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2.G, Laminar Flow of Falling Film on Outside of a Circular Tube In a gas absorption experiment a viscous fluid flows upward through a small circular iube and then downward on the outside. (See Fig. 2.G.) Set up a momentum balance over a shell of thickness Ar in the film, as shown in the figure. Note that the "Momentum in" and "Momentum out" arrows are always taken in the positive r-direction in setting up the balance, even though in this case the momentum turns out to be flowing in the negative r-direction. 4. Show that the velocity distribution in the falling film (neglecting end effects) is BIR? + 2a* In (2.6-1) 414 R b. Obtain an expression for the volume rate of flow in the film. c. Show that the result in (b) simplifies to Eq. 2.2-19 if the film thickness is very small, ly Distributions in Laminar Flow Velocity distribution inside tube Velocity stributie Outside Momentum in to shell of thickness A Moment out of the of thickness Ar Gravity force acting on the volume 2 TL L ak Fig. 2.6. Velocity distributions and momentum balance for falling film on outside of 2 Circular tube