Thermal performance enhancement of diesel engine cylinder head using water and water–ethylene glycol based MgO and ZnO nanofluids

This research presents an experimental investigation of the cooling performance of diesel engine cylinder heads using magnesium oxide (MgO) and zinc oxide (ZnO) nanofluids as alternative coolants. The nanofluids were prepared using the two-step method by dispersing MgO and ZnO nanoparticles into both water and a 50:50 ethylene glycol-water mixture (EG/W) via magnetic stirring followed by ultrasonic agitation, and tested on an actual diesel engine cylinder head grade 300 (GG30). GG30 cylinder heads hold critical importance in automotive and industrial engine applications due to their unique combination of mechanical strength, thermal stability, and vibration damping properties. Experiments covered nanoparticle volumetric concentrations (φ) ranging from 0.25% to 1%. The experiments covered flow velocities between 1 and 2 m/s, bulk fluid temperatures from 70 °C to 90 °C, and heat fluxes spanning 30 to 430 kW/m². The findings are based on experimental measurements of the thermophysical properties of each tested nanofluid. At a flow velocity of 2 m/s, MgO-water and ZnO-water nanofluids with 1% nanoparticle concentration increased the heat transfer coefficient (h) by 61.69% and 28.46%, respectively, compared to pure water. For EG/W mixture as the base fluid, the maximum heat transfer coefficient enhancements at 2 m/s reached 40.71% for MgO and 18.39% for ZnO at φ = 1% and 0.75%, respectively. These enhancements provide substantial practical advantages for engine cooling, including an extended engine lifespan and reduced risk of thermal failure. The experimental findings were also used to develop empirical correlations to predict the Nusselt number of nanofluids in engine cooling applications. Thermophysical property measurements for water based nanofluids. Nanofluids Tested in full-scale diesel engine cylinder head under heat fluxes 30–430 kW/m². MgO–water nanofluid improved heat transfer coefficient by 61.7% when compared to pure water. ZnO–water nanofluid achieved 28.5% heat transfer enhancement under same conditions. With 50:50 EG/W, MgO improved by 40.7%, ZnO by 18.4%. New Nusselt number correlations achieved R² =0.986 with < 3% prediction error.