Enhancement of Flow Boiling Heat Transfer in High Quality Region in a Vertical Tube

(1)为实现管内流动沸腾强化传热，对管内流动沸腾传热进行了实验研究。增强剂采用特氟龙扭带插件。试验液体为氟里昂113，均匀加热管入口处的压力为0.3 MPa。质量流速范围为150 ~ 1500 kg/m^2s。(2)在光管中，除了核态沸腾区和两相对流沸腾区外，还观察到了螺旋带强化传热的现象。(3)在非沸腾区单相液体的强化作用随带扭比的减小而增大。增强率在捻比为10时为10%，在捻比为5.9时为12%。(4)对于带插入物，观察到相反的效果，增加和减少，在管壁温度突然开始上升的临界质量。(5)在干燥后的区域中的增强也随着带扭转比的减小而增加。

(1) An experimental study on flow boiling heat transfer is performed to attain heat transfer enhancement in a tube. Twisted tape-insert made of Teflon is adopted as the enhancement promoter. Test liquid is freon 113 and pressure at the inlet to the uniformly heated tube is 0.3 MPa. The range of mass velocity is 150 to 1500 kg/m^2s.(2) Heat transfer enhancement by the twisted tape-insert in a plain tube is observed, except for the nucleate boiling region and the two-phase convective boiling region.(3) The enhancement in the non-boiling region of the single phase of liquid increases with decreasing tape twist ratio. The enhancement ratio is 10% at a twist ratio of 10, and 12% at a twist ratio of 5.9.(4) Opposite effects, increase and decrease, on the critical quality at which tube wall temperature abruptly starts to rise are observed for the tape-insert.(5) The enhancement in the post dryout region also increase with decreasing tape twist ratio.