Experimental investigation of laminar forced convective heat transfer of Graphene-water nanofluid inside a circular tube

In this paper, convective heat transfer coefficient of Graphene-water nanofluid in a laminar flow through a circular pipe with uniform wall heat flux is investigated experimentally. To achieve this aim, the nanofluid is synthesized chemically in various concentrations, and a testbed is constructed. The effective thermal conductivity and viscosity of the Graphene-water nanofluids are measured via hot wire method and an Ubbelohde viscometer, respectively. Results show that addition of low amounts (up to 0.02% volume fraction) of Graphene nanoparticles to water considerably increases the thermal conductivity and the convective heat transfer coefficient of the working fluid. Maximum enhancements are observed at 0.02% concentration. These enhancements are 10.3% for thermal conductivity and 14.2% for heat transfer coefficient at Re = 1850. Moreover, the stability of the prepared nanofluids is examined by using the UV-vis spectroscopy and is proved to be acceptably high. Finally, the results of the taken AFM images implied no agglomeration of nanopartides. (C) 2015 Elsevier Masson SAS. All rights reserved.