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fix Super high COP in VRFFluidTCtrl model #10752

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fix Super high COP in VRFFluidTCtrl model #10752

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e4dcfb7
fix TotalHeatingCapacity, it missed cycling ratio
Sep 19, 2024
6c9b079
Consider cycling in defrost power
Sep 20, 2024
5556102
Merge remote-tracking branch 'origin/develop' into fixVRFhighCOP
Sep 20, 2024
d08b956
Here VRFRTF is not initialized, don't multiply here to defrost
Sep 20, 2024
61760ed
move defrost RTF adjust out of the if block
Sep 20, 2024
1828d18
move defrostPower adjustment after VRFRTF is initialized
Sep 23, 2024
3c62414
Fix min pressure lower bound
Sep 24, 2024
335cf0f
fix warning of Cooling Coil Type SI to IP unit conversion
Sep 25, 2024
54be7dc
resolve err counter integer overflow
Sep 25, 2024
0d49054
fix another overflow place, use this->errors[].count as counter
Sep 25, 2024
d5f8c45
clang-format
Sep 26, 2024
55c51df
Merge remote-tracking branch 'origin/develop' into fixVRFhighCOP
Oct 1, 2024
aba83c7
Merge remote-tracking branch 'origin/develop' into fixVRFhighCOP
Oct 7, 2024
0dfe6b5
Cycling ratio need to be applied inside VRFOU_CalcCompH
Oct 18, 2024
0554057
remove C_cap_operation in demand calculation in cyclingRatio
Oct 24, 2024
4e05f26
Merge remote-tracking branch 'origin/develop' into fixVRFhighCOP
Oct 24, 2024
a39086f
fix unit test
Oct 25, 2024
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4 changes: 2 additions & 2 deletions src/EnergyPlus/FluidProperties.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -3279,7 +3279,7 @@ namespace FluidProperties {
ReturnValue = this->getSatEnthalpy(state, Temperature, 1.0, fmt::format("{}:{}", routineName, CalledFrom));
// send warning
if (!state.dataGlobal->WarmupFlag) {
this->errors[(int)RefrigError::SatSupEnthalpy].count += df->SatErrCountGetSupHeatEnthalpyRefrig;
this->errors[(int)RefrigError::SatSupEnthalpy].count++;
// send warning
if (this->errors[(int)RefrigError::SatTempDensity].count <= df->RefrigErrorLimitTest) {
ShowWarningMessage(
Expand Down Expand Up @@ -3886,7 +3886,7 @@ namespace FluidProperties {
} else { // All data is at zero: we are completely inside the saturation dome. Best thing we can do is return saturation value
++df->SatErrCountGetSupHeatDensityRefrig;
// send warning
this->errors[(int)RefrigError::SatSupDensity].count += df->SatErrCountGetSupHeatDensityRefrig;
this->errors[(int)RefrigError::SatSupDensity].count++;
// send warning
if (this->errors[(int)RefrigError::SatSupDensity].count <= df->RefrigErrorLimitTest) {
ShowWarningMessage(
Expand Down
19 changes: 9 additions & 10 deletions src/EnergyPlus/HVACVariableRefrigerantFlow.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -1192,10 +1192,9 @@ void CalcVRFCondenser(EnergyPlusData &state, int const VRFCond)

vrf.ElecHeatingPower =
(vrf.RatedHeatingPower * TotHeatCapTempModFac) * TotHeatEIRTempModFac * EIRFPLRModFac * HREIRAdjustment * VRFRTF * InputPowerMultiplier;

// adjust defrost power based on heating RTF
vrf.DefrostPower *= VRFRTF;
}
// adjust defrost power based on RTF
vrf.DefrostPower *= VRFRTF;
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This looks correct.

vrf.VRFCondRTF = VRFRTF;

// calculate crankcase heater power
Expand Down Expand Up @@ -11592,7 +11591,8 @@ void VRFCondenserEquipment::CalcVRFCondenser_FluidTCtrl(EnergyPlusData &state, c
Tdischarge = this->refrig->getSatTemperature(state, max(min(Pdischarge, RefPHigh), RefPLow), RoutineName);

// Evaporative capacity ranges_Min
CapMinPe = min(Pdischarge - this->CompMaxDeltaP, RefMinPe);
// suction pressure lower bound need to be no less than both terms in the following
CapMinPe = max(Pdischarge - this->CompMaxDeltaP, RefMinPe);
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This looks correct. Not sure why this didn't show up during the original model develolpment.

