Experimental Study on Thermophysical Properties of Propylene Glycol-Based Graphene Nanofluids

This study determined the optimal dispersion conditions of nanofluids by orthogonal experiments. Stable graphene/propylene glycol nanofluids are successfully prepared by a "two-step method" using a 60 wt % propylene glycol deionized water solution as the base fluid, and its thermal conductivity and viscosity are evaluated. Additionally, the effects of the graphene mass concentration and nanofluid temperature on thermal conductivity and viscosity are expounded, and a model for the prediction of thermophysical properties is established. The combined effect of thermal conductivity and viscosity on the heat transfer enhancement of nanofluids is analyzed theoretically, and the optimum mass concentration of graphene is determined. The results show that the thermal conductivity of nanofluids increases with the increase of the graphene concentration and nanofluid temperature. Also, the viscosity of nanofluid increases with the increase of the graphene concentration and decreases significantly with the increase of the nanofluid temperature. When the mass concentration of graphene is higher than 0.2 wt %, the increase in thermal conductivity caused by the increase of the graphene mass concentration decreases significantly, while the increase of viscosity increases significantly, and the effect of the heat transfer enhancement is almost not improved.