THESIS
2021
1 online resource (xxiv, 240 pages) : illustrations (some color)
Abstract
Thermal management of high heat flux devices is becoming a key challenge, mainly due to
dense packaging, chip miniaturization, high power density and enhanced output performance.
Despite high heat removal rates achieved in phase change processes, such as the spray cooling,
immense heat dissipation in high heat flux devices may not be thermally managed by
conventional heat transfer fluids (such as water and dielectric fluids) due to their limited
cooling capacity. This research is an effort to address heat dissipation issues in high heat flux
devices (for instance, electric vehicle high power electronics) using an advanced thermal fluid,
that is, the hybrid nanofluid, in a droplet based spray cooling process.
This research shows that as hybrid nanofluid spray droplets evaporate, a porous...[
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Thermal management of high heat flux devices is becoming a key challenge, mainly due to
dense packaging, chip miniaturization, high power density and enhanced output performance.
Despite high heat removal rates achieved in phase change processes, such as the spray cooling,
immense heat dissipation in high heat flux devices may not be thermally managed by
conventional heat transfer fluids (such as water and dielectric fluids) due to their limited
cooling capacity. This research is an effort to address heat dissipation issues in high heat flux
devices (for instance, electric vehicle high power electronics) using an advanced thermal fluid,
that is, the hybrid nanofluid, in a droplet based spray cooling process.
This research shows that as hybrid nanofluid spray droplets evaporate, a porous residue
comprising hybrid nanoparticles is formed over a substrate. As a main novelty of this thesis,
wetting and phase change behavior of the subsequent hybrid nanofluid droplet over a residue
formed by evaporation of the preceding hybrid nanofluid droplet for various mixing ratios and
residue sizes are investigated. Analytical and semi-analytical mathematical models are
developed to estimate the hybrid nanofluid droplet evaporation rate over plain copper and
porous residue surfaces. This research indicates that both the residue size as well as the mixing
ratio considerably affect the evaporation and boiling performances of the subsequent hybrid
nanofluid droplet sitting over the residue from previously evaporated hybrid nanofluid droplet. Therefore, the residue effect on evaporation performance of subsequent droplets is important
to consider in hybrid nanofluid spray cooling of high heat flux devices.
In this thesis, the hybrid nanofluid spray cooling performance for various particle
concentrations is investigated and compared with the benchmark fluid (water). Finally, it is
demonstrated that the hybrid nanofluid spray cooling has a potential to keep high power
electronics of current and future electric vehicles within safe temperature levels thus preventing
device failures that may not be achieved using existing thermal fluids.
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