A Two Zone Interfacial Shear Stress and Liquid Film Velocity Model for Vertical Annular Two-Phase Flow

The standard approach in estimating the interfacial shear between the vapor and the liquid film in annular two-phase flow is to include the effect of waves using a two-phase friction factor. This has been successful for low pressure annular flows in large hydraulic diameter ducts (wave heights ≪ H/2). It does not, however, work well for high pressure flows in smaller hydraulic diameter ducts (wave heights ∼ H/2). This suggests the need for a more detailed approach to incorporate wave effects in annular flow.