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passage dimensions & fluid behavior

passage dimensions & fluid behavior

passage dimensions & fluid behavior

(OP)
Are there any charts or formula available which determine flow rate through given ID and length at a given pressure?  I'm working with water at 5000 psi down to close to 1000.   My IDs are a maximum of .5"  to hopefullya minimum of .125", with maximum straight passage lengths of 10".  I'd like flow through the system not exceed 75 liters/minute.  I've searched the web for answers to these questions, but have only been directed to expensive software, or scientific studies dealing generally with low pressure using complex formula solving problems irrelevant to mine.

I wish to create a 4000 psi pressure drop not with a tiny orifice, but by harassing and impeding fluid flow at an interval of the system through some circuitous path with minimum passage not exceeding .125".  I have a cylindrical volume of .875" by 4" in which to contain an assembly which will create the pressure drop.  Is this possible?  Heat generation is not a problem, unless my uneducated assumptions are far out of whack.  
I only have vague mental concepts of how such a path could be designed efficiently, and can't afford the machine work to try out my whimsical guesses through trial and error.  I'm thinking about a repetition of maybe expansion volumes, and perhaps reversing flow direction repeatedly to take the energy out of the fluid by inertia, but again, I'm only imagining.  I can find gobs of information on how to minimize fluid flow friction, but none on how to create it with maximum efficiency.  I'm not a trained engineer and don't have access to one with knowledge in this field.  I've worked with hydraulics for years, but generally just trouble shooting and assembling systems with off the shelf components and that's where my knowledge base lies.     

    I hope my questions make sense, and maybe one of you can point me in the right direction.  Thanks for any help.
 

RE: passage dimensions & fluid behavior

Pressure and flow are different variables.
There are many ways to change the flow rate of a given system. However to do so efficiently means designing a system with that intention in the first place.
Here's a couple of guidelines:
Try not to exceed these flow rates for maximum efficiency.
4 feet per second on an inlet line to a pump
16 feet per second in pressure(working) lines.
8 feet per second in tank lines.
The standard American formula for determining flow through a known conductor is as follows:
          
Velocity = (.32083333*Gallons per min)/Internal Area(SqIn)

Creating heat is very much an issue when controlling flow via increasing a pressure drop. The formula for created heat is as follows:

Heat(Btu's/Hr) = Gallons Per Min*1.485*Pressure Drop in PSIG

Seeing as your using nearly 20GPM I'll use that to demonstrate.

20*1.485*4000=118800 BTU's/hr

That's easily enough to heat a 600 square meter home.

If you have a pressure drop without doing work you generate heat.

Your theory of rerouting fluid to cause a pressure drop is somewhat plausible but only in a very limited capacity. You could cause turbulence in the system which would, in turn, cause vibration thus consuming some of the energy in the fluid. However, this would be a very limited tool.

Consider instead using a load sensing pump which can de-stroke the pump after a pressure differential is met and decrease fluid flow when it is not needed. This is a much more efficient method of controlling flow.
-Matt

 

RE: passage dimensions & fluid behavior

One more thing...
Pick up a Fluid Power Designers' Lightning Reference Handbook.
It will contain the charts you are looking for as well as many, many more helpful formulas and common component information.

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