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# Hydraulics involving VERY thick fluids?

## Hydraulics involving VERY thick fluids?

(OP)
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...

Thanks,

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.

http://pubs.acs.org/doi/abs/10.1021/ie50588a042?jo...

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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