Computational Fluid Dynamics Modeling of Two-Phase Flow Topologies in a Boiling Water Reactor Fuel Assembly

Abstract

This paper presents recent advances in the development and validation of the two-phase flow topology models implemented in CFD-BWR, an advanced Computational Fluid Dynamics (CFD) computer code that allows the detailed analysis of the two-phase flow and heat transfer phenomena in Boiling Water Reactor (BWR) fuel assemblies under various operating conditions. The local inter-phase surface topology plays a central role in determining the mass, momentum, and energy exchanges between the liquid and vapor phases and between the two-phase coolant and the fuel pin cladding. The paper describes the topology map used to determine the local inter-phase surface topology and the role of the local topology in determining the inter-phase mass, momentum, and energy transfer. It discusses the relationship between the local interphase surface topology and the traditional channel flow regimes and presents results of experiment analyses in which computed local topologies are aggregated into flow regimes and compared with experimental observations.

High-Fidelity Light Water Reactor Analysis with the Numerical Nuclear Reactor

“…The extension of the boiling model to treat other expected flow regimes is in progress along with comparisons to the aforementioned rod bundle experiments. 36 An initial application of the newly developed BWR version of the NNR is currently in progress. In this program the NNR will be used to identify local thermal-hydraulic conditions under BWR operating conditions that will help explain the development of socalled tenacious crud, which may be responsible for some observed fuel failures.…”

“…Implementation and validation of a new Eulerian two-phase-boiling heat transfer model in the fluid dynamics module STAR-CD and its application for prototypic BWR fuel assembly configurations as part of the integrated analysis capabilities of NNR are an ongoing effort. 36 …”

Validation of CFD-BWR, a new two-phase computational fluid dynamics model for boiling water reactor analysis

“…These models have been described in Refs. [1,2] and will be briefly reviewed in this section of the paper. The boiling model was recently expanded to include conjugate heat transfer so that the complete heat transfer system, including the heat conduction in the fuel and cladding, can be studied.…”

“…The CFD-BWR code is being developed as a customized module built on the foundation of the commercial CFD-code STAR-CD which provides general two-phase flow modeling capabilities. We have described in [1] the model development strategy that has been adopted by the development team for the prediction of boiling flow phenomena in a BWR fuel bundle. The strategy includes the use of local inter-phase surface topology map and topology specific phenomenological models in conjunction with an interface transport and topology transport approach.…”

Multi-Scale Thermal-Hydraulic Analysis of PWRS Using the Cupid Code

“…The interfacial drag force for the bubbly and mist flow regimes is expressed as For the stratified flow regime, it is given by where CD and Ci(φ) are drag force coefficients with Ishii [22] and Tentner [18] correlations are used for the calculation of the drag force coefficients. The lift force is given by where CD is the lift force coefficient given by the Tomiyama correlation [23].…”