超临界压力CO_2在垂直管内对流换热准则关联式

Correlations of CO_2 at Supercritical Pressures in a Vertical Circular Tube

对垂直圆管（d=2 mm）内的超临界压力CO2,在压力为7.8~9.5 MPa、进口温度为25~40℃、进口雷诺数Re为3×103～2×104,向上流动和向下流动时的对流换热实验研究结果进行了分析。在无浮升力影响和浮升力影响较大两种情况下,将实验结果与已有的准则关联式进行了比较,发现两者偏差较大。因此,在基于实验结果的基础上,提出了新的预测超临界流体换热的准则关联式。

The experiment results of convection heat transfer of CO2 at supercritical pressures in a 2 mm diameter vertical circular tube for upward flow and downward flow were analyzed for pressures ranging from 78 to 95 bar,inlet temperatures from to 25 to 40℃,and inlet Re numbers from 3000 to 20000.The results were compared with some well known empirical correlations for the heat transfer without buoyancy effects and the heat transfer with strong buoyancy effects.It is found that there is a big deviation between the ex-periment results and empirical correlations.Based on the experiment data,correlations are developed for the local Nusselt correlations of CO2 at supercritical pressures in vertical circular tubes.