Wettability, nanofluid, pool boiling, heat transfer
In refrigeration and air-conditioning systems, evaporator performance can be enhanced by avoiding dry-out of the tube wall. There are a myriad of other multiphase systems that can benefit from enhanced surface wetting. Using nanofluid boiling nanoparticle deposition (NBND), surface wettability can be enhanced significantly due to the formation of a porous layer that modifies liquid spreading. This paper will present an investigation of surfaces modified by nanofluid boiling using various types of nanofluids, namely, alumina, silica, titania and copper oxide nanoparticle aqueous suspensions. Scanning Electronic Microscopy (SEM) images show the growth of aluminum oxide hydroxide on the aluminum substrate, which enhances affinity with water, and the micro-structures introduced by nanoparticle deposition. Atomic Force Microscopy (AFM) reveals the physics of the wettability enhancement by NBND on ultra-smooth substrates, which is described by Wenzelâ€™s wetting model. The impact of this change in wettability on boiling heat transfer will also be discussed with data from pool boiling experiment. These results will guide the design of nanoporous superhydrophilic coatings to enhance heat transfer from a surface science point of view.