Comparison of Polarization Phenomena and Changes in Relative Permittivity in Mineral- and Ester-Based Nanofluids

Two different phenomena were observed in nanofluids with different oil-based fluids. While the relative permittivity increases in mineral oil-based oxide nanofluids, the opposite effect is seen in ester nanofluids. This paper describes the relaxation times and polarizations in pure oil samples and nanofluids, using Havriliak-Negami formula, a mathematical explanation of this phenomenon is attempted. An experiment was conducted where pure samples of the mineral oil Nynas Lyra, the natural ester rapeseed oil, and synthetic ester oil MIDEL 7131, and then their nanofluids with SiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> additive were measured. The measurements were carried out using Broadband dielectric spectroscopy as a function of frequency and temperature.