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Yeah, I'm surprised as well.

CapMinTe = this->refrig->getSatTemperature(state, max(min(CapMinPe, RefPHigh), RefPLow), RoutineName);
CompEvaporatingCAPSpdMin = this->CoffEvapCap * this->RatedEvapCapacity * CurveValue(state, this->OUCoolingCAPFT(1), Tdischarge, CapMinTe);
CompEvaporatingPWRSpdMin = this->RatedCompPower * CurveValue(state, this->OUCoolingPWRFT(1), Tdischarge, CapMinTe);
Expand Down Expand Up @@ -11664,8 +11664,7 @@ void VRFCondenserEquipment::CalcVRFCondenser_FluidTCtrl(EnergyPlusData &state, c
Tdischarge,
h_IU_cond_out_ave,
this->IUCondensingTemp,
// Te can't be smaller than user input lower bound
max(this->IUEvapTempLow, CapMinTe),
CapMinTe,
Tfs,
Pipe_Q_h,
Q_c_OU,
Expand Down Expand Up @@ -11697,7 +11696,6 @@ void VRFCondenserEquipment::CalcVRFCondenser_FluidTCtrl(EnergyPlusData &state, c
}

// Key outputs of this subroutine
Ncomp *= CyclingRatio;
Q_c_OU *= CyclingRatio;
this->CompActSpeed = max(CompSpdActual, 0.0);
this->Ncomp = max(Ncomp, 0.0) / this->EffCompInverter;
Expand Down Expand Up @@ -12237,6 +12235,7 @@ void VRFCondenserEquipment::CalcVRFCondenser_FluidTCtrl(EnergyPlusData &state, c
this->ElecHeatingPower = 0;
}
this->VRFCondRTF = VRFRTF;
this->DefrostPower *= VRFRTF;
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@rraustad rraustad Sep 25, 2024 •
edited
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This looks correct. A plot of DefrostPower vs RTF or CyclingRatio would show it's working.

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This is a plot of heat pump defrost power vs cycling ratio

image

When the defrost power is non-zero, it is proportional to cycling ratio

The output file is here:
eplusout_defrost_vs_cyclingRatio.xlsx

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Why is defrost electricity so small? at 6 E -9

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I used this test file. Its "Resistive Defrost Heater Capacity" is 0.0000001
US+SF+CZ5B+hp+slab+IECC_2021_VRFPhysics_v2_hrdsize_V2420.expidf.zip


// Calculate CrankCaseHeaterPower: VRF Heat Pump Crankcase Heater Electric Power [W]
if (this->MaxOATCCHeater > OutdoorDryBulb) {
Expand Down Expand Up @@ -14136,7 +14135,7 @@ void VRFCondenserEquipment::VRFOU_CalcCompC(EnergyPlusData &state,
T_suction + 8,
T_discharge - 5);

Cap_Eva0 = (TU_load + Pipe_Q) * C_cap_operation; // New Pipe_Q & C_cap_operation
Cap_Eva0 = TU_load + Pipe_Q; // New Pipe_Q & C_cap_operation
Cap_Eva1 = this->CoffEvapCap * this->RatedEvapCapacity *
CurveValue(state, this->OUCoolingCAPFT(CounterCompSpdTemp), T_discharge, T_suction); // New Tc
CapDiff = std::abs(Cap_Eva1 - Cap_Eva0);
Expand Down Expand Up @@ -14337,7 +14336,7 @@ void VRFCondenserEquipment::VRFOU_CalcCompH(
T_suction + 8,
IUMaxCondTemp - 5);

