Boiling on a Wire Heater: Exponential Vaporization Fronts and Vibrations

Vapor bubble nucleation on thin strip heaters is explored theoretically and experimentally. Vibrations of the heating surface due to nucleate boiling is also studied theoretically and experimentally. The fundamental phenomena resulting in subcooled boiling-induced vibration (SBIV) is demonstrated to be intrinsically related to the entrained liquid circulation driven by vapor bubble nucleation. In the case of high heat fluxes at the heater, vaporization fronts occur along the thin strip heaters leading to a sudden and violent transition to film boiling. The resulting vaporization front propagation along the heater was studied experimentally and shown to exponentially increase in time, contrary to the prior views of linear propagation. A theoretical description of this new phenomenon, the vaporization fronts, is given and confirmed experimentally. The theory has also provided an explanation and description of the critical heat flux (CHF) and film boiling inception.