Visualization Study of Condensation on Copper Surface

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, R141b 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 R141b 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.