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

(1)为实现管内强化传热，进行了流动沸腾传热实验研究。采用聚四氟乙烯制成的扭曲带插入片作为增强促进剂。试验液体为氟利昂113，均匀加热管入口压力为0.3 MPa。质量速度范围为150 ~ 1500kg /m^2s。(2)除有核沸腾区和两相对流沸腾区外，在普通管中插入扭曲带对传热有增强作用。(3)随着带捻比的减小，液体单相非沸腾区的增强作用增大。当捻度比为10时，增强率为10%；当捻度比为5.9时，增强率为12%。(4)胶条对管壁温度突然开始上升的临界质量有增大和减小的相反影响。(5)干后区的增强也随着带捻比的减小而增大。

(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.