Not meeting specified minimum air flow/design OA

asked 2017-03-15 13:49:14 -0500

updated 2017-03-17 16:52:11 -0500

Created a simplified lab building model in EnergyPlus with high OA/total air change rate (6 ACH), however, the simulation results show actual airflow is not following specified air flow rate in EnergyPlus.

In this 4-zone lab building, I created 3 simple lab zones and one mechanical room. The minimum OA and minimum air flow for labs are 6 ACH according to the design (100% OA). I had entered 6 ACH in Sizing:Zone - Cooling Minimum Air Flow(converted to m3/s), AirTerminal:SingleDuct:VAV:Reheat, DesignSpecification:OutdoorAir objects, and followed this post, I assigned DesignSpecification:OutdoorAirobjects to AirTerminal:SingleDuct:VAV:Reheat, in order to enable OA-controlled ventilation.

The simulated ventilation rate hardly rises above 4 ACH for any of the lab spaces. Is there anything else I had missed to specify the min air flow? Could you please share your strategies to mandate the minimum air flow in EnergyPlus model for an air-flow-driven space.

Below are the zone areas and volumes in the format of Zone ID---area(m2)---volume(m3)

  • AGL1-DRKMM-001---174---743
  • AGL1-LABOR-003---223---951
  • AGL1-LCORR-002---140---595
  • AGL1-MECHE-004---58---248

The E+ Model: 4zoneLab.idf

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I suggest you check a few other variables such as the outdoor air fraction and a few of the node flow rates in the air loop. Odds are, it's either your sizing object(s) or you operation settings are causing the problem (I know, real helpful).

Adam Hilton gravatar imageAdam Hilton ( 2017-03-20 08:21:11 -0500 )edit

Adam, thanks for your suggestion. It does not look like I had anything funny in the operation schedules, nor the zone sizing. Or maybe I misunderstood - were you referring to other objects? I guess to rephrase the question, are there any successful strategies/examples through/in which the min. air flows are controlled correctly?

yiyuan-jia gravatar imageyiyuan-jia ( 2017-03-20 14:50:17 -0500 )edit

I believe the way you've approached it is correct. I was just wondering if you could check some variable outputs to see if that helps point to the issue, like making sure the OA fraction is actually 1.

Adam Hilton gravatar imageAdam Hilton ( 2017-03-20 15:28:13 -0500 )edit