Sensitivity study of momentum and turbulence models for subcooled boiling phenomena simulation

Abstract

This sensitivity analysis of the momentum and turbulence equations uses the Eulerian two-phase approach and intends to achieve a validated modeling for subcooled boiling flows. The studied regime is relevant to many industry applications and to the critical heat flux phenomenon, an important process for design and safety analyses of water-cooled nuclear power plants. Ascending water flows in heated circular pipes are modeled under subcooled boiling condition and applying a combination of computational multi-fluid dynamics (CMFD) models, each one for the estimation of specific terms of the governing equations. Turbulence closure, drag, lift, turbulent interaction, turbulent dispersion, wall lubrication and interfacial area models are investigated through variations around a reference model set defined based on the literature review, changing each model one at a time to study their impacts on the simulation results. Key parameters, such as void fraction and temperature profiles, are chosen for the evaluation of the results. Despite the difficulty of tracking the contributions of simultaneously applied models, the Legendre-Magnaudet lift force and the Burns et al. turbulent dispersion force models show good agreement with the experimental data of a flow at 4.5 MPa used for the quality verification of the simulations. These models are also applied for flows with pressures ranging from 1.5 to 15 MPa, and they lead to promising results. This study gives interesting insights on the influence of the distinct models composing momentum and turbulence calculations, contributing to the validation effort of the CMFD approach for subcooled boiling flows.