Pool-boiling enhancement on periodic micro/nano ripple-structured surfaces fabricated by femtosecond laser

• Published in: International communications in heat and mass transfer Vol. 148; p. 107072
• Main Authors: Lee, Seunghwan, Kim, Yeonsu, Ki, Hyungson, Lee, Jaeseon
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.11.2023
• Subjects: Bubble nucleation; Critical heat flux; Femtosecond laser; LIPSS; Pool boiling; CHF; LIPSS; ONB; PC; Bubble nucleation; HTC; Femtosecond laser; Critical heat flux; Pool boiling; PEEK; BHT; TC
• ISSN: 0735-1933; 1879-0178
• DOI: 10.1016/j.icheatmasstransfer.2023.107072

A study was conducted on whether periodic micro/nano ripple structures generated on metal surfaces using femtosecond laser processing could improve pool boiling heat transfer. Depending on the laser irradiation conditions on the metal surface, a surface structure with different geometrical characteristics is created. Changes in sample surface morphology caused by the laser irradiation intensity are examined using scanning electron microscopy and confocal laser microscopy. Pool boiling tests are conducted to compare three laser irradiation conditions fabricated samples and the bare copper surface. The working fluid is deionized water. The pool boiling curves of each sample surface were compared with each other. Visualization of bubble nucleation is performed using a high-speed camera. The superheat, bubble departure diameter, and bubble growth period of each sample are measured and compared at the onset of nucleate boiling (ONB). The most efficient periodic micro/nano ripple-structured surface reduces the superheat at the ONB by 6.13 °C in comparison with that at the bare Cu surface. The enhanced surface structure reduced the bubble departure diameter and renewal period by 60.5% and 55.6% in comparison with that of the smooth surface. Further, the structured surface showed 178.5% enhancement in heat transfer coefficient and 39.1% in critical heat flux, respectively. Thus, the combination of increased nucleate site density, high nucleation site activation, and a wicking effect in the periodic micro/nano ripple structure significantly improves the pool boiling heat transfer. •Femtosecond laser irradiation create periodic micro/nano-ripple structures.•Bubbles are easily created with high nucleate density on metal surface•Bubbles with a small diameter detach from the laser-treated surface.•Bubble characteristics are confirmed using high-speed camera visualization.•Periodic micro/nano surface structure can enhance HTC by 178.5% and CHF by 39.7%.•Increased nucleation site density and wicking effect enhances HTC and CHF.