Annular Film

Annular film is a thin liquid layer that forms on the inner surface of a pipe, tube, or conduit when a liquid flows along with a gas in a two-phase flow system.  This flow configuration is common in industrial applications such as oil and gas production, chemical processing, and refrigeration systems.

In an annular flow pattern, the liquid typically flows as a continuous film along the walls of the conduit, while the gas phase occupies the central core and flows at a higher velocity.  The gas may also carry entrained liquid droplets within the core, creating a dynamic interaction between the two phases.

Key Points about Annular Film

Stability  -  The film can be stable or unstable, depending on factors like flow velocity, pressure, and fluid properties.
Thickness  -  The film thickness varies around the circumference of the pipe and can be influenced by gravity, surface tension, and flow rate.
Applications  -  Annular films are important in heat and mass transfer processes, as they can enhance or hinder the efficiency of such operations.