Abstract In pressurized water reactor (PWR) with multiple loops, abnormal working conditions occur when coolant pumps do not work in some loops. In these closed-loop pipelines, thermal stratification is formed under the effect of natural convection cooling and this poses a threat to the safe operation of the reactor. In this paper, the sequential function specification method (SFSM) is implemented to simultaneously predict the spatially and temporally varying internal fluid temperature and convective heat transfer coefficient of two-dimensional pipe under thermal stratification. In the direct problem, the finite volume method (FVM) is adopted to solve the governing equations subjected to initial and boundary conditions. In the inverse problem, the least-square method is employed to obtain the heat flux of the inner wall, and then Newton's law of cooling and the natural-convection correlation are adopted to obtain the fluid temperature and convective heat transfer coefficient. Numerical experiments of natural convection cooling are carried out under different outer wall boundary conditions to demonstrate the effectiveness of the proposed inversion method. The results of temperature estimation are consistent with the results of natural cooling numerical experiment and the relative error is below 4%, whereas the convective heat transfer coefficient is slightly worse due to the difference in the extraction positions. The effects of the number of involved future time steps and the measurement noise on the accuracy of the inverse analysis are also investigated in detail. Our results show that the fluid temperature and convective heat transfer coefficient of natural cooling may be effectively estimated using the proposed inverse method.

中文翻译：

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用序列函数指定方法同时估计流体温度和对流传热系数

摘要 在多回路压水堆（PWR）中，当部分回路的冷却剂泵不工作时，就会出现异常工况。在这些闭环管道中，在自然对流冷却的作用下形成热分层，对反应堆的安全运行构成威胁。在本文中，采用序列函数规范方法（SFSM）同时预测热分层下二维管道的时空变化的内部流体温度和对流传热系数。在直接问题中，采用有限体积法（FVM）求解受初始和边界条件影响的控制方程。在反问题中，采用最小二乘法求出内壁的热通量，然后牛顿' 采用冷却定律和自然对流关系式求得流体温度和对流传热系数。在不同的外壁边界条件下进行了自然对流冷却的数值实验，以证明所提出的反演方法的有效性。温度估算结果与自然冷却数值实验结果一致，相对误差在4%以下，而对流换热系数因提取位置不同而略差。还详细研究了所涉及的未来时间步数和测量噪声对逆分析精度的影响。