Guideline for selecting appropriate mixing ratio of hybrid nanofluids in thermal management systems

To investigate the effect of different nanoparticles on thermophysical properties of hybrid nanofluids, 15 groups of Al2O3-Cu-CuO/water (W) ternary hybrid nanofluids were prepared with 0.5 vol% and various mixing ratios of components using a two-step method. Moreover, CATREG (Category Regression) and sensitivity analysis were used to analyze the experimental data. The results showed that the contribution of the three particles to viscosity and thermal conductivity were found in the following ascending order: Cu < Al2O3 < CuO and CuO < Cu < Al2O3, respectively. Finally, the CATREG method was used to predict the values of viscosity and thermal conductivity of hybrid nanofluids. The average deviations between the experimental and predicted values were ±2.24% and ±0.53% for viscosity and thermal conductivity, respectively. The optimum mixing ratio of Al2O-Cu-CuO/W hybrid nanofluid was determined to be 20:50:30 for application in laminar and turbulent convective heat transfer applications.