Subcooled liquid boiling: details of the mechanism and phenomenological description

Abstract

Abstract Using high-speed filming (with a frame frequency up to 100 kHz) the important details of the subcooled liquid boiling mechanism are specified, which allow to conclude that Snyder-Bergles phenomenological model describes the process with the maximal likelihood. This model accounts for the main subprocesses of the subcooled liquid boiling (evaporation of the liquid microlayer located under the bubble near the dry spot boundary, vapor condensation at the bubble dome, liquid inflow to the microlayer). It corresponds to the modern ideas regarding to boiling mechanism and qualitatively well meets the experimental data. On the basis of the conducted experiments the description of several subprocesses of the model is defined more exactly: nucleation sites deactivation, het removal from the bubble dome by means of unsteady heat conduction, bubble size evolution as a result from the balance of masses of the evaporating and condensing vapors. It was shown that large vapor agglomerates appear in the flow due to small vapor bubbles coalescence with a heat flux density increase. Formation of dry patches under the agglomerates was studied. These dry patches are precursors of the boiling crisis. Superheating of the surface under dry patches immediately leads to the heating surface burnout.