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Formula for water pressure, flow and power 
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#1
Aug707, 06:04 PM

P: 1

I feel like this should be readily available, but I cannot find any information about it through google.
I am trying to find a formula that will tell me the amount of energy necessary to inject water into a system at a given pressure. Put another way: I have a pipe of a known size and water (pipe a) is flowing through it at a know pressure (pressure x). I want to hook a pipe (pipe b) up to that original pipe a to inject additional water into it. I want to make sure that I am injecting the water into that system at a fixed flow (measured in GPM). I need to find out how much energy (say in horsepower or kPA) I would need to use to inject the water. or graphically what is the energy necessary to inject a constant stream of water at point O, given pressure x?: PIPE A (pressure x) O>>>>>>>>  ^ P I P E ^ B  I know that if pressure x is low, then I will not need very much energy to inject the water into that pipe, and if it is high, I will require quite a bit of energy. I however, do not know the specific formula that is used to calculate this energy requirement. Any links, or simply the formula, if known, would be greatly appreciated. Thanks very much. 


#2
Aug907, 01:34 PM

Sci Advisor
P: 5,095

[tex]P = p*\dot{V}[/tex]
Where: [tex]P[/tex] is the power required [tex]p[/tex] is the pressure required [tex]\dot{V}[/tex] is the volumetric flow rate Make sure your units are consistent, i.e. use the standard units, m, sec, N or Lbf, ft, s. If you are pumping water and need it quick you can use this too: [tex]HP = \frac{\tex{psi}*\tex{GPM}}{1714}[/tex] Where: [tex]HP[/tex] is the power in horesepower [tex]psi[/tex] is the pumping pressure in psi(g) [tex]GPM[/tex] is the flow rate in gallons per minute 


#3
Apr2910, 02:40 AM

P: 1

I would like to calculate the power need for fulfilling a pressurized airflow stream. With water it is simple but since air is a compressible gas it gets more difficult, or not? I've seen different alternatives. Please help!
regards /k 


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