Study on insulating properties of mineral oil based zno nanofluid using dielectric spectroscopy

Abstract

This thesis basically proposes some advance methods to predict the time after the instant of preparation and the percentage concentration of nanofluids using dielectric spectroscopic methods. For this purpose, zinc oxide (ZnO) nanofluids based on mineral oil is prepared in the laboratory with different concentrations (i.e. 0.01%, 0.03%,0.05%, and 0.07%). First, ZnO nanoparticles are synthesized by low temperature hydrothermal method in laboratory. By employing X-ray diffraction methods, the average diameter of the ZnO nanoparticles is found to be 28.21nm. After that, ZnO nanofluids is prepared using two-Step process. To ensure the uniform dispersion of the nanoparticles, sonication followed by stirring process is employed. After the preparation of nanofluids, Polarization & Depolarization Current and Frequency Domain Spectroscopy measurement is conducted with different concentration along with several hours from the instant of sample preparation. From the time domain spectroscopy, various parameters are extracted using extended Debye model which are sensitive to the time after the instant of preparation and the percentage concentration of nanofluids. Similarly, from frequency domain spectroscopy, low frequency dispersion of capacitances and dielectric dissipation factor are evaluated which are found to be sensitive to the time after the instant of preparation and the percentage concentration of nanofluids. Using those aforementioned parameters, fourteen empirical relations are established. Then, to validate these relations, two samples are prepared in the laboratory with two different percentage concentrations of nanofluids. After that, the same experiments are conducted at two specific different instants from the time of preparation. Finally, percentage errors are calculated using those measured and obtained values. Based on this errors value, it can be stated that, using this method the time after the instant of preparation and the percentage concentration of nanofluids can be predicted accurately. This study further helps to prepare a long term stable nanofluids which may be used as a good alternative to mineral oil.