Performance investigation of multiwall carbon nanotubes based water/oil nanofluids for high pressure and high temperature solar thermal technologies for sustainable energy systems

Nanofluids are of paramount importance for the development of efficient and competitive heat transfer fluids. The research paper presents a comprehensive study of the thermal properties for developing water and Therminol oil-based nanofluids to operate at high pressure and temperature, which will ultimately support the development of a more comprehensive understanding for nanofluids based heat transport phenomena. Multiwall carbon nanotubes were suspended in water and Therminol 66 at three different weight concentrations from 0.05% to 0.5% with Acacia Gum and oleic acid as surfactants for water and Therminol 66, respectively. The experimental results show more than a 35% enhancement in the thermal conductivity for both the water-based nanofluids and Therminol-66 based nanofluids. This thermal conductivity was also found to be similar with small increment at high pressures for both the base fluid and nanofluids, up to 70 bar pressure and 300 °C. Furthermore, the simulations carried out on parabolic trough collector solar thermal system using nanofluid properties and system advisor model software, showed an enhancement in energy production along with 10.37% reduction in real power purchase agreement price as well as 21% reduction on the thermal energy storage volume.