Highly wettable CuO: Graphene oxide core-shell porous nanocomposites for enhanced critical heat flux

Abstract

Copper oxide nanoparticles nanofluids (CuO-NPs-NF) are promising candidates for pool boiling critical heat flux (CHF) applications due to their multifaceted advantages like easy tunability, eco-friendliness, cost-effectiveness, easy chemical modification and higher thermal conductivities. In addition, entrapping the CuO-NPs in/on to graphene oxide (GO) improves the CHF values compared to CuO-NPs alone. This paper reports a high performance hybrid NFs based on CuO and GO nanocomposites (CuO:GO-NCs-NFs), exhibiting higher pool boiling CHF values even at very low concentrations. The proposed novel NFs have higher thermal conductivities compared with the DI water. The 0.06wt% CuO:GO-NCs-NF shows the highest CHF value, ca.160%, which is much higher than that of pure CuO-NPs-NF (99%). Atomic force microscope (AFM) and field-emission SEM (FE-SEM) micrographs of the wire after the pool boiling experiments revealed a rough surface having high wettability and lower contact angle (CA) with 47° due to the formation of a layer-on-layer network on the wire surface. In addition, we have developed a method for in situ generation of core-shell template model CuO-NPs using Ostwald's ripening method in isopropanol-water system. Eventually, the CuO:GO-NCs-NF could show robust and high performance CHF pool boiling even at low concentrations that are required in realistic applications. Schematic illustration of pool boiling CHF values of CuO-NPs and CuO:GO-NCs on nichrome wire surface. (a) Built-up layer roughness average by atomic force microscope (AFM) and (b) FEM-SEM. (c) comparison of pool boiling CHF experiment