Drag reduction and heat transfer characteristics of graphene oxide nanosheet suspensions

Abstract

This study investigated graphene oxide nanosheets, with excellent thermal conductivity and water dispersibility, as additives that could achieve a trade-off relationship between drag reduction and heat transfer improvement. We experimentally clarified the heat flow characteristics of graphene oxide nanosheet suspensions in a circular pipe. The graphene oxide nanosheets have a size of 0.8 nm × 3 μm × 3 μm. The test suspension concentrations were 0.1 wt%, 0.3 wt%, and 0.5 wt%. For a comparison, a 0.5 wt% TiO₂ suspension showing an improvement in the heat transfer coefficient and a 15 ppm Peo solution with drag reduction were also prepared. The experimental results show that the frictional coefficient of the graphene oxide nanosheet suspensions was reduced by up to 36.5% compared to that of distilled water in the turbulent flow region. The amount of drag reduction increased with the increase of Reynolds number. After reaching the maximum value, it gradually approached a constant value. Meanwhile, the Nusselt number of the graphene oxide nanosheet suspensions increased by 10 – 20% in the range of the Reynolds number where the drag reduction occurred. This result indicates that the nanosheets improved the heat transfer performance, which increased with increasing concentration and Reynolds number. In conclusion, improvements in both drag reduction and heat transfer cannot be achieved in the TiO₂ suspension and Peo solution, but these properties were found in the graphene oxide nanosheet suspensions used herein.