CFD Modeling of Subcooled Boiling in Vertical Bubbly Flow Condition Using ANSYS CFX 12

Subcooled boiling in upward non-isothermal turbulent bubbly flow in tubes is numerically modeled using ANSYS-CFX 12 in this contribution. The approach is based on the RPI wall boiling model developed by Kurul and Podowski [1]. The interfacial non-drag forces are also investigated and included in the model. The Antal [5] model with different coefficients is used for the wall lubrication force. The lift force was calculated in two ways, with the Tomiyama model [4] and based on a constant value. The void fraction axial profiles for high pressure subcooled boiling in tubes are compared against the experimental data of Bartolomej [17] [18]. The pressure varies from 3 up to 6.89 MPa and the wall heat flux from 0.38 to 1.2 MW m−2. The mass flux range is between 900 and 1500 kg s−1m−2. The computational domain has up to 70000 nodes, and represents one eighth of a vertical pipe. In general, the models give predictions in close agreement with experimental results if the axial mean values are considered. The main difficulties for the simulation are observed for flow in transition to flow regimes with high void fraction, when the bubbly flow is not able to maintain the spherical condition of the bubbles, which is a requirement of the boiling models.