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Proceedings of the 27th National and 5th International ISHMT-ASTFE Heat and Mass Transfer Conference December 14-17, 2023, IIT Patna, Patna-801106, Bihar, India
December, 14-17, 2023, Bihar, India

Numerical Study of Sub-cooled Flow Boiling towards High Void Fraction Flow Regimes using Coupled Wall Boiling and Population Balance Model

Get access (open in a dialog) DOI: 10.1615/IHMTC-2023.1210
pages 749-754


The Eulerian-Eulerian based two-fluid model is developed with flow-regime dependent interfacial interactions for mass, momentum and energy transfers using AIAD framework. The discrete population balance model predicts the bubble size distribution in the flow channel considering the coalescence and breakage effects. The RPI wall boiling model is used to handle the near heated wall energy transfer within the subcooled nucleate boiling. The coupling is achieved between the wall boiling and the population balance model for the nucleation and growth of the vapor bubbles near the heated wall. The developed two-fluid model with coupled wall boiling and population balance model is used to analyze the sub-cooled nucleate flow boiling of water in a vertical flow channel over a range of mass flux, wall heat flux, and subcooling values. At low wall heat flux, the wall boiling generates dispersed vapor bubbles along the heated channel. With further rise in the wall heat flux, larger bubbles are formed by coalescence and evaporation and it moves onto the channel core region with increased void fraction. This causes the flow regime transition from bubbly to slug regime. The benchmark experimental case of Lee et al. [1] is used to predict the bubbly flow and slug flow regime characteristics with the developed model. The experimental data is available for various vapor bubble parameters such as the variation of vapor fraction, vapor velocity, and the interfacial area concentration (IAC) in the radial direction at four different elevations along the heated length. The comparison is made for the numerical predictions of these parameters with the experimental values and better agreement is obtained.