Nanofluids have become a popular way of increasing the efficiency in solar energy applications and enhancing the thermophysical properties of the fluid. This thesis contributes to the field of solar energy utilization by two distinct projects. The first part is a thermal analysis involving a single plasmonic nanoparticle, exposed to radiation, in a solid medium that undergoes phase change creating a liquid film around the particle. The temperature profiles for the particle, film, and solid medium are analyzed. It is shown that the larger particle heats faster, developing a smaller surrounding film; however, the integrity of the smaller particle will stay intact for longer. Compromise between the thermal resistance at the interface of the particle and film as well as the absorption from radiation in order to determine the proper particle type, size, and medium is studied. The effect of the inclusion of the particle/film interface resistance is clarified.
In the second part of the thesis, a nanofluid mixture containing two or more different types of plasmonic nanoparticles, based on the absorption of the particles when exposed to radiation, is optimized. Because of the tunable plasmonic properties of metallic nanoparticles and the many possible variables to consider, two different optimization techniques were used in order to determining the correct recipe of nanoparticles submerged in water for a given temperature in order to get the maximum absorption. This contribution will help to determine which particle mixture would be required when exposed to radiation depending on the particular set of particles, size of particles, height of the container, concentration, and incident temperature.