Experimental investigation on thermal performance of kerosene–graphene nanofluid

• Effect of various surfactants on stability of GNP/kerosene nanofluid.
• Determination of stability and thermal conductivity with time.
• Mechanisms responsible for temperature dependency on thermal conductivity.
• Effect of GNP size and mass concentration on thermo-physical properties.
• Total heat transfer performance at turbulent flow regime.

Current study experimentally investigates the thermal performance of kerosene based nanofluid containing graphene nanoplatelets (GNP) for its potential use in regenerative cooling of semi-cryogenic rocket thrust chamber. Stable kerosene–GNP nanofluids at 0.005, 0.02, 0.05, 0.1, 0.2 weight percentage (wt%) and 300, 500, 750 m2/g, specific surface area (SSA) are prepared using ultrasonication and steric stabilization technique. Oleylamine is found to be the suitable surfactant with an optimum oleylamine to GNP mass ratio of 0.6, for maximum stability of nanofluid. Dynamic Light Scattering (DLS) technique along with thermal conductivity measurements are used to identify the stability of nanofluid with time. 23% enhancement in thermal conductivity and 8% increase in viscosity at room temperature are observed for 750 SSA, 0.2 wt% kerosene–GNP nanofluid. Lower enhancement in thermal conductivity and viscosity are noticed for nanofluid that is prepared with lower SSA GNPs. The study shows less significant effect of temperature on the thermal conductivity of kerosene–GNP nanofluid compared to kerosene–alumina nanofluid. The behaviour observed is collaborated due to the combined effect of Brownian motion in smaller size sheets and thermal conduction in longer chain structure. Maximum effect of temperature on thermal conductivity is observed for 750 SSA nanofluid as compared to other sizes of GNPs. Experimental study on convective heat transfer performance of the nanofluids at turbulent flow regime show significant improvement in heat transfer performance of kerosene–GNP nanofluid as compared to pure kerosene. 49% enhancement in convective heat transfer coefficient is noticed for 750 SSA, 0.2 wt% kerosene–GNP nanofluids. A correlation for friction factor based on the experimental data is also determined. Merit number, used to determine the total heat transfer performance shows the utility of these nanofluids as heat transfer fluids.