Development of a Model for Predicting the Effective Thermal Conductivity of Nanofluids: A Reliable Approach for Nanofluids Containing Spherical Nanoparticles

The effective thermal conductivity of nanofluid is an essential thermophysical property, which associates with a volume fraction of nanoparticles, particle size distribution of nanoparticles, temperature and the density of the base fluid. The available experimental results indicate that the effective thermal conductivity of nanofluid highly relies on thermal conductivity of nanoparticle. It can be argued that when high thermal conductivity nanoparticles are added, Brownian movements of nanoparticles in the base fluid are increased. Moreover, Brownian movements of nanoparticles highly rely on the viscosity of the base fluid. In literature, numerous theoretical models have been proposed to predict the effective thermal conductivity of nanofluid. Nonetheless, most of these models were not able to predict the thermal conductivity adequately for a variety of nanofluids. In the present paper, the model was developed by studying Maxwell model, Hamilton and Crosser model, Koo and Kleinstreuer model and various experimental results. The correlation enables to predicts the thermal conductivity of a variety of nanofluids, (TiO₂, CuO, Fe₃O₄, ZnO, Al₂O₃)-Ethylene glycol, (CuO, Al₂O₃, Fe₃O₄, TiO₂, Nano Diamond (ND))-water, (SiO₂)-Synthetic oil and suits with the experimental data. The correlation was derived from 505 values of nanofluids thermal conductivity, 76% of them are correlated within a mean deviation of ±5%.