Dryout quality prediction for boiling two-phase flow in vertical helically coiled tubes

- A dryout quality prediction model for vertical helically coiled tubes is proposed.
- Three dimensionless numbers are used to modify the net entrainment rate.
- The dryout quality model for helical tube is assessed by the experimental data.

An analytical model for the prediction of the onset of dryout quality in annular flow regime in helically coiled tubes is present in this paper. According to the liquid film dryout mechanism, film dryout is primarily dependent on the competition between droplet entrainment and deposition with a certain heat flux. To this effect, it is necessary to define the net entrainment rate in the helical tube. The factors significantly affecting the droplet entrainment and deposition characteristics in the helical tube are analyzed theoretically. Three dimensionless numbers are used to modify the net entrainment rate in straight tube. A total of 252 experimental points from 6 different datasets are used to test the performance of the model. Comparisons between the calculated and experimental results in literatures indicate that the present model has good predictive capability in predicting onset of dryout in helically coiled tubes.