Promotion of dropwise condensation by silicones

"Within this rather extensive field of study, transfer of heat through fluid films and heat transfer during the condensation process have been the subject of considerable thought and investigation both from a theoretical standpoint and with the aim of collecting data on specific systems to aid the design and construction of equipment in which heat transfer is involved….The phenomenum of dropwise condensation has not become a common one in industrial practive for a number of reasons, namely, the difficulty in maintaining the activity of the promoter without frequent makeup because of impermanent attachment and volatility, the difficulty in finding substances which are extremely nonwettable by the condensing vapors in thin films and will form tenacious bonds with the tube surface, and the roughness of commercial heat exchange surfaces. The properties of silicone films plus their ease of application seem to point to them as one solution to the promoter phase of the problem.The sizable decrease in resistance to flow of heat (one tenth to one twentieth that of film) due to dropwise condensation, fully utilized by proper design of equipment, can effect considerable reductions in size and, hence, cost or equipment, and can accelerate the flow of heat in a given apparatus if this mode of condensation is maintained"--Introduction, pages 1, 3.