A comprehensive, mechanistic heat transfer modeling package for dispersed flow film boiling—Part 2—Implementation and assessment

• Implementation of a Lagrangian subscale dry contact heat transfer model in COBRA-IE.
• Comparisons of COBRA-IE predictions using Forslund–Rohsenow and mechanistic model.
• Reduction in RMS temperature error from 86.56 K to 46.96 K using mechanistic model.
• Reduction in standard deviation of temperature error from 82.15 K to 44.75 K.

A mechanistic, first-principles based Dispersed Flow Film Boiling (DFFB) heat transfer package has been implemented within the existing framework of an in-house version of COBRA-TF, called COBRA-IE. Several sensitivities studies were performed on the proposed model to determine how to characterize the droplet size distribution and to validate the use of a quasi-static Lagrangian subscale trajectory calculation within COBRA-IE. Assessing the proposed model against experimental data from 118 experimental runs in four separate facilities has shown a marked improvement over the predictions of the base line COBRA-IE DFFB model set. Over the entire assessment database, the proposed model has reduced the mean error, RMS error, and standard deviation of the error in the wall temperature predictions and improved the prediction in the axial variation of the wall temperature. The proposed DFFB model marks a step-change in the use of mechanistically based DFFB models in reactor safety analysis codes resulting in improved predictive capabilities.