Transient CHF Phenomena Due to Exponentially Increasing Heat Inputs

다국어 초록 (Multilingual Abstract)

The critical heat flux (CHF) levels that occurred due to exponential heat inputs for varying periods to a 1.0-mm diameter
horizontal cylinder immersed in various liquids were measured to develop an extended database on the effect of high subcoolings
for quasi-steady-state and transient maximum heat fluxes. Two main mechanisms of CHF were found. One mechanism is due to
the time lag of the hydrodynamic instability (HI) which starts at steady-state CHF upon fully developed nucleate boiling, and the
other mechanism is due to the explosive process of heterogeneous spontaneous nucleation (HSN) which occurs at a certain HSN
superheat in originally flooded cavities on the cylinder surface. Steady-state CHFs were divided into three regions for lower,
intermediate and higher subcooling at pressures resulting from HI, transition and HSN, respectively. HSN consistently occurred in
the transient boiling CHF conditions that correspond to a short period. It was also found that the transient boiling CHFs gradually
increased, then rapidly decreased and finally increased again as the period became shorter.

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