Cap_Eva0 = Q_evap_req * C_cap_operation;
Cap_Eva0 = Q_evap_req;
Cap_Eva1 =
this->CoffEvapCap * this->RatedEvapCapacity * CurveValue(state, this->OUCoolingCAPFT(CounterCompSpdTemp), T_discharge, T_suction);
CapDiff = std::abs(Cap_Eva1 - Cap_Eva0);
Expand All @@ -14353,7 +14352,7 @@ void VRFCondenserEquipment::VRFOU_CalcCompH(
CyclingRatio = 1.0;
}

Ncomp = this->RatedCompPower * CurveValue(state, this->OUCoolingPWRFT(CounterCompSpdTemp), T_discharge, T_suction);
Ncomp = this->RatedCompPower * CurveValue(state, this->OUCoolingPWRFT(CounterCompSpdTemp), T_discharge, T_suction) * CyclingRatio;
// Cap_Eva1 is the updated compressor min speed capacity
OUEvapHeatExtract = Cap_Eva1;
this->EvaporatingTemp = T_suction;
Expand Down
4 changes: 2 additions & 2 deletions src/EnergyPlus/OutputReportPredefined.cc
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Expand Up @@ -352,7 +352,7 @@ namespace OutputReportPredefined {
s->pdchCoolCoilArea = newPreDefColumn(state, s->pdstCoolCoil, "Nominal Coil Surface Area [m2]");

s->pdstDXCoolCoil = newPreDefSubTable(state, s->pdrEquip, "DX Cooling Coil Standard Ratings 2017");
s->pdchDXCoolCoilType = newPreDefColumn(state, s->pdstDXCoolCoil, "Cooling Coil Type [1]");
s->pdchDXCoolCoilType = newPreDefColumn(state, s->pdstDXCoolCoil, "Cooling Coil Type (1)");
s->pdchDXCoolCoilNetCapSI = newPreDefColumn(state, s->pdstDXCoolCoil, "Standard Rating Net Cooling Capacity [W][2]");

s->pdchDXCoolCoilCOP = newPreDefColumn(state, s->pdstDXCoolCoil, "Standard Rating Net COP [W/W][2]");
Expand All @@ -363,7 +363,7 @@ namespace OutputReportPredefined {

// for DX Cooling Coil AHRI Standard 2023 Ratings | SEER2
s->pdstDXCoolCoil_2023 = newPreDefSubTable(state, s->pdrEquip, "DX Cooling Coil Standard Ratings 2023");
s->pdchDXCoolCoilType_2023 = newPreDefColumn(state, s->pdstDXCoolCoil_2023, "Cooling Coil Type [1]");
s->pdchDXCoolCoilType_2023 = newPreDefColumn(state, s->pdstDXCoolCoil_2023, "Cooling Coil Type (1)");
s->pdchDXCoolCoilNetCapSI_2023 = newPreDefColumn(state, s->pdstDXCoolCoil_2023, "Standard Rating Net Cooling Capacity [W][2]");

s->pdchDXCoolCoilCOP_2023 = newPreDefColumn(state, s->pdstDXCoolCoil_2023, "Standard Rating Net COP2 [W/W][2,4]");
Expand Down
12 changes: 6 additions & 6 deletions tst/EnergyPlus/unit/HVACVariableRefrigerantFlow.unit.cc
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Expand Up @@ -2591,9 +2591,9 @@ TEST_F(EnergyPlusFixture, VRF_FluidTCtrl_VRFOU_Compressor)

// Test
EXPECT_NEAR(1.0, CyclingRatio, 0.01);
EXPECT_NEAR(4654, OUEvapHeatExtract, 1); // low load calculation, min speed capacity should use the curve corresponding to the lowest speed
EXPECT_NEAR(3536, OUEvapHeatExtract, 1); // low load calculation, min speed capacity should use the curve corresponding to the lowest speed
EXPECT_NEAR(1500, CompSpdActual, 1);
EXPECT_NEAR(2080, Ncomp, 1);
EXPECT_NEAR(2082, Ncomp, 1);
EXPECT_EQ(state->dataLoopNodes->Node(state->dataHVACVarRefFlow->VRFTU(1).VRFTUInletNodeNum).MassFlowRate, 0.0);

