Experiments and modeling of boiling heat transfer of GNP nanofluids with metallic elements.

This study investigates the boiling characteristics of graphene (GNP) nanofluids, graphene-copper (GNP-Cu) composite nanofluids, and graphene-iron (GNP-Fe) composite nanofluids with mass fractions of 0.001%, 0.002%, and 0.003%. The results indicate that GNP-Cu and GNP-Fe nanofluids can simultaneously enhance the critical heat flux (CHF) and heat transfer coefficient (HTC). Among different mass fractions, GNP-Cu nanofluids with a mass fraction of 0.003% exhibited the highest CHF and HTC. Through the observation of bubbles, the research elucidated that the presence of copper and iron elements is crucial in enhancing heat transfer. Based on the experimental results, this study modified the boiling curve equation of Rohsenow into a linear function. The modified model can predict the boiling curves of GNP-Cu, GNP-Fe, and GNP-Ag nanofluids at various concentrations. Furthermore, the experimental findings indicated a quadratic relationship between the boiling heat transfer coefficient and the heat flux in GNP, GNP-Cu, GNP-Fe, and GNP-Ag nanofluids. As a result, this study investigates the differences in heat transfer and bubble dynamics among GNP nanofluids modified with various metallic elements during boiling. It explores the underlying heat transfer mechanisms and proposes boiling curve equations that are applicable to a range of nanofluids. The findings suggest that acid-mixing treatment and metal-functionalization play a facilitating role in heat transfer of GNP nanofluids. Furthermore, nanofluids loaded with different metallic elements exhibit similar trends in their boiling curve equations. [ABSTRACT FROM AUTHOR]