Suspension Stability of Transformer Oil-Based Nanofluids

The transformer oil-based nanofluids (TNFs) formed by adding nanoparticles into the pure transformer oil not only can improve the heat exchange properties but also can enhance the dielectric withstand characteristics of transformer oil, which show a wide prospect of application. Investigation on the suspension stability is of great significance to guiding the design and preparation of stable nanofluids system. In this paper, the effects of ultrasonic oscillation time, dispersant and temperature on stability of TNFs were analyzed by ultraviolet-visible spectrophotometry (UV-vis) and dynamic light scattering (DLS) methods. In addition, the molecular dynamics simulation was adopted to study the stability mechanism of TNFs, which provides a new perspective in guiding the preparation of TNFs. The experimental results indicate that there is an optimal ultrasonic shock time for the preparation of stable nanofluids, and the addition of dispersant can improve the long-term stability. But the increase of temperature will make the stability worse. By molecular dynamics simulation, it can be found that the main reason for improving the stability of transformer oil-based nanofluids by ultrasonic oscillation time is to reduce the diffusion coefficient of nanoclusters by reducing the particle size of nanoclusters. The dispersant increases the distance between the particles and reduces the van der Waals attraction potential between the particles

I. Introduction

To make transformer oil-based nanofluids widely applied in power equipment, the main problem that needs to be solved is the stability of transformer oil-based nanofluids. At present, there are many methods for evaluating the stability of nanofluids, mainly including sedimentation method, absorbance method, particle size analysis method and Zeta potential method. Each method has its own advantages and disadvantages. According to the research object and the observation time, choosing the right measurement method is important for accurately assessing the stability of the nanofluid. In this paper, particle size analysis and UV-vis spectrophotometry were used to comprehensively evaluate the stability of transformer oil-based nanofluids.