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Centrifugal Pumps Design and Application 2nd ed - Val S. Lobanoff, Robert R. Ross (Butterworth-Heinemann, 1992)

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NPSH 109<br />

Notation<br />

KI Friction <strong>and</strong> acceleration loss coefficient<br />

Ka Blade entry loss coefficient<br />

NPSHR Net positive suction head requir<strong>ed</strong> (bas<strong>ed</strong> on test or by calculation)<br />

NPSHA Net positive suction head available on site<br />

CMI Average meridional velocity at blade inlet (ft/sec) =<br />

.321 Q/Ae<br />

w Relative velocity of flow (ft/sec)<br />

U t Peripheral velocity of impeller blade (ft/sec) = D t N/229<br />

g Gravitational acceleration (ft/sec 2 )<br />

0 Angle of flow approaching blade<br />

a Angle of incidence<br />

„ Sigma = M|H<br />

H Head generat<strong>ed</strong> per impeller (ft)<br />

B 1 Blade angle at outer radius of impeller eye<br />

C b Gas-to-liquid ratio factor<br />

Q Pump capacity (GPM)<br />

Q L Recirculat<strong>ed</strong> leakage entering impeller (GPM)<br />

R t Factor in determining BI<br />

D t Diameter at blade tip (in.)<br />

N Spe<strong>ed</strong> (RPM)<br />

N<br />

N CO^°- 5<br />

ss Suction specific spe<strong>ed</strong> =<br />

vv/ —<br />

(for double suction impellers, use (Q/2)° 5 )<br />

BEP Best efficiency point on performance curve<br />

N s Specific spe<strong>ed</strong> = N ffi°' 5<br />

Ae<br />

U h<br />

Ci<br />

Impeller eye area at blade entry (sq in.)<br />

Peripheral velocity of impeller blade at hub (ft/sec)<br />

Absolute velocity of flow (ft/sec)<br />

References<br />

Hydraulic Institute St<strong>and</strong>ards Of <strong>Centrifugal</strong> Rotary And Reciprocating<br />

<strong>Pumps</strong>, 14th <strong>ed</strong>ition.<br />

<strong>Lobanoff</strong>, V., "What Is This NPSH, Oil &as Journal, February 24,<br />

1958.<br />

<strong>Ross</strong>, R. R., "Theoretical Pr<strong>ed</strong>iction of Net Positive Suction Head Requir<strong>ed</strong><br />

(NPSHR) for Cavitation Free Operation of <strong>Centrifugal</strong> <strong>Pumps</strong>,"<br />

Unit<strong>ed</strong> <strong>Centrifugal</strong> <strong>Pumps</strong>,

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