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非能动余热排除系统(Passive Residual Heat Removal system,PRHR)是非能动核电厂的重要安全设施,在全厂断电事故下,大部分的堆芯衰变热是通过PRHR热交换器传递至内置换料水箱(In-containment Refueling Water Storage Tank,IRWST)。但PRHR热交换器属于大型非稳态换热器,其传热机理十分复杂。基于PRHR系统的重要性和复杂性,有必要研究PRHR系统的流动和传热特性。利用计算流体动力学(Computational Fluid Dynamics,CFD)软件针对非能动堆芯冷却系统试验装置中的PRHR系统进行建模计算,分析了PRHR热交换器及IRWST的流动和传热特性,发现IRWST内部沿垂直高度上呈现明显的温度分层现象,温度沿水平方向的分布趋于均匀;IRWST内部的流动主要是沿着C型传热管竖直段向上流动,流速逐渐增大,但在两相阶段,水箱上部区域流动明显增强;C型传热管上部水平段和竖直段上部区域的换热系数要明显高于其它区域,且在上部水平段与竖直段连接弯管处换热系数最大,在两相阶段,上部区域的换热系数明显增大。
Passive Residual Heat Removal System (PRHR) is an important security facility for passive nuclear power plants. Most of the core decay heat is transferred to the built-in refueling water tank through the PRHR heat exchanger (In-containment Refueling Water Storage Tank, IRWST). However, the PRHR heat exchanger belongs to a large unsteady heat exchanger and the heat transfer mechanism is very complicated. Based on the importance and complexity of the PRHR system, it is necessary to study the flow and heat transfer characteristics of the PRHR system. The computational fluid dynamics (CFD) software was used to model and calculate the PRHR system in the passive cooling device test system. The flow and heat transfer characteristics of the PRHR heat exchanger and IRWST were analyzed. The vertical temperature showed obvious temperature stratification and the temperature distribution along the horizontal direction tended to be uniform. The flow inside the IRWST mainly flowed upward along the vertical section of the C-type heat transfer tube and the flow rate increased gradually. However, in the two-phase stage , And the flow in the upper area of the tank was significantly enhanced. The heat transfer coefficient of the upper horizontal section and the upper vertical section of the C-type heat transfer tube was significantly higher than that of the other sections, and the maximum heat transfer coefficient at the upper horizontal section and the vertical section In the two-phase stage, the heat transfer coefficient in the upper region increased significantly.