Evaluation of models and correlations for onset of significant void in subcooled boiling flows in channels with various geometries

Abstract

To achieve a deeper understanding of the prediction performance, this paper presents a comprehensive review and evaluation of existing mechanistic models and empirical correlations for the onset of significant void (OSV) in subcooled boiling for vertical upward flows based on an extensively collected database. First, 5 mechanistic models and 21 empirical correlations are summarized. Subsequently, an experimental database for thermal equilibrium vapor quality at OSV is prepared, which covers a wide range of operation conditions and comprises 448 data points from 27 sources. The models and correlations are then evaluated under low-pressure (P ≤ 1 MPa) and high-pressure (P > 1 MPa) conditions in different channels based on the experimental database, and it is determined that the Saha-Zuber correlation exhibits inadequate performance in both rectangular and annular channels, while the Okawa model and the Levy model exhibit the highest prediction accuracy for low-pressure and high-pressure conditions, respectively. Meanwhile, the Okawa model also demonstrates the highest overall prediction performance among the reviewed models and correlations, with a mean-relative-error of 37.3 %. On the other hand, sensitivity analysis of key parameters reveals that the Okawa model has limitations in accurately predicting the influence of pressure and heat flux.