Flow instability onset in tubes, channels, annuli, and rod bundles.

摘要

A theoretical model for the onset of flow instability for vertical upflow and downflow of a boiling fluid in a constant pressure drop flow channel is developed. The model is based on the momentum and energy balance equations for these flows with an algebraic modeling of two-phase velocity-slip effects. Predictions of the model are tested against experimental data for heat flux, length, inlet subcooling, and exit fluid quality effects. The model predictions of the dependency of the minimum mass flux on these variables are in complete agreement with the trends of the data. The experimental data have been taken from round tube, rectangular channel, annulus, and rod bundle geometries, with vertical upflow and downflow, under both non-bulk boiling and net vapor generation conditions. The data collection given in the report appears to be among the most complete available in the literature. The theoretical model results suggest two methods for correlating about limited ranges of operating state parameters for a fixed geometry. These correlating methods are given in the paper along with specific correlating lines for one of the methods. 30 refs., 12 figs., 2 tabs.