窄缝通道内低雷诺数蒸汽流动换热特性数值模拟研究

Numerical simulation study of flow and heat transfer characteristics of steam with low Reynolds number in a narrow channel

为探究窄缝通道在大破口失水事故下再淹没过程中低雷诺数(Re_(in)=1 881~10 348)过热蒸汽的流动换热特性,采用计算流体力学(computational fluid dynamics, CFD)方法,基于优选出的湍流模型,探究加热面热流、压力条件和入口速度对低雷诺数过热蒸汽流动换热特性的影响规律。对比了Gnielinski关联式与Dittus-Boelter关联式,并对Dittus-Boelter经验关联式进行修正。计算结果表明:雷诺时均(Reynolds average Navier-Stokes, RANS)湍流模型中SST k-ω的模拟结果与大涡模拟(large eddy simulation, LES)的模拟结果最为接近,且计算量小;过热蒸汽对流换热能力随压力和入口流速的增加而增强,随加热面热流增加而减弱;相对于数值模拟结果,Dittus-Boelter和Gnielinski经验关联式预测的Nu数偏低,修正后的新关联式误差在15%以内,可为再淹没过程低雷诺数过热蒸汽的流动换热分析程序开发提供参考。

We have investigated the flow and heat transfer characteristics of superheated steam with low Reynolds number(Re_(in)=1881−10348)during the reflooding process in a narrow channel after a large break loss of coolant accident(LBLOCA).The computational fluid dynamics(CFD)method is used to investigate the influence of heating surface heat flux,pressure conditions and inlet velocity on the flow and heat transfer characteristics of low Reynolds number superheated steam based on the selected turbulent model.The Gnielinski and Dittus−Boelter empirical correlations are compared,and a modified Dittus−Boelter empirical correlation is proposed.The results show that the simulation using the SST k−ωturbulence model in the Reynolds average Navier−Stokes(RANS)approach is the closest to the results obtained by large eddy simulation(LES),and the calculation requirement is lower.The convective heat transfer capacity of superheated steam increases with the increase of pressure and inlet velocity,