Boiling-induced surface aging and crystallization fouling of functionalized smooth and laser-textured copper interfaces

• Published in: Applied thermal engineering Vol. 242; p. 122540
• Main Authors: Berce, Jure, Arhar, Klara, Hadžić, Armin, Zupančič, Matevž, Može, Matic, Golobič, Iztok
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.04.2024
• Subjects: Crystallization fouling; Heat transfer; Laser-texturing; Pool boiling; Surface aging; Surface engineering; Surface aging; Laser-texturing; Surface engineering; Crystallization fouling; Pool boiling; Heat transfer
• ISSN: 1359-4311
• DOI: 10.1016/j.applthermaleng.2024.122540

[Display omitted] •Surface superheat increases during long-term operation in water and salt solutions.•Nucleation activity drops due to wetting, surface chemistry and topography changes.•Boiling curve stability is an uncertain indication of surface’s long-term operation.•Aging mechanisms found in water appear in solutions with lower relative importance.•Laser-texturing improves resistance to boiling-induced degradation by up to tenfold. Long-term boiling stability marks an important and often overlooked characteristic when engineering advanced interfaces for efficient phase-change heat removal. This study presents long-term pool boiling on functionalized smooth and laser-textured copper interfaces in de-ionized water and in an aqueous solution of calcium sulphate. Each surface was exposed to nucleate boiling for several hundred hours and wettability, morphology and surface chemistry were evaluated prior to and after each test. In addition, consecutive pool boiling curves were recorded on all samples. Our findings indicate an increase of wall superheat on all samples, caused by added thermal resistance in the salt solution and by diminished nucleation activity in water. The latter resulted from spatially non-uniform and interconnected mechanisms of wettability transition towards hydrophilicity, surface chemistry changes and topography deformation. These mechanisms also appeared in salt solutions, where their relative importance compared to dominant influence of scaling was linked to crystallization-mitigative ability of the interface. In both liquids, laser-textured surfaces exhibited up to an order of magnitude lower degradation rates. Our results also emphasize the importance of evaluation times of several days to accurately gauge boiling-induced changes to the surface and the ambiguity of evaluating the latter through boiling curve stability.