CFD simulation of Departure from Nucleate Boiling in vertical tubes under high pressure and high flow conditions

Abstract

In this study, Departure from Nucleate Boiling (DNB) is investigated in vertical tubes under high pressure and high mass flux conditions using two-fluid Eulerian approach coupled with improved wall boiling model. It is essential to determine the near wall void fraction accurately in order to predict DNB. After accessing the theoretical and experimental basis of the correlations used for bubble departure diameter and nucleation site density, existing correlations are recalibrated to capture the phenomena at high pressure conditions. Sensitivity analysis is performed to analyze the impact of boiling and momentum closures. The effect of mass flux, inlet temperature, and exit quality on DNB is studied. The proposed model predicted DNB within 15%. This result indicates that CFD is a promising tool for predicting DNB.