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Merge pull request #10353 from NREL/vrfFluidCtrlFixCoolingCycling
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Fix VRFFluidCtrl cooling cycling issue by moving cycling ratio calc in compressor spd calc
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@Myoldmopar
Myoldmopar authored Sep 11, 2024
2 parents 57c067a + 5907d73 commit e2692dd
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Showing 5 changed files with 146 additions and 67 deletions.
151 changes: 91 additions & 60 deletions src/EnergyPlus/HVACVariableRefrigerantFlow.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -266,7 +266,7 @@ void SimulateVRF(EnergyPlusData &state,

if (state.dataHVACVarRefFlow->VRF(VRFCondenser).VRFAlgorithmType == AlgorithmType::FluidTCtrl) {
// Algorithm Type: VRF model based on physics, applicable for Fluid Temperature Control
state.dataHVACVarRefFlow->VRF(VRFCondenser).CalcVRFCondenser_FluidTCtrl(state);
state.dataHVACVarRefFlow->VRF(VRFCondenser).CalcVRFCondenser_FluidTCtrl(state, FirstHVACIteration);
} else {
// Algorithm Type: VRF model based on system curve
CalcVRFCondenser(state, VRFCondenser);
Expand Down Expand Up @@ -11010,7 +11010,7 @@ void VRFTerminalUnitEquipment::CalcVRFIUVariableTeTc(EnergyPlusData &state,
}
}

void VRFCondenserEquipment::CalcVRFCondenser_FluidTCtrl(EnergyPlusData &state)
void VRFCondenserEquipment::CalcVRFCondenser_FluidTCtrl(EnergyPlusData &state, const bool FirstHVACIteration)
{

// SUBROUTINE INFORMATION:
Expand Down Expand Up @@ -11141,7 +11141,7 @@ void VRFCondenserEquipment::CalcVRFCondenser_FluidTCtrl(EnergyPlusData &state)
Real64 Pipe_DeltP_h; // Piping Loss Algorithm Parameter: Pipe pressure drop (h) [Pa]
Real64 Pipe_Q_c; // Piping Loss Algorithm Parameter: Heat loss (c) [W]
Real64 Pipe_Q_h; // Piping Loss Algorithm Parameter: Heat loss (h) [W]
Real64 Q_c_TU_PL; // Cooling load to be met at heating mode, including the piping loss(W)
Real64 Q_c_TU_PL; // Cooling load to be met at cooling mode, including the piping loss(W)
Real64 Q_h_TU_PL; // Heating load to be met at heating mode, including the piping loss (W)
Real64 Q_h_OU; // outdoor unit condenser heat release (cooling mode) [W]
Real64 Q_c_OU; // outdoor unit evaporator heat extract (heating mode) [W]
Expand Down Expand Up @@ -11419,56 +11419,40 @@ void VRFCondenserEquipment::CalcVRFCondenser_FluidTCtrl(EnergyPlusData &state)
C_cap_operation = this->VRFOU_CapModFactor(
state, h_comp_in, h_IU_evap_in, max(min(Psuction, RefPHigh), RefPLow), Tsuction + SH_Comp, Tsuction + 8, CapMinTc - 5);

if (Q_c_TU_PL * C_cap_operation < CompEvaporatingCAPSpdMin) {
// Required cooling load is less than the min cooling capacity, on-off strategy

this->VRFOperationSimPath = 11;

CyclingRatio = Q_c_TU_PL * C_cap_operation / CompEvaporatingCAPSpdMin;
double CyclingRatioFrac = 0.85 + 0.15 * CyclingRatio;
double HPRTF = CyclingRatio / CyclingRatioFrac;
Ncomp = CompEvaporatingPWRSpdMin * HPRTF; //
CompSpdActual = this->CompressorSpeed(1); //
this->CondensingTemp = CapMinTc; //

} else {
// Required cooling load is greater than or equal to the min cooling capacity
// Iteration_Ncomp: Perform iterations to calculate Ncomp (Label10)
Counter = 1;
Ncomp = TU_CoolingLoad / this->CoolingCOP;
Ncomp_new = Ncomp;
Label10:;
Q_h_OU = Q_c_TU_PL + Ncomp_new; // Ncomp_new may be updated during Iteration_Ncomp Label10

