Determination and measurement of some thermophysical properties of nanofluids and comparison with literature studies

Abstract

The thermophysical properties of nanofluids must be determined to evaluate their thermal performances like heat transfer, convection heat transfer coefficient, Nusselt number. The purpose of this study is to obtain the thermophysical properties of nanofluids. Al2O3, TiO2, and ZnO are used as a nanoparticle, while deionized water is used as base fluid. The solutions included nanoparticles in a way to be each with 0.5%, 0.7%, and 1.0% volumetric concentration were prepared. SDS was added to the solutions as a surfactant to prevent instability that occurred due to agglomeration and sedimentation. For thermal conductivity measurement, the device that works by the transient hot-wire method was used between 30-60?C temperatures. Also, for viscosity measurement, the device that works as based on the vibrating plate method was used between 20-50?C temperatures. Density and specific heat values are obtained with the help of the well-known equations while thermal conductivity and viscosity are measured. Thanks to this study, it is emphasized how thermophysical properties of nanofluids change according to temperature and volumetric concentration. Moreover, their curve fitting equations are obtained. All of the thermophysical properties compared with the studies in the literature. It is established that the thermal conductivity of nanofluids is proportional to temperature, and viscosity of it is proportional to volumetric concentrations but inversely with temperature. Finally, the effects of the augmentation in dynamic viscosity on pumping power were considered as well as the increase in thermal conductivity; thus, no abnormal heat transfer enhancement was observed.