竖直环形通道内的湍流混合对流数值分析  

Numerical Analysis of Turbulent Mixed Convectionin Vertical Annular Channel

作　　者：胡相杰 温济铭 高璞珍[1] 田瑞峰[1] HU Xiangjie;WEN Jiming;GAO Puzhen;TIAN Ruifeng(Heilongjiang Provincial Key Laboratory of Nuclear Power System and Equipment,College of Nuclear Science and Technology,Harbin Engineering University,Harbin 150001,China;Department of Nuclear Safety,China Institute of Atomic Energy,Beijing 102413,China)

机构地区：[1]哈尔滨工程大学核科学与技术学院,黑龙江省核动力装置性能与设备重点实验室,黑龙江哈尔滨150001 [2]中国原子能科学研究院核安全研究所,北京102413

出　　处：《原子能科学技术》2023年第7期1355-1362,共8页Atomic Energy Science and Technology

摘　　要：自下而上的湍流混合对流在特定工况下表现出独特的传热现象,在工程上受到广泛关注。本文基于CFD方法,对竖直环形通道内的湍流混合对流现象进行了数值模拟研究。计算结果表明,当格拉晓夫数(Gr)较小时,浮升力抑制对流传热,使得混合对流努塞尔数(Nu_(M))低于相同雷诺数(Re)纯强迫对流的努塞尔数(NuF);随着Gr的增加,Nu_(M)逐渐恢复甚至增强。拟合得到了Symolon形式的混合对流传热关联式,并将混合对流现象划分为强迫对流区、混合对流传热抑制区和自然对流传热强化区。混合对流对传热的影响可以归纳为间接效应,即浮升力改变平均速度场,导致湍流的层化或恢复,使得对流传热被抑制或强化。Reactor cavity cooling system(RCCS)is a competitive residual heat removal scheme for small modular reactors.In this paper,the RCCS has been simplified to a scenario that ascending air flow is got heated in vertical annular channels and driven by mixed convection.The mixed convection is a combination condition of forced convection(external-applied pressure difference)and natural convection(internal-generated buoyancy force).The scenario has been analyzed by numerical approach using SST(shear stress transport)k-ωturbulent model,which can obtain good accuracy at near-wall low Reynolds number region.Buoyancy number,which is defined as Gr/Re^(3),increases with heat loading,and it represents the relative intensity of natural convection and forced convection.The result shows that,heat transfer in ascending turbulent mixed convection is impaired with respect to forced convection at moderate heat loadings,and enhanced at high heat loadings.Thus,mixed convection can be divided into forced convection dominant region,mixed convection impairment region and natural convection enhancement region.According to different aspect ratios of vertical channels,the most serious impairment occurs when buoyancy number equals to 1×10^(-5).Additionally,the impairment in narrow channel is more serious than wide channel.The mixed convection heat transfer correlations are fitted based on Symolon’s correlation,which shows the best agreement with numerical analysis results in predicting the heat transfer.The mechanism of turbulent mixed convection phenomenon can be explained as turbulent laminarization and intensify,which is caused by non-uniformity of density and variation of gravitational body force.With increasing heat loading,non-uniform buoyancy effects cause marked distortion of the flow structure,with the velocity maximum moving from the core of flow to the near-wall region.Velocity profiles switch from inverted U-profile to M-profile,which is a typical profile of mixed convection.At the same time,Reynolds stress at near-wall region r

关 键 词：竖直环形通道 湍流混合对流 浮升力 数值模拟 

分 类 号：TL33[核科学技术—核技术及应用]