Flowrate Discrepancy

[seng]

Using v13.20 and designing some subsurface drip systems I am seeing discrepancies between reported flowrates on labels (#ACTFLOW#) and reported flowrate in Zone Design Summary, the label-reported flowrate as much as 10% higher. In each case the system is designed, Connectivity is good, and Management is complete (one system flow) and design is done (have used LP or Velocity). The flowrate showing up with Management is the same as listed with Zone Summary Report. YET when I multiply the average emitter flowrate (from Z.D.Summary) times the number of emitters, I get a total flowrate the same as what the labels report. I have multiple labels because I have two sizes of tape in the one management zone to reflect the different length of tapes across the field. Please advise me. Thanks,

[phil]

Without seeing an example of a design that shows this problem it is a little difficult to tell for sure what the problem could be. However I think that this is a minor problem that has been fixed recently and will be available in the V13.28 patch that should be released within a few days. You are welcome to download a copy of this patch early, I'll send a link via Email. PLease let us know if this solves the problem.

Regards

Phil

[jovivier]

Thanks for sending the design, we have had a look at it and the discrepancies are a consequence of not running “detailed” analysis. If you set the valve pressure in Zone Design Configuration to what you want, run detailed analysis, and then re-generate the labels the flows will all look consistent.
Without doing this what happens is the flow used for the design/nominal analysis is based upon the tape inlet pressure you specified (22 Psi) since we don’t know yet what the actual pressures will be. Once the design/analysis is finished the labels (or reports for individual tapes) can be populated by the flows based on the inlet pressures resulting from the analysis. If these pressure are significantly different from the nominal inlet pressure you get the differences you see. Essentially it’s a “chicken and egg” situation (for non-compensating emitters) which is solved in detailed analysis by iterating around until all the pressures and flows balance out.