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Include lighting return air fraction input during sizing when ZoneAirMassFlowConservation is used #10469

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merged 2 commits into from May 3, 2024
Merged

Include lighting return air fraction input during sizing when ZoneAirMassFlowConservation is used #10469

merged 2 commits into from May 3, 2024

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rraustad
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Pull request overview

NOTE: ENHANCEMENTS MUST FOLLOW A SUBMISSION PROCESS INCLUDING A FEATURE PROPOSAL AND DESIGN DOCUMENT PRIOR TO SUBMITTING CODE

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  • Title of PR should be user-synopsis style (clearly understandable in a standalone changelog context)
  • Label the PR with at least one of: Defect, Refactoring, NewFeature, Performance, and/or DoNoPublish
  • Pull requests that impact EnergyPlus code must also include unit tests to cover enhancement or defect repair
  • Author should provide a "walkthrough" of relevant code changes using a GitHub code review comment process
  • If any diffs are expected, author must demonstrate they are justified using plots and descriptions
  • If changes fix a defect, the fix should be demonstrated in plots and descriptions
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@rraustad rraustad added the Defect Includes code to repair a defect in EnergyPlus label Apr 15, 2024
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rraustad commented Apr 15, 2024 •
edited

Defect file results when RA fraction = 0.2:

 Zone Sizing Information, SPACE1-1, Cooling, 2638.67311, 2638.67311, 0.22166, 0.22166
 Zone Sizing Information, SPACE1-1, Heating, 3863.32620, 3863.32620, 0.11659, 0.11659

Defect file results when RA fraction = 0.0:

 Zone Sizing Information, SPACE1-1, Cooling, 2955.41740, 2955.41740, 0.24826, 0.24826
 Zone Sizing Information, SPACE1-1, Heating, 3847.48587, 3847.48587, 0.11611, 0.11611

20% of Zone 1 lighting is 1584 * 0.2 = 316.8, plus 2638.67 = 2955.47 for summer design day where lighting schedule = 1, and a fraction of 0.05 for winter design day yields 316.8 * 0.05 + 3847.49 = 3863.33.

Lights,
  SPACE1-1 Lights 1,       !- Name
  SPACE1-1,                !- Zone or ZoneList or Space or SpaceList Name
  LIGHTS-1,                !- Schedule Name
  LightingLevel,           !- Design Level Calculation Method
  1584,                    !- Lighting Level {W}
  ,                        !- Watts per Zone Floor Area {W/m2}
  ,                        !- Watts per Person {W/person}
  0.2,                     !- Return Air Fraction
  0.6,                    !- Fraction Radiant
  0.2,                     !- Fraction Visible
  0,                       !- Fraction Replaceable
  GeneralLights;           !- End-Use Subcategory

Schedule:Compact,
  LIGHTS-1,                !- Name
  Fraction,                !- Schedule Type Limits Name
  Through: 12/31,          !- Field 1
  For: WeekDays SummerDesignDay CustomDay1 CustomDay2, !- Field 2
  Until: 8:00,0.05,        !- Field 3
  Until: 9:00,0.9,         !- Field 5
  Until: 10:00,0.95,       !- Field 7
  Until: 11:00,1.00,       !- Field 9
  Until: 12:00,0.95,       !- Field 11
  Until: 13:00,0.8,        !- Field 13
  Until: 14:00,0.9,        !- Field 15
  Until: 18:00,1.00,       !- Field 17
  Until: 19:00,0.60,       !- Field 19
  Until: 21:00,0.20,       !- Field 21
  Until: 24:00,0.05,       !- Field 23
  For: Weekends WinterDesignDay Holiday, !- Field 25
  Until: 24:00,0.05;       !- Field 26

rraustad
rraustad commented Apr 16, 2024
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src/EnergyPlus/ZoneEquipmentManager.cc
AdjustedTotalReturnMassFlow = min(AdjustedTotalReturnMassFlow, zoneEquipConfig.AirLoopDesSupply);
if (!state.dataGlobal->DoingSizing) {
AdjustedTotalReturnMassFlow = min(AdjustedTotalReturnMassFlow, zoneEquipConfig.AirLoopDesSupply);
}
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@rraustad rraustad Apr 16, 2024 •
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There are actually 3 places that need this change (line 4564). However, I would rather find a place during zone sizing where zoneEquipConfig.AirLoopDesSupply could be set = to zone air mass flow rate for this time step. This would eliminate these conditionals during the simulation. I have not found that place yet.

