CR Ducts and CR Bends
The difference in straight ducts and in bends of corresponding measurements is limited. These can be seen in Diagrams 2-4 on the following pages. For example, a straight sheet metal duct Ø160 with 100 l/s airflow possesses a pressure loss of 2.0 Pa. A Ø160 CR Duct has 1.5 Pa pressure loss with the same airflow. A 90° bend of sheet metal with radius = diameter with matching airflow has 5.5 Pa loss; the corresponding CR product has 3.0 Pa. (A short bend of sheet metal with radius = .6* has a pressure loss of 17 Pa.) A 45° sheet metal bend has a pressure loss of 2.8 Pa. A CR 45° has 1.9 Pa. Therefore, if you choose corresponding components and products there is no practical difference, though the CR Duct System will always posses a lower pressure loss value.
The difference between CR T-Pieces and corresponding products in sheet metal are more noticeable. This is because CR T-Pieces have the same inner radius as CR Bends, with a radius that matches the diameter. In sheet metal, the T-Pieces typically have a relatively small inner radius in the transfer to the branch.
CR has knowingly chosen to design and manufacture T-Pieces with radius = diameter as the most crucial pressure loss in the average installation exists in those T-Piece branches.
How large the difference between applications is difficult to apply generally, but it grows with airflow speed. Diagrams 5-8 show T-Piece pressure loss values.
- avoid bends with a radius lower than the diameter;
- utilize CR T-Pieces;
- enjoy the ability of CR Ducts to be mounted rectangular. The transfer from round to rectangular accounts for a pressure loss of 1 Pa. See Pictures 1-4.
Pressure Loss – Diagrams
Pressure Loss – Pictures