Evaluating Performance of Two Group Interfacial Area Transport Equation for Large Diameter Pipes

In the two-fluid transport model, the coupling of mass, momentum and energy transfer between phases is highly dependent on interfacial area transfer terms. Several research efforts in the past have been focused on the development of an interfacial area transport equation model (IATE), in an attempt to eliminate the drawbacks of static flow regime maps currently used in best-estimate thermal-hydraulic system codes. The IATE attempts to model the dynamics that are involved in two phase flows by accounting for the different interaction mechanisms affecting bubble transport in the flow.
The further development and validation of IATE models has been hindered by the lack of adequate experimental data, especially in regions beyond the bubbly flow regime for large diameter pipes. At the Helmoltz Zentrum Dresden Rossendorf (HZDR) experiments utilizing wire mesh sensors have been performed over all flow regimes, establishing a database of high-resolution (in space and time) data [1]. A 195 mm diameter pipe with a 64 by 64 wire mesh sensor is utilized in the air-water experimental database used in this work. Analysis of flow conditions in the bubbly flow and churn turbulent flow regimes is presented.
The performance of the current two-group IATE model is evaluated. While the qualitative propagation of interfacial area is predicted sufficiently well, there is a discrepancy in magnitude between the model’s prediction and the experimental results. Overall, the study suggests that differences exist in the incidence of interaction mechanisms between small and large diameter pipes and further efforts are needed in order to extend the range of validity of current IATE models.