Predicting the Onset of a Low-Frequency, Limit-Cycle Type of Oscillatory Flow Instability in Multitube Condensing Flow Systems

A means was developed for extending the predictive capability of the Equivalent Single-Tube Model (ESTM) to accurately predict the onset of a self-sustained oscillatory flow instability for a multitube condensing flow system. The model includes the effects of compressibility, subcooled liquid inertia, and thermal and flow distribution asymmetry. Previously, liquid inertia, a necessary mechanism for the instability, had not been modeled for a multitube system. Extensive experimental data was obtained for a two-tube system that verifies not only the predictive capability of the ESTM, but also its accuracy and its wide range of applicability.