超临界CO_(2)水平管内动态冷却传热特性数值模拟研究

Numerical Study of the Transient Cooling Heat Transfer Performance of Supercritical CO_(2)

该文利用有限元与CFD的方法建立一维和三维模型,对超临界CO_(2)的动态冷却传热性能进行研究。该文比较了两种模型在外部热流密度发生扰动时的动态响应与反馈,并探讨浮升力效应对管内超临界CO_(2)动态流动换热影响。结果表明:超临界CO_(2)动态冷却的三维动态模拟与一维动态模拟所得出口参数的响应时间具有较大差距;三维模型和一维模型的出口参数动态响应时间在温度接近临界区且管径较大的时候有着较大的差异,浮升力作用是造成两者差异的主要原因之一;浮升力效应通过理查德森数进行量化,在相同管径条件下,Ri越大,三维模型和一维模型之间的差距越大,在Ri大于0.1时,三维动态和一维动态之间响应时间差距较为明显。

In this paper,the transient cooling heat transfer performance of supercritical CO_(2) is simulated using the one-dimensional and three-dimensional models.The transient heat transfer performances predicted by the two models are compared and the buoyancy effect is discussed.The results show that the response periods predicted by the 1-D model have a large deviation from that predicted by the 3-D model;the difference between the two models is enlarged when the fluid temperature is closed to the critical temperature;and the tube diameter is large.The buoyancy effect is considered to be one of the main reasons for the difference.The Richardson number is used to quantify the buoyancy effect.It is found that the difference between the response periods predicted by the 1-D model and the 3-D model is significant if the Richardson number is larger than 0.1.