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How does viscosity effect HPSHr?
2

How does viscosity effect HPSHr?

How does viscosity effect HPSHr?

(OP)
If the NPSHr of a pump is normally measured using water, how does the actual viscosity of the pumped fluid effect the NPSHr?  I would have thought that increased fluid velocity would have increased the pressure drop between the pump suction and impellar and as such the NPSHr of a pump would increase with increasing viscosity.  I can't find any details of viscosity correction for NPSHr.  Anyone able to confirm if NPSHr should be corrected for viscosity.

RE: How does viscosity effect HPSHr?

2
Generally NPSH values given in the performance curve sheets are measured values which correspond to a loss of discharge head of 3%.
The total heads and the performance characteristic shown on these curves, apply to media with a density of 1 kg/dm3 and a kinematic viscosity up to 20 mm2/s. If the density is other than 1 the friction must be multiplied by rho.

You can learn a little bit more of viscosity correction on pumps here:
http://www.mcnallyinstitute.com/14-html/14-04.htm

Also, the following link has an excel datasheet that uses the Hydraulic Institute method to predict how a centrifugal pump will perform with higher viscosity fluids:
http://www.chemengsoftware.com/pipesize/pumpds.htm

Hope you find it useful,

EB

RE: How does viscosity effect HPSHr?

i have the performance correction chart, if you need it i could mail it to you!. Just let me know

EB

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