Surface wettability effects in heat and fluid flow

Effects of surface wettability on liquid-vapor phase change phenomena and single- and two-phase flow in tube have been studied in wide range of contact angles using superhydrophilic (SH) and super-water-repellent (SWR) surfaces. Heat transfer in failing film evaporation on a TiO2-coated SH surface is tremendously enhanced due to very thin stable film. In pool boiling, critical heat flux (CHF) and minimum heat flux (MHF) increase with the decrease in contact angle. Wetting limit temperature of water drop on heated surface increases with the decrease in contact angle. In pool boiling on SWR surface, bubble nucleation and film boiling occur in extremely small superheating. Drag reduction was observed in water flow in tube with SWR coating in laminar flow region, and on the other hand, in two-phase flow pressure drop for the SH wall is smaller than that for the SWR wall.