Register to reply

Formula for water pressure, flow and power

by cens
Tags: flow, formula, power, pressure, water
Share this thread:
cens
#1
Aug7-07, 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.
Phys.Org News Partner Science news on Phys.org
World's largest solar boat on Greek prehistoric mission
Google searches hold key to future market crashes
Mineral magic? Common mineral capable of making and breaking bonds
FredGarvin
#2
Aug9-07, 01:34 PM
Sci Advisor
FredGarvin's Avatar
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
KristoferE
#3
Apr29-10, 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


Register to reply

Related Discussions
Basic water pressure formula General Engineering 5
Tap water flow and water diameter at end of it (Bernoulli eqzn...) Introductory Physics Homework 4
Air Pressure + Water formula Introductory Physics Homework 7
Air Pressure and flow to power calculations? Mechanical Engineering 6
HELP! relationship between rate of flow of water and height of water column Introductory Physics Homework 1