Turning Vanes

You need to give a little more information if you want help here.

Such as:

• The size of these 45 degree elbows.
• Are they really Elbows (as in Pipe) or are they Bends (as in Duct work)?
• If they are Elbows in pipe what is the commodity?
• If they are Elbows in pipe why do you think you need "turning vanes"?
  

THESE ARE BENDS AS IN DUCT WORK. THE SIZE VARRIES. RIGHT NOW I AM IN THE PROCESS OF BUILDING 20"X18" 45 DEGREE BENDS. THE CHEEKS WILL BE THE 18" SIZE.THESE ARE USED FOR MOVING CONDITIONED AIR .

THANK YOU,MIKE

Any time turning vanes are used they CREATE a certain amount of pressure drop. The "trick" is to use them so that their drop is less than would occur if they were not in place.

The big issue comes from the INERTIA of the moving air. It WANTS to keep going straight, curved elbows create a gradual force to keep pushing the air around the ell but square throat ells will let the air "impact" the outside wall and then build up a pressure pocket which will push on the other side of the ELL and the be pushed out the opposite side opening- triggering lots of pressure drop and eddying of airflow which triggers lots of sound. The turning vanes slice into sections of the air and create small radius elbow effects (with some pressure drop) but relatively quiet and smooth airflow to the next duct section.

They are NORMALLY used to allow the installer to use a compact elbow- less metal and smaller size- rather than a correctly sized full radius elbow. The only OTHER time they have value is if the outlet is VERY close to the elbow, so that the air does not get pushed to the outer side of the ell, causing eddying and inconsistent airflow at the outlet.

Generally, 45 ells do not create enough loss or "pooling" of the air flow enough to cause a problem and they are almost never near an outlet. The slight amount of inertial pooling is quickly dissipated by the straight duct following the elbow.

Another option- about the same area but less air disruption and resulting drop- would be to transition to a wide, shallow duct elbow which would mimic the turn vanes but in a whole duct sort of way. However, the cost of the transitions, making the wide elbow, and installing same would likely be higher than the turn vanes. However, I really do not believe the is a need for turn vanes in 45 ELLs. especially a low velocity duct.

Please turn off your caps lock key! ALL CAPS is considered shouting, and you don't need to shout for us to 'hear'.

Why would you use turning vanes unless directed to. What authority is requesting them?? At 1000'/min. is seems odd for low pressure duct to do so without specific requirements. Residential ducts dont have them unless your looking at a 1950's design. The cost and benefit are not there unless something really big is being designed. Also what are the duct dimensions? Again why would you do this effort without the customer specs. requiring it, specifically? Woody

At that velocity and with 45 instead of 90 elbows I think turning vanes would be gililding lilies. A check of pressure drop charts would help you make the decision.

Lou Bindner