Abstract

Experimental study of convective heat transfer in nano-fluid, containing Fe3O4 powder nano-particles without stabilizer and nano-fluid containing colloidal nanoparticles of Fe3O4, with stabilizer, is the main aim of this work. For this purpose, the Nytro Libra oil, as a conventional oil in power transformers has been considered as the base oil. Results show that the use of nanoparticles, improves the base fluid heat transfer characteristics. Also based on the experimental observations, the use of nanoparticles in the powder form, decreases and in the colloidal form increases the dielectric properties of transformer oil. Hence, the thermal behavior of the two types of nano-oils would be important. The results in present study showed that the convective heat transfer coefficient of nano-fluid, containing nano-particles in the powder form in a tube with constant heat flux, and volume concentration of 0.1% and 0.3%, is 7% and 9.5% mare than nano-oil containing colloidal particles and also 6.5% and 2.4% higher than the base oil, respectively. Finally, thermal behavior of different nano-oils samples are discussed, and other researcher’s arguments are also taken into consideration.