Application of central composite design approach for predicting and optimization of viscosity of TiO2-MWCNT/Water-EG nanofluids

In this research, a central composite design was employed to appraise the effect of parameters of volume fraction, temperature and shear rate on rheological behavior of TiO2-MWNCT/water-EG nanofluids. TiO2- MWNCT/water-EG nanofluid is used because there exists a relationship for viscosity of TiO2-MWNCT/water-EG nanofluid in terms of volume fraction, temperature and shear rate that is not yet provided. The viscosity was evaluated in different volume fractions ranging from 0.05 to 0.85. modeling analysis indicated good fit of the experimental data to the quadratic polynomial model with coefficient of determination (R2) value of 0.9861 and F-value of 111.49 The results revealed that all three parameters of volume fraction, temperature and shear rate and the interaction between them affect the nanofluid viscosity. The optimum value of volume fraction, temperature and shear rate for viscosity of TiO2-MWNCT/water-EG nanofluid were 0.85%, 50 oC and 100 rpm, respectively. Viscosity measurements also showed that the viscosity decreases with increasing temperature and rises with an increase in the solid volume fraction.

Keywords:

Nanofluid , Viscosity , Analysis of Variance (ANOVA) , Central composite design (CCD) , Ethylene glycol , TiO2 , MWNCT