The effect of TiO2 doped multi-walled carbon nanotubes synthesis on the thermophysical and heat transfer properties of transformer oil: A comprehensive experimental study

The study was performed on the impact of adding hydrophobic TiO2 doped on multi-walled carbon nanotubes (MWCNTs) on the heat transfer performance, breakdown voltage (BDV), and thermophysical properties (thermal conductivity coefficient, volumetric specific heat, resistivity, diffusivity, viscosity, and viscosity index (VI)) of transformer oil (TO). The novelty of this study is the use of TiO2 doped MWCNTs nanoparticles synthesized in TO and a comprehensive experimental investigation of the properties of nanofluids. Experiments were conducted in heat transfer systems with four nanofluids, comprising TiO2 doped MWCNTs/TO at concentrations of 0.05, 0.1, 0.15, and 0.2 wt % in four input powers of 50.5, 75.6, 100, and 124 (W) in two current regimes, free air flow and forced air flow (using two blowers). For these purposes, hybrid nanoparticles were synthesized and the nanoparticles were confirmed using analyses including FTIR, XRD, SEM, and EDX. The maximum enhancement in the VI of nanofluids at 0.2 wt% of hybrid nanoparticles was equal to 34.86%. The maximum improvement in natural and forced heat transfer coefficient of nanofluids (NCHT and FCHT), which increased by 23.08% and 24.68%, respectively. According to the results, nanofluid with 0.1 wt% had good performance compared to other concentrations of nanofluids.