Thermophysical properties and heat transfer performance of graphene nanofluid: An experimental analysis

The objective of this study is to experimentally analyze the thermophysical properties of 0.1% and 0.2% volume concentration (v.c.) Graphene nanofluids and their performance in cooling of Photovoltaic Panels using thermal collector system. Stability of nanofluids confirmed by Sedimentation photograph method and UV-Visible spectrometer. Thermophysical properties of nanofluids such as thermal conductivity, viscosity and density were experimentally measured over the temperature of 25 0 C to 60 0 C. Thermal conductivity of 0.1% and 0.2% v.c. nanofluids found to be increased with temperature as compared to base fluid. The maximum thermal conductivity of 0.824 W/m.K observed for 0.2% v.c. nanofluid at 50 0 C. The viscosity of nanofluids linearly increased with nanoparticle loading corresponding to the temperature and shear rate. The viscosity of 0.1%v.c. and 0.2%v.c nanofluid decreased by 46.91% and 42.75% when temperature increased from 25 0 C to 60 0 C. The rheological analysis depicted the shear thinning behavior of nanofluids. The good degree of fit between rheological data and Cross model indicated that Cross model successfully captured all key non-Newtonian regimes. The experimental values of thermophysical properties are compared with values predicted by their respective theoretical models. The heat transfer performance of de-ionized water and nanofluids analyzed and observed maximum thermal efficiency of 91.18%, 69.46% and 28.47%, heat removal rate of 314.03 W, 231.01 W and 79.63 W for 0.2%, 0.1% v.c. nanofluid and DI water respectively by optimizing the flow rate. Maximum difference in surface temperatures of PVT and reference PV module was observed to be 10.2 0 C, 7.2 0 C and 4 0 C for corresponding fluids.