Understanding heat transfer under near-critical pressure conditions is essential for the safe design of thermal-hydraulic systems such as future supercritical water reactors. While these systems operate under supercritical conditions during normal operation, subcritical states may occur during start-up, shutdown, or loss-of-pressure accidents. Under such conditions, a boiling crisis may develop if the critical heat flux (CHF) is exceeded, resulting in a sudden deterioration of heat transfer and a sharp increase in heating surface temperature. This behavior poses a significant safety concern, as excessive wall temperatures can result in fuel cladding degradation or failure and compromise overall system integrity. Experimental investigations on the boiling crisis, the associated critical heat flux, and heat transfer under post-CHF conditions have been conducted for several decades, leading to the development of various predictive approaches. However, most studies have focused on pressure ranges relevant to conventional pressurized water reactors. In contrast, experimental data at reduced pressures in the range 0.7 0.7). • Water dataset generated at pr > 0.7 using an industrial-scale test-rig. • 176 CHF and post-CHF experiments with fully documented datasets. • Parametric trends identified at high subcritical pressures.
Oettig et al. (Sun,) studied this question.