Page 89 - Bird R.B. Transport phenomena
P. 89
74 Chapter 2 Shell Momentum Balances and Velocity Distributions in Laminar Flow
(a) Make an unsteady-state mass balance on a portion of the film between z and z + Az to get
-^(v )8 = ~ (2D.2-1)
z
(b) Use Eq. 2.2-18 and a quasi-steady-assumption to obtain the following first-order partial
differential equation for 6(z, t):
2
^
Ц + 5 Ц = 0 (2D.2-2)
(c) Solve this equation to get
What restrictions have to be placed on this result?
