Investigating the effects of carbon-based nanofluids on the interfacial evaporation of salt water under infrared light

Abstract

Among the numerous alternatives to solving global water scarcity, carbon-based nanoparticles seem to be the likely preference for obtaining fresh water, due to their thermal conductivity, affordability, and effectiveness. In this study, carbon-based nanofluids were prepared using carbon black and graphene inclusions to determine the impact of nanoparticles on salt water evaporation rates and to evaluate the photothermal, heat transfer, and water evaporation kinetics. Different percentages (0.05. 0.5, and 0.1 wt%) of carbon black and graphene were added into a 3.5 wt% sodium chloride (NaCl) solution (simulated sea water), tap water, and deionized (DI) water. Test results revealed that 0.1 wt% of carbon-based nanoparticles homogenized with a base fluid provided higher water evaporation rates than either the 0.5% or 0.05% carbon-based nanoparticles under a simulated infrared light with a power of 125 W and intensity of 440 W/m2 for 2 h. For instance, using 0.1 wt% carbon black along with a black absorber increased evaporation rates by 18.77% for salt water, 17.98% for tap water, and 16.05% for DI water under the same conditions. Adding a black absorber at the base of the fluid further increased the evaporation rate and water temperatures by a considerable amount. Due to the existence of carbon-based nanoparticles, the base fluid’s temperature was increased, and the surface tension was decreased, which in turn increased the water evaporation rates significantly. In all the tests, the addition of carbon black nanoparticles showed slightly better evaporation results than the rest of the nanoparticles, which may be because of the changes in surface oxidation, agglomeration, density and surface area. This study may provide a new direction for fabricating more advanced systems using carbon-based nanoparticles for industrial applications such as solar desalination, wastewater treatment, solvent evaporation, environmental cleaning, and salt and mineral production.