Nucleate boiling enhancement on bubble-induced assembly of graphene oxide/carbon black hybrid networks

Abstract

The efficiency and capacity of nucleate boiling can be enhanced by the bubble-induced assembly of nanoparticles, which are dispersed in a boiling liquid. Recently, carbon nanomaterials have attracted appreciable research interest for boiling heat transfer enhancement. This study presents nucleate boiling performance on interconnected graphene/carbon black hybrid films formed through the bubble-induced self-assembly of suspended particles. Aqueous graphene/carbon black hybrid solutions at varying concentration ratios (GO:CB; 1:0, 1:1, 1:5) were prepared via probe sonication. The solutions were then saturated and subjected to pool boiling under atmospheric pressure on a custom-made boiling test apparatus with a flat copper heating surface. Experiments were carried out at a stepwise increasing heat flux until the critical heat flux was reached. A heat transfer coefficient and critical heat flux enhancement of 223.0% and 182.4%, respectively, were achieved at a GO:CB concentration ratio of 1:5. The change in surface characteristics and, subsequently, the boiling performance were elaborated by conducting a series of surface characterizations such as Field Emission Scanning Electron Microscopy, Energy Dispersive X-Ray analysis, contact angle analysis, and surface profilometry. Nucleate boiling enhancement was attributed to the contribution of multiple factors such as surface roughening, increased effective surface area, decent interfacial contact within the assembly structure, improved capillarity, and lateral heat conduction.