Equivalent length of a 90° elbow with different bend radius?
Equivalent length of a 90° elbow with different bend radius?
(OP)
Using the ASHRAE tables I'm able to get an equivalent length for copper fittings if it's a short radius or long radius fitting. In some of our pipework we also bend to 2xDiameter bend radius and 1.5xDiameter bend radius. How can I find or calculate the equivalent lengths for these?
RE: Equivalent length of a 90° elbow with different bend radius?
For instance, 2x diameter bend radius would have a length of (2 x diameter bend radius x Pi / 2). Units remain unchanged.
RE: Equivalent length of a 90° elbow with different bend radius?
5D maybe, but not 1.5 to 2D
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RE: Equivalent length of a 90° elbow with different bend radius?
RE: Equivalent length of a 90° elbow with different bend radius?
RE: Equivalent length of a 90° elbow with different bend radius?
RE: Equivalent length of a 90° elbow with different bend radius?
RE: Equivalent length of a 90° elbow with different bend radius?
RE: Equivalent length of a 90° elbow with different bend radius?
Also allow for some field-changes, like routing around a structural element. And your plans may show a 90°, and the contractor will use an assembly of 45° or some other deviation since the sprinkler guy decided to install his pipes before the ducts.
RE: Equivalent length of a 90° elbow with different bend radius?
Unfortunately for you, the r/d values are integers, and there is a big difference between 1 and 2.
The K value then gets plugged into a formula that includes the "Friction Factor" from the Moody diagram, which in turn is dependent on pipe roughness and the flow Reynolds number.
How many of those inputs do you know with any certainty? (Hint: Probably none)
Unless pipe bends are a dominant feature it's really not worth the effort of going through the work when all the inputs are guesses.
RE: Equivalent length of a 90° elbow with different bend radius?