Update maximum sensible heat ratio calculation by lymereJ · Pull Request #11031 · NatLabRockies/EnergyPlus

lymereJ · 2025-04-12T05:43:19Z

Pull request overview

Fixes defect from this comment: DX Cooling Coil Negative Bypass Factor Fatal Error #10738 (comment)
Related issue ticket: SHR autosizing can produce bad results #6113

Description of the purpose of this PR

When calculating a coil bypass factor, prevent coil outlet temperature to be lower than dew point temperature at the same humidity ratio and avoid negative bypass factor.

Pull Request Author

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

Reviewer

…mall temperature diff to avoid CBF = 1.

…capacity and flow rate and inlet conditions.

github-actions · 2025-04-16T17:31:02Z

⚠️ Regressions detected on macos-14 for commit `c73195e`

Regression Summary

EIO: 134
EDD: 7
ESO Small Diffs: 86
Table Small Diffs: 95
ESO Big Diffs: 38
MTR Small Diffs: 98
Table Big Diffs: 35
ERR: 18
Table String Diffs: 8
JSON Big Diffs: 1
MTR Big Diffs: 3

github-actions · 2025-04-17T05:25:25Z

⚠️ Regressions detected on macos-14 for commit `835e4c3`

Regression Summary

EIO: 136
EDD: 8
ESO Small Diffs: 64
Table Small Diffs: 53
ESO Big Diffs: 60
MTR Small Diffs: 82
Table Big Diffs: 77
ERR: 18
MTR Big Diffs: 19
Table String Diffs: 17
Audit: 3
JSON Big Diffs: 1

github-actions · 2025-04-17T06:52:00Z

⚠️ Regressions detected on macos-14 for commit `8bb002a`

Regression Summary

EIO: 136
EDD: 8
ESO Small Diffs: 64
Table Small Diffs: 53
ESO Big Diffs: 60
MTR Small Diffs: 82
Table Big Diffs: 77
ERR: 18
MTR Big Diffs: 19
Table String Diffs: 17
Audit: 3
JSON Big Diffs: 1

lymereJ

Walkthrough:

lymereJ · 2025-04-17T19:55:31Z

src/EnergyPlus/Coils/CoilCoolingDXCurveFitSpeed.cc

+        Real64 ADiff = -A0 / AirMassFlow;
+        if (ADiff >= DataPrecisionGlobals::EXP_LowerLimit) {
+            CBF = std::exp(ADiff);
+        } else {
+            CBF = 0.0;
+        }


When the bypass factor is 0, set the adjusted bypass factor to 0. Current code would calculate A0 = 0 and CBF = std::exp(ADiff) would be 1.

lymereJ · 2025-04-17T20:24:22Z

src/EnergyPlus/DXCoils.cc

+    Real64 enthalpyMaxADP = InletAirEnthalpy - DeltaH;
+    Real64 tempADPMax = PsyTsatFnHPb(state, enthalpyMaxADP, DataEnvironment::StdPressureSeaLevel, CallingRoutine);
+    Real64 humRatADP = PsyWFnTdbH(state, tempADPMax, enthalpyMaxADP, CallingRoutine);
+    Real64 enthalpyTempinHumRatADP = PsyHFnTdbW(RatedInletAirTemp, humRatADP);
+    Real64 shrADPMax = min(1.0, (enthalpyTempinHumRatADP - enthalpyMaxADP) / (InletAirEnthalpy - enthalpyMaxADP));


Calculate the SHR corresponding to the apparatus dewpoint temperature based on the enthalpy difference that corresponds to the ratio of rated capacity to mass flow rate. Use this value as the "maximum" SHR.

lymereJ · 2025-04-17T20:24:29Z

src/EnergyPlus/DXCoils.cc

-        DeltaH = TotCap / AirMassFlow;
-        InletAirEnthalpy = PsyHFnTdbW(RatedInletAirTemp, RatedInletAirHumRat);


Move these outside of the while so they are only calculated once.

