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 DI-water on bare (without texturing) and textured (by μ-CNC machine) copper surfaces were 60o and 82o at the ambient temperature, respectively. Surface temperature was fixed as 100±0.2oC, measured by resistance temperature detector (RTD) sensors with data logger. During the experiments, the ambient temperature was 22oC with the relative humidity of 32%. At the initial stage, the dynamic contact angle (DCA) of 0.01 vol.% nanofluid droplet on the textured surface drastically increased over its own ECA by generated large bubble due to lower surface energy. However, the initial contact angle of 0.1vol.% nanofluid droplet on textured surface decreased with the surface tension. After that, DCA gradually decreased 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 the contact area with the heated surface.ater. The equilibrium contact angles (ECA) of DI-water on bare (without texturing) and textured (by μ-CNC machine) copper surfaces were 60o and 82o at the ambient temperature, respectively. Surface temperature was fixed as 100±0.2oC, measured by resistance temperature detector (RTD) sensors with data logger. During the experiments, the ambient temperature was 22oC with the relative humidity of 32%. At the initial stage, the dynamic contact angle (DCA) of 0.01 vol.% nanofluid droplet on the textured surface drastically increased over its own ECA by generated large bubble due to lower surface energy. However, the initial contact angle of 0.1vol.% nanofluid droplet on textured surface decreased with the surface tension. After that, DCA gradually decreased 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 the contact area with the heated surface.