件子通道出口温度分布（工况1）
Figure 10. Sub-channel Oultle Temperature Distribution by CFD Calculation (Condition 1)
图 11 CORTH计算得到组件子通道出口温度分布（工况1）
Figure 11. Sub-channel Oultle Temperature Distribution by CORTH Calculation (Condition 1)
表 1 CFD计算工况参数设置
Table 1. Parameter Settings of CFD Calculation Conditions
工况编号 出口
压力/MPa入口
温度/℃入口质量
流速/(kg·m−2·s−1)雷诺数Re 工况1 15.5 292.2 3236.8 363427.7 工况2 15.5 292.2 2000.0 224562.6 工况3 15.5 220.0 1000.0 82366.1 工况4 15.5 220.0 2000.0 164732.2 工况5 15.5 220.0 3236.8 266599.4 工况6 10.0 220.0 3236.8 269521.4 工况7 10.0 220.0 2000.0 166537.8 
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表 2 参考组件TDC计算结果
Table 2. Results of TDC Calculation for Reference Assembly
工况编号 TDC TDC平均值 工况1 0.049 0.045 工况2 0.045 工况3 0.043 工况4 0.043 工况5 0.047 工况6 0.047 工况7 0.043
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表 3 定位格架对TDC计算结果的影响
Table 3. Influence of Spacer Grid on CFD Calculation Results
格架状态 TDC 不带定位格架 0.002 带定位格架 0.049
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