// *VRF OU TeTc calculations
m_air = this->OUAirFlowRate * RhoAir;
SC_OU = this->SC;
this->VRFOU_TeTc(state, HXOpMode::CondMode, Q_h_OU, SC_OU, m_air, OutdoorDryBulb, OutdoorHumRat, OutdoorPressure, Tfs, this->CondensingTemp);
this->CondensingTemp = min(CapMaxTc, this->CondensingTemp);
this->SC = SC_OU;

// *VEF OU Compressor Simulation at cooling mode: Specify the compressor speed and power consumption
this->VRFOU_CalcCompC(state,
TU_CoolingLoad,
Tsuction,
this->CondensingTemp,
Psuction,
T_comp_in,
h_comp_in,
h_IU_evap_in,
Pipe_Q_c,
CapMaxTc,
Q_h_OU,
CompSpdActual,
Ncomp,
CyclingRatio);

// Iteration_Ncomp: Perform iterations to calculate Ncomp (Label10)
Counter = 1;
Ncomp = TU_CoolingLoad / this->CoolingCOP;
if ((std::abs(Ncomp - Ncomp_new) > (Tolerance * Ncomp_new)) && (Counter < 30)) {
Ncomp_new = Ncomp;
Label10:;
Q_h_OU = Q_c_TU_PL + Ncomp_new; // Ncomp_new may be updated during Iteration_Ncomp Label10

// *VRF OU TeTc calculations
m_air = this->OUAirFlowRate * RhoAir;
SC_OU = this->SC;
this->VRFOU_TeTc(
state, HXOpMode::CondMode, Q_h_OU, SC_OU, m_air, OutdoorDryBulb, OutdoorHumRat, OutdoorPressure, Tfs, this->CondensingTemp);
this->CondensingTemp = min(CapMaxTc, this->CondensingTemp);
this->SC = SC_OU;

// *VEF OU Compressor Simulation at cooling mode: Specify the compressor speed and power consumption
this->VRFOU_CalcCompC(state,
TU_CoolingLoad,
Tsuction,
this->CondensingTemp,
Psuction,
T_comp_in,
h_comp_in,
h_IU_evap_in,
Pipe_Q_c,
CapMaxTc,
Q_h_OU,
CompSpdActual,
Ncomp);

if ((std::abs(Ncomp - Ncomp_new) > (Tolerance * Ncomp_new)) && (Counter < 30)) {
Ncomp_new = Ncomp;
Counter = Counter + 1;
goto Label10;
}
Counter = Counter + 1;
goto Label10;
}

// Update h_IU_evap_in in iterations Label12
Expand All @@ -11490,6 +11474,8 @@ void VRFCondenserEquipment::CalcVRFCondenser_FluidTCtrl(EnergyPlusData &state)
}

// Key outputs of this subroutine
Ncomp *= CyclingRatio;
Q_h_OU *= CyclingRatio;
this->CompActSpeed = max(CompSpdActual, 0.0);
this->Ncomp = max(Ncomp, 0.0) / this->EffCompInverter; // 0.95 is the efficiency of the compressor inverter, can come from IDF //@minor
this->OUFanPower = this->RatedOUFanPower; //@ * pow_3( CondFlowRatio )
Expand Down Expand Up @@ -11975,7 +11961,7 @@ void VRFCondenserEquipment::CalcVRFCondenser_FluidTCtrl(EnergyPlusData &state)

this->HeatingCapacity = 0.0; // Include the piping loss
this->PipingCorrectionHeating = 1.0; // 1 means no piping loss
state.dataHVACVarRefFlow->MaxHeatingCapacity(VRFCond) = MaxCap; // yujie: default value is MaxCap = 1e+20, not 0
state.dataHVACVarRefFlow->MaxHeatingCapacity(VRFCond) = MaxCap; // default value is MaxCap = 1e+20, not 0

this->CoolingCapacity = 0.0; // Include the piping loss
this->PipingCorrectionCooling = 1.0;
Expand Down Expand Up @@ -12348,6 +12334,25 @@ void VRFCondenserEquipment::CalcVRFCondenser_FluidTCtrl(EnergyPlusData &state)

