An Experimental Study of Rod Bundle Dispersed-Flow Film Boiling with High-Pressure Water

Dispersed-flow film boiling data were obtained in a large rod bundle (8 × 8) under steady-state and transient conditions with upward flowing high-pressure, high-temperature water. The bundle is equipped with detailed thermometry, and has geometry typical of later generation pressurized water reactors with 17 × 17 fuel assemblies. Comparisons with the data to empirical correlations commonly used to predict heat transfer in dispersed flow indicate that the Dougall-Rohsenow and Groeneveld-Delorme correlations overpredict and underpredict heat transfer, respectively, while the Groeneveld 5.7 and Condie-Bengston IV correlations perform reasonably well. Spacer grids are shown to cause rod surface temperature depressions of up to 100 K from the upstream to downstream side of the grid. Grid effects persist for 20 to 30 hydraulic diameters downstream of the grid.