Also not sure what the purpose of this test is other than for single zone air loops. And if there are 2 air loops connected to the zone then the AirLoopDesSupply from the second will be used. For multi-zone air loops this seems like it could be improved but given the zone RA flow is based on zone supply, exhaust and mixing then not sure how to do that. This variable is set one time in SimAirServingZones::InitAirLoops to the design system flow rate.

for (int ZoneNum = 1; ZoneNum <= state.dataGlobal->NumOfZones; ++ZoneNum) {
    if (!state.dataZoneEquip->ZoneEquipConfig(ZoneNum).IsControlled) continue;
    // sets design supply air flow rate in the ZoneEquipConfig struct for use with zone air mass balance
    for (int returnNum = 1; returnNum <= state.dataZoneEquip->ZoneEquipConfig(ZoneNum).NumReturnNodes; ++returnNum) {
        int airLoop = state.dataZoneEquip->ZoneEquipConfig(ZoneNum).ReturnNodeAirLoopNum(returnNum);
        if (airLoop > 0) {
            state.dataZoneEquip->ZoneEquipConfig(ZoneNum).AirLoopDesSupply = state.dataAirLoop->AirLoopFlow(airLoop).DesSupply;
        }
    }
}

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I agree that this needs improvement to allow for multiple air loops serving the same zone.

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Added issue #10493.

Myoldmopar
Myoldmopar approved these changes May 3, 2024
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Code changes seem reasonable here.

src/EnergyPlus/ZoneEquipmentManager.cc
max(0.0, TotInletAirMassFlowRate - TotExhaustAirMassFlowRate + ZoneMixingNetAirMassFlowRate);
if (!state.dataGlobal->DoingSizing) {
AdjustedTotalReturnMassFlow = min(AdjustedTotalReturnMassFlow, zoneEquipConfig.AirLoopDesSupply);
}
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I'm all for shrinking the scope of these variables. Definitely helps make sure we know what the intent of the variable is when reviewing the code. Otherwise I have no comment on it.

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@mjwitte do you have any additional comments/review on this one? If not then I'm inclined to merge it soon.

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FWIW, it builds and tests happily with updated develop pulled in.

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mjwitte commented May 3, 2024

@Myoldmopar I'll take a quick look see.

mjwitte
mjwitte approved these changes May 3, 2024
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@rraustad This looks good as a part 1. Please post a new issue for the comment below.

src/EnergyPlus/ZoneEquipmentManager.cc
AdjustedTotalReturnMassFlow = min(AdjustedTotalReturnMassFlow, zoneEquipConfig.AirLoopDesSupply);
if (!state.dataGlobal->DoingSizing) {
AdjustedTotalReturnMassFlow = min(AdjustedTotalReturnMassFlow, zoneEquipConfig.AirLoopDesSupply);
}
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I agree that this needs improvement to allow for multiple air loops serving the same zone.

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Awesome, thanks @mjwitte ! OK, I'm going to move forward with this then, merging, thanks @rraustad !

@Myoldmopar Myoldmopar merged commit 696bda5 into develop May 3, 2024
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@Myoldmopar Myoldmopar deleted the 10468-ZoneAirMassFlowConservation-with-RAFraction branch May 3, 2024 15:53
@rraustad rraustad mentioned this pull request May 3, 2024
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@Myoldmopar Myoldmopar Myoldmopar approved these changes

@mjwitte mjwitte mjwitte approved these changes

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Successfully merging this pull request may close these issues.

ZoneAirMassFlowConservation causes no change in zone sizing when Lights: Return Air Fraction is changed
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