We will see in Chapter 8 that the pressure drop in fully developed pipe flow is sometimes computed with the aid of a friction factor, defined by

\[ f=\frac{\Delta p}{\frac{1}{2} ho V^{2}} \frac{D}{\ell} \]

where \(V\) is the average velocity and \(\ell\) is the length of pipe over which \(\Delta p\) occurs. For laminar fully developed flow, \(f\) can be evaluated from

\[ f=\frac{C}{\operatorname{Re}} \]

where \(C\) is a constant and Re is the Reynolds number, given by \(\operatorname{Re}=ho V D / \mu\). Find the constant \(C\) for a parallel plate channel. Take \(D\) as \(2 h\).