PRESSURE-DROP AND DENSITY-WAVE INSTABILITY THRESHOLDS IN BOILING CHANNELS.

A criterion for linearized stability with respect to both the pressure-drop and the density-wave oscillations is developed for a single channel upflow boiling system operating between constant pressures with upstream compressibility introduced through a surge tank. Two different two-phase flow models, namely a constant- property homogeneous flow model and a variable property drift-flux model, have been employed. The results are compared with experimental findings. Comparisons show that the drift-flux formulation offers a simple and reliable way of determining the instability thresholds. The homogeneous flow model can be used to acquire a physical understanding of the problem.