Thermophysical properties of nanofluids and empirical correlations

Nanofluids are two phased systems and colloidal suspensions of nanoparticles in convenient carrier fluids and used in a wide variety of applications from medicine to engineering. Among these potential applications, nanofluids in heat transfer devices has been comprehensively studied in recent years as it was shown that the thermophysical properties of base fluids are highly affected by the addition of nanoparticles. By considering the significant role of the thermophysical properties of materials in heat transfer applications, the investigation of these features of nanofluids such as density, viscosity, and thermal conductivity is crucial in order to use them efficiently in practical applications. In addition, it is known that nanofluids are not conventional suspensions thus, their thermophysical properties are not described by classical theories. Although models that are capable of predicting the aforementioned properties for particular nanoparticle-base fluid systems were presented in the literature, correlations that can be used for a more extensive class of nanofluids are limited. Therefore, it is necessary to formulate empirical correlations to estimate thermophysical properties of nanofluids where direct measurement is not applicable. Current study focuses on the investigation of the thermophysical properties such as density, viscosity, and thermal conductivity of conventional heat transfer fluids consisting of magnetite, copper oxide and silver nanoparticles. Furthermore, it is intended to generate empirical correlations that serve to predict the thermophysical properties of nanofluids as a function of particle loading and temperature by using the measured data. The results indicate that the viscosity and thermal conductivity of base fluids are highly affected by the addition of nanoparticles as compared to density for which the corresponding base fluid values may be considered for applications. In addition, the empirical models which were formulated by using the measured data demonstrated the possibility of estimating system specific thermophysical properties and inability of forming generalized correlations