Unsteady flow dynamics of kerosene and ethylene glycol hybrid nanofluids: thermal performance of ZnO-ZrO ₂ in a stratified medium

Kerosene is a common fuel in jet engines. When enhanced with zinc oxide (ZnO) and zirconium dioxide (ZrO2) nanoparticles, it can improve thermal conductivity, aiding in efficient heat dissipation and enhancing performance. Antifreeze such as ethylene glycol is frequently added to water in automobile cooling systems to prevent damage to radiators. With this motivation, the current study evaluates the thermal performance of kerosene and ethylene glycol base fluids dispersed with hybrid nanoparticles (ZnO + ZrO2) in a naturally convective boundary layer flow through a vertical cone in a thermally stratified medium. The comparative analysis focuses on the influence of magnetic field, radiation, variable thermal conductivity, and variable viscosity aiming to optimize hybrid nanofluid performance for industrial and engineering applications. The model equations of hybrid nanofluids are transformed into dimensionless form using an appropriate set of non-dimensional numbers. We solve the coupled PDE equations using the Crank–Nicolson finite difference methodology. The flow pattern for distinct parameters reveals the physical impacts with all other parameters fixed. Ethylene glycol nanofluids absorb and retain 24.34% more thermal energy than kerosene hybrid nanofluids due to their radiative characteristics. The local skin friction of variable viscosity 0.1≤γ≤0.3 increases at the rate of 25.50% in kerosene and 26.34% in Ethylene glycol. The findings are expected to provide insights into the suitability of these hybrid nanofluids in energy systems, automotive cooling, and heat exchangers.