Orientation effects on bubble dynamics and nucleate pool boiling heat transfer of graphene-modified surface

• Published in: International journal of heat and mass transfer Vol. 108; pp. 1393 - 1405
• Main Authors: Kim, TaeJoo, Kim, Ji Min, Kim, Ji Hoon, Park, Su Cheong, Ahn, Ho Seon
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.05.2017
• ISSN: 0017-9310; 1879-2189
• DOI: 10.1016/j.ijheatmasstransfer.2016.12.099

•2D and 3D graphene film enhanced pool boiling performance both boiling heat transfer coefficient (BHTC) and critical heat flux (CHF) on various orientation angles from upward (0°) to downward (180°).•On downward-facing (120–170°), graphene film showed early onset of nucleate boiling and increased nucleate site density, which led early mature of nucleate boiling regime, i.e. slug flow, resulting in enhanced BHTC.•The graphene film could delay CHF trigger efficiently even though it was covered with larger slug vapor. Modified surfaces with graphene coatings were evaluated experimentally to enhance nucleate boiling performance on an orientated surface, from upward to downward (0°, 45°, 90°, 120°, 135°, 150°, 160°, and 170°). Two-dimensional (2D) laminate and three-dimensional (3D) porous graphene were prepared for surface modification, and their boiling heat transfer coefficient (BHTC) and critical heat flux (CHF) values were evaluated according to orientation angle. Moreover, their boiling structures were observed and analyzed using high-speed visualization. The results showed that the surfaces coated with 2D and 3D graphene had enhanced BHTC and CHF performance in comparison with the bare surface with no graphene modification. The 2D graphene surface showed increased nucleate site density and early onset of nucleate boiling, resulting in enhanced BHTC, by 40%, in the downward condition. The enhancement ratio of CHF was 40% on 2D graphene and 20–25% on 3D graphene.