New Models of Droplet Deposition and Entrainment for Prediction of Dryout in Uniform and Non-Uniform Heated Annuli

In this paper, we present a phenomenological modeling of annular flow for dryout prediction in vertical annuli by adopting a new set of correlations of droplet deposition and entrainment. The performance of the new correlations is tested by using the experimental data of Becker and Letzter [1] measured in a 3000mm annulus under bilateral as well as unilateral heating conditions, and the experimental data of Becker et al. [2] obtained in a 3650mm long annulus in respect of eight different axial heat flux profiles. The applicability of two widely used correlations of droplet deposition and entrainment in annuli which were derived from flows in vertical tubes was also checked. It was shown that large discrepancies were observed for the tube-based correlations, while for our present model the predicted CHFs as well as the positions of dryout occurrence in the case of non-uniformly heated annuli agree well with the experimental data.