5×5花瓣形燃料棒组件内过冷沸腾流动与换热特性数值研究

Numerical Study on Flow and Heat Transfer Characteristics of Subcooled Boiling in 5×5 Petal-shaped Fuel Rod Assembly

使用欧拉两流体模型和伦斯勒理工学院(RPI)壁面沸腾模型并考虑燃料棒组件内流固耦合传热,探究了5×5花瓣形燃料棒组件在均匀体积热源条件下的过冷沸腾流动与换热特性,分析了不同子通道内的速度场、温度场、空泡份额分布以及换热系数分布规律等。研究发现,棒束通道内二次流强度沿轴向呈周期性波动变化;过冷沸腾工况下花瓣形燃料组件内空泡份额峰值出现在靠近出口处,汽泡主要在燃料棒内凹弧处产生,呈逆时针偏心分布,且角子通道的汽相体积份额明显大于中心子通道;在本文模拟工况下,芯块最高温度达到657.9 K,沿轴向燃料棒芯块高温区面积逐渐增大,且角子通道的冷却剂温度高于边子通道,中心子通道冷却剂平均温度最低,各子通道的换热系数沿轴向呈周期性波动。

Based on the Eulerian two-fluid model and the Rensselaer Polytechnic Institute(RPI)wall boiling model,and considering the fluid-solid coupling heat transfer in fuel rod assembly,the flow and heat transfer characteristics of subcooled boiling in the 5×5 petal-shaped fuel rod assembly under the condition of uniform volume heat source was studied,and the velocity field,temperature field,void fraction distribution and heat transfer coefficient distribution in different subchannels were analyzed.The results show that the secondary flow intensity in the rod bundle channel changes periodically along the axial direction.Under subcooled boiling condition,the peak value of void fraction in petal-shape fuel assembly appears near the outlet.The bubbles are mainly generated at the elbow of the fuel rod and distribute eccentrically counterclockwise,and the volume fraction of vapor in the corner subchannel is obviously larger than that in the center subchannel.Under the simulated conditions in this paper,the maximum temperature of the pellet reaches 657.9 K.The area of high temperature zone of the fuel rod pellet increases gradually along the axial direction,and the coolant temperature in the corner subchannel is higher than that of the edge subchannel.The average coolant temperature of the central subchannel is the lowest,and the heat transfer coefficient of each subchannel fluctuates periodically along the axial direction.