Drift-flux correlation for rod bundle geometries

• Recirculating flow patterns may affect drift flux parameters in rod bundles.
• A drift-flux correlation is developed considering low pressure and low liquid flow.
• Improvement over earlier correlations is demonstrated with a performance analysis.
• The new correlation is demonstrated as scalable to high pressure conditions.

A new drift-flux correlation has been developed to predict void fraction over a wide range of two-phase flow conditions in rod bundle geometries. An experimental database that represents low liquid flow and low pressure conditions in a scaled 8 × 8 rod bundle test facility is emphasized for this work. At these conditions, recirculating flow patterns may affect two-phase flow characteristics. Such effects may not be appropriately considered in earlier rod bundle correlations for drift velocity and distribution parameter. In the current approach, an existing drift-flux correlation that accounts for the effect of recirculating flow as two-phase flow regimes transition from bubbly to cap-bubbly flow is incorporated to determine distribution parameter. A performance analysis demonstrates that the proposed correlation improves upon existing correlations with an average relative error of ±4.5% when predicting the database utilized for in this work. The new correlation is also demonstrated to scale appropriately to prototypic plant conditions.