摘要
针对部分极端工况下表面热流密度高、分布不均匀的特点,采用数值计算分析方法研究非均匀热流对超临界二氧化碳流动与换热特性的影响。针对内径为4 mm水平圆管内超临界压力二氧化碳的流动传热,依次在相同总热流不同变化斜率、不同总热流相同变化斜率的2组线性非均匀热流工况下进行数值模拟,得到线性非均匀热流工况下热物性分布、浮升力影响对流换热特性规律。仿真结果表明:相较于均匀热流,非均匀热流工况下加热段入口处附近上壁面传热恶化更严重,线性非均匀热流分布下该处管壁温度可达均匀热流工况下的1.85倍;对给定的实际表面热流边界条件下的超临界二氧化碳流动换热进行数值仿真,加热段入口处上壁面最大温度达出口温度的3.41倍,改变流动方向后这一比值降低到1.50,据此对采取超临界二氧化碳为工质的相关冷却方案给出了建议。
In some extreme conditions,heat flux with high density is non-uniformly distributed on the surface.To address this issue,this paper analyzed the influence of non-uniform heat flux on the flow and heat transfer characteristics of supercritical carbon dioxide by employing numerical calculation and analysis methods.Numerical simulations were sequentially performed to analyze the flow and heat transfer of supercritical carbon dioxide in a horizontal circular tube with a diameter of 4 mm under two sets of linear non-uniform heat flux conditions including the same total heat flux with different slopes,as well as different total heat fluxes with the same slope.The influence of the distribution of thermophysical properties and buoyancy lift on the convective heat transfer characteristics under linear non-uniform heat flux conditions was obtained.The simulation results show that the heat transfer of the upper wall near the entrance of the heating section under non-uniform heat flux conditions severely deteriorates compared with that under uniform heat flux.The maximum tube wall temperature under linear non-uniform heat flux is 1.66 times that under uniform heat flux.Furthermore,numerical simulations of flow and heat flux of supercritical carbon dioxide on a given actual surface heat flux boundary are carried out,and the maximum tube wall temperature at the entrance of the heating section is 3.41 times that at the outlet,while the ratio decreases to 1.50 when the flow direction changes.Relevant suggestions are offered for cooling solutions using supercritical carbon dioxide as a working medium.
作者
代威
石申舟
付衍琛
左洋
DAI Wei;SHI Shenzhou;FU Yanchen;ZUO Yang(Beijing Institute of Astronautical Systems Engineering,Beijing 100076,China;Research Institute of Aero-Engine,Beihang University,Beijing 100191,China)
出处
《北京航空航天大学学报》
EI
CAS
CSCD
北大核心
2024年第10期3074-3083,共10页
Journal of Beijing University of Aeronautics and Astronautics
基金
国家自然科学基金(51906009)。
关键词
非均匀热流
超临界流体
二氧化碳
对流换热
浮升力
non-uniform heat flux
supercritical fluids
carbon dioxide
convective heat transfer
buoyancy lift
