Droplet evaporation is a common and natural phenomenon under an unsaturated vapor pressure. This process appears in many applications such as spray cooling, inkjet printing and fuel combustion. Nanofluids are advanced fluids with thermophysical properties that are different from their base fluids. The thermophysical properties include thermal conductivity, viscosity and enthalpy of vaporization etc. Owing to the change of thermophysical properties, nanofluids are used in many applications such as heat transfer, automobiles and electronics.

The evaporation kinetics directly influences the performance of the applications and the nanoparticle size affects the thermophysical properties and hence it changes the evaporation kinetics of the nanofluid. Researchers are interested to inv...[ Read more ]

Droplet evaporation is a common and natural phenomenon under an unsaturated vapor pressure. This process appears in many applications such as spray cooling, inkjet printing and fuel combustion. Nanofluids are advanced fluids with thermophysical properties that are different from their base fluids. The thermophysical properties include thermal conductivity, viscosity and enthalpy of vaporization etc. Owing to the change of thermophysical properties, nanofluids are used in many applications such as heat transfer, automobiles and electronics.

The evaporation kinetics directly influences the performance of the applications and the nanoparticle size affects the thermophysical properties and hence it changes the evaporation kinetics of the nanofluid. Researchers are interested to investigate how the particle size influences the evaporation kinetics of nanofluids of different concentrations. After evaporation, a residue pattern is left on a substrate which relates to the evaporation kinetics, particle size and concentration. Therefore, this study is about the evaporation kinetics and residue pattern of different particle sizes and concentrations.

9 nm, 13 nm, 20 nm, 80 nm and 135 nm diameters of Al2O3 particles suspended in water were investigated, experimentally, in relation to the evaporation kinetics. The sessile droplet was deposited on a stainless steel substrate. It was found that the evaporation kinetics of any concentrations of 9 nm and 13 nm, where are 0.14 and 0.18 respectively, are higher than those of 20 nm, 80 nm and 135 nm, where are around 0.12 to 0.13. The evaporation kinetics affects the residue pattern. From the results, the patterns can be classified into two types: (1) ring-shaped and (2) uniform. It is noted that concentrations below 1 vol% of 9 nm and 13 nm result in ring-shaped residue patterns while the patterns of concentrations above 1 vol% of 9 nm and 13 nm and any concentrations of 20 nm, 80 nm and 135 nm are uniform. The different pattern is because of the various internal flows of different particle size.