Microscopic experimental study of nanoparticle motion for droplet evaporation enhancement in nanofluids

Abstract

Adding nanoparticles to liquids to promote gas-liquid mass transfer has attracted attention in recent years. However, previous research mainly involved macroscopic experiments to determine the macroscopic behavior of nanoparticles to enhance absorption. In this paper, the microscopic state of the gas-liquid mass transfer of nanoparticles in the process of droplet evaporation is studied. The ability of nanoparticles to enhance mass transfer was measured and analyzed. Experimental results show that the concentration of nanoparticles gradually increases and becomes stable. In the initial stage of evaporation, the velocity of TiO2 nanoparticles caused by Brownian motion is 1.71 mm/s, but it decreases at 200 s, and then increases to 2.13 mm/s. The particle concentration at the gas-liquid mass transfer interface was initially very low, only 0.31 N/mm2 after 112 s, and gradually increased to 6.54 N/mm2 as the gas-liquid mass transfer progressed. The maximum enhancement factor E values of 60 nm and 100 nm TiO2 nanoparticles with a solid content of 0.4 g/L are 1.19 and 1.06, respectively. The effect of nanoparticles on the enhancement of deionized water droplet evaporation was determined to characterize the effect of nanoparticles on the enhancement of gas-liquid mass transfer.