Centrifugal Pumps and Viscosity

When a liquid flow through a pump, hydrodynamic losses depends on fluid viscosity

When a 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

centrifugal pump viscosity fluids

The head, flow and capacity at other viscosities than used in the original documentation can be modifying 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)

Head

hv = ch h          (2)

where

hv = head compensated for viscosity (m, ft)

ch = viscosity head coefficient

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

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