Snip

"They found that the increased
turbulence reduced velocity and hurt transport."

Right on. The same is true for wood chips and dust. Reduce velocity and the
material falls out of the air stream. Smooth is much better. JG

DonkeyHody wrote:

W Canaday wrote:
Okay ... folks had me just about convinced to buy 4" pvc piping for the
major portion of my DC waste runs and then I read a posting that said, in
essence "Nope ... you NEED the turbulance in a corrugated pipe to keep the
dust & chips in suspension."


I believe you need VELOCITY in your pipe, not turbulence. Velocity
creates turbulence, but turbulence is the enemy of velocity. I don't
think you need to do anything to increase turbulence. Besides, I don't
envision the chips sailing along suspended in the air very far. I
think after a short distance they fall out and are scooted along on the
"floor" of the pipe. You need enough velocity to keep them moving
right along so they don't pile up.

I work in the dredging industry. The principles involved in keeping
sediment moving in a pipe full of water are similar to the principles
in keeping chips moving in a pipe full of air. But in this case it IS
important that the sediment remain in suspension because of the long
distances it must travel (sometimes several miles). Still you often
get a "moving bed" of sediment on the bottom that has fallen out of
suspension. Many years ago, they ran some controlled tests to see if
deliberately increasing the turbulence by using spiral welded pipe
would improve sediment transport. They found that the increased
turbulence reduced velocity and hurt transport.

DonkeyHody
"Even an old blind hog finds an acorn every now and then."