Scale effects on the latent heat of phase change & the effect of dynamic contact angles on dynamic capillary pressure
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Surface tension is an important material property that affects the behavior of micro/nano size thermal-fluid systems. In this dissertation, I investigate how surface tension affects the latent heat of a phase change in nanoscale systems as well as on the movement of water in microstructures. Classical thermodynamic models were developed to describe how the latent heat of melting in nano-pores depends on scale and were extended to the melting of metallic nano-particles. The results from these models were verified by comparison with experimental data from the open literature for hydrocarbons and water in nano-size pores, as well as for free standing metallic nano particles. A classical thermodynamic model was also developed to describe how the latent heat of vaporization depends on scale. This was verified experimentally using a Thermogravimetric Analysis/Differential Scanning Calorimeter available in the core facilities of the Texas Materials Institute. This verified that the latent heat of vaporization for water confined nano-pores decreases with pore size. A model for dynamic capillary pressure in porous media was analyzed using experimentally derived data for the velocity dependent contact angle of water on SiO₂ glass. The data were derived from images of microfluidic flows in capillary tubes, obtained using high speed digital microscopy.