Steady and unsteady simulations for annular internal condensing flows, part II: Instability and flow regime transitions

The algorithm for the accurate and relevant numerical solution technique given in part I of this article is used to obtain the results for shear-driven annular condensing flows in horizontal channelswith or without transverse gravity. The unsteady wave simulation capability is used to implement a unique non-linear stability analysis. The steady and unsteady simulations' results for millimeter scale (hydraulic diameter 4-8mm), modest mass-flux (5-120kg/m(2)/s), and refrigerant vapors (FC-72, R113, etc.) are used to mark the approximate location beyond which the annular regime typically transitions to a non-annular regime. These are used to develop correlations for local heat transfer coefficients and the approximate length that marks the transition from annular to non-annular regimes.