Improved wettability of graphene nanoplatelets (GNP)/copper porous coatings for dramatic improvements in pool boiling heat transfer

摘要

Graphene nanoplatelets (GNP) are known for their excellent thermal and mechanical properties making them suitable candidates for a variety of engineering applications. In this work, a novel GNP/Cu porous coating obtained via a multistep electrodeposition technique is presented and tested for their efficacy in improved critical heat flux (CHF) and heat transfer coefficient (HTC). An array of hierarchical porous coatings was obtained by systematically increasing the GNP concentration in the electrodeposition bath and were found to be superhydrophilic with very high wicking rates. Our pool boiling tests indicate that 2% GNP/Cu (wt/vol.) surfaces yielded a CHF of 286 W/cm(2) and a heat transfer coefficient of 204 kW/m(2)-degrees C, representing an improvement of 130% in CHF and 290% in HTC compared to pristine copper surfaces. The reported CHF and HTC represent the highest values reported in the literature till date for pool boiling on a plain surface. This enhancement in heat transfer properties is attributed to the hierarchical pores that serve as the nucleation sites and influence the overall bubble dynamics that is responsible carry the heat between liquid and vapor phases. The porous surfaces also improved the surface wickability and wettability that further promoted nucleation and microlayer evaporation. (C) 2018 Elsevier Ltd. All rights reserved.