Zero gravity two-phase flow regime transition modeling compared with data and relap5-3d predictions
Ghrist, Melissa Renee
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This thesis compares air/water two-phase flow regime transition models in zero gravity with data and makes recommendations for zero gravity models to incorporate into the RELAP5-3D thermal hydraulic computer code. Data from numerous researchers and experiments are compiled into a large database. A RELAP5-3D model is built to replicate the zero gravity experiments, and flow regime results from the RELAP5-3D code are compared with data. The comparison demonstrates that the current flow regime maps used in the computer code do not scale to zero gravity. A new flow regime map is needed for zero gravity conditions. Three bubbly-to-slug transition models and four slug-to-annular transition models are analyzed and compared with the data. A mathematical method is developed using least squares to objectively compare the accuracy of the models with the data. The models are graded by how well each represents the data. Agreement with data validates the recommendations made for changes to the RELAP5-3D computer code models. For smaller diameter tubes, Dukler?s bubbly-to-slug model best fits the data. For the larger tubes, the Drift Flux model is a better fit. The slug-to-annular transition is modeled best by Creare for small tubes and Reinarts for larger tubes. A major finding of this thesis work is that more air/water data is needed at equally distributed flow velocities and a greater variety of tube diameters. More data is specifically needed in the predicted transition regions made in this study.