Premium
Self‐Oscillation of Locally Heated Water Vapor Microbubbles in Degassed Water
Author(s) -
Namura Kyoko,
Okai Shunsuke,
Kumar Samir,
Nakajima Kaoru,
Suzuki Motofumi
Publication year - 2020
Publication title -
advanced materials interfaces
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.671
H-Index - 65
ISSN - 2196-7350
DOI - 10.1002/admi.202000483
Subject(s) - materials science , subcooling , microscale chemistry , boiling , oscillation (cell signaling) , bubble , nucleate boiling , water vapor , heat flux , thermodynamics , mechanics , heat transfer , meteorology , chemistry , biochemistry , physics , mathematics education , mathematics
The self‐oscillation of water vapor microbubbles in degassed water is experimentally investigated by using the photothermal conversion effect of an FeSi 2 thin film. A laser spot on the FeSi 2 thin film is used as a heat resistant and localized heat source with flexible size and power. The local heating of the degassed water leads to the generation of a water vapor microbubble, which shows self‐oscillation at 0.1–0.7 MHz under continuous heating. The bubble oscillation frequency shows the maximum value when the absorbed power density reaches 1 mW µm −2 ( = 1 × 10 9 W m −2 ), regardless of the laser spot size. This value is close to the critical heat flux for highly subcooled boiling of water. The anomalous dependence of the self‐oscillation frequency on the input power density is explained by the transition from nucleate boiling to local film boiling. Additionally, a numerical analysis suggests that the bubble oscillation exceeding 1 mW µm −2 is attributed to the dried region on the laser spot and the periodic contact of the liquid water to the small heater. These results are useful for understanding and enhancing the flow generated around the water vapor bubble, and the design of microscale cooling devices.