Vertical film climbing

Fig. 5 Boiling in a narrow vertical tube. (A) Boiling suppressed by head, natural convection is shown (B) bubble formation (C) slug formation due to bubble coagulation (D) fully developed slug flow (E) breakdown of slugs at high vapor rates (F) annular-flow-climbing film.

Two-phase flow patterns in vertical tubes. The liquid flow rate is upward at a small, constant velocity. The gas flow rate upward increases steadily from left to right. The annular pattern shown is often referred to as climbing film flow. [From D. J. Nicklin and J. F. Davidson, The onset of instability in two-phase slug flow, in Symposium in Two-Phase Flow, Institution of Mechanical Engineers, London, 1962. Reproduced by permission j of the publisher.]... 

The preferred types in use today are (1) climbing-film long-tube vertical type, (2) forced-circulation type, and (3) falling-film long-tube vertical type. Examples of these types are shown in Fig. 4-3. Mechanical compression and multiple effect are favored where high evaporation temperatures and relatively high fuel costs exist. 

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