基于CFD的安全壳内浮力驱动自然对流特性分析

CFD based study of natural convection characteristics driven by buoyancy in containment

在核反应堆发生严重事故时,自然对流、传热和湍流现象对安全壳内的气体流动和分布起着重要作用。为研究事故发生时安全壳内气体流动和换热现象,并分析自然对流下的温度分布。采用计算流体力学(Computational Fluid Dynamics,CFD)方法开展数值模拟研究,首先利用差异加热空腔实验数据对CFD方法分析封闭空间内自然对流换热现象的适用性进行验证,然后建立了与THAI(Thermal-hydraulics,Hydrogen,Aerosols and Iodine)-TH21实验装置相对应的几何模型,分析了实验过程中安全壳内压力变化以及达到稳定状态后装置内的流动换热特性。结果表明:本文采用的计算方法对分析安全壳内气体流动换热具有较好的适用性,模拟得到的准静态压力高于实验压力1.61%,冷壁面附近温度分布与实验数据吻合良好,热壁面附近温度分布误差在2%以内。研究有助于相关数值方法与模型的验证与开发,并可为反应堆事故发生时安全壳内气体流动及分布提供一定的参考。

[Background] Natural convection, heat transfer and turbulence phenomena play important roles in the gas flow and distribution in containment during a severe accident in a nuclear reactor. [Purpose] This study aims to explore the gas flow and heat transfer phenomena inside the containment during the accident, and to analyze the temperature distribution under natural convection. [Methods] Numerical simulation study was conducted using the computational fluid dynamics(CFD) method. Firstly, the applicability of CFD method to analyze natural convective heat transfer phenomena in a closed space was verified by using experimental data of differential thermal cavity, and then, the geometric model corresponding to the Thermal-hydraulics, Hydrogen, Aerosols and Iodine(THAI)-TH21experimental device was established to analyze the pressure change in the containment during the experiments and the flow heat transfer characteristics in the device after reaching the steady state. [Results] The results show that the calculation method used in this paper has good applicability for analyzing the gas flow heat transfer in the containment. The simulated quasi-static pressure is 1.61% higher than the experimental pressure, and the temperature distribution near the cold wall is in good agreement with the experimental data, and the temperature distribution error near the hot wall surface is within 2%. [Conclusions] The study contributes to the validation and development of relevant numerical methods and models, and can provide some reference for the gas flow and distribution in the containment during the reactor accident.