// Calculate the IU Te/Tc for the next time step
this->CalcVRFIUTeTc_FluidTCtrl(state);
// update coil and IU evaporating temperature, also keep coil RTF updated with the condenser side cycling ratio, for the FluidTCtrl model
for (int VRFTUNum = 1; VRFTUNum <= state.dataHVACVarRefFlow->NumVRFTU; ++VRFTUNum) {
auto const &thisTU = state.dataHVACVarRefFlow->VRFTU(VRFTUNum);
auto &coolingCoil = state.dataDXCoils->DXCoil(thisTU.CoolCoilIndex);
if (this->adjustedTe && (!FirstHVACIteration)) {
coolingCoil.EvaporatingTemp = this->EvaporatingTemp;
this->IUEvaporatingTemp = this->EvaporatingTemp;
}

int PLF;
if (coolingCoil.PLFFPLR(1) > 0 && this->VRFCondCyclingRatio < 1.0) {
PLF = Curve::CurveValue(state, coolingCoil.PLFFPLR(1), this->VRFCondCyclingRatio); // Calculate part-load factor
} else {
PLF = 1.0;
}
if (coolingCoil.TotalCoolingEnergyRate > 0.0) {
coolingCoil.CoolingCoilRuntimeFraction = this->VRFCondCyclingRatio / PLF;
}
}
}

void VRFTerminalUnitEquipment::ControlVRF_FluidTCtrl(EnergyPlusData &state,
Expand Down Expand Up @@ -13847,14 +13852,16 @@ void VRFCondenserEquipment::VRFOU_CalcCompC(EnergyPlusData &state,
Real64 MaxOutdoorUnitTc, // The maximum temperature that Tc can be at heating mode [C]
Real64 &OUCondHeatRelease, // Condenser heat release (cooling mode) [W]
Real64 &CompSpdActual, // Actual compressor running speed [rps]
Real64 &Ncomp // Compressor power [W]
Real64 &Ncomp, // Compressor power [W]
Real64 &CyclingRatio // Cycling Ratio [W]
)
{

// SUBROUTINE INFORMATION:
// AUTHOR Xiufeng Pang
// DATE WRITTEN Feb 2014
// MODIFIED Rongpeng Zhang, Jan 2016
// MODIFIED Yujie Xu, Sep 2023
// RE-ENGINEERED na

// PURPOSE OF THIS SUBROUTINE:
Expand Down Expand Up @@ -13910,7 +13917,8 @@ void VRFCondenserEquipment::VRFOU_CalcCompC(EnergyPlusData &state,
Real64 RefPHigh; // High Pressure Value for Ps (max in tables) [Pa]
Real64 T_discharge_new; // Condensing temperature, for temporary use in iterations [C]
Real64 Tfs; // Temperature of the air at the coil surface [C]]
Real64 Tolerance(0.05); // Tolerance for condensing temperature calculation [C}
Real64 constexpr Tolerance(0.05); // Tolerance for condensing temperature calculation [C]
Real64 constexpr TeTol(0.5); // Tolerance for the difference between Te and SmallLoadTe
Array1D<Real64> CompEvaporatingPWRSpd; // Array for the compressor power at certain speed [W]
Array1D<Real64> CompEvaporatingCAPSpd; // Array for the evaporating capacity at certain speed [W]

Expand Down Expand Up @@ -13939,6 +13947,7 @@ void VRFCondenserEquipment::VRFOU_CalcCompC(EnergyPlusData &state,
C_cap_operation = this->VRFOU_CapModFactor(
state, Pipe_h_comp_in, Pipe_h_IU_in, max(min(P_suction, RefPHigh), RefPLow), T_suction + Modifi_SH, T_suction + 8, T_discharge - 5);

this->adjustedTe = false;
for (CounterCompSpdTemp = 1; CounterCompSpdTemp <= NumOfCompSpdInput; CounterCompSpdTemp++) {
// Iteration to find the VRF speed that can meet the required load, Iteration DoName1

Expand Down Expand Up @@ -13987,14 +13996,26 @@ void VRFCondenserEquipment::VRFOU_CalcCompC(EnergyPlusData &state,
MinRefriPe = this->refrig->getSatPressure(state, -15, RoutineName);
MinOutdoorUnitPe = max(P_discharge - this->CompMaxDeltaP, MinRefriPe);
MinOutdoorUnitTe = this->refrig->getSatTemperature(state, max(min(MinOutdoorUnitPe, RefPHigh), RefPLow), RoutineName);
// Te can't be smaller than user input lower bound
MinOutdoorUnitTe = max(this->IUEvapTempLow, MinOutdoorUnitTe);

auto f = [&state, T_discharge_new, CondHeat, CAPFT](Real64 const T_suc) {
return CompResidual_FluidTCtrl(state, T_discharge_new, CondHeat, CAPFT, T_suc);
};

