27 Jun 11 16:04
If you split the flow in proportion to the areas then by definition the sum of the branch flows has to be equal to the total flow. Check your calculation.
Crane example 4-19 is for the case where you have the same
mass flowrate all along the pipeline, but the diameter of the pipe changes somewhere. This method allows you to treat the compound pipeline (i.e. more than one diameter) as a single entity by bringing all the K values to a common basis, and applying them to a single velocity. In your case the flowrate is not constant because it splits at the header. You have to calculate the pressure drop for each segment having a constant flowrate, and then add the pressure drops for the pipes that are in series
You need to calculate a pressure drop in the main, where you have the flow of 325 gpm, from its source to the header. Call this pressure drop "M". Then calculate the pressure drop for each branch from the header to the piece of equipment it serves - based on the flowrate in that branch. Call these pressure drops "A", "B" and "C". The pressure drop from the source to the first piece of equipment will be M+A, to the second M+B and so on.
You could use the Crane example 4-19 method on the branch that has a 3" and a 2" section to allow it to be treated as a single pipe - assuming the flowrate is constant in mass terms for both sections.
Over and out.
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