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 hole-patterned textured (by µ-
CNC machine) copper surfaces were 60o and 82o. Also, advancing and receding contact angles were 73.3o and 25.8o for
bare surface, and 101.3o and 55.2o for textured surface. 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 due to the generation of large bubbles inside the
droplet. However, the contact angle of 0.1vol.% nanofluid droplet at t = 5 s was smaller than that of 0.01vol.% case
because the increase in nanofluid concentration caused the reduction of 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.