基于OpenFOAM的液态铅铋冷却光滑19棒束湍流普朗特数模型敏感性研究

Sensitivity Study of Turbulent Prandtl Number Model for Lead-Bismuth Eutectic Cooled Bare 19-Rod Bundle Based on OpenFOAM

液态铅铋(LBE)具有较低的普朗特数(Pr)物性特征,导致计算流体力学(CFD)模拟中常用的恒定湍流普朗特数(Tr_t)模型会影响其传热计算的准确性。为提高LBE的数值传热精度,国内外的学者构建了多个液态金属Pr_t模型。为评估常用液态金属Pr_t模型在快堆常见三角形排列棒束中的适用性,本工作首先基于开源计算流体力学软件OpenFOAM的稳态传热求解器buoyantSimpleFoam,添加多个液态金属Pr_t模型。然后针对Pr分别为0.01与0.025时的常物性LBE在光滑19棒束内部的充分发展湍流换热过程进行了数值研究,并将努塞尔数(Nu)结果与Mikityuk等[Nucl Eng Des,2009,239(4):680]提出的三角形棒束换热关系式进行了对比分析。结果表明:当采用SSTk-ω湍流模型时,Aoki等[Bull Tokyo Inst Tech,1963,54:63]基于全局流动参数建立的Pr_t模型以及Kays等[ASME Journal of Heat Transfer,1994,116:284]基于局部湍流参数建立的Pr_t模型计算得到的Nu结果与Mikityuk关系式吻合较好;而Pr_t=0.85模型引起的各项误差均较大,在工程计算中应谨慎使用;LBE的分子热传导作用对温度场及热通量场的影响较大,使用合适的Pr_t模型可以改进其CFD传热计算的准确性。

Liquid lead-bismuth eutectic(LBE) has a low Prandtl number(Pr),leading to inaccuracies in heat transfer calculations when using the constant turbulent Prandtl number(Pr_t) model,which is commonly employed in computational fluid dynamics(CFD) simulations.To improve the numerical accuracy of heat transfer calculations for LBE,researchers both domestically and internationally have developed several Pr_(t) models for liquid metals.To assess the applicability of these liquid metal Pr_(t) models in the commonly used triangular arrangement of fast reactor rod bundles,this study incorporates multiple liquid metal Pr_(t) models into the steady-state heat transfer solver buoyantSimpleFoam from the open-source CFD software OpenFOAM.A numerical study was then conducted on the fully developed turbulent heat transfer process within a smooth 19-rod bundle for Prandtl numbers of 0.01 and 0.025,and the resulting Nusselt number(Nu) was compared to the heat transfer correlation for triangular rod bundles proposed by Mikityuk et al.[Nucl Eng Des,2009,239(4):680].The results show that when using the SSTk-ω turbulence model,the Nu results calculated using the Pr_(t) model developed by Aoki et al.[Bull Tokyo Inst Tech,1963,54:63],based on global flow parameters,and the Pr_(t) model constructed by Kays et al.[ASME Journal of Heat Transfer,1994,116:284],based on local turbulence parameters,demonstrate good agreement with the Mikityuk correlation.In contrast,the Prt=0.85 model produced significant errors and should be applied with caution in engineering calculations.Additionally,molecular heat conduction in LBE has a substantial impact on the temperature and heat flux fields,and the use of an appropriate Pr_(t) model can improve the accuracy of CFD heat transfer simulations.