Formula for water pressure, flow and power

In summary, the conversation revolves around finding a formula to calculate the energy required to inject water into a system at a given pressure. The formula P = p*\dot{V} is suggested, where P is the power required, p is the pressure required, and \dot{V} is the volumetric flow rate. Alternatively, the formula HP = \frac{\tex{psi}*\tex{GPM}}{1714} can be used for quickly pumping water. The question of finding a formula for calculating the power needed for pressurized airflow is also brought up.
  • #1
cens
1
0
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.
 
Physics news on Phys.org
  • #2
[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
 
Last edited:
  • #3
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
 

1. What is the formula for calculating water pressure?

The formula for calculating water pressure is P = F/A, where P is pressure, F is force, and A is area. This means that pressure is equal to the force applied divided by the area over which the force is applied.

2. How is water flow rate calculated?

The formula for calculating water flow rate is Q = AV, where Q is flow rate, A is cross-sectional area, and V is velocity. This means that flow rate is equal to the cross-sectional area of the pipe multiplied by the velocity of the water.

3. What affects the water pressure in a system?

The water pressure in a system is affected by the height of the water source, the diameter of the pipe, and any obstacles or restrictions in the flow of water. Other factors such as friction, viscosity, and temperature can also affect water pressure.

4. How is power related to water pressure and flow?

The power of a water system is directly related to the water pressure and flow rate. The formula for calculating power is P = QHρg, where P is power, Q is flow rate, H is height, ρ is density, and g is the acceleration due to gravity. This means that the higher the water pressure and flow rate, the more power is generated by the system.

5. Can the formula for water pressure, flow, and power be applied to any type of liquid?

Yes, the formula for water pressure, flow, and power can be applied to any type of liquid as long as the appropriate units are used. For example, if the liquid has a different density than water, the value for ρ would need to be adjusted accordingly.

Similar threads

Replies
204
Views
2K
  • Introductory Physics Homework Help
Replies
16
Views
1K
  • Introductory Physics Homework Help
Replies
5
Views
362
  • Introductory Physics Homework Help
Replies
6
Views
247
  • Introductory Physics Homework Help
Replies
8
Views
2K
  • Introductory Physics Homework Help
Replies
1
Views
842
  • Introductory Physics Homework Help
Replies
1
Views
889
  • Introductory Physics Homework Help
2
Replies
60
Views
3K
  • General Engineering
Replies
2
Views
303
  • Introductory Physics Homework Help
2
Replies
56
Views
2K
Back
Top