Sonneting critical heat flux: New insights in boiling multiphase flow

Boiling—a process widely used for its good heat transferability—is limited by a phenomenon known as critical heat flux (CHF). Our experiments revealed a new CHF mechanism that is different from previously believed theories; we refer to it as “sonneting CHF.” At CHF, the flow pattern changes from bubbly flow to slug/churn flow and then to an unusual reverse annular flow, leading to a significant rise in the heater surface temperature. The reverse annular flow, however, does not sustain but breaks down into a chaotic flow pattern, resulting in unprecedented quenching of the heater surface. The flow pattern shortly reverts back to bubbly flow; this entire process repeats for a few cycles, where the heater surface temperature rises and falls with amplitudes increasing in each cycle until the heater trips. The maximum removal-surface heat flux is significantly higher than the CHF. This new understanding will enable flexible and innovative boiling systems for several energy applications.