lymereJ · 2025-04-17T20:25:04Z

tst/EnergyPlus/unit/DXCoils.unit.cc

+TEST_F(EnergyPlusFixture, DXCoil_ValidateADPFunctionAlone)
+{
+    state->init_state(*state);
+    // Define coil parameters
+    Real64 constexpr RatedInletAirTemp(26.666699999999999);
+    Real64 constexpr RatedInletAirHumRat(0.011184700000000001);
+    state->dataDXCoils->DXCoil.allocate(1);
+    state->dataDXCoils->DXCoil(1).DXCoilType = "Coil:Cooling:DX:SingleSpeed";
+    state->dataDXCoils->DXCoil(1).Name = "Test Coil";
+    state->dataDXCoils->DXCoil(1).RatedTotCap(1) = 4480.6580719394560;
+    state->dataDXCoils->DXCoil(1).RatedAirVolFlowRate(1) = 0.23519298920287324;
+    state->dataDXCoils->DXCoil(1).RatedSHR(1) = 0.75045855035287490;
+    std::string const CallingRoutine("DXCoil_ValidateADPFunctionAlone");
+
+    // Calculate new SHR
+    Real64 newSHR = ValidateADP(*state,
+                                state->dataDXCoils->DXCoil(1).DXCoilType,
+                                state->dataDXCoils->DXCoil(1).Name,
+                                RatedInletAirTemp,
+                                RatedInletAirHumRat,
+                                state->dataDXCoils->DXCoil(1).RatedTotCap(1),
+                                state->dataDXCoils->DXCoil(1).RatedAirVolFlowRate(1),
+                                state->dataDXCoils->DXCoil(1).RatedSHR(1),
+                                CallingRoutine);
+
+    // Make sure that the outlet conditions are below the saturation
+    Real64 airMassFlowRate =
+        state->dataDXCoils->DXCoil(1).RatedAirVolFlowRate(1) *
+        Psychrometrics::PsyRhoAirFnPbTdbW(*state, DataEnvironment::StdPressureSeaLevel, RatedInletAirTemp, RatedInletAirHumRat, CallingRoutine);
+    Real64 deltaH = state->dataDXCoils->DXCoil(1).RatedTotCap(1) / airMassFlowRate;
+    Real64 inletAirEnthalpy = Psychrometrics::PsyHFnTdbW(RatedInletAirTemp, RatedInletAirHumRat);
+    Real64 hTinHumRatOut = inletAirEnthalpy - (1.0 - newSHR) * deltaH;
+    Real64 outletAirHumRat = Psychrometrics::PsyWFnTdbH(*state, RatedInletAirTemp, hTinHumRatOut); // 0.0098703703931385892
+    Real64 outletAirEnthalpy = inletAirEnthalpy - deltaH;                                          // 38853.039955973931
+    Real64 outletAirTemp = Psychrometrics::PsyTdbFnHW(outletAirEnthalpy, outletAirHumRat);         // 13.846750113203081
+    Real64 dewPointTempOutHumRat = Psychrometrics::PsyTdpFnWPb(*state, outletAirHumRat, DataEnvironment::StdPressureSeaLevel);
+    ASSERT_TRUE(dewPointTempOutHumRat < outletAirTemp);
+}
+


New unit test that reproduces the defect file conditions.

lymereJ · 2025-04-17T20:28:19Z

tst/EnergyPlus/unit/Autosizing/CoolingSHRSizing.unit.cc

    EXPECT_ENUM_EQ(AutoSizingResultType::NoError, sizer.errorType);
    EXPECT_TRUE(sizer.wasAutoSized);
-    EXPECT_NEAR(0.7763, sizedValue, 0.000001);
+    EXPECT_NEAR(0.776167, sizedValue, 0.000001);


Changes in the SHR calculation has marginally impacted several unit test such as this one.

lymereJ · 2025-04-17T20:29:59Z

src/EnergyPlus/DXCoils.cc

+            if (SlopeAtConds > 0) {
+                Error = (Slope - SlopeAtConds) / SlopeAtConds;
+            } else {
+                Error = 0; // SHR = 1


if SlopeAtConds == 0 then SHR = 1 hence we want to keep the initial guess, the dew point temperature at the coil outlet humidity ratio.

lymereJ · 2025-04-17T22:14:34Z

The diffs do not include any additional psychometrics related warning or error that I could see. On the contrary, the proposed changes remove existing psychometrics related warnings in all the following files:

