自然循环条件下蒸汽发生器倒U型管流量分配特性研究

Research on Flow Distribution Characteristics of Inverted U-Shaped Tube of Steam Generator under Natural Circulation Condition

以欧洲压水堆热工实验装置(PWR PACTEL)一回路系统蒸汽发生器为研究对象,首先,基于流体一维流动模型的质量、动量和能量守恒方程建立管道进出口压降以及传热与流体流量之间的关系;其次,以遗传算法为基础开发倒U型管蒸汽发生器流量分配计算程序,采用基准实验对程序正确性和可靠性开展验证;最后,利用流量分配程序计算蒸汽发生器倒U型管管组的流量分布情况,研究管高、管长以及一/二次侧换热系数对蒸汽发生器内流量分配的影响。结果表明,所开发流量分配程序计算结果与实验吻合良好;在选定的自然循环工况下,该蒸汽发生器中长管更易发生倒流,且倒流现象呈现分布范围广、单管流量低的特点;倒U型管内正流流速与管长成反比,与管高成正比,倒流流速随着管长的增加保持不变,与管高呈反比关系;传热系数较低时,总流量与传热系数成反比关系,当传热系数高于特定值后部分管内发生倒流,总流量骤降。

Taking the steam generator of the primary circuit system of the PACTEL PWR thermal experiment device as the research object, the pressure drop and the relationship between heat transfer and fluid flow of the U-tube are established based on the equations of mass conservation, momentum conservation and energy conservation of the one-dimensional fluid flow model. Then, the flow distribution calculation program of the inverted U-tube steam generator based on genetic algorithm was developed, and the correctness and reliability of the program were verified by benchmark experiments. Finally, the flow distribution among the U-tube groups of the steam generator is calculated by using the flow distribution program, and the influences of the tube height, tube length and the heat transfer coefficient of the first/second side on the flow distribution within the steam generator are studied. The results of the developed flow allocator are in good agreement with the experiment. Under the selected natural cycle conditions, the backflow is more likely to occur in the long tube of the steam generator, and the backflow phenomenon is characterized by a wide distribution range and low single-tube flow rate. The velocity of the forward flow in an inverted U-tube is inversely proportional to the length of the tube and proportional to the height of the tube. The backflow velocity remained unchanged with the increase of pipe length and was inversely proportional to pipe height. When the coefficient of heat transfer is low, the total flow is inversely proportional to the heat transfer coefficient. When the heat transfer coefficient is higher than a specific value, the backflow occurs in part of the tubes and the total flow drops sharply.