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VRF heating fluid control heating: add SC adjustment for high demand case #10337

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VRF heating fluid control heating: add SC adjustment for high demand case #10337

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e3434a4
add SC adjustment for high demand case
Dec 18, 2023
6f9bc19
Merge remote-tracking branch 'origin/develop' into VRFhighDemandSCadjust
Jan 31, 2024
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77 changes: 54 additions & 23 deletions src/EnergyPlus/DXCoils.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -17522,32 +17522,64 @@ void ControlVRFIUCoil(EnergyPlusData &state,
BF = state.dataDXCoils->DXCoil(CoilIndex).RateBFVRFIUCond;

// Coil sensible heat transfer_minimum value
CalcVRFCoilSenCap(state, FlagHeatMode, CoilIndex, Tin, TeTc, SC, BF, QinSenPerFlowRate, Ts_1);
To_1 = QinSenPerFlowRate / 1005 + Tin;
QinSenMin1 = FanSpdRatioMin * Garate * QinSenPerFlowRate; // Corresponds real SH

CalcVRFCoilSenCap(state, FlagHeatMode, CoilIndex, Tin, TeTc, MaxSC, BF, QinSenPerFlowRate