Page 131 - Modelling in Transport Phenomena A Conceptual Approach

4.5. FLOW IN CIRCULAR PIPES 111

so that the friction factor, based on the hydraulic equivalent diameter, is related
.'"(E) (4.538)
to Reh in the form

where $2 depends on the geometry of the system. Since R = 1 only for a circular
pipe, the use of the hydraulic equivalent diameter has not been recommended for
laminar flow (Bird et al., 1960; Fahien, 1983). The hydraulic equivalent diameter
for various geometries is shown in Table 4.4.

Thble 4.4 The hydraulic equivalent diameter for various geometries.

Geometry Dh
I

b 26

2ab
a+b

.-- Do - Di