Feasibility test to acoustic dianosis of hydrodynamic instability in boiling crisis

Abstract

The general behavior of the heat flux depending on the superheated temperature during the quenching process is reverse hysteresis of typical boiling curve, while the boiling crisis of quenching process is represented as the collapse of vapor film. Hydrodynamic instability model proposed correlations for the minimal heat flux that maintains film boiling based on the Rayleigh-Taylor instability using the concept of most dangerous wavelength. The evidence of hydrodynamic instability in boiling crisis is revealed by using acoustic emission (AE) signal in this study. Acoustic characteristics at different boiling regimes give a clue to relate AE signal with the hydrodynamic instability. The film boiling and nucleate boiling generate no AE signal, while the initiation of vapor film collapse produces notable AE signal. The generation of AE signal is maintained until the nucleate boiling dominates the entire surface of the test section. It is observed that AE signal depends on the area where the vapor film collapses. Based on the relationship between the area of collapsed vapor film and AE signal, the hydrodynamic instability of vapor, which determines the spatial information of vapor film collapse, is discussed.