Development of CUPID-SG for the analysis of two-phase flows in PWR steam generators

Highlights: • A code for analysis of steam generator developed based on CUPID. • The code supports unstructured meshes to fit complex geometry of steam generators. • The code can predict subcooled boiling with its wall heat partitioning model. • The predictions show good agreement with the FRIGG experiment data. - Abstract: CUPID-SG (CUPID code for Steam Generators) is a computer code for analyzing two-phase flows and heat transfer in PWR steam generators. It was derived from CUPID (Component Unstructured Program for Interfacial Dynamics), which is a component-scale thermo-hydraulic analysis code developed at KAERI (Korea Atomic Energy Research Institute). CUPID-SG shares the code structure with CUPID, which adopts two-fluid, three-field conservation equations, and semi-implicit numerical algorithms. CUPID-SG supports unstructured meshes to handle complex geometries, and adopts constitutive models of two-fluid model based system analysis codes for two-phase boiling flows. FRIGG tests are the benchmark in confirming the correct implementation of the transport models and the applicability of CUPID-SG to two-phase flows over heated tube bundles. A comparison with the FRIGG experiments showed that the constitutive models are properly implemented, and that CUPID-SG is capable of analyzing vertical two-phase boiling flows over tube bundles typically appearing in steam generators.