蒸气在铜表面冷凝的可视化实验  

Visualization Study of Condensation on Copper Surface

作　　者：张雷刚[1] 陈振乾[1] 

机构地区：[1]东南大学能源与环境学院,南京210096

出　　处：《空间科学学报》2016年第4期547-551,共5页Chinese Journal of Space Science

基　　金：载人航天工程空间应用系统天舟一号货运飞船科学实验项目资助(TZYY08001)

摘　　要：通过建立蒸气冷凝过程的可视化实验装置,在地面重力条件下对蒸气在铜表面的冷凝情况进行实验.采用高速摄像仪对蒸气在铜表面上发生的冷凝过程进行观测,并对比分析了H_2O,R141b以及FC-72蒸气的冷凝情况.研究发现水蒸气在冷凝过程中一些大液滴在合并周围小液滴后会发生回弹现象,从而清理掉周边区域的小液滴.随着冷凝的进行,被清理掉小液滴的区域又会重新生成小液滴.这种回弹现象相当于延长了滴状冷凝的时间,从而起到强化冷凝换热效果.R141b及FC-72在光滑铜表面上均未发生滴状冷凝.在加大过冷度后,冷凝器内残留的空气还会在冷凝液膜上冷凝成小水滴,产生滴膜共存现象.水蒸气在铜表面冷凝过程中,滴状冷凝转换成膜状冷凝后热流量降低约20%,因此需要对铜表面进行改性处理,降低其表面能,从而强化冷凝换热.In this paper,the visualization experiment device for vapor condensation is established,and vapor condensation on the copper surface is studied by use of the device.Firstly,vapor condensation on the copper surface is observed by using high-speed camera.The condensations of H2O,R141 b and FC-72 are analyzed.The observation results show that a rebound phenomenon emerge after small droplets are merged by the nearby large droplets,thus the small droplets around large droplets are cleaned out.As the condensation has progressed,small droplets are regenerated in the region where they are merged.The rebound phenomenon is equivalent to prolong the dropwise condensation time,and accordingly enhance the effect of condensation heat transfer.Dropwise condensation does not occur as R141 b and FC-72 condenses on the smooth surface of copper.After increasing the degree of subcooling,the residual air in the condenser condenses into small droplets on the condensation film,and coexistence phenomenon of droplet and liquid film emerge.In the process of water vapor condensing on the copper surface,heat flux decreases about 20%when dropwise condensation turns into film condensation.Therefore,the copper surface should be modified to reduce its surface energy,so as to enhance the condensation heat transfer.

关 键 词：地面重力 冷凝 可视化 

分 类 号：V524[航空宇航科学与技术—人机与环境工程]