Evaporative Characteristics of Al2O3 Nanofluid Droplet on Heated Surface

Abstract

The present study experimentally investigates the evaporative characteristics for a nanofluid droplet on heated surface.For experiments, the alumina (Al2O3) nanoparticles having a 50 nm average diameter were distributed in deionized (DI)water. The equilibrium contact angles (ECA) of DIwater on bare (without texturing) and holepatterned textured (by آµCNC machine) copper surfaces were 60o and 82o. Also, advancing and receding contact angles were 73.3o and 25.8o forbare surface, and 101.3o and 55.2o for textured surface. Surface temperature was fixed as 100آ±0.2oC, measured byresistance temperature detector (RTD) sensors with data logger. During the experiments, the ambient temperature was22oC with the relative humidity of 32%. At the initial stage, the dynamic contact angle (DCA) of 0.01 vol.% nanofluiddroplet on the textured surface drastically increased over its own ECA due to the generation of large bubbles inside thedroplet. However, the contact angle of 0.1vol.% nanofluid droplet at t = 5 s was smaller than that of 0.01vol.% casebecause the increase in nanofluid concentration caused the reduction of surface tension. After that, DCA graduallydecreased until dried out, and total evaporation time was significantly delayed in the case of textured surface. Moreover,the heat transfer characteristics during evaporation phenomenon was affected by the nanofluid concentration and thecontact area with the heated surface.