INFLUENCE OF SURFACE PROPERTIES OF POLYMER FILM ON DROPWISE CONDENSATION HEAT TRANSFER

The objective of this paper is to investigate the influence of the surface properties of polymer film on dropwise condensation heat transfer of steam, in order to prepare a viable polymer film sustaining long- term dropwise condensation. The PTFE films are coated on the external surfaces of brass tubes, copper tube, stainless steel tube and carbon steel tube by using the dynamic ion- beam mixed implantation technique, under a variety of surface processing conditions. It is found that the surface properties are greatly dependent on the surface processing conditions, and hence leading to different condensation modes and heat transfer characteristics. The experimental results indicate that condensation heat flux and heat transfer coefficient are increased by 0.4-1.5 times and 1.6-28.6 times of film condensation values, respectively, for the brass tubes treated under different conditions. Meanwhile, the surface processing condition is also crucial to the adhesion between polymer film and metal substrate. The fact that different substrate materials require different optimal processing conditions and demonstrate different condensation heat transfer coefficient, can be drawn from the present results.