The Effect of Temperature on the Viscosity of Cobalt Ferrite Nanofluids

Abstract

The temperature dependence of viscosity is an essential property of the magnetic fluids applied for heat transfer systems. This property was considered in our work for Cobalt ferrite nanofluids - one of the most explored magnetic materials recently by their improved magnetic characteristics. Cobalt ferrite nanoparticles (CFNPs) were prepared by the co-precipitation method. The characterization of the synthesized particles was analyzed by various techniques such as X-ray diffraction, transmission electron microscopy, vibrating sample magnetometry, and thermal gravimetric analysis. The effect of temperature on the viscosity of Cobalt ferrite nanofluids was investigated. Experiments were carried out in the range of particle concentration from 0.5 to 7 % without and with a magnetic field application. The dynamic viscosities of these nanofluids were measured as the shear rate and temperature dependence under the magnetic field of different intensities, using a standard rotating rheometer. The cobalt ferrite fluids exhibit a yield shear-thinning behavior at all the temperatures from 25 to 55 oC. The experimental results show that the viscosity decreases when the temperature is increased. This variation is exponentially and dependent on the shear rate. The temperature-dependent viscosity is not influenced significantly by either particle concentration or magnetic field. From the obtained results, the Arrhenius equation for the viscosity-temperature relationship is applied.