倾斜圆管内超临界压力CO2流动换热数值分析  

Numerical analysis on flow and heat transfer characteristics of supercritical pressure CO2 in inclined tube

作　　者：闫晨帅 朱兵国 尹少军 孙恩慧[1] 徐进良[1] 刘欢[1] YAN ChenShuai;ZHU BingGuo;YIN ShaoJun;SUN EnHui;XU JinLiang;LIU Huan(Beijing Key Laboratory of Multiphase Flow and Heat Transfer for Low Grade Energy,North China Electric Power University,Beijing 102206,China)

机构地区：[1]华北电力大学低品位能源多相流与传热北京市重点实验室,北京102206

出　　处：《中国科学：技术科学》2020年第5期571-581,共11页Scientia Sinica(Technologica)

基　　金：国家重点研发计划(编号:2017YFB0601801);中央高校基本科研业务费专项资金(编号:2018ZD02,2019QN017)资助项目。

摘　　要：对超临界压力CO2在内径为10 mm、加热长度为2000 mm、倾斜角度α=45°的倾斜光管内向上和向下两个方向的流动与传热行为进行数值计算.采用SST k-ω低雷诺数湍流模型,通过超临界压力CO2在垂直光管内向上流动传热的实验数据验证了计算模型的可靠性和准确性,分析了倾斜圆管内壁温度Tw,i和对流换热系数h沿圆管轴向和周向的变化规律.基于超临界压力CO2在类临界温度Tpc处发生类气-类液"相变"的"类沸腾"假设,研究了超临界CO2在倾斜圆管内不同方向流动时顶母线壁温分布产生差异的原因,通过获取圆管横截面内速度分布、物性分布和湍流分布等详细信息,重点分析了产生这一差异的传热机理.计算结果确定了类气膜厚度、轴向速度u、湍动能k和黏性底层厚度δy+=5是影响不同流动方向时顶母线壁温分布差异的主要因素.In this study, numerical simulation of flow and heat transfer of S-CO2(supercritical CO2) in the inclined upward and downward smooth tubes with an inner diameter of 10 mm and a heating length of 2000 mm at an inclination angle of 45° were conducted. The SST k-ω low Reynolds number turbulence model was used, and the accuracy of the calculation model was verified by the experimental data of S-CO2 flowing upward in the vertical smooth tube. The variation characteristics of the axial and circumferential inner wall temperature Tw,i and the convective heat transfer coefficient h were analyzed. The S-CO2 would undergo the phase change from a liquid-like to the vapor-like at the pseudocritical temperature Tpcby assuming supercritical pseudo-boiling. Based on this assumption, the reasons for a difference in the wall temperature distribution at the top generatrix during S-CO2 flowing in different directions were studied. By the detailed analysis of the velocity distribution, thermophysical properties distribution, including specific heat capacity at constant pressure cpand thermal conductivity λ, and the turbulent kinetic energy k distribution in the cross-sections of the inclined circular tube, the heat transfer mechanism related to the wall temperature difference at upward and downward was studied. The results showed that the thickness of vapor-like film, axial velocity u, turbulent kinetic energy k, and the thickness of viscosity sub-layer δy+=5 were the main factors affecting the difference in the wall temperature distribution at the top generatrix in different flow directions.

关 键 词：超临界二氧化碳 倾斜圆管 传热 流动 数值模拟 

分 类 号：TM621[电气工程—电力系统及自动化] TK124[动力工程及工程热物理—工程热物理]