Heterogeneous nucleation in cfd simulation of flashing flows in converging-diverging nozzle

Flashing flow is an important industrial phenomenon present in many contexts. In flashing flow, a liquid boils in response to a depressurization. CFD is used to simulate the complex two-phase nature of flow, but nucleation is frequently neglected in these simulations. In this work, 3 models for wall nucleation in flashing flow are tested and compared against experimental data. The models are implemented as source terms at the walls only, consistent with experimental observations. The model proposed by Blinkov et al. (1993) is found to provide the best agreement with no parameter fitting. Axial properties and mass flow can be well predicted, but matching the radial profiles requires the addition of a bulk heterogeneous nucleating term, which is small in comparison to wall nucleation and has little impact on average properties but has a large effect on the vapour structure. Additionally, other effects such as coalescence influencing bubble size should be taken into account, since radial distribution of the vapour phase depends directly on the bubble size.