先进压水堆带定位格架5×5燃料棒束通道热工水力特性CFD数值模拟

CFD Simulation of Flow and Heat Transfer Characteristics in a 5×5 Fuel Rod Bundles with Spacer Grids of Advanced PWRs

首先对带有定位格架的5×5燃料棒束国际基准题——MATi S-H进行模拟,得到了压水堆带定位格架燃料棒束计算流体力学(CFD)数值模拟的最佳用户实践指南,在此基础上建立了先进压水反应堆(APWR)带定位格架5×5燃料棒束详细CFD模型,研究了定位格架对子通道内冷却剂流动换热的影响,得到了冷却剂的速度、温度分布以及子通道内压降情况,揭示了搅混翼的搅混效果。结果表明,格架基体区域的横向速度主要由弹簧和刚突引起,搅混翼对冷却剂的搅混作用更加强烈,搅混翼顶部所在截面的冷却剂最大横向速度达到3.24 m/s,平均横向速度为1.44 m/s;横向速度在格架下游30个水力直径长度范围内一直大于零,且逐渐变小;格架区域的冷却剂压降急剧增大,搅混翼会大幅度改变冷却剂流动方向,导致冷却剂流道温度分布不均匀,强化传热。

The international benchmark MATiS-H with 5×5 fuel rod bundles with spacer grids was studied carefully and the best user practice guideline for the rod bundles simulation was achieved firstly.A 5×5 rod bundles CFD model with spacer grid in the advanced pressurized water reactor(APWR)was established.The effect of the spacer grid on the flow and heat transfer of the coolant in the sub-channel was studied.The velocity and temperature distribution of the coolant and the pressure drop in the sub-channel were obtained.The mixing effect of the mixing vanes was revealed.Results show that the lateral velocity in the region of spacer grids is mainly caused by the springs and dimples,while the mixing vanes have a stronger mixing effect on the coolant,resulting in the maximum lateral velocity of the coolant in the section located at the top of the mixing vanes maximum being 3.24 m/s,and the average lateral velocity is 1.44 m/s.Lateral velocity always exists in the range of 30 hydraulic diameters in the downstream of the spacer grid and gradually decreases.The coolant pressure drop in the spacer grid area increases sharply,and the mixing vanes greatly changes the coolant flow direction,resulting in the uneven coolant flow temperature distribution and enhanced heat transfer.