Modeling and Multi-Objective Optimization of Thermophysical Parameters of Hybrid Nanodiamond–Ni-Based Nanofluids via Response Surface Methodology

The present study comprises the modeling and optimization of the thermal and viscous properties of nanodiamond–nickel (Ni) particle-based nanofluid in ethylene glycol. The temperature and nanoparticle weight percentage are selected as the process variables, which are considered crucial for the operational condition of the application and the economic factor. The impact of these process variables was investigated on thermal conductivity and viscosity simultaneously using response surface methodology (RSM). The models for thermal conductivity and viscosity were developed and validated using experimentally measured property data. The validated model was further used for the prediction. A detailed multi-objective optimization study was conducted to maximize thermal conductivity and minimize viscosity. The optimum results suggested that the maximum values for thermal conductivity and viscosity of nanofluids were estimated to be 0.282 Wm/°C and 5.867 mPa·s, respectively. The optimum values for the input parameters such as temperature and nanodiamond–Ni concentration were calculated to be 60°C and 2.998 wt.%, respectively. The coefficient of determination R2 for the developed model showed 0.9971 and 0.9975 for thermal conductivity and viscosity, respectively.