Critical heat flux and the dryout of liquid film in vertical two-phase annular flow

•The dryout of liquid film in single species two-phase annular flow is characterized.•Heat transfer coeficient is greatest when the local position is dry 5% of the time.•Time-resolved liquid-film thickness measurements are made during dryout-rewet cycles.•Disturbance waves in the liquid film govern both the dryout and rewet mechanisms.•Dryout event statistics are collected and show there is a characteristic dryout time.