Prediction of Thermal Conductivity and Convective Heat Transfer Coefficient of Nanofluids by Local Composition Theory

Abstract

In this study, a new method based on the local composition theory has been developed to predict thermal conductivity, convective heat transfer coefficient, and viscosity of nanofluids. The nonrandom two liquid (NRTL) model is used for this purpose. The effects of temperature and particle volume concentration on thermal conductivity, convective heat transfer coefficient, and viscosity are investigated. The adjustable parameters of the NRTL model were obtained by fitting with experimental data. The results of the local composition theory are compared with the experimental data of CuO/water, Al2O3/water, TiO2/water, Cu/water, Au/water, Ni/water, TiO2/ethylene glycol, and Al/ethylene glycol (EG) nanofluids and a good agreement between the theory and the experimental data is observed. The absolute average deviation of the model for thermal conductivity was 1.51% in comparison to 42% in conventional models. This parameter for viscosity and convective heat transfer coefficient were 2.91% and 2.13%, respectively. Moreover, a new equation for calculating convective heat transfer coefficient of nanofluids is proposed and tested.