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

•Bubble departure diameter and nucleation site density models are recalibrated for high pressure conditions.•Theoretical and experimental basis for boiling and momentum closures are discussed.•CFD model is developed and DNB is predicted within 15% absolute error and the error is less than 6% under high subcooled conditions.•Sensitivity analysis is performed to understand the impact of boiling and momentum closures.•The effect of mass flux, inlet subcooling and exit quality on DNB prediction is studied in detail. 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.