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

Abstract

A new code, CFD-BWR [1], is being developed for the simulation of two-phase flow phenomena inside a BWR fuel bundle. These phenomena include coolant phase changes and multiple flow regimes which directly influence the coolant interaction with fuel assembly and, ultimately, the reactor performance. CFD-BWR is a specialized module built on the foundation of the commercial CFD code STAR-CD [2] which provides general two-phase flow modeling capabilities. New models describing the inter-phase mass, momentum, and energy transfer phenomena specific for BWRs have been developed and implemented in the CFD-BWR module. A set of experiments focused on two-phase flow and phase-change phenomena has been identified for the validation of the CFD-BWR code and results of two experiment analyses focused on the radial void distribution are presented. The close agreement between the computed results, the measured data and the correlation results provides confidence in the accuracy of the models.

Assessment of the two-phase flow models in the CUPID code using the downcomer boiling experiment

“…The topology in each mesh cell is determined by two parameters, a void fraction (a g ) and a gradient of the void fraction (g ¼ djra g j). Tentner et al [12,13], Ioilev et al [14] and Ustinenko et al [15] have established a significant progress to verify and validate this approach. The interphase topology concept proposed by Tentner et al [13] was employed in the CUPID code to deal with the flow pattern change from the bubbly flow to the churn and mist flow.…”

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 details of the boiling model and the wall heat partitioning model can be found in Refs. [1][2][3][4]. In coupling the flow analysis with neutronics, temperatures of the fuel the cladding of the fuel pins must be determined together with the fluid temperatures as a conjugate heat transfer (CHT) problem.…”

The Cupid Code Development and Assessment Strategy

“…The transitional topologies are the overlapping regions of two or three main topologies [18]. Tentner et al [20,21], Ioilev et al [22] and Ustinenko et al [23] have established significant progress to verify and validate this approach.…”