Influence of Structure and Wettability of Porous Silver Surfaces on Enhancing Phase Change Heat Transfer

The influence of the surface wettability and microstructure of porous silver surface layers on heat transfer during pool boiling and the evaporation of sessile drops from these surfaces was studied. These porous films were prepared by a modified freeze casting process and the wettability was found to be strongly influenced by the mass loading of silver nanoparticles in the starting colloidal suspension. As- prepared films typically show superhydrophylic behavior, most likely due to polyvinyl alcohol (PVA) binder remaining in the structure. The removal of this PVA by a hot wash in DI water revealed the intrinsic wettability of the surfaces. Heat transfer during the nucleate stage of pool boiling was found to be most efficient on hydrophilic surfaces with high Ag loading. The evaporation of sessile droplets from hot surfaces was also favored by more hydrophilic surfaces. The long term stability of these surfaces still remain an issue.