A limited evaporation model for flashing applications

Modelling of flashing phase change has been challenging due to it occurring at high pressures and temperatures. Unlike the more established flash boiling models, flash evaporation modelling is a work in progress and a reliable model applicable at different flow rates is much needed. In this work, a limited evaporation model is developed and tested for experimental cases from the Brookhaven National Laboratories (BNL), using an open source software OpenFOAM. A dual diameter approach is used with different models to calculate the heat transfer coefficient and interphase momentum forces. The mass transfer rates are limited and the limit is based on the critical work of nucleation. It is found that this new model is able to adjust its mass transfer rates based on different flow rates and to provide very good compliance for area averaged pressure and volume fractions. The importance of inter-momentum forces used in the Euler- Euler scheme in predicting the momentum transfer in bubble dominant flows is discussed. The predictions for radial distribution of volume fractions, however, do not match very well with experiments and possible strategies to improve them are elaborated upon. Finally, sensitivity studies are conducted on the model parameters and their effects on pressure and volume fractions are discussed.