Pipe air flow and turbulence noise

[JimPA]

I'm working on a soil vapor extraction (SVE)/sub-slab depressurizatation system. I want to use 2" PVC pipe routed through the building space to connect the roof mounted blower to the SVE points on the floor. I'm wondering if anybody has a refference for pipe air flow limits for silent operation. Thanks!

 

[bimr]

When the velocity of gas in a pipe is close to sonic velocity, noise and vibration increase because of the turbulence. A rule of thumb is that the maximum velocity should be limited to about half the sonic velocity.

Bela G. Liptak recommends to keep the velocity at 500 ft/sec.

http://books.google.com/books?id=Tx...k_result&ct=result&resnum=2&ved=0CBsQ6AEwATgK

For example, the speed of sound in air at 20 degrees Celsius comes out to approximately 1,125 feet per second. You should not have any noice if you limit the velocity to 500 ft/sec. Oversizing the piping slightly is also relatively inexpensive.

The major source of noise is usually the blower. The selected operating point of a blower has a major effect on the noise generated; the point of maximum efficiency produces the best acoustical effect.

Most straight piping naturally attenuates noise. Acoustic lining (insulation) increases noise attenuation.