Prediction of dryout heat flux in uniformly heated vertical round tubes and annuli

We modeled liquid film dryout process for both tube and annulus channels, which are controlled by uniform heat flux. We set phenomenological initial conditions; The initial void fraction on the onset of the annular flow location is derived from the physical churn-to-annular flow transition model with the help of the drift-flux-model. The initial thermodynamic-equilibrium-quality is calculated by iteration with the flow quality to find the onset of the annular-flow location. The present model predicts dryout heat flux very well at lower exit qualities and slightly under-estimates it at higher exit qualities. It is found that the prediction error of the present model is gradually increased as the inlet subcooling approaches saturation. We obtained excellent results from the water experimental data for both tube and annulus channels as the mean of 0.97 and root-square error of 11% for the number of 3883 experimental data of tubes, and of 0.96 and of 12% for 593 on annuli. The present model improved the prediction performance and extended the applicable range to low quality by 10%. (author)