On the Ledinegg instability in parallel channels: A new and exact criterion

Ledinegg instability has important influence on boiling two-phase flow. A new and exact Ledinegg stability criterion for parallel channels is established by using the matrix analysis method based on the characteristic equation. The new criterion agrees well with the previous experimental results for the parallel three channels, and is proved to be equivalent to the criterion obtained by using Hurwitz theorem for a single channel, parallel two-channels, and parallel three-channels, respectively. The new criterion is found to be independent of the fluid equivalent inertia. And it is also found that, when the slope of pump pressure head versus flow rate curve is negative, there is at most one channel whose slope of the pressure drop versus flow rate curve is less than or equal to zero while the other channels' slopes of the pressure drop versus flow rate curves should be greater than zero, in order to make sure that parallel channels is stable. In addition, the new criterion shows that decreasing the slope of pump pressure head versus flow rate curve and introducing extra restrictor can improve the stability of parallel channels.