An experimental study on the wall vibration induced by single-bubble dynamics during subcooled pool boiling

During subcooled boiling, bubble nucleation, growth, departure, condensation, and collapse generate transient wall-pressure fluctuations and high-frequency structural vibrations, which may affect the operational stability of nuclear reactor systems and other boiling-based thermal equipment. However, the relationship between single-bubble evolution and the resulting wall vibration response remains insufficiently understood owing to the limited availability of synchronized visualization and vibration measurements. In this study, an experimental platform combining high-speed imaging and vibration measurement was developed to investigate the evolution of single bubbles on a vertical thin wall under different heat fluxes, degrees of subcooling, and surface wettability conditions. The results show that the initial inertia-controlled bubble growth stage generally produced the dominant vibration response. Increasing the heat flux substantially enhanced the excitation intensity. Over the investigated range, the primary peak vibration velocity increased by several times, while the integrated kinetic energy during the initial growth stage exhibited a much stronger, nonlinear increase. The condensation-related vibration energy ratio, α, increased from approximately 40.0–56.9% with increasing degree of subcooling, indicating that the relative contribution of departure-, condensation-, and collapse-related excitation became more significant under high-subcooling conditions. Surface wettability also strongly affected the characteristics of the vibration response: at a liquid subcooling of 20 K, the hydrophobic surface generated sustained structural oscillations lasting approximately 30 ms, with an amplitude about twice that observed on the hydrophilic surface, possibly due to contact-line pinning and delayed rewetting. These findings clarify the dominant excitation mechanisms associated with single-bubble evolution and provide experimental guidance for vibration control in boiling heat-transfer systems.