Thermal conductivity enhancement of ethylene glycol and water with graphene nanoplatelets

In the present work, we report the effective thermal conductivity of ethylene glycol and water with graphene nanoplatelets. Sodium deoxycholate, a bile salt was used as the surfactant to prepare stable nanofluid dispersions. Stability tests were performed using UV-vis absorption spectrometry and zeta potential to monitor the stability of the prepared nanofluids as a function of time. Thermal conductivity measurements were carried out using transient hot wire technique. Thermal conductivity of the nanofluids significantly increases with respect to graphene loading. Maximum thermal conductivity enhancements of similar to 21% and similar to 16% at a loading of 0.5 vol% was obtained for the nanofluids with graphene nanoplatelets seeded in ethylene glycol and water respectively. Analysis of experimental results with Maxwell-Garnett type effective medium theory reveal that despite the high thermal conductivity of graphene, interfacial thermal resistance between graphene and the surrounding base fluid limits the thermal conductivity enhancement significantly. The interfacial thermal resistance between graphene sheet and ethylene glycol was found to be 2.2 x 10(-8) m(2) KW-1 while between graphene sheet and water was found to be 1.5 x 10(-8) m(2) Kw(-1) respectively for the present nanofluids. (C) 2016 Elsevier B.V. All rights reserved.