Investigation of electrical breakdown and heat transfer properties of coconut oil-based nanofluids

This paper presents the evaluation of two grades of coconut oil - RBD (refined, bleached, and deodorized) and virgin coconut oil, plus MIDEL eN1215 as standard natural ester, by dispersing Zinc oxide (ZnO) nanoparticles to improve their breakdown strength and cooling properties. It is shown that a stable nanofluid can be realized at different concentrations of ZnO nanoparticles with or without Oleic acid as a surfactant depending upon the moisture content in oil. Dry and wet nanofluids at 1 and 0.04–0.05 wt% nanoparticles concentration, respectively, showed increased AC breakdown voltage w.r.t individual base oils. As the temperature is raised to 85 °C, the increase in AC breakdown voltage has been insignificant except for wet oils, wherein the AC breakdown voltage increases by 20–36 %. RBD coconut oil shows better viscosity and heat transfer properties, and the latter enhances further by the addition of ZnO nanoparticles. Further, the resistance to thermal aging of various nanofluids at optimum wt% of nanoparticles in terms of various physical (viscosity, pour point, flash point) and electrical properties (resistivity, dissipation factor, AC breakdown voltage) have also been analyzed and discussed. [Display omitted] •AC breakdown voltage of RBD coconut oil is comparable to commercial natural ester•Coconut oils possesses lower viscosity and superior heat transfer than natural ester.•Improved AC breakdown voltage and heat transfer is possible in coconut oils with ZnO nanoparticles.•Long-term stability of the improved properties of Coconut oil based-nanofluid need to be verified.