DENSITY-WAVE OSCILLATIONS IN PARALLEL CHANNELS - AN ANALYTICAL APPROACH

Density wave oscillations in parallel channel systems are analytically investigated. A new model is presented, from which explicit expressions are obtained for the stability limits and periods of oscillation of a two-identical channel system. The two modes correspond to the channels oscillating in-phase or out-of-phase, in both cases with the same amplitude. A two-channel system with a power skew is then analyzed with two different approaches. In the first approach a pertubative method is used, which shows that the normal modes are no longer the in-phase and out-of-phase ones. In the second approach of a fourth order eigenvalue problem is solved with a computer. For different power skews the stability thresholds, amplitude ratio and phase difference between the oscillations of the variables of the two channels and the periods of oscillation are obtained. It is also shown that larger power skews make the system more unstable, except in the very low inlet subcooling region.