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Unformatted text preview: ocity or the flow rate. We cannot know both, or else we could immediately compute
d
4Q/( V).
Let us assume that we know the flow rate Q. Note that this requires us to redefine
the Reynolds number in terms of Q:
Red Vd 4Q
d (6.67) Then, if we choose (Q, , ) as scaling parameters (to eliminate d), we obtain the functional relationship
4Q
d Red fcn gh f
,
L5 Q (6.68) and can thus solve d when the righthand side is known. Unfortunately, the writer knows
of no formula for this relation, nor is he able to rearrange Eq. (6.64) into the explicit
form of Eq. (6.68). One could recalculate and plot the relation, and indeed an ingenious “pipesizing” plot is given in Ref. 13. Here it seems reasonable to forgo a plot
or curve fitted formula and to simply set up the problem as an iteration in terms of the
Moodychart variables. In this case we also have to set up the friction factor in terms
of the flow rate:
f hf gh f d 5
8 LQ2
2 d 2g
L V2 (6.69) The following two examples illustrate the iteration. EXAMPLE 6.11
0.342 m3/s and
950 kg/m3, Work Example 6.9 backward, as...
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 Spring '08
 Sakar

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