Abstract
In the present work, the boiling heat transfer coefficient (BHTC) and fluid flow characteristics of graphene oxide nanoplatelets (GONPs) nano-suspensions in an annular heat exchanger (AHEX) were experimentally investigated. The BHTC, pressure drop (PD) and the friction factor (FF) of the heat exchanger was quantified, and effects of various operating conditions including heat flux (HF), flow rate (FR), the temperature of the nano-suspension and the mass concentration (MC) of the GONPs on the HTC and the PD of the system was assessed. Results showed that by increasing the HF, the weight concentration of the GONPs, and the temperature of the working fluid, the BHTC of the system increases. Also, the presence of GONPs can augment the friction forces, viscosity, and, as a result, increase the PD and the FF of the system. For all the experiments, the BHTC of the system was more significant than water. A comparison between water- perfluorohexane and water-n-pentane nano-emulsions revealed that water-n pentane has better thermal performance and lower PD in comparison with perfluorohexane despite the presence of the GONPs within the bulk of the nano-emulsion. (C) 2020 The Authors. Published by Elsevier B.V. on behalf of Faculty of Engineering, Alexandria University.