Development of water-based CuO, TiO2 and ZnO nanofluids and comparative study of thermal conductivity and viscosity

The present investigation elucidated the influence of nanoparticle volume fraction and temperature on the thermal conductivity and viscosity of water-based CuO, TiO₂ and ZnO nanofluids. All the nanoparticles used in the present study were synthesised using the chemical co-precipitation method and their structural and morphological features were explored by XRD and FESEM techniques, respectively. The investigated fluids were prepared using the two-step method by dispersing 0.1–0.5 wt% nanoparticles in distilled water. The thermal conductivities of all the nanofluids were determined in the temperature range of 30–70°C and viscosity in the range of 300–360 K. The experimental study demonstrated that the thermal conductivity and viscosity of the nanofluids depend on volume fraction and temperature. The dynamic viscosity and the thermal conductivity of all the nanofluids increased with the increase in the volume concentration of solid particles. The viscosity decreased and thermal conductivity increased with an increase in temperatures. When the three nanofluids are compared at the specified temperature range, CuO nanofluids showed higher thermal conductivity of 0.5856–0.6332 W\({/}\)mK for 0.1 wt% and 0.6476–0.7465 W\({/}\)mK for 0.5 wt% volume concentration and better viscosity than TiO₂ and ZnO nanofluids. The obtained experimental data were compared with some existing thermal conductivity and viscosity models. While comparing the thermal conductivity models, the P Bhattacharya model showed good agreement, whereas no viscosity model agrees with the experimental results. Thus, the obtained results of the prepared nanofluids are useful for conducting further studies in nanofluids.