Redo the solution for this problem (book 2.5), such that (a) you explicitly draw a shell and (b) write all the terms that must be included in the shell balance. (c) Provide any missing steps and ensure you know how to derive all the results from 1-21 in this solved example. (d) Assuming pressure change of 5 kPa (or 5000 Pa), and viscosity of water and air calculate the momemtum and velocity at the fluid fluid interface. Comment on your result.

Thickness of a falling film. Water at 20C is flowing down a vertical wall with Re = 10. Calculate (a) the flow rate, in gallons per hour per foot of wall width, and (b) the film thickness in inches. Answer: (a) 0.727 gal/hr - ft; (b) 0.00361 in