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The Practical Pumping Handbook
3.2.4.2 The effect of head change on flow rate
When the Static Head is changed, again without changing the pipe size,
the approximate change in Flow Rate can be estimated as shown.
where Q = Flow Rate
Hs = Static Head
3.2.5 Pipe size changes in a system
The change in pipe diameter may be necessary to reduce friction losses,
or increase the NPSH available to the pump (see Chapter 4.4.2).
Therefore, when capacity is unchanged (Q2 = Q1), the friction loss is in
INVERSE proportion to the 5th power of the change in the pipe
diameter, as shown below.
where D = Pipe Diameter
Hf = Friction Loss
To operate with the same head (i.e. H 2 = H1), such as from a lake or
river, with the new pipe size, the following approximation will apply.
D2] 2.5 Q2
-D1 el
where = Pipe Diameter
Q = Flow Rate
m 34 I ~
