▎ 摘　　要

This study aims to research the flow, heat transfer and energy efficiency of a novel hybrid nanofluid containing graphene nanoplatelets decorated with platinum nanoparticles in a chaotic twisted minichannel. This geometry develops chaotic advection owing to geometrical perturbations. Dean roll-cells are formed in the channel, and are the cause for irregular trajectories of fluid particles. The channel includes four bends, such that the chaotic motions are strengthened gradually along the bends, and reach a maximum rate at the exit of them, which causes minimum wall temperature in those regions. To better evaluate the merit of chaotic channel, simulations are also performed in a simple channel. The convective heat transfer and pumping power in both channels augment by increasing either concentration or Dean number. The chaotic channel has higher heat transfer and pressure drop than the simple one. Due to the excellent attributes of graphene, not only heat transfer enhances significantly but also pressure drop does not increase noticeably by adding nanoparticles. Figure of merit, i.e. ratio of enhancement in convective hear transfer to enhancement in pumping power in the case of employing the chaotic channel rather than the simple channel, is always greater than 1.5, which demonstrates a promising outcome. (C) 2018 Elsevier Ltd. All rights reserved.