At the 5th International Heat Transfer Conference, Whalley et al (1) showed that a model of annular two-phase flow could be used to calculate the critical heat flux and occurrence of dryout in a round, vertical tube under steady flow conditions. The essential feature of the model is an analysis of the evolution of the liquid distribution, based on mass balances which account for the detailed variation of droplet entrainment from the liquid film, and its subsequent redeposition.
This paper describes how the model has been modified and extended to cope with more realistic physical processes, different boundary conditions, complex geometries and time dependent situations. The results are compared with experimental data, where available, and in all of the above cases the model produces results of acceptable accuracy when compared with experiment.
We conclude that the basic model contains all the essential ingredients for a successful description of the annular two-phase flow regime, although there is ample room for refinement in several areas.