Retrieve correct runtime fraction for AirLoopHVAC:UnitaryHeatCool to be used by AFN
#11367
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…crepancy between heating coil and system sizes.
…ndexes are not found.
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Code changes walk-through:
| SetupOutputVariable(m_state, | ||
| "AFN Zone Infiltration Mass Flow Rate", | ||
| Constant::Units::kg_s, | ||
| AirflowNetworkZnRpt(i).infilMassFlow, | ||
| OutputProcessor::TimeStepType::System, | ||
| OutputProcessor::StoreType::Average, | ||
| Zone(i).Name); |
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Add a new output variable so users don't have to manually calculate the mass flow rate from the ACH.
| if (state.dataSize->FinalSysSizing(state.dataSize->CurSysNum).FractionOfAutosizedHeatingCapacity > 0) { | ||
| // apply sizing factor and reset it to 1.0 so it doesn't get apply again during heating coil sizing | ||
| thisFurnace.DesignHeatingCapacity *= | ||
| state.dataSize->FinalSysSizing(state.dataSize->CurSysNum).FractionOfAutosizedHeatingCapacity; | ||
| state.dataSize->FinalSysSizing(state.dataSize->CurSysNum).FractionOfAutosizedHeatingCapacity = 1.0; | ||
| } |
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System size is determined first, then heating coil size is determined after. In the former, the FractionOfAutosizedHeatingCapacity is not taken into account when sizing the system, but it is when sizing the coil. If the coil is part of a system, the system size is used for the coil and is modified by FractionOfAutosizedHeatingCapacity. Here we're applying FractionOfAutosizedHeatingCapacity to the system size and reset to 1 so it doesn't get used again to size the heating coil.
With develop:
Component Sizing Information, AirLoopHVAC:UnitaryHeatCool, ACANDF_UNIT1, Nominal Heating Capacity [W], 8519.83583
Component Sizing Information, Coil:Heating:Fuel, MAIN FUEL HEATING COIL_UNIT1, Design Size Nominal Capacity [W], 10649.79479
With this branch:
Component Sizing Information, AirLoopHVAC:UnitaryHeatCool, ACANDF_UNIT1, Nominal Heating Capacity [W], 10649.79479
Component Sizing Information, Coil:Heating:Fuel, MAIN FUEL HEATING COIL_UNIT1, Design Size Nominal Capacity [W], 10649.79479
| // Save the current AFNLoopHeatingCoilMaxRTF for comparison with the one calculated below | ||
| Real64 refAFNLoopHeatingCoilMaxRTF(0.0); | ||
| if (state.afn->distribution_simulated) { | ||
| refAFNLoopHeatingCoilMaxRTF = state.dataAirLoop->AirLoopAFNInfo(AirLoopNum).AFNLoopHeatingCoilMaxRTF; | ||
| } | ||
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Save the maximum RTF that may have been previously determined from another component and use it later to determine the actual maximum RTF.
| // Get the actual maximum RTF for AFN simulations | ||
| if (state.afn->distribution_simulated) { | ||
| Real64 heatingCoilRTF = 0.0; | ||
| Real64 suppHeatingCoilRTF = 0.0; | ||
| bool errorFound(false); | ||
| if (thisFurnace.HeatingCoilType_Num == HVAC::Coil_HeatingGasOrOtherFuel || | ||
| thisFurnace.HeatingCoilType_Num == HVAC::Coil_HeatingElectric || thisFurnace.HeatingCoilType_Num == HVAC::Coil_HeatingDesuperheater) { | ||
| int heatingCoilIndex; | ||
| HeatingCoils::GetCoilIndex(state, thisFurnace.HeatingCoilName, heatingCoilIndex, errorFound); | ||
| if (heatingCoilIndex > 0) { | ||
| heatingCoilRTF = state.dataHeatingCoils->HeatingCoil(heatingCoilIndex).RTF; | ||
| } | ||
| } | ||
| if (errorFound) { | ||
| ShowSevereError(state, format("The index of \"{}\" is not found", thisFurnace.HeatingCoilName)); | ||
| ShowContinueError(state, format("...occurs for {}", thisFurnace.Name)); | ||
| errorFound = false; | ||
| } | ||
| if (thisFurnace.SuppHeatCoilType_Num == HVAC::Coil_HeatingGasOrOtherFuel || | ||
| thisFurnace.SuppHeatCoilType_Num == HVAC::Coil_HeatingElectric || | ||
| thisFurnace.SuppHeatCoilType_Num == HVAC::Coil_HeatingDesuperheater) { | ||
| int suppHeatingCoilIndex; | ||
| HeatingCoils::GetCoilIndex(state, thisFurnace.SuppHeatCoilName, suppHeatingCoilIndex, errorFound); | ||
| if (suppHeatingCoilIndex > 0) { | ||
| suppHeatingCoilRTF = state.dataHeatingCoils->HeatingCoil(suppHeatingCoilIndex).RTF; | ||
| } | ||
| } | ||
| if (errorFound) { | ||
| ShowSevereError(state, format("The index of \"{}\" is not found", thisFurnace.SuppHeatCoilName)); | ||
| ShowContinueError(state, format("...occurs for {}", thisFurnace.Name)); | ||
| errorFound = false; | ||
| } | ||
| state.dataAirLoop->AirLoopAFNInfo(AirLoopNum).AFNLoopHeatingCoilMaxRTF = | ||
| max(refAFNLoopHeatingCoilMaxRTF, heatingCoilRTF, suppHeatingCoilRTF); | ||
| } |
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Set the maximum RTF at the furnace level, overwriting the one calculated at the heating coil level (==1).
| // Check that the runtime fraction is less than one so the impact of cycling fan is correctly accounted for in the AFN | ||
| EXPECT_TRUE(state->dataAirLoop->AirLoopAFNInfo(1).AFNLoopHeatingCoilMaxRTF < 1); | ||
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| // Check that the system heating capacity is the same as the heating coil | ||
| EXPECT_NEAR(state->dataHeatingCoils->HeatingCoil(1).NominalCapacity, state->dataFurnaces->Furnace(1).DesignHeatingCapacity, 1e-6); |
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New unit test that checks for both fixes. develop fails both assertions.
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Here's a plot of the conditioned zone infiltration sensible heat loss: in blue is shown the case with no leakage and in maroon the original case with leakage, and in orange is the case with leakage but from this branch. As expected, we do see still difference with the case with no leakage, but much less. 
Simulation results of the defect case now show that the case with increased leakage uses more heating energy than the case with no leakage. Big diffs are only shown for |
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lymereJ
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the
AirflowNetwork
Pull request overview
Description of the purpose of this PR
The defect files highlighted two issues:
AirLoopHVAC:UnitaryHeatCoolfurnace-type system, is currently determined by the heating coil code. However, during the furnace simulation, the furnace's full load output is calculated with the heating coil'sRTF == 1. As a result, the maximum heating RTF is always set to 1 for the airflow network calculations, which does not appropriately capture the impact of cycling fan operations.AirLoopHVAC:UnitaryHeatCoolnominal capacity does not account for theSizing:System'sFraction of Autosized Heating Design Capacitywhen theHeating Design Capacity Methodis set toFractionOfAutosizedHeatingCapacity, whereas the heating coil does.This pull request fixes both issues.
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