Influence of processing conditions of polymer film on dropwise condensation heat transfer

The effect of processing conditions of polymer film on dropwise condensation heat transfer of steam under atmospheric pressure is investigated to find an effective technique to prepare a viable polymer film sustaining long-term dropwise condensation pattern state. The polytetrafluoroethylene (PTFE) films were coated on the external surfaces of brass tubes, copper tube, stainless steel tube and carbon steel tube by means of the dynamic ion-beam mixed implantation technique, with a variety of surface processing conditions. The experimental results indicated that heat flux is increased by 0.3-4.6 times and condensation heat transfer coefficient by 1.6-28.6 times of film condensation values for the brass tubes treated with various conditions. The surface processing condition is crucial to the adhesion between polymer film and metal substrate, different substrate material requires different optimal processing condition, and leads to different condensation heat transfer characteristic. (C) 2002 Elsevier Science Ltd. All rights reserved.