Influence of surface modified Fe3O4 nanoparticles on the dielectric properties of Natural ester based Nanofluid
Investigations during the last decade has shown that nanoparticles can be dispersed in insulating oils and form Nanofluids. There are promising results showing that the addition of nanoparticles to conventional transformer oils can improve their electrical and thermal characteristics. However, it is a challenge to surmount the problem of the agglomeration and expand the investigation to natural ester liquids apart from minerals.
In this paper, a study on the dielectric properties of a Natural ester based oil Fr3TM with the addition of surface modified Fe3O4 nanoparticles is presented. Surface modification of the nanoparticles is a vital procedure to avoid nanoparticle agglomeration in insulating Nanofluids. Herein, the Fe3O4 nanoparticles, known as magnetite, were ultrasonic dispersed and mechanically stirred with ethanol. The surface modified magnetite nanopartices with oleic acid were subjected to centrifugation, dried, grounded and ultrasonic dispersed into the natural ester oil for 1 hour.
Hereby, the Nanofluid is stressed under AC Voltage according to IEC 60156 and compared with pure natural ester oil and mineral. Furthermore, measurements of Dissipation Factor (DP) of Nomex ® Dupont TM insulating paper impregnated in Nanofluid and pure natural ester oil Fr3 TM respectively were carried out and compared. The measurements were carried out according to IEC 60250. After 0.25 gr of oleic acid/100 mL of ethanol were added to the mixture and were subjected to ultrasonic dispersion for 3 hours. The outcome results from the AC breakdown Voltage was that the values of the Nanofluid are slightly higher from the pure natural ester, however the Nanofluid keeps the higher thermal conductivity of the magnetite. The primary results of the comparative tests for the Dissipation factor, indicate a distinct decrease around 10% of the tand until a maximum rated voltage of 2 kV between the Nomex ® with Nanofluid compared with Nomex ® with pure natural ester oil.
Concluding, in this paper a Natural ester-based Nanofluid with surface modified magnetite nanoparticles (<50nm) was developed and its dielectric properties were studied. With the surface modification we accomplished the minimum agglomeration. Furthermore, we accomplished to improve the AC Breakdown Voltage and decrease the DP. Unfortunately, the basic physical mechanisms leading to such improvement are still not clear.