Conversão fototérmica em nanofluidos utilizando coletor plano montado em posicionador solar

Abstract

This study investigated experimentally photothermal conversion silver nanofluids / water with different concentrations of nanoparticles dispersed in the base fluid. Stable nanofluids were obtained with high-pressure homogenizer and the experiments were performed under direct sunlight during different times of the day, simulating actual operating conditions. To obtain the best possible performance, a solar positioner was developed, and this enabled the monitoring of the sun as much as the time variation in changing the inclination of the sun's rays and also in other controlled variables. We studied the different concentrations of nanoparticles in nanofluids, seeking to verify the influence of this variable in the energy absorption process and also in modifications of thermo-physical properties of the fluid. The conduct of the tests complied with the regulatory standards and possible expands the knowledge about the photothermal conversion using nanofluids. The results showed that the lowest nanofluid presented photothermal conversion capability that distilled water circuit directly, using natural convection as a means of fluid circulation. The water tank grew by up to 4.5°C in average temperature since the reservoir with nanofluid (=0,008% de Ag) showed lower temperature rises, or up to 2.2°C. This was due to the increased dynamic viscosity nanofluid which leads to increased pressure drop in the flow and consequently the reduction of mass flow.