Flow structure when film boiling in vertical tubes

Results of the study of vapor-liquid flow in the process of liquid nitrogen boiling in vertical tubes are presented. Experiments are conducted in channels 12, 19, 35 and 70 mm in diameter in case of ascending and descending flow of coolant at flow rate from 40 to 3500 kg/m2 x s and pressure from 0.12 to 0.55 MPa. The existence of core-type, transition, dispersion-circular and disperse modes of film boiling and the structure of flow in them are shown. Data on drop distribution as to their sizes are generalized. Generalizing dependences on heat transfer and friction on interface surface and channel wall are presented in criterion form