Stability and Thermophysical Properties of Silicon Carbide and Carbon Nanofibers Thermal Oil Hybrid Nanofluids

Abstract

Hybrid Nanofluids (HNFs) have been widely investigated to improve the thermal efficiency of energy systems, thereby reducing overall energy consumption. Silicon Carbide (SiC) nanoparticles offer excellent thermal stability, and Carbon Nanofibers (CNF) provide superior phonon-mediated thermal conduction. However, their synergistic combination as HNFs remains largely unexplored. In this study, SiC and CNF are dispersed in thermal oil (THO) at concentrations of 0.1%, 0.3%, 0.5%, 1.0%, and 2.0% by mass, using ultrasonication and the surfactant Span 85. The batch sedimentation stability analysis is performed on four stages to achieve the long-term stability of SiC-CNF HNFs. The thermophysical properties of the SiC-CNF HNFs are investigated over the temperature range 25 –75 °C. SiC-CNF HNFs exhibit a maximum thermal conductivity enhancement of 32.3% at 0.5 wt% compared to THO at 55 °C. A maximum viscosity and density enhancement of 18.7% and 1.55%, respectively, is calculated. SiC-CNF HNFs followed both the power law and the Herschel-Bulkley model and exhibited non-Newtonian behavior. Artificial neural network (ANN) models are developed to predict the thermophysical properties of SiC-CNF HNFs effectively. The optimized models achieved coefficients of determination (R²) values of 0.7606 for thermal conductivity, 0.9844 for viscosity, and 0.9999 for density, respectively. These experimental and modeling results indicate the significance of SiC-CNF-based HNFs for effective thermal management systems integration.