The use of surfaces with wettability gradient aims to cover
the surface with drops of small size to allow a large heat
exchange. Thus, the action of the wettability gradient on the
surface of the substrate is twofold: on the one hand, it allows the
preservation of a dropwise condensation regime for which the
heat exchange coefficient is particularly important and, on the
other hand it allows the evacuation of the dispersed phase, thus
promoting a renewal of the surface with very important heat
exchanges during the nucleation phase. Thereby, a heat transfer
enhancement factor up to 3.4 has been experimentally measured.
Papers presented at the 13th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Portoroz, Slovenia on 17-19 July 2017 .