Enhancement of Exhaust Manifolds Using Hybrid Graphene-TiO₂ Nano Fluids in Multi-Cylinder Diesel Eng

This work is about graphene-TiO₂ hybrid nanofluid used for cooling a diesel engine exhaust manifold via coupled CFD simulations and experimental validation. The authors of this paper confirmed grid independence at more than 800 mesh elements with the pressure converging within -6 to 4 Pa. At 4.102 m/s velocity, the hybrid nanofluid caused a 7.016 Pa pressure drop, whereas the same for the conventional coolants was only 4.620 Pa thereby, the 52% rise in the pressure differential that correlates with the convective mixing enhancement. Streamline visualization depicted flow regularity improvement with the use of nanofluids, whereas turbu-lent kinetic energy increased steadily from 0.05 to 0.25 m²/s² over the 0-4 m/s velocity range, thereby promoting heat transfer directly. The enhancements in thermal conductivity of 5% and the heat transfer coefficients of 6% (with respect to the baseline fluid) have made it possi-ble to reduce the peak manifold temperature by 340°C. The pressure gradient or the change in pressure remained very stable (within ±6 Pa) all over the domain, which is a clear indication that the hydrodynamic behavior was under control. The experimental data corroborated the CFD predictions with temperature and pressure drop accuracy percentages of 30% and 20%, respectively. These results confirm that graphene-TiO₂ nanofluids are capable of resulting in specific improvement metric of "15% faster heat dissipation" or "20°C lower operating temperatures" in automotive exhaust systems and establish a validated computational framework for nanofluid-based thermal management design in internal combustion engines.