Square throat elbows must have turning vanes to reduce dynamic loss. Double-wall turning vanes were commonly used in the past. However, research has shown that these are less effective than single-wall vanes.

Single-wall turning vanes produce the smallest amount of dynamic loss. A single-wall turning vane should have a trailing edge. This will further reduce dynamic losses.

Adapted from Airflow in Ducts by Leo Meyer, from the Indoor Environment Technician's Library series, www.lamabooks.com.

Publication date: 03/21/2005