加热条件下倾斜管中超临界CO_(2)流动与传热特性数值模拟

Numerical Simulation of Flow and Heat Transfer Characteristics ofSupercritical CO_(2) in Inclined Tube Under Heating Condition

超临界CO_(2)(SCO_(2))布雷顿循环具有广阔的应用前景,其流动与传热特性规律对系统发电效率及安全运行至关重要。基于FLUENT软件进行数值模拟,分析加热条件下倾斜上升管及下降管中SCO_(2)的流动与传热特性。研究了倾斜角度、流动方向、运行工况等参数对SCO_(2)的阻力与传热系数的影响。结果表明:在上升管中,倾斜角度的增加会使沿程压力降低,对流传热系数和阻力系数升高;在下降管中,倾斜角度的增加会使对流传热系数和沿程压力升高,阻力系数降低;倾斜角度的变化对浮升力和热加速效应几乎没有影响;下降管的综合传热性能整体优于上升管,并且竖直下降管的综合传热性能最优;压力和热流密度对SCO_(2)对流传热系数的影响较小,质量通量对其影响较大。

The supercritical CO_(2)(SCO_(2))Brayton cycle has a broad application prospect,and the flow and heat transfer characteristics of SCO_(2) are very important for the power generation efficiency and safe operation of the system.The flow and heat transfer characteristics of SCO_(2) in inclined up-tube and down-tube under heating condition were analyzed by FLUENT numerical simulation software.The effects of tilt angle,flow direction and operating conditions on the resistance and heat transfer coefficient of SCO_(2) were studied.The results show that,the pressure decreases and the convective heat transfer coefficient and resistance coefficient increase with the increase of the up-tube tilt angle.The convective heat transfer coefficient and the pressure increase and the resistance coefficient decreases with the increase of the down-tube tilt angle.The change of tube tilt angle has little effect on the uplift and thermal acceleration effect.The overall heat transfer performance of down-tube is better than that of up-tube,and the comprehensive heat transfer performance of vertical down-tube is the best.The influence of pressure and heat flux on SCO_(2) convective heat transfer coefficient is small,but the influence of mass flux is larger.