THESIS
2015
xiii, 81 pages : illustrations (some color) ; 30 cm
Abstract
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...[
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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.
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