Experimental Analysis of Nanofluid Circulation in Automobile Radiators: Thermal Efficiency and Flow Behaviour

The heat transfer of coolant advancement through radiators significantly influences the optimization of fuel consumption in automobiles. In order to cool the circulating fluid, which is typically water or a water-based mixture, forced convection heat transfer is employed in automotive radiators. This study experimentally assessed the heat-transfer performance of an automobile radiator by evaluating the thermal performance of a specially prepared nanofluid. The nanofluid was created using a two-step process, involving demineralized water enhanced with graphene (GPN) nanoparticles at concentrations of 0.1 and 0.5 vol. %, along with the addition of GPN to cetyltrimethylammonium bromide (CTAB) surfactant in a 1:0.5 ratio for extended stability at the same concentrations. The experiments varied the liquid-side Reynolds number from 10,000 to 27,000, keeping the radiator inlet liquid at a constant temperature of 60–80 °C. This study thoroughly examined the impact of these variables on the overall heat-transfer coefficient. The experimental results show that the maximum increases in both thermal conductivity ratio and viscosity ratio were 32% and 144% without surfactant, and 33% and 165% with the addition of CTAB surfactant. The maximum average increases in the Nusselt number were 18.55% and 26.49% for the GPN/water nanofluid, and 49.05% and 57.56% for the GPN-CTAB/water nanofluid, respectively. The highest performance evaluation criteria relative to the Reynolds number using the GPN/water nanofluid at concentrations of 0.1 and 0.5 vol. % were recorded as 1.30 and 1.29, while for the GPN-CTAB/water nanofluid, the performance values were 1.14 and 1.10. Furthermore, the findings confirm that incorporating nanoparticles and surfactants into the base fluid results in superior performance compared to using water alone.