Experimental investigation on vibration characteristics of subcooled and saturated pool boiling

•Subcooled and saturated boiling induced vibration were measured by LDV.•The turbulence mainly excites the first natural frequency of ∼45 Hz.•The bubble collapse excites the second natural frequency ∼1120 Hz.•The dominant excitation changed with the decreasing of the subcooling value. To investigate the characteristics and the mechanisms of boiling-induced vibration, pool boiling experiments are carried out with deionized water partially filled in a glass vessel under atmospheric pressure. A Laser Doppler Vibrometer (LDV) is employed to acquire the vibration velocity under different heat fluxes (0.30–0.65 MW/m2) and subcooled temperatures (0–55 °C). Two mechanisms leading to the vibration have been observed: the turbulence and the bubble collapse due to condensation. The turbulence mainly excites the first natural frequency (∼45 Hz) of the tested vessel while the bubble collapse mainly excites the second natural frequency (∼1120 Hz). For the turbulence induced vibration, the peak amplitude of the first natural frequency increases gradually with the increase of heat flux and the decrease of subcooling degree. For the bubble collapse induced vibration, the pressure pulses are determined by the number of the bubbles and the bulk subcooled temperature (or condensation process). Thus, under the certain bulk subcooled temperature, the corresponding peak amplitude of the second natural frequency increases with the increase of the heat flux when the bulk subcooled temperature is greater than 10 °C, and tends to be stable for the lower bulk subcooled temperatures as the number of bubbles keep constant; while under the certain heat flux, the peak amplitude will increase first and then decrease with the decreasing of the bulk subcooled temperature. The dominant mechanism changes from the bubble collapse to the turbulence with the decreasing of the bulk subcooled temperature for a certain heat flux, and the transition point for all the tested cases is between 10–15 °C. In addition, corresponding to the maximal root-mean square (RMS) value of vibration velocity, the bulk subcooled temperature increases with the increase of the heat flux.