垂直向上流动通道内环状流干涸点的理论研究

Theoretical Investigation on Dryout Point of upward Annular Flow in Narrow Gap with Bilateral Heating

本文基于分离流模型,建立了垂直向上流动环形通道内环状流的三流体模型,并对干涸点进行了数值模拟。比较计算结果和实验结果,发现两者符合较好。结果显示:当干涸点发生在内管并且外管热流密度不变时,临界含汽率随曲率和间隙的减小而增大,当干涸点发生在外管且内管热流密度不变时,情况相反;对于固定的间隙,当外管内径大于20 mm时,或间隙小于0.5 mm时,压力和质量流速对临界含汽率的影响非常微弱。

Based on the separated flow model, a theoretical three-fluid model predicting for dryout point of annular upward flow in a vertical narrow annuli with bilateral heating has been developed in the this paper. The predicted results agree well with the experimental data. The numerical results show that： a） when the dryout point occurs on the inner tube, critical quality will increase with decreasing the curvature of tube and gap size for a fixed heat flux of outer tube. When the dryout point occurs on the outer tube, the case is reverse for a fixed heat flux of inner tube; b） the influences of pressure and mass flow rate on critical quality is very slight when the gap size is smaller than 0.5mm or the outer diameter of inner tube is larger than 20mm with a fixed gap size.