Numerical modeling of the thermophysical performance of mineral oil-based dielectric nanofluids to improve the cooling in power transformers

Searching for ways to improve the thermophysical properties of insulating oils used in power transformers is crucial to increasing heat transfer efficiency and keeping this effective device in the electrical network as long as possible. Nanotechnology has provided promising solutions for high voltage engineers to use in enhancing the thermal properties of dielectric fluids through the thoughtful incorporation of nanoparticles. This study presents a numerical modelling of the thermophysical properties of dielectric nanofluids based on the finite element method. To shed light on the role of nanoparticles in improving the thermal performance of mineral oils, three types of conductive, semiconducting and insulating nanoparticles were used separately in the dielectric fluid (SiC, TiO2, and Al2O3) and at different volume concentrations (0 vol.%, 0.25 vol.%, 0.44 vol.%, 0.62 vol.%, 1.1 vol.%). Furthermore, the physical properties were measured over a large temperature range of 20-80 ?C The results showed an increase in the value of thermal conductivity, viscosity, and density of the insulating fluid when nanoparticle were added, where the effect was more evident with the integration of larger quantities of nanoparticles. This increase was suppressed by the change in temperature. The improved thermal conductivity contributes to enhancing the cooling capacity, but the high viscosity and density of the nanofluids lead to a decrease in pressure and an increase in pumping requirements. On the contrary, a reduction in the specific heat capacity of mineral oil was observed at addition of nanoparticles, which can negatively affect the thermal performance.