Effect of surfactants on thermal conductivity of graphene based hybrid nanofluid

Abstract

Various hybrid nanofluids have been researched in this decade. The quality of this said-to-be alternate heat transfer medium depends on two major features – long term stability and high thermal conductivity. In recent years, graphene-based nanofluid was reported to exhibit distinguished heat transfer performance compared to most materials investigated in past studies. This study aims to compare the effect of different surfactants on thermal conductivity of graphene-based nanofluid. Sodium dodecylbenzenesulfonate (SDBS) and hexadecyltrimethylammonium bromide (CTAB) were mixed separately in advance with the mixture of water and ethylene glycol. After mixing surfactants and base fluid, total 0.025 to 0.1 wt% of nanoparticles were added into the mixture and followed by ultrasonication. Mono nanofluid was produced by adding graphene nanoplatelets (GnP) only whereas a novel hybrid combination was composed of graphene nanoplatelets and titanium dioxide. Stability of each sample was inspected using zeta potential analysis and Uv-vis spectroscopy. Thermal conductivity of samples from 30 oC to 60 oC was measured using Decagon KD2 Pro. Both surfactants contributed to high zeta potential value and minimal sedimentation for all nanofluids. CTAB improved the thermal conductivity of hybrid nanofluid more compared to SDBS, with 11.72% difference at 0.1 wt% nanoparticles concentration when compared to base fluid at 60 oC. The highest enhancement (23.74%) on base fluid was spotted at 60 oC, where 0.1 wt% of GnP was mixed with CTAB. These findings could strengthen literature on suitable surfactant to be used on graphene based nanofluid since limited comparison work has been done. High thermal conductivity of the hybrid nanofluid at high temperature could be used as coolant in cooling system.