Specific values

If SI units were used then Ns (and N) should be in rev/s.

Specific diameter

Specific diameter Ds is the impeller diameter of the geometri­cally similar or homologous fan for which the specific speed has been calculated.

2000 and above

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Composite charts

Reference to Figure 4.29 show that it is possible to plot all of a manufacturer’s product range on a single chart. Specific diam­eter and efficiency have been plotted against specific speed. It will be seen that the specific speed at maximum efficiency is a unique value for a particular design.

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Figure 4.27 Effects on medium width centrifugal fan with backward inclined im­peller

SPECIFIC SPEED N_

Q » Votum*tr>c flowrgt«

P * Fan ortMure Pa

U — npciMr t« «pccti m/a *7TDN 0 — «nxHt*- «mitf m N — ftalatono) uMd r«v/«

A• ini*» or цenawy kg/«3. [12 os wo)

PLOW C06FFlCЂNT «jrf« — 0 ЬЦ5

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