Investigation of critical heat flux of annular flow in vertical upward round tube

Prediction of Critical Heat Flux at high mass quality is important for the safety of once-through steam generator and the reactor core under accidental conditions. Based on the theory for droplet entrainment, droplet deposition and liquid film evaporation, the film thickness and film mass flow rate distribution along axis are calculated at vertical upward round tube. The dryout emerges at the point where the film is depleted due to the balance of entrainment, deposition and evaporation. The theoretical CHF values are higher than that of experimental data, with error within 30%. (authors)