// Inputs_condition for an even lower load, and a more strict Te lower bound
Expand Down Expand Up @@ -2625,14 +2625,14 @@ TEST_F(EnergyPlusFixture, VRF_FluidTCtrl_VRFOU_Compressor)
Ncomp,
CyclingRatio);

EXPECT_NEAR(0.20, CyclingRatio, 0.01);
EXPECT_NEAR(0.22, CyclingRatio, 0.01);
Real64 x = T_discharge;
Real64 y = -5; // in low load modification
Real64 CurveValueEvap = 3.19E-01 - 1.26E-03 * x - 2.15E-05 * x * x + 1.20E-02 * y + 1.05E-04 * y * y - 8.66E-05 * x * y;
Real64 CurveValuePower = 8.79E-02 - 1.72E-04 * x + 6.93E-05 * x * x - 3.38E-05 * y - 8.10E-06 * y * y - 1.04E-05 * x * y;
EXPECT_NEAR(CurveValueEvap * state->dataHVACVarRefFlow->VRF(1).RatedEvapCapacity, OUEvapHeatExtract, 1);
EXPECT_NEAR(1500, CompSpdActual, 1);
EXPECT_NEAR(CurveValuePower * state->dataHVACVarRefFlow->VRF(1).RatedCompPower, Ncomp, 1);
EXPECT_NEAR(CurveValuePower * state->dataHVACVarRefFlow->VRF(1).RatedCompPower * CyclingRatio, Ncomp, 1);
EXPECT_EQ(state->dataLoopNodes->Node(state->dataHVACVarRefFlow->VRFTU(1).VRFTUInletNodeNum).MassFlowRate, 0.0);
}

Expand Down Expand Up @@ -2676,7 +2676,7 @@ TEST_F(EnergyPlusFixture, VRF_FluidTCtrl_VRFOU_Compressor)
thisVRF.RatedEvapCapacity * CurveValue(*state, thisVRF.OUCoolingCAPFT(1), thisVRF.CondensingTemp, thisVRF.EvaporatingTemp);
Real64 CompEvaporatingPWRSpdMin =
thisVRF.RatedCompPower * CurveValue(*state, thisVRF.OUCoolingPWRFT(1), thisVRF.CondensingTemp, thisVRF.EvaporatingTemp);
EXPECT_NEAR(0.35, CyclingRatio, 0.01);
EXPECT_NEAR(0.33, CyclingRatio, 0.01);
EXPECT_NEAR(OUEvapHeatExtract, CompEvaporatingCAPSpdMin + Ncomp, 1e-4);
EXPECT_NEAR(1500, CompSpdActual, 1);
EXPECT_NEAR(Ncomp, CompEvaporatingPWRSpdMin, 1e-4);
Expand Down Expand Up @@ -13365,7 +13365,7 @@ TEST_F(EnergyPlusFixture, VRF_FluidTCtrl_ReportOutputVerificationTest)
EXPECT_NEAR(5645.5696, thisVRFTU.TotalCoolingRate, 0.0001);
EXPECT_NEAR(84.8359, thisFan->totalPower, 0.0001);
EXPECT_NEAR(thisDXCoolingCoil.TotalCoolingEnergyRate, (thisVRFTU.TotalCoolingRate + thisFan->totalPower), 0.0001);
EXPECT_NEAR(0.4124, state->dataHVACVarRefFlow->VRF(1).VRFCondCyclingRatio, 0.0001);
EXPECT_NEAR(0.4036, state->dataHVACVarRefFlow->VRF(1).VRFCondCyclingRatio, 0.0001);
EXPECT_NEAR(state->dataHVACVarRefFlow->VRF(1).OUFanPower,
state->dataHVACVarRefFlow->VRF(1).RatedOUFanPower * state->dataHVACVarRefFlow->VRF(1).VRFCondCyclingRatio,
0.0001);
Expand Down
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