Thermo-Hydraulic Analysis of a Hybrid Nano-Coolant (TiO2–CGnP/Water-EG) in a Louvered-Fin Vehicle Radiator: Incorporation of Experimentally Measured Properties with 3D Simulation

The present study investigates the thermo-hydraulic performance of an automotive radiator equipped with louvered fins and flat tubes operating with a hybrid nano-coolant consisting of TiO 2 –carboxyl functionalized graphene nanoplatelets (CGnP) dispersed in a water–ethylene glycol base fluid (40:60). Effective thermophysical properties, including thermal conductivity and dynamic viscosity, are experimentally measured for single-component and hybrid nano-coolants over the temperature range of 47–57°C and then incorporated into three-dimensional CFD simulations under turbulent operating conditions. All nano-coolants exhibit higher thermal conductivity than the base fluid, and among all tested nanofluids, NF4 (1.0% TiO 2 + 1.0% CGnP) delivers the highest thermal conductivity across the entire temperature range. It outperforms the base fluid by 5.69–9.11%, with the maximum enhancement of 9.11% occurring at the highest temperature. Numerical results indicate that increasing the nano-coolant flow rate and inlet air velocity enhances radiator performance, with the Nusselt number increasing by about 36%, across the investigated operating range. The performance evaluation criterion (PEC) exhibited a local minimum near an inlet air velocity of 35 m/s, associated with unfavorable vortex formation within the louver passages. Despite this localized behavior, the PEC remains greater than unity throughout the operating range, confirming that heat transfer enhancement outweighs the corresponding hydraulic penalties and demonstrating the practical feasibility of hybrid nano-coolants for advanced automotive cooling applications. The findings suggest that combining high-conductivity CGnP with stable TiO 2 nanoparticles provides a promising strategy for improving radiator efficiency while maintaining realistic operational constraints.