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Correction of FEI Calculation #10572

Merged
merged 2 commits into from
Jun 25, 2024
Merged

Correction of FEI Calculation #10572

merged 2 commits into from
Jun 25, 2024

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RKStrand
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Pull request overview

  • Fixes Fan Energy Index (FEI) calculations use reference standard air density at elevation instead of at sea level #10509
  • It was identified that there was an issue with the fan FEI calculation where it was not using the correct density values for a density ratio of design conditions to assumed conditions at sea level. In the ANSI/AMCA Standard 207-17, the value for density at sea level is defined as 1.2 kg/m^3. This was implemented along with changes to the design conditions density which is now assumed to be 21C, 50% RH at the elevation of the location. The function that was used to do the FEI calculation was modified to conform to the standard with these assumptions. Existing unit tests were updated to accommodate this change and an existing unit test was significantly expanded to more fully test the FEI calculation function. Minor edits (additions) were made to the Engineering Reference in the section that docments the FEI calculation. There are a number of differences in the output. These are all changes to the report table that shows the FEI result. Since the FEI calculation has changed, this was in line with expectations.

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

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@RKStrand
Code fixes for Issue #10509
2aefda8 
EnergyPlus code modifications to implement fix for GitHub Issue #10509.  Updates to existing unit tests that use the function modified and expansion of an existing unit test to more fully exercise the various cases of the function updated.
@RKStrand
Documentation mods for Defect #10509
a4d3fb4 
Additional text added to the FEI documentation contained in the engineering reference.  Also found and corrected a typo in the input/output reference.
@RKStrand RKStrand added the Defect Includes code to repair a defect in EnergyPlus label Jun 18, 2024
@RKStrand RKStrand added this to the EnergyPlus 24.2 milestone Jun 18, 2024
@RKStrand RKStrand self-assigned this Jun 18, 2024
rraustad
rraustad reviewed Jun 18, 2024
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src/EnergyPlus/Fans.cc
@@ -2643,8 +2643,7 @@ void FanSystem::set_size(EnergyPlusData &state)
}
}
}
Real64 _rhoAir = Psychrometrics::PsyRhoAirFnPbTdbW(state, state.dataLoopNodes->Node(inletNodeNum).Press, inletAirTemp, inletAirHumRat);
designPointFEI = report_fei(state, maxAirFlowRate, designElecPower, deltaPress, _rhoAir);
designPointFEI = report_fei(state, maxAirFlowRate, designElecPower, deltaPress);
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@rraustad rraustad Jun 18, 2024 •
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report_fei is called in 2 places during sizing, 1 for the component model and another place for all other fan types. During sizing there is no indication of inlet condition other than what is determined by sizing. And if sizing is not requested then there is no data to grab when calling report_fei. So I think this is a reasonable solution to random 0's found for temperature at the inlet of the fan when this function is called. In the Eng Ref the equation is provided right above the description so the user does have a way to adjust this value if needed.

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@rraustad could you clarify if you are asking for changes here or not? The random 0's phrase has me curious...

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I was just talking this through. The random 0's for T or w at the fan inlet node is what was previously used to calculate rhoAir, now rhoAir uses a reference condition (i.e., non-zero T and w). This is good to go.

Real64 constexpr tempAirFan = 21.0; // Standard fan inlet temperature in Celsius
Real64 constexpr hrAirFan = 0.5;    // Standard fan inlet humidity ratio (50%)
Real64 _wAirFan = Psychrometrics::PsyWFnTdbRhPb(state, tempAirFan, hrAirFan, state.dataEnvrn->StdBaroPress);
Real64 _rhoAirFan = Psychrometrics::PsyRhoAirFnPbTdbW(state, state.dataEnvrn->StdBaroPress, tempAirFan, _wAirFan);

Myoldmopar
Myoldmopar reviewed Jun 25, 2024
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Seems fine to me; I'll yield to @rraustad's thoughts on the sizing comment before approving/merging.

tst/EnergyPlus/unit/Fans.unit.cc
@@ -90,7 +90,7 @@ TEST_F(EnergyPlusFixture, Fans_FanSizing)
fan1->set_size(*state);
EXPECT_DOUBLE_EQ(1.00635, fan1->maxAirFlowRate);
state->dataSize->DataNonZoneNonAirloopValue = 0.0;
EXPECT_NEAR(1.0371, fan1->designPointFEI, 0.0001);
EXPECT_NEAR(1.0352, fan1->designPointFEI, 0.0001);
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Personal preference here: maybe just loosen up the precision to 0.01 or something, but this is fine.

src/EnergyPlus/Fans.cc
@@ -2643,8 +2643,7 @@ void FanSystem::set_size(EnergyPlusData &state)
}
}
}
Real64 _rhoAir = Psychrometrics::PsyRhoAirFnPbTdbW(state, state.dataLoopNodes->Node(inletNodeNum).Press, inletAirTemp, inletAirHumRat);
designPointFEI = report_fei(state, maxAirFlowRate, designElecPower, deltaPress, _rhoAir);
designPointFEI = report_fei(state, maxAirFlowRate, designElecPower, deltaPress);
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@rraustad could you clarify if you are asking for changes here or not? The random 0's phrase has me curious...

@Myoldmopar
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Ran regressions locally and just table diffs no other issues. Looks good to go in. This will cause table diffs in other branches, so they will need updated develop. Thanks @RKStrand and @rraustad

@Myoldmopar Myoldmopar merged commit 7f3151c into develop Jun 25, 2024
15 of 17 checks passed
@Myoldmopar Myoldmopar deleted the 10509feiUseStdDensityAtSeaLevel branch June 25, 2024 17:37
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@Myoldmopar Myoldmopar Myoldmopar left review comments

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Fan Energy Index (FEI) calculations use reference standard air density at elevation instead of at sea level
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@RKStrand @Myoldmopar @rraustad @nrel-bot @nrel-bot-2 @nrel-bot-3 @nrel-bot-2b @nrel-bot-2c