Effect of a graphene oxide coating layer on critical heat flux enhancement under pool boiling

We report an investigation of the boiling heat transfer characteristics of graphene-based materials. Pool boiling experiments were carried out to investigate the critical heat flux (CHF) enhancement in a graphene oxide (GO) colloidal suspension with various concentrations as the working fluid with a Nichrome wire heat source. We found that nucleate boiling resulted in deposition of the GO colloids onto the heated wire, whereby the GO flakes formed a smooth laminated film, and that the thickness of this layer was approximately proportional to the observed increase in the CHF. The surface wettability could not explain the enhancement in the CHF. Instead, we focused on thermal activity analysis based on heat dissipation effects of the GO layer with extraordinary thermal properties. The large thermal conductivity of the GO layer inhibited the formation of local hot spots, thus preventing the formation of dryout regions and delaying the CHF. Furthermore, a thermal reduction of the GO colloids led to further increase of its thermal conductivity, also thermal activity, and hence additional enhancement of the CHF. (C) 2014 Elsevier Ltd. All rights reserved.