Viscosity and thermal conductivity correlations for various nanofluids based on different temperature and nanoparticle diameter

Nanofluids properties such as viscosity, thermal conductivity, specific heat and density are needed to analyze the coefficients of convective heat transfer. By the mixture relations in the literature, the nanofluids specific heat and density can be measured conveniently. In contrast, thermal conductivity and viscosity are the most sophisticated parameters which are strongly depending on the nanofluid temperature and diameter of the nanoparticles. The properties of nanofluids have been determined by researchers for various base fluids and temperatures. This research is going to analyze the existent data to extend the correlation based on linear regression for measuring the viscosity and thermal conductivity of water and EG-based nanofluids. In this work, the nanofluids are considered as homogenous medium. Also, the effective parameters of thermophysical properties are considered too. Because of the nanofluids thermophysical properties analysis, equations are extended as parameters function. The strong dependence of thermal conductivity increment and viscosity reduction with temperature change the range of usability of nanofluids for heat transfer utilizations. The proposed correlations are compared with other literature relations to validate them. The obtained correlations show that they are able to calculate the viscosity and thermal conductivity of various sorts of water and EG-based nanofluids at different temperature (5oc <= T-nf <= 70oc), various particle diameters (5 nm <= d(np) <= 150 nm) and different nanoparticle concentrations (1% <= phi <= 5%) very well.