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Proceedings of the 27th National and 5th International ISHMT-ASTFE Heat and Mass Transfer Conference December 14-17, 2023, IIT Patna, Patna-801106, Bihar, India
December, 14-17, 2023, Bihar, India

Coupled vapor bubble and microlayer dynamics during nucleate flow boiling on nanocoated surfaces offering varying wettability

Get access (open in a dialog) DOI: 10.1615/IHMTC-2023.1640
pages 1011-1016


Phenomenon of boiling heat transfer is strongly influenced by the wetting characteristics of the substrate surface. Some of the important mechanisms associated with boiling phenomena, such as the dynamics of growing and/or departing vapor bubble and the corresponding microlayer characteristics are intricately linked with wetting nature of the substrate surface, which, in turn, govern the overall boiling heat transfer rates. Realizing the importance of such a complex phenomenon, researchers, in the recent past, have widely adopted various approaches to modify the wettability of the heated substrate. However, these efforts have primarily been limited to pool boiling regime and experimental studies under nucleate flow boiling configuration have been highly scarce. With a motivation to bridge this gap, this study aims to investigate the sole influence of surface wettability on bubble and microlayer dynamics under nucleate flow boiling regime by employing three different surfaces: 60 nm SiO2(silicon oxide)-coated, 30 nm-SiO2 coated, and bare glass under various subcooling and flow conditions. The transients associated with bubble and microlayer are captured in tandem using rainbow schlieren-based high-speed videography and thin-film interferometry. Experimental results indicate a strong dependence of vapor bubble and microlayer dynamics on the wetting nature of the heated substrate. Experimental observations further revealed that the surfaces coated with SiO2 show a shift towards a relatively lesser/weaker hydrophilic behaviour. Microlayer dynamics captured in the form of thin-film interferograms showed that as the surface becomes less hydrophilic, both microlayer diameter and size of the dry patch show an increasing trend.