Physics-informed coarse-mesh method for thermohydraulic analysis: Two-phase model extension and validation against flow boiling in tubes and rod bundles with mixing vane spacers

Accurate and efficient analysis of flow and heat transfer within energy equipment is crucial for optimizing energy systems and improving energy utilization efficiency. Two-phase flow boiling, as the core mechanism for thermal management in energy systems, ensures the efficient and safe operation of equipment. However, given the extensive application of large-scale complex tube bundles in energy equipment, efficient and accurate analysis of two-phase flow boiling within these structures remains computationally prohibitive. To address this challenge, a two-phase Physics-Informed Coarse-Mesh (PICM) method is proposed. In detail, the PICM method employs coarse meshes for calculations to minimize computational costs. To ensure accuracy, empirical correlations for flow and heat transfer based on lumped parameters are employed to model wall effects. A flow regime map is employed to classify flow structures, and regime-specific correlations are selected to model interphase interactions. To account for detailed structure effects, the cross-flow model, additional pressure loss model, and heat transfer enhancement model are introduced. Validation demonstrates that the PICM method accurately simulates two-phase flow boiling in rod bundles with mixing vane spacers. It can also regress to a 1D system method. Compared to the CFD method, the mesh size and computational time of the PICM method are reduced by three orders of magnitude. A full-core thermohydraulic analysis of a small modular pressurized water reactor with mixing vane spacers further demonstrates its practical applicability. This study provides an effective method for the refined analysis of large-scale complex tube bundles and a foundational framework for multi-scale coupling in energy systems.