Single bubble dynamics and transient pressure during subcooled nucleate pool boiling

Abstract

This article investigates the growth and collapse of a single vapor bubble during subcooled nucleate pool boiling of water at a vertical copper surface. Two high-speed cameras and a hydrophone were used for a synchronized measurement of the bubble life cycle and the pressure transient in the surrounding liquid at a system pressure of 25 kPa. A pressure transient with the basic form of one and a half sine was expected. This expectation was basically confirmed, but additional significant minima and maxima corresponding to a frequency of approximately 60 Hz were found in the pressure transient. The comparison of the bubble volume and the pressure transient leads to the conclusion, that heat transfer effects will have to be considered to explain the deviations from the sine. Pressure wave reflections inside the evaporator are of minor importance since their wave length is much larger than the extensions of the evaporator.