管径对超临界CO2管内流动换热的影响研究  

Numerical Study on the Effect of Diameter on Supercritical CO_2 Heat Transfer and Flow in Horizontal Tubes

作　　者：刘占斌[1] 费继友[2] 杨一凡[1] 何雅玲[1] 

机构地区：[1]西安交通大学能源与动力工程学院,热流科学与工程教育部重点实验室,西安710049 [2]大连交通大学机械工程学院,大连116023

出　　处：《工程热物理学报》2016年第2期357-360,共4页Journal of Engineering Thermophysics

基　　金：国家自然科学基金项目(No.51436007,No.51176155)

摘　　要：超临界CO_2管内流动与冷却换热过程中,物性发生剧烈变化,流动换热特性独特,研究管径影响超临界CO_2流动换热性能的内在机理和规律具有一定的实用价值。本文采用能够精确计算超临界CO_2物性的NIST实际气体模型,通过对比不同湍流模型,得到计算超临界CO_2流动换热性能效果最优的计算模型,并利用该计算模型对超临界CO_2管内流动换热过程进行模拟计算。结果发现温度场变化使得超临界CO_2物性发生剧烈变化,引起二次流强度变化,影响了流场分布和换热性能。随着管径的增大,二次流涡中心向管壁移动,且涡扭曲程度增强;格拉晓夫数Gr随管径的增大而迅速增大,表明浮升力对换热的影响增大,因此有效换热系数迅速增大。The characteristics of supercritical CO_2 cooled flow and heat transfer in tubes are unique due to the sharply change of properties with pressure and temperature.The study on the effect of diameter on supercritical CO_2 heat transfer and flow characteristics is valuable.We used the NIST real gas model for calculating the properties of supercritical CO_2,and acquired optimal numerical model for modeling supercritical CO_2 heat transfer and flow process by comparing with the existing turbulent models.We found that the properties of supercritical CO_2 sharply change with variation of temperature field,and leat to a change of the secondary flow intensity.The effects of secondary flow on velocity field and heat transfer performance are notable.As the tube diameter increases,the vortex center of the secondary flow approaches the near wall region,and the vortex shape becomes more distorted.In addition,the grashof number Gr increases sharply,which implies that the effect of buoyant force on the heat transfer is enhanced.So,the effective heat transfer coefficient increases with increased tube diameter.

关 键 词：超临界CO_2 变管径 数值计算 流动换热特性 NIST实际气体模型 

分 类 号：TK124[动力工程及工程热物理—工程热物理]