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Hydraulics involving VERY thick fluids?

Hydraulics involving VERY thick fluids?

Hydraulics involving VERY thick fluids?

I am working on a mechanical design with a hydraulic component that has me baffled. I'm pretty sure some basic hydraulics formula will work (despite the unusual parameters), but I can't find a method that produces output in the units I need. They're all about flow rates or HP, and I need required psi.

The problem in a nutshell is this: What pressure (in psi) would be required to force grease with a viscosity of 250 down a 6 in diameter x 6" long cylinder, through a 6" long square to round conical transition terminating with an opening that measures 5" x 1/4" and out at a rate of 0.5 gpm?

Picture the tiny little plastic tip that a cake decorator uses, the one with about a half inch wide slot. Now enlarge that by 10, put it on the bottom of a coffee can, fill the can with axle grease and put a piston in the top. Now, how much pressure would I need to exert to get a 1/4" thick by 5" wide ribbon to come out at 1/2 gallons per minute?

It's making my head hurt, so I'd sure appreciate some hydraulic help...


Roger Mc

RE: Hydraulics involving VERY thick fluids?

I don't have any experience with grease calculations and a quick look suggests my concern that this material is not a newtonian fluid is correct. Not an area that I have experience in.

1/4" by 5" = 0.13 ft/sec at 0.5 gpm and it's far slower in the main cylinder.


Have you tried contacting any grease handling companies to see if they can point you towards reference material in this area? http://www.raytokcn.com/fluid-flow-through-the-bra...

Ultimately, flow rates, Hp and psi are all related. Sorry, that's likely not what you were hoping to get.

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