Investigation on the Effect of Al2O3 Nanoparticle with Surfactant on Electrical Performance of Synthetic Ester Liquid

Nanofluids with surfactants show uniform dispersion of nanoparticles in the base fluid. In the present study, nano-alumina particles were dispersed in synthetic ester fluid with Span 80 as a surfactant. Uniform dispersion and stability of nanoparticles were ascertained through zeta potential measurements. The performance of nanofluids with surfactant was analysed by carrying out breakdown studies under AC, and lightning impulse voltages. The optimized surfactant-modified nanofluid was observed to have improved positive Lightning Impulse breakdown voltage by 12.5 %, along with an increase in the time to breakdown ( $\Delta\mathrm{t}$ ). The modified version of Abedian and Sonin's theory is used to deduce the wall charge density coefficient for Al 2 O 3 -ester-based nanofluid in a Couette flow using a spinning disk system. The study of streaming current due to flow electrification shows that surfactant-modified nanofluid has higher streaming current as compared to unmodified nanofluid. The effect of temperature on electrification current has been observed within a temperature range of 30°C to 90 °C at different angular velocity. The streamline pattern along with surface velocity magnitude is simulated under different disk velocity and dimension using COMSOL to realize the hydrodynamic condition of flow of nanofluid.