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...[ Read more ]

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.