# Fewer Dimensions for Higher Thermal Performance: A Review on 2D Nanofluids
## 3 Application of 2D Nanofluids
### Transformers  
The high TC and superior dielectric performance of 2D nanofluids, together with their general low-cost synthesis processes, makes them a strong solicitant for application in thermal management devices and systems, such as electrical transformers. The present section elucidates upon the improved thermophysical properties, and the possible applications and research gaps related to the employment of two-dimensional nanofluids in electrical transformers. To ameliorate the transformer oil thermoelectric characteristics, diverse experimental works based on the replacement of the traditional transformer mineral oil with vegetable oils have been performed, since these possess improved insulation and thermal performance. However, vegetable oils become easily contaminated which can result in the degradation of the oil properties, which in turn alters the chemical reactivity with the transformer operating parts. The degradation of the inner parts of the transformer may result in serious faults, economic losses, and extended shutdown. To solve these problems and to enhance the heat transfer and insulation features of the transformer, nanoparticles suspended in a base fluid are becoming of great interest to researchers in this field. Particularly, 2D layered nanomaterials are gaining importance in the transformers field of research and 2D nanofluids may be a promising alternative to two-dimensional fillers in the transformer liquid insulation circuit due to their very high surface area, surface-to-volume ratio, and improved stability. The facile and low-cost synthesis of 2D nanofillers makes them useful in the thermal management systems of transformers and in the breakdown voltage of the insulating fluid. Beheshti et al. [149] incorporated MWCNTs into a transformer mineral oil and found a marked enhancement in the TC, a reduction in the viscosity, and a rising temperature in comparison to those properties of the transformer oil. Moreover, the authors Maharana et al. [150] prepared a nanofluid with mineral oil as the base fluid and with the incorporation of h-BN and titanium oxide nanoparticles to be used as a transformer coolant. They exfoliated 1 \(\upmu\)m-sized bulk h-BN nanoparticles into 2D nanosheets with dimensions of 150 nm to 200 nm, increasing the surface area of the exfoliated h-BN. After the zeta-potential analysis, the weight fractions of 0.01% wt. and 0.1% wt. of the nanoparticles were selected to evaluate the heat transfer and insulation characteristics of these fractions dispersed in mineral oil, which are the main functionalities of a transformer oil. The TC and charging dynamics analysis were performed by the authors to infer the potential of the developed nanofluids to be used as dielectric fluid for transformers in comparison to the traditional mineral oil. Particularly, the charging dynamics investigation confirmed the increase in the AC breakdown voltage of the exfoliated h-BN nanofluids. Considering the results, the authors arrived at the following conclusions:  
* The inclusion of 0.01 wt.% of exfoliated h-BN nanoparticles resulted in a more stable solution and possessed the most improved cooling and insulation properties. * The high aspect ratio and enhanced surface charges in h-BN were the main factors contributing to the higher TC of the mineral oil-based h-BN nanofluid. The higher moisture content in the mineral oil and nanofluids reduced the AC breakdown voltage. Nonetheless, the exfoliated h-BN nanoparticles possess low affinity towards moisture and increase the AC breakdown voltage in reference to mineral oil and other nanofluid fillers. In the study developed by Almeida et al. [151], the thermophysical and electric characteristics of a traditional transformer oil were determined with the incorporation of 0.01% wt., 0.03% wt., and 0.05% wt. Gr nanoparticles within a temperature range of 20-90 \({}^{\circ}\)C. Based on the experimental results, the authors stated the following conclusions:  
* The 0.05% wt.