高压条件下燃料组件内过冷沸腾过程传热不均匀性研究

Study on Non-Uniformity of Sub-Cooled Boiling Heat Transfer of High Pressure Water in Fuel Assembly

基于流体动力学软件Fluent中的流体体积函数(VOF)两相流模型,通过编写用户自定义函数(UDF)程序添加控制方程源项,建立过冷沸腾模型,对压水堆带定位格架的5×5燃料组件棒束通道内的过冷沸腾现象进行数值模拟。根据模拟结果,从空泡份额、燃料棒周向传热方面对比分析各个子通道内传热特性。研究发现各子通道内空泡份额的分布不均匀性较大,同样加热条件下,边通道的沸腾程度高于角通道。此外,对棒束周向的传热特性进行了分析,燃料棒周向努塞尔数呈不均匀性分布,燃料棒0°、90°、180°、270°等方向附近的传热能力较强,其相应的横向速度较大,对应的沸腾程度较强。

Based on the VOF model in Fluent, a sub-cooled boiling model was established and was inserted by UDF code into the control equations. Sub-cooled boiling in the 5×5 rod bundles channel with spacer grid was simulated. Heat transfer characteristics in sub-channels were analyzed by investigating the void fraction distribution and the heat transfer characteristics of the fuel rods. The results show that the void fraction distribution is different even if the heating condition is the same, and the void fraction is larger in the edge channel than that in the angular channel. The analysis of the heat transfer characteristics around the rod shows that, the heat transfer of the direction of 0°, 90°, 180°, 270° of fuel rod is better, the x velocity is larger, and the boiling is stronger.