Dilatants and thixotropic liquids pump sizing considerations 2

[5250081]

I would like to know how does one compensate for liquids with changing viscosities when agitated or shear force is applied to it. Of greater interest is the motor sizing since the resistance to flow increases with an increase in shear force in the case of dilatant liquids and the resistance to flow decreases with an increase in shear force in the case of thixotropic liquids.

 

[BigInch]

The pump characteristics are corrected for higher viscosity according to the following,

http://www.mcnallyinstitute.com/14-html/14-04.htm

The "trick" with these types of liquids is determining what the viscosity is at any given time, in order to determine what the effect on the pump is at that same time. If you are writing a dynamic simulation program, typically you will have to enter coefficients of a curve for a function that describes the precise variations in viscosity vs velocity that you mention and have the program calculate both the velocity and the resulting viscosity, using the curve function you defined, at each hydraulic node in the piping system and integrate the shear force throughout to arrive at the system's total frictional resistance. The pump power consumption for each time step during the simulation can then be predicted.





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"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[Latexman]

A reference I have found extremely valuable over the years was a series of articles in Chemical Engineering magazine by M. H. Wohl (Monsanto) titled "Designing for Non-Newtonian Fluids". They appeared in Jan. 15, Feb. 12, March 25, April 8, May 6, and June 3, 1968.

Good luck,
Latexman