Experimental investigation of the propylene glycol-treated graphene nanoplatelets for the enhancement of closed conduit turbulent convective heat transfer

This research investigated the heat transfer characteristics of propylene glycol-treated graphene nanoplatelet-based water (PGGNP-Water) nanofluid. To reach a stable collide in liquid media, miscible PG was decorated. The PGGNP-Water with specific surface area of 750 m(2)/g used under closed conduit turbulent convective heat transfer inside a circular copper tube was subjected to constant wall heat fluxes 23,870 W/m(2) and 18,565 W/m(2). The experiments were conducted for a Reynolds number range of 3900-11,700. The impact of the dispersed nanoparticles concentration on thermal properties, convective heat transfer coefficient, Nusselt number, Friction factor, performance index, pumping power and efficiency of loop are investigated. An enhancement in thermal conductivity of PGGNP was observed in between 20% and 32% compared to base fluid. It was found that the PGGNP-Water has a maximum of 119% higher heat transfer coefficient compared to base fluid at 0.1 wt.%. The performance index and pumping power showed the positive effect. The results indicated that both Nusselt number and friction factor of the nanofluid increase with increasing particle volume concentration and Reynolds number. It appears that PGGNP-Water nanofluids can function as working fluids in heat transfer applications and provide good alternatives to conventional working fluids in the thermal fluid systems. (C) 2016 Elsevier Ltd. All rights reserved.