Experimental investigation on the transient film boiling heat transfer during quenching of FeCrAl

Abstract

As one of the promising accident tolerant fuel (ATF) cladding materials, FeCrAl can efficiently reduce the hydrogen generation and heat release under accident conditions due to its excellent oxidation resistance. In the case of postulated accidents, such as the loss of coolant accident (LOCA), coolant is immediately ejected to achieve rapid cooling of reactor core. In order to investigate the liquid-vapour interface behavior and film boiling heat transfer of FeCrAl, experiments are carried out with FeCrAl. The rodlets are first heated up to 600 °C before plunging into the liquid pool. The quench behavior is recorded by a high-speed camera, and the temperature variation of the test section is measured by thermocouples. A stable vapor layer is formed preventing the direct contact between the heated surface and liquid, and K-H instability wave is recognized due to the velocity difference between the liquid and vapor. It is found that as the liquid subcooling degree increases, the quenching time is decreased, and minimum film boiling temperature is increased. The quenching time and minimum film boiling temperature is also influenced by surface roughness and surface wettability. Based on the image processing method, it is found that the vapor layer thickness decreases with the increase of liquid subcooling degree and surface roughness. Based on the one-dimensional inverse heat conduction code, the surface heat flux and temperature is calculated. The film boiling heat transfer coefficient is found to increase with liquid subcooling, and it is relatively insensitive with surface roughness. Taking into account of the effect of liquid subcooling, a generalized correlation for film boiling heat transfer is developed.