基于流热固耦合的核电蒸汽发生器传热管热应力数值模拟

Numerical Simulation on Thermal Stress of Tube in Steam Generator of Nuclear Power Plant Based on Fluid-thermal-structure Interaction

以大亚湾核电站蒸汽发生器为原型,基于相似模化原理建立了蒸汽发生器简化物理模型。采用两流体模型及热弹性力学基本关系式分别描述气液两相流沸腾相变过程和热应力变化规律。利用CFX对一、二回路侧流体流动传热及与传热管的耦合换热过程进行了数值模拟,并在ANSYS WORKBENCH中实现了流体温度场载荷向结构的传递,进而对传热管进行稳态热分析和热应力分析。计算结果表明:二回路出口质量含汽率为24.5%,冷却剂出口温度为296.2℃,均与大亚湾蒸汽发生器实际运行参数相符;传热管热应力与其壁面温差分布一致,且沿壁厚方向先减小后增大,并存在中性层,传热管最大热应力为54.5MPa。研究结果为蒸汽发生器的优化设计及安全运行提供了一定的理论支撑。

Taking the steam generator of Daya Bay Nuclear Power Plant as the prototype ,the simplified physical model of steam generator was established based on the similarity principle .The vapor-liquid two-phase flow boiling phase change process and thermal stress variation were simulated by two-fluid model and the basic thermal elasticity mechanics formula respectively .The flowing heat transfer on both the primary and the secondary sides and the coupled heat transfer between fluid and heat transfer tubes were numerically simulated using CFX software .The temperature load of fluid was transferred to the tubes in ANSYS WORKBENCH ,and then steady-state thermal analysis and thermal stress analysis were carried out .The simulation results show that the steam quality at outlet of the secondary side is 24.5% and the temperature of coolant at outlet is 296.2 ℃ ,which are in good agreement with the actual operating parameters of steam generator in Daya Bay Nuclear Power Plant .The distribution of the thermal stress is consistent with that of temperature difference of the tube’s wall .In addition , thermal stress along the wall thickness direction decreases and then increases , and neutral layer exists in the tube .The maximum thermal stress of the tube is 54.5 MPa . These results can provide theoretical support to the optimization of the design and safe operation in steam generator .