EMSCustomOutputVariable
EMSThermochromicWindow
Fenestration_RefBldgSmallHotelNew2004_Chicago
PythonPluginCustomOutputVariable
PythonPluginCustomTrendVariable
PythonPluginThermochromicWindow
RefBldgSmallHotelNew2004_Chicago
ThermochromicWindow
VRFMultispeedFan

The warnings were as follows:

** Warning ** For object = Coil:Cooling:DX:SingleSpeed, name = "PSZ-AC:2_COOLC DXCOIL"
**   ~~~   ** Calculated outlet air relative humidity greater than 1. The combination of
**   ~~~   ** rated air volume flow rate, total cooling capacity and sensible heat ratio yields coil exiting
**   ~~~   ** air conditions above the saturation curve. Possible fixes are to reduce the rated total cooling
**   ~~~   ** capacity, increase the rated air volume flow rate, or reduce the rated sensible heat ratio for this coil.
**   ~~~   ** If autosizing, it is recommended that all three of these values be autosized.
**   ~~~   ** ...Inputs used for calculating cooling coil bypass factor.
**   ~~~   ** ...Inlet Air Temperature     = 26.67 C
**   ~~~   ** ...Outlet Air Temperature    = 13.90 C
**   ~~~   ** ...Inlet Air Humidity Ratio  = 1.118470E-002 kgWater/kgDryAir
**   ~~~   ** ...Outlet Air Humidity Ratio = 9.904953E-003 kgWater/kgDryAir
**   ~~~   ** ...Total Cooling Capacity used in calculation = 9598.60 W
**   ~~~   ** ...Air Mass Flow Rate used in calculation     = 0.587717 kg/s
**   ~~~   ** ...Air Volume Flow Rate used in calculation   = 0.508077 m3/s
**   ~~~   **  During Warmup, Environment=LAS_VEGAS ANN HTG 99.6% CONDNS DB, at Simulation time=01/21 00:00 - 00:10
**   ~~~   ** CalcCBF: SHR adjusted to achieve valid outlet air properties and the simulation continues.
**   ~~~   ** CalcCBF: initial SHR = 0.80015
**   ~~~   ** CalcCBF: adjusted SHR = 0.79913

rraustad · 2025-04-17T22:32:21Z

src/EnergyPlus/DXCoils.cc

-                bStillValidating = false; // have to stop somewhere, this is the upper limit of SHR empirical model (see Autosizing/CoolingSHRSizing)
+            if (SHR > shrADPMax) {
+                SHR = shrADPMax;
+                bStillValidating = false;


This all looks good. I think it would be a good idea to report a severe that describes why the user inputs, or I guess autosized inputs, cause the outlet condition to exceed the saturation curve. A warning the shows the supply air T, w and the DP at saturation(w) that shows the outlet T is left of the saturation curve. At least then the user will know what caused the design failure and a warning will be available to help correct the initial problem. This input issue might be happening more than we know.

Sure! I'll push some changes.

github-actions · 2025-04-18T05:53:44Z

⚠️ Regressions detected on macos-14 for commit `23694ff`

Regression Summary

EIO: 136
EDD: 8
ESO Small Diffs: 64
Table Small Diffs: 53
ESO Big Diffs: 60
MTR Small Diffs: 82
Table Big Diffs: 77
ERR: 18
MTR Big Diffs: 19
Table String Diffs: 17
Audit: 3
JSON Big Diffs: 1

nrel-bot-2 · 2025-05-21T15:02:28Z

@lymereJ @Myoldmopar it has been 33 days since this pull request was last updated.

nrel-bot-2c · 2025-06-25T00:33:33Z

@lymereJ @Myoldmopar it has been 34 days since this pull request was last updated.

nrel-bot-2c · 2025-08-02T00:50:35Z

@lymereJ @Myoldmopar it has been 38 days since this pull request was last updated.

nrel-bot-2c · 2025-08-30T00:55:25Z

@lymereJ @Myoldmopar it has been 28 days since this pull request was last updated.

rraustad · 2025-09-25T15:59:25Z

@lymereJ I have reviewed and this looks ready to merge. There are conflicts that must be resolved before that can happen.

