Thermo-physical properties investigation of a TiO2-POE nano-oil

Several studies have been recently carried out on nanofluids due to their potentiality to enhance thermophysical and tribological properties of common fluids, especially when used in thermal energy systems. In particular, the available literature shows that the use of nano-oils in a refrigeration plant as compressor lubricant allows getting better performances due to lower compression work and better heat exchange conditions. The present work aims at investigating some thermophysical properties of nano-oils formed by a commercial POE oil and Titanium oxide (TiO2) nanoparticles. A two-step procedure has been used to prepare few nano-oils with different TiO2 concentrations: commercial nanoparticles have been added to the base oil, and then homogenously dispersed using ultrasonic technique. Good dispersion and stability have been obtained by optimizing sonication time and power. No dispersant has been added. Stability has been evaluated through a Dynamic Light Scattering system. Nano-oils have been characterised by measuring thermophysical properties, namely thermal conductivity and viscosity, by means of a Hot Disk thermal conductivity-meter and a cone-plate rheometer, respectively. Both pure oil and nano-oils have been analysed to compare their physical properties. No increments in conductivity and very low enhancements in viscosity have been observed increasing the nanoparticles concentration.