Dropwise condensation provides larger heat transfer coefficients compared to filmwise condensation, as discovered in the year 1930 by Schmid et al. Dropwise condensation can be described as a phenomenon of the incomplete wettability of a surface.
The wettability of the surface is responsible for the formation of the respective type of condensation and has a very strong effect on the performance of the heat transfer process. Likewise, the wettability of the surface has a very strong effect on the subcooling of the condensate, for constant cooling performance.
Although the conditions necessary for promoting dropwise condensation are well known since several decades, and experiments with coatings as promoters have been carried out successfully, at least in part, the application of dropwise condensation is still today in a testing phase.
The main problems in the realization of dropwise condensation are the insufficiency of the theoretical description of working boundary surface phenomena, such as complete or incomplete wettability and their strong dependence on influences caused in the practical operation by contamination, oxidation of the surface, adsorption layers, and gas enclosures.