An improved model for the axial vapor velocity in the DEBORA databank

Abstract

This study addresses the limitations of the vapor velocity data derived from the DEBORA C2900 campaign, which is frequently used for analysing boiling flow physics and validating Multiphase Computational Fluid Dynamics (MCFD) codes. While this campaign offers high spatial resolution in the radial direction, the values it provides for the vapor velocity rely on a modelling law rather than direct measurements. Comparisons with actual vapor velocity data from a different DEBORA campaign, featuring a lower resolution, reveal that the original model underestimates vapor velocity in flows outside of the highly subcooled domain. In response, we propose an alternative model for vapor velocity, based on said measurements. This model employs a turbulent profile law for radial velocity distribution and derives the mean vapor velocity from mass quality, using linear interpolation between two limit behaviours: homogeneous mixture at low void fractions and saturated flow at high void fractions. Our revised model demonstrates improved consistency with central symmetry and enhanced accuracy for higher void fractions. Additionally, we recalculated the estimations of bubble diameter originally featured in the databank using this new approach.