HANGING FILM PHENOMENON IN VERTICAL ANNULAR 2-PHASE FLOW

Vertical tubes with diameters between 0. 25 in. (6. 35 mm) and 5. 5 in. (140 mm) were set up in the laboratory. Both glass and transparent plastic (plexiglas) tubes were used. A liquid film was created either by overflowing water over a weir formed by the flat top of the tube, or by causing it to run down a tapered inlet funnel. At high gas velocities the film was blown upwards into the upper reservoir, while at lower velocites it ran downwards into a separation chamber. When excess liquid was supplied to the upper reservoir, the maximum possible downwards liquid flow at a given gas velocity was found to depend on the design of the ends of the tube, as well as whether the film flowed with a smooth surface or in periodic pulses. For a variety of these conditions, the data were found to vary typically by a factor of about 2. Phenomena are defined which were not dependent on these end conditions or past history. One of these turned out to be the ″hanging film″ point. By reducing the air velocity, after the tube had been dried out at a high velocity, an interface between a wavy liquid film and a dry wall was obtained.