hrvatski

NANOFLUIDI NA OSNOVI TRANSFORMATORSKOG ULJA I ŽELJEZOVOG OKSIDA

U ovom radu provedena su ispitivanja stabilnosti i primjenskih svojstava nanofluida na osnovi mineralnog transformatorskog ulja i nanočestica Fe3O4. Dosadašnja ispitivanja pokazala su kako dodatkom nanočestica u bazni fluid može doći do poboljšanja toplinske vodljivosti i probojnog napona baznog fluida. Rezultati preliminarnih ispitivanja gdje su upotrijebljene komercijalno dostupne površinski aktivne tvari (oleinska, palmitinska i stearinska kiselina) nisu pokazali zadovoljavajuću stabilnost nanofluida. Stoga su sintetizirane vlastite površinski aktivne tvari na osnovi kopolimera metil-, dodecil-, i dimetilaminoetil-metakrilata. Kopolimeri odabranih sastava sintetizirani su izravno u transformatorskom ulju u izotermnim uvjetima uz diperoksidni inicijator. Određena im je raspodjela molekulskih masa i viskoznost razrijeđenih polimernih otopina. Sintetizirani kopolimeri pokazali su se uspješnima kroz ispitani period od sedam dana gdje je utvrđeno da je raspršeno 22-26 mas. % čestica. Dodatak nanočestica Fe3O4 u transformatorsko ulje uz prisutnu polimernu površinski aktivnu tvar uzrokuje sniženje probojnog napona, međutim, dobivene vrijednosti su i dalje u granicama propisanima odgovarajućom normom. In this paper, main task was to perform investigations of stability and application properties of nanofluids based on mineral transformator oil and Fe3O4 nanoparticles. Previous investigations have shown that the addition of nanoparticles in the base fluid can improve the thermal conductivity and breakdown voltage of the base fluid. Results of preliminary tests where commercially available surfactant (oleic, palmitic and stearic acid) were used have not showed satisfactory stability of nanofluids. Therefore, new surfactants were synthesized based on copolymers of methyl-, dodecyl-, and dimethylaminoethyl-methacrylate. Copolymers of selected compositions were synthesized directly in the transformer oil under isothermal conditions by using bifunctional peroxide initiator. Distribution of molecular mass of polymers were obtained by GPC/SEC method and viscosity of polymer dilute solution by capillary viscometry method. The synthesized copolymers have shown as effective surfactants - it was found that after seven days the 22-26 mass.% of nanoparticles was dispersed. Addition of Fe3O4 nanoparticles in transformer oil along with present polymeric surfactant causes a decrease of the breakdown voltage. However, the obtained values are still within the limits required by corresponding standards.

nanofluid; transformatorsko ulje; Fe3O4; stabilnost; polimerna površinski aktivna tvar

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