Experimental Investigation of the Resuspended Nanofluid Droplet Evaporation at Periodically Varying Electric Field

Abstract

The addition of nanoparticles can significantly increase the evaporation rate of droplets. However, there is still no consistent conclusion on whether the factor promoting droplet evaporation is the motion of suspended nanoparticles or the deposited nanoparticles changing the structure of the solid surface. Therefore, the fully deposited surfaces were prepared by drying 0.005-0.015 vol.% Al<sub>2</sub>O<sub>3</sub>-water nanofluids and the resuspension process of nanoparticles was investigated by applying periodically varying electric field. The mechanism of nanoparticle influence on the droplet evaporation process was investigated by measuring the contact angle, droplet height, and contact surface radius. The results show that the motion of suspended nanoparticles promotes the droplet evaporation. The evaporation time of droplets on the nanoparticle-deposited surface is longer than that on the nondeposited surface without electric field, while the trend is opposite in the presence of the electric field. After the electric field is applied, the nanoparticles are resuspended into the droplet due to the instability of the deposition layer structure. The motion of nanoparticles leads to an increase in the droplet evaporation rate, and the enhancement effect is optimal when the electric field switching frequency is 90 Hz.