Phenomenological modelling of non-equilibrium flows with phase change

Abstract Calculations are described in which new models for deposition and entrainment in annular flow are applied to a variety of conditions in annular and related flows. These include steady adiabatic flow, flow with evaporation, flow with dryout and post-dryout regions, flow with condensation and transient flows. The transient cases considered include both excursions with a flow decrease (transient dryout) and excursions with a flow increase (transient rewetting). Wherever possible, the predictions are compared with experimental data; this shows that the new models give improved predictions in every case. Although it is not possible to make comparisons with experimental data in the case of flow transients leading to rewetting, several new aspects of this process emerged from the calculations. Specifically, it is found that the rewetting rate could be governed either by the progress of a front at which the film flow rate is zero (the reverse of a transient dryout situation) or by a front the velocity of which is limited by the sputtering phenomenon.