General::SolveRoot(state, 1.0e-3, MaxIter, SolFla, SmallLoadTe, f, MinOutdoorUnitTe,
T_suction); // SmallLoadTe is the updated Te'
if (SolFla < 0) SmallLoadTe = 6; // MinOutdoorUnitTe; //SmallLoadTe( Te'_new ) is constant during iterations
T_suction); // SmallLoadTe is the updated Te'
if (SolFla == -1) {
// show error not converging
ShowWarningMessage(state, format("{}: low load Te adjustment failed for {}", RoutineName, this->Name));
ShowContinueErrorTimeStamp(state, "");
ShowContinueError(state, format(" Iteration limit [{}] exceeded in calculating OU evaporating temperature", MaxIter));
} else if (SolFla == -2) {
// demand < capacity at both endpoints of the Te range, assuming f(x) is roughly monotonic than this is the low load case
assert(f(T_suction) < 0);
// TeTol is added to prevent the final updated Te to go out of bounds
SmallLoadTe = 6 + TeTol; // MinOutdoorUnitTe; //SmallLoadTe( Te'_new ) is constant during iterations
}

// Get an updated Te corresponding to the updated Te'
// VRFOU_TeModification( VRFCond, this->EvaporatingTemp, SmallLoadTe, Pipe_h_IU_in, OutdoorDryBulb, Pipe_Te_assumed,
Expand All @@ -14006,6 +14027,7 @@ void VRFCondenserEquipment::VRFOU_CalcCompC(EnergyPlusData &state,
NumIteTe = 1;
MaxNumIteTe = (this->EvaporatingTemp - SmallLoadTe) / 0.1 + 1; // upper bound and lower bound of Te iterations
Pipe_Te_assumed = this->EvaporatingTemp - 0.1;
this->adjustedTe = true;

Label11:;
Pipe_m_ref = 0; // Total Ref Flow Rate( kg/s )
Expand Down Expand Up @@ -14072,14 +14094,14 @@ void VRFCondenserEquipment::VRFOU_CalcCompC(EnergyPlusData &state,

T_suction = this->refrig->getSatTemperature(state, max(min(Pipe_Pe_assumed - Pipe_DeltP, RefPHigh), RefPLow), RoutineName);

if ((std::abs(T_suction - SmallLoadTe) > 0.5) && (Pipe_Te_assumed < this->EvaporatingTemp) && (Pipe_Te_assumed > SmallLoadTe) &&
if ((std::abs(T_suction - SmallLoadTe) > TeTol) && (Pipe_Te_assumed < this->EvaporatingTemp) && (Pipe_Te_assumed > SmallLoadTe) &&
(NumIteTe < MaxNumIteTe)) {
Pipe_Te_assumed = Pipe_Te_assumed - 0.1;
NumIteTe = NumIteTe + 1;
goto Label11;
}

if (std::abs(T_suction - SmallLoadTe) > 0.5) {
if (std::abs(T_suction - SmallLoadTe) > TeTol) {
NumIteTe = 999;
T_suction = SmallLoadTe;
Pipe_SH_merged = 3.0;
Expand Down Expand Up @@ -14131,12 +14153,21 @@ void VRFCondenserEquipment::VRFOU_CalcCompC(EnergyPlusData &state,
goto Label13;
}

if (CapDiff > (Tolerance * Cap_Eva0)) NumIteCcap = 999;
// when it gets here, either NumIteCcap = 30 or CapDiff > (Tolerance * Cap_Eva0)
if (CapDiff > (Tolerance * Cap_Eva0) && (Cap_Eva1 - Cap_Eva0) >= 0.0) {
NumIteCcap = 999;
CyclingRatio = Cap_Eva0 / Cap_Eva1;
} else {
CyclingRatio = 1.0;
}

