Rewetting and autowave change of boiling modes

Heat transfer is investigated under conditions of autowave change from a metastable boiling mode to a stable one. The classification of boiling curves is suggested that depends on the temperature gradient and on the directions of flow velocity and velocity of temperature wave motion. A hypothesis is advanced according to which a considerable variation of regularities of heat transfer in the zone of temperature waves is caused by local disequilibrium of boiling. Experimental investigations are performed of heat transfer under conditions of water boiling in pipes upon autowave change of boiling modes in the pressure range from $3$ to $10$ MPa and in a wide range of values of steam quality and mass velocity. It is demonstrated that the change of boiling modes in pipes in the form of autowave is observed at less-than-boundary values of steam quality. The possibility is discussed of using the obtained data in simulating emergency conditions in the reactor core.