mitchute · 2025-09-25T20:45:37Z

Last call for any final review comments here.

github-actions · 2025-09-25T22:28:23Z

⚠️ Regressions detected on ubuntu-24.04 for commit `381a005`

Regression Summary

EIO: 137
EDD: 8
ESO Small Diffs: 64
Table Small Diffs: 53
ESO Big Diffs: 61
MTR Small Diffs: 83
Table Big Diffs: 80
Table String Diffs: 19
ERR: 19
MTR Big Diffs: 19
Audit: 3
JSON Big Diffs: 1

github-actions · 2025-09-25T22:45:27Z

⚠️ Regressions detected on macos-14 for commit `381a005`

Regression Summary

EIO: 137
EDD: 8
ESO Small Diffs: 64
Table Small Diffs: 53
ESO Big Diffs: 61
MTR Small Diffs: 83
Table Big Diffs: 80
ERR: 19
MTR Big Diffs: 19
Table String Diffs: 17
Audit: 3
JSON Big Diffs: 1

Limit the coil outlet temperature to the dew point temperature. Add s…

955a531

…mall temperature diff to avoid CBF = 1.

lymereJ added the Defect Includes code to repair a defect in EnergyPlus label Apr 12, 2025

lymereJ added this to the EnergyPlus 25.2 IO Freeze milestone Apr 12, 2025

lymereJ added 5 commits April 14, 2025 15:26

Move DP limit and handle CBF = 0.

7fcd94d

Remove unecessary formatting changes.

233abaf

Bound the SHR calculation to a maximum SHR determined based on rated …

0054874

…capacity and flow rate and inlet conditions.

Revert unecessary formatting changes.

1f48690

Missing braces.

d7846f1

NatLabRockies deleted a comment from github-actions bot Apr 15, 2025

Clean up.

1822b64

lymereJ added 2 commits April 16, 2025 14:08

Removing old limit.

7e2d0be

Add unit tests and correct expected values for exisiting failing tests.

b2cd35f

Undo unwanted clang formatting.

34f8203

lymereJ changed the title ~~Prevent coil outlet temperature to be lower than dew point temperature at the same humidity ratio~~ Update maximum sensible heat ratio calculation Apr 17, 2025

lymereJ commented Apr 17, 2025

View reviewed changes

lymereJ marked this pull request as ready for review April 17, 2025 22:16

rraustad reviewed Apr 17, 2025

View reviewed changes

Add error messages.

bc2477f

mitchute added 2 commits September 25, 2025 14:21

Merge branch 'develop' into fix_negative_bpf

3f5da88

cleanups

05165e7

mjwitte modified the milestones: EnergyPlus 25.2 IO Freeze, EnergyPlus 25.2 Sep 25, 2025

mitchute merged commit 08aab32 into develop Sep 26, 2025
11 checks passed

mitchute deleted the fix_negative_bpf branch September 26, 2025 01:23

		DeltaH = TotCap / AirMassFlow;
		InletAirEnthalpy = PsyHFnTdbW(RatedInletAirTemp, RatedInletAirHumRat);

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lymereJ commented Apr 12, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Pull request overview

Description of the purpose of this PR

Pull Request Author

Reviewer

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github-actions bot commented Apr 16, 2025

⚠️ Regressions detected on macos-14 for commit c73195e

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⚠️ Regressions detected on macos-14 for commit 835e4c3

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github-actions bot commented Apr 17, 2025

⚠️ Regressions detected on macos-14 for commit 8bb002a

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github-actions bot commented Apr 18, 2025

⚠️ Regressions detected on macos-14 for commit 23694ff

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⚠️ Regressions detected on ubuntu-24.04 for commit 381a005

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⚠️ Regressions detected on macos-14 for commit 381a005

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lymereJ commented Apr 12, 2025 •

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⚠️ Regressions detected on macos-14 for commit `c73195e`

⚠️ Regressions detected on macos-14 for commit `835e4c3`

⚠️ Regressions detected on macos-14 for commit `8bb002a`

⚠️ Regressions detected on macos-14 for commit `23694ff`

⚠️ Regressions detected on ubuntu-24.04 for commit `381a005`

⚠️ Regressions detected on macos-14 for commit `381a005`