Raise Air Pressure in Pipes?

[Ruffian]

Im not exactly sure if this is the right section of the forums, but here is my question; is there any way to raise the air pressure inside a pipe for example, the only thing is, both ends lead into larger sections that open to the atmosphere.

Air will be (for example) blown into the pipe from one end, is there anyway to raise the pressure of the air inside the pipe?

 

[P.Ramesh]

As long as your pipe is communicated to atmosphere that too with larger section, static pressure can not be raised. But total pressure (Static head + Velocity pressure Head) can be raised by injecting air with higher velocities.

 

[Q_Goest]

If you increase flow rate through a pipe high enough, you'll create a shock wave at the exit. Increasing the flow through the pipe further will continue to increase pressure inside the pipe.

If on the other hand, you're simply trying to pressurize the pipe (for example, to verify leak tightness as required by ASME piping code) the most common thing to do is to temporarily plug the end.

 

[russ_watters]

As long as your pipe is communicated to atmosphere that too with larger section, static pressure can not be raised. But total pressure (Static head + Velocity pressure Head) can be raised by injecting air with higher velocities.

Unless there is a wording issue there, you aren't correct. Static pressure does rise when you blow air through a pipe unless the walls of the pipe are perfectly smooth. At 1, 2, or 4 inches of water gage, it may not seem like a lot, but in a large duct or in a tight room, the forces can be enormous.

How much pressure are you looking for and how big is the section of pipe, Ruffian?

 

[Ruffian]

Thanx for the replies, so in order to raise the pressure inside the pipe, the 'faster' i can make the air flow through the pipe, the higher the pressure will be at the other end?

As for the amount of pressure, there is no number in particular, just heigher that what it would usuall be.
The pipe itself is not a cylinder, but has a rectangular cross-section, of say about, 10cm X 7cm

 

[Q_Goest]

so in order to raise the pressure inside the pipe, the 'faster' i can make the air flow through the pipe, the higher the pressure will be at the other end?

Yes, there will be a pressure gradient in the pipe with the lowest pressure being at the opening and highest at the source. The pressure at the outlet can be well above atmospheric. Note this situation comes up quite often in vent headers, especially relief valve vent headers. I've seen vent headers with over 100 psi at the outlet.