Pseudoplastic fluid behavior

[rinalmj]

I am working with a high viscosity, gel-type product that exhibits pseudoplastic (shear-thinning) behavior. The product is blended in a mixing tank and then pumped through a filter and to a drum filling station. I would like to be able to define the viscosity profile throughout the system. I know the shear rate in the pump (13,000 sec-1), but only have shear rate-viscosity data for very low shear rates (0.7-2.6 sec-1). Is there a way to extrapolate this data to cover the high shear rate in the pump? Also, is there a relation to estimate the "viscosity recovery" of the fluid as it exits the pump and makes its way toward the drum filling station?

 

[Endrju]

You can catch 2-3 point of viscosity against shear rate and try to fit parameteres for one of rheological model. Then you can extrapolate the value for high shearing - but you should bear in mind that extrapolation is always a risky thing...

 

[leakyseal]

You could try to fit your existing data to a power law viscosity relationship, but extrapolation between your existing values and the high shear rates in the pump render this activity fairly questionable (although it is a log relationship so maybe this dampens the danger...?) Presumably the vendor is not able to provide visc data at higher rates?

Changes in torque on the pump are a good crude measure of relative changes in visc...

Don't recall off hand how (or indeed if it is possible) to estimate the viscosity recovery. A really crude way would be with a couple of pressure taps in the transfer line and a H-P type relationship, but of course this is Newtonian so it's cheating. Can you sample the fluid and do a crude dropping-tube or dipstick type experiment, or you need to know.

Eh, just thinking out loud. I've managed to forget most of the rheology I ever knew *shakes tiny fist at Grad School down the road*