Stability Optimization of Al2O3/SiO2 Hybrid Nanofluids and a New Correlation for Thermal Conductivity: An AI-Supported Approach

Due to their high thermal conductivity compared to traditional coolants, nanofluids are preferred; however, their high thermal conductivity alone is meaningless without ensuring their stability. Therefore, when determining the appropriate mixing ratio (hybrid ratio) for hybrid nanofluids, which are starting to replace mono nanofluids today, the primary factor to consider should be stability. In this study, sedimentation and zeta potential measurements, which are methods for evaluating stability, were used to assess the stabilities of mono Al₂O₃/water and SiO₂/water nanofluids with mass fractions of 1 %, 2 %, and 3 %, as well as hybrid Al₂O₃/SiO₂/water (2 % to 1 %, 1 % to 2 %) nanofluids together for the first time in the literature, and the optimum Al2O₃/SiO₂ hybrid ratio was determined in terms of stability. The results showed that the optimal hybrid ratios for the stability of Al₂O₃–SiO₂/water nanofluids are 1 and 0.714. Furthermore, the thermal conductivities of stable mono and hybrid nanofluids were measured between 25 and 60 °C, and a new correlation valid for both mono and hybrid nanofluids was proposed by modeling with artificial neural networks (MSE = 8.2175E−5 and R² = 0.99958), with a maximum deviation ratio of 3.839 % (for mono SiO₂/water) from the experimental measurements.