Thermophysical performance of graphene based aqueous nanofluids

Study of thermophysical properties and forced convective heat transfer performance and flow characteristics for single layer graphene (GNP) based nanofluids was undertaken. Experimental results reveal that GNP mass fraction increases both the effective thermal conductivity and viscosity of the nanofluid. Furthermore, the graphene nanofluid suspensions exhibit a shear thinning behavior, which follows the Power Law viscosity model with a flow behavior index of about 0.938, suggesting particle-particle interactions. Experimental results show that inclusion of GNP in the host fluid increases pressure drop by 112-161% at the same flow rates. A new friction factor correlation is proposed for 1 wt% GNP nanofluids flowing through a circular pipe as non-Newtonian fluid. Furthermore, the Nusselt number (Nu) of GNP nanofluids decreases with axial distance at a much slower rate than that of the base fluid (water) due to viscous effect and particle interactions within the nanofluids. In addition, Nu values of GNP nanofluids are higher than for water under laminar flow conditions. Based on the classic Nu model for non-Newtonian flow in a uniformly heated circular pipe under laminar flow conditions, a new Nu correlation is proposed for 1 wt% GNP nanofluids, which fits the experimental data well.