A model for temperature and particle volume fraction effect on nanofluid viscosity

A theory based model is presented for viscosity of nanofluids and evaluated over the entire range of temperature and volume fraction of nanoparticles. The model is based on Eyring's viscosity model and the nonrandom two liquid (NRTL) model for describing deviations from ideality (Eyring-NRTL model). The equation for viscosity is composed of a contribution due to nonrandom mixing on the local level and another energetic section related to the strength of intercomponent interactions which inhibit components from being removed from their most favorable equilibrium position in the mixture. The experimental data were used to evaluate existing models which do not contain adjustable parameters and Eyring-NRTL model. The Eyring-NRTL model was found to agree well with the experimental data with the restriction that contains adjustable parameters which were interactions in the form of NRTL constants. However, the agreement was even better if temperature dependent interaction parameters were used. Comparisons of predicted and actual viscosity over the entire temperature and volume fraction range illustrate an improvement over the conventional nanofluid viscosity models with 2.91% AAD. (C) 2010 Elsevier B.V. All rights reserved.