Ncomp = this->RatedCompPower * CurveValue(state, this->OUCoolingPWRFT(CounterCompSpdTemp), T_discharge, T_suction);
OUCondHeatRelease = Ncomp + Cap_Eva1;

this->CondensingTemp = T_discharge; // OU Tc' is updated due to OUCondHeatRelease updates, which is caused by IU Te' updates
// during low load conditions
this->EvaporatingTemp = T_suction;
this->IUEvaporatingTemp = T_suction;

break; // EXIT DoName1

Expand Down Expand Up @@ -14212,7 +14243,7 @@ void VRFCondenserEquipment::VRFOU_CalcCompH(
Real64 RefTSat; // Saturated temperature of the refrigerant [C]
Real64 RefPLow; // Low Pressure Value for Ps (>0.0) [Pa]
Real64 RefPHigh; // High Pressure Value for Ps (max in tables) [Pa]
Real64 Tolerance(0.05); // Tolerance for condensing temperature calculation [C}
Real64 constexpr Tolerance(0.05); // Tolerance for condensing temperature calculation [C}
Array1D<Real64> CompEvaporatingPWRSpd; // Array for the compressor power at certain speed [W]
Array1D<Real64> CompEvaporatingCAPSpd; // Array for the evaporating capacity at certain speed [W]

Expand Down
8 changes: 5 additions & 3 deletions src/EnergyPlus/HVACVariableRefrigerantFlow.hh
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Original file line number Diff line number Diff line change
Expand Up @@ -387,6 +387,7 @@ namespace HVACVariableRefrigerantFlow {
Real64 VRFOperationSimPath; // simulation path indicating the VRF operation mode [--]
bool checkPlantCondTypeOneTime;
int CondenserCapErrIdx; // recurring condenser capacity error index
bool adjustedTe;

// Default Constructor
VRFCondenserEquipment()
Expand Down Expand Up @@ -427,7 +428,7 @@ namespace HVACVariableRefrigerantFlow {
RatedHeatCapacity(0.0), RatedCompPower(14000.0), RatedCompPowerPerCapcity(0.35), RatedOUFanPower(0.0), RatedOUFanPowerPerCapcity(0.0),
RateBFOUEvap(0.45581), RateBFOUCond(0.21900), RefPipDiaSuc(0.0), RefPipDiaDis(0.0), RefPipLen(0.0), RefPipEquLen(0.0), RefPipHei(0.0),
RefPipInsThi(0.0), RefPipInsCon(0.0), SH(0.0), SC(0.0), SCHE(0.0), SHLow(0.0), SCLow(0.0), SHHigh(0.0), SCHigh(0.0),
VRFOperationSimPath(0.0), checkPlantCondTypeOneTime(true), CondenserCapErrIdx(0)
VRFOperationSimPath(0.0), checkPlantCondTypeOneTime(true), CondenserCapErrIdx(0), adjustedTe(false)
{
}

Expand All @@ -449,7 +450,7 @@ namespace HVACVariableRefrigerantFlow {

void SizeVRFCondenser(EnergyPlusData &state);

void CalcVRFCondenser_FluidTCtrl(EnergyPlusData &state);
void CalcVRFCondenser_FluidTCtrl(EnergyPlusData &state, const bool FirstHVACIteration);

void CalcVRFIUTeTc_FluidTCtrl(EnergyPlusData &state);

Expand Down Expand Up @@ -526,7 +527,8 @@ namespace HVACVariableRefrigerantFlow {
Real64 MaxOutdoorUnitTc, // The maximum temperature that Tc can be at heating mode [C]
Real64 &OUCondHeatRelease, // Condenser heat release (cooling mode) [W]
Real64 &CompSpdActual, // Actual compressor running speed [rps]
Real64 &Ncomp // Compressor power [W]
Real64 &Ncomp, // Compressor power [W]
Real64 &CyclingRatio // Cycling Ratio [W]
);

void
Expand Down
2 changes: 1 addition & 1 deletion src/EnergyPlus/HeatBalanceSurfaceManager.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -356,7 +356,7 @@ void InitSurfaceHeatBalance(EnergyPlusData &state)
}
}

// yujie: variable thermal solar absorptance overrides
// variable thermal solar absorptance overrides
UpdateVariableAbsorptances(state);

// Do the Begin Environment initializations
Expand Down
2 changes: 1 addition & 1 deletion src/EnergyPlus/HeatRecovery.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -517,7 +517,7 @@ namespace HeatRecovery {
thisExchanger.EconoLockOut = static_cast<bool>(toggle);
}

// yujie: read new curves here
// read new curves here
thisExchanger.HeatEffectSensibleCurveIndex =
Curve::GetCurveIndex(state, state.dataIPShortCut->cAlphaArgs(11)); // convert curve name to number
thisExchanger.HeatEffectLatentCurveIndex =
Expand Down
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