Single bubble dynamics during subcooled nucleate boiling on a vertical heater surface: An experimental analysis of the effects of surface characteristics. (June 2017)

• Record Type: Journal Article
• Authors: Sarker, D.; Franz, R.; Ding, W.; Hampel, U.
• Is Part Of: International journal of heat and mass transfer. Volume 109(2017)
• Page Start: 907
• Page End: 921
• Publication Date: 2017-06
• Subjects: Vertical heater -- Nucleate boiling -- Bubble dynamics -- Wettability -- Optimal roughness; Heat -- Transmission -- Periodicals; Mass transfer -- Periodicals; Chaleur -- Transmission -- Périodiques; Transfert de masse -- Périodiques; Electronic journals; 621.4022
• DOI: 10.1016/j.ijheatmasstransfer.2017.02.017
• Languages: English
• ISSNs: 0017-9310

Abstract

Highlights: Surface characteristics effect on bubble dynamics over vertical heater is studied. High resolution imaging techniques captured the life-cycle of a nucleated bubble. Surface wettability has influential effect on bubble growth and sliding. The interaction of surface profile and bubble base affects bubble growth process. Much more impact on bubble growth process is found for an 'optimal roughness'. Abstract: In the present experimental study we investigated the effects of surface characteristics, such as wettability and roughness, on nucleate boiling in de-ionized water at a vertical heater. In the experiments, bubbles were generated from an artificial nucleation site on a stainless steel heater surface. High-resolution optical imaging has been used to capture the bubble life cycle, that is, departure, sliding, and lift-off. We found, that the lower wettability leads to larger departure diameter, longer sliding and larger lift-off diameter of bubbles. Also surface roughness effects have been analyzed and it was found that bubble departure and lift-off diameters are smaller and departure period is longer for a smooth surface. Bubble sliding velocity was found faster for a rough surface compared to a smooth surface. It was also found that the roughness is very influential to bubble growth and departure, which can be explained by considering its interaction with the microlayer underneath the bubble. An "optimal roughness", which accelerates the bubble growth, was found. The knowledge gained from this study shall be particularly useful to improve nucleate boiling models for numerical simulations.