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# Centrifugal Pumps - Viscosity Influence

## Hydrodynamic losses through pumps depends on fluid viscosities.

When a more viscous fluid is handled by a centrifugal pump

• brake horsepower requirement increases
• the head generated is reduced
• capacity is reduced
• efficiency of pump is reduced and the Best Efficiency Point - BEP - is moved

The head, flow and capacity with fluids with other viscosities than used in the original documentation can be modified with coefficients.

### Flow

qv = cq q                                (1)

where

qv = flow compensated for viscosity (m3/h, gpm)

cq = viscosity flow coefficient

q = original flow according pump curve (m3/h, gpm)

hv = ch h                               (2)

where

hv = head compensated for viscosity (m, ft)

h = original head according pump curve (m, ft)

### Efficiency

μv = cμ μ                             (3)

where

μv = effciency compensated for viscosity

cμ = viscosity efficiency coefficient

μ = original efficiency according pump curve

### Power - SI units

Pv = qv hv ρv g / (3.6 106  μv)                            (4)

where

Pv = power compensated for viscosity (kW)

ρv = density of viscous fluid (kg/m3)

g = acceleration of gravity (9.81 m/s2)

### Power - Imperial units

Pv = qv hv SG / (3960 μv)                              (5)

where

Pv = power compensated for viscosity (bhp)

SG = specific gravity of viscous fluid

## Related Topics

• Pumps - Piping systems and pumps - centrifugal pumps, displacement pumps - cavitation, viscosity, head and pressure, power consumption and more.
• Viscosities - Viscosities of products and chemical species at varying conditions.

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Temperature

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Length

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yards
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Area

m2
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Volume

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liters
in3
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Weight

kgf
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Velocity

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Pressure

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mm H2O
kg/cm2
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Flow

m3/s
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US gpm
cfm

3 30