Rheological properties of diethylene glycol-based MgAl2O4 nanofluids

Abstract

Nanofluids (suspensions of nanoparticles in liquids) have been studied very intensively because they may find many applications in many fields including science, industry and medicine. Numerous studies have been carried out on the physical properties of nanofluids including thermal conductivity. However, sufficient and good quality experimental data do not exist to date to create a complete theoretical model of the rheological properties of nanofluids. This paper provides new experimental results in this field. The paper presents original experimental data from the rheological measurements of a MgAl2O4–DG nanofluid. Series of experiments were performed in a wide range of shear rates (from 0.01 s−1 to 1000 s−1) to determine the viscosity curves of this nanofluid and to characterize its Newtonian or non-Newtonian character. We have measured the viscosity of the nanofluid in the temperature range from 0 °C to 50 °C at a constant shear rate. We have also analyzed the visco-elastic structure of this nanofluid. Experimental data from diethylene glycol-based MgAl2O4 nanofluids clearly evidence a non-Newtonian behavior. In this paper we describe the unexpected behavior of MgAl2O4–DG nanofluids. It has been shown that the viscosity curve as a function of temperature can be approximated using the exponential function. It is shown that after the destruction of the thixotropic structure the viscosity curve can be approximated using the Cross model.