Steady-state and transient critical heat fluxes (CHFs) were measured using a 1.0 mm diameter horizontal cylinder in a pool of highly wetting liquid, such as ethanol, due to steady and transient heat generation rate for wide range of subcoolings and pressures. Boiling CHF was assumed to happen based on a kind of hydrodynamic instability (HI) at CHF, and the model is supposed that the increase in vapor generation from the cylinder surface causes a limit of the steady-state vapor escape flow when CHF occurs. However, it has been understood that the CHF value changes systematically depending on experimental conditions according to a series of experiment. As the reason, a large part of the transition processes to film boiling at CHF highly subcooled liquid at high pressure was not explained by the mechanism of heat transfer crisis based on the HI model. Another mechanism assumed is that the transition occurs due to the explosive-like heterogeneous spontaneous nucleation (HSN) in originally flooded cavities on the cylinder surface in liquid. This research is to find the mechanism in the transition boiling CHF, which is confirmed that it depends on the HI and HSN.
Pool boiling
Transient boiling
Critical heat flux
Exponential heat generation rate