Most of the recent subchannel analysis codes are based on a multifluid model, and an accurate evaluation of the constitutive equations in the model is essential. In order to get an accurate interfacial friction force in two-phase bubble flows, experimental data on drag coefficient and interfacial area concentration have been obtained for air-water flows in a 2×1 rod channel simplifying a boiling water nuclear reactor fuel rod bundle. In order to know the effects of liquid properties on the data, the temperature of the test water was changed from 18°C to 50°C. The data are compared with the existing correlations reported in literatures. As a result, the semitheoretical correlation of Hibiki and Ishii (2001, “Interfacial Area Concentration in Steady Fully-Developed Bubbly Flow,” Int. J. Heat Mass Transfer, 44, pp. 3443–3461) was found to give the best prediction against the present interfacial area concentration data. The correlation of Delhaye and Bricard (1994, “Interfacial Area in Bubbly Flow: Experimental Data and Correlations,” Nucl. Eng. Des., 151, pp. 65–77) also gave a reasonably good prediction if their correlation was modified by incorporating liquid property effects. As for the drag coefficient, no correlation exists, which can predict the present data well. Therefore, we developed a new correlation, including three dimensionless numbers, i.e., bubble capillary number, Morton number, and Eötvös number. The correlation predicted the data of Liu et al. (2008, “Drag Coefficient in One-Dimensional Two-Group Two-Fluid Model,” Int. J. Heat Fluid Flow, 29, pp. 1402–1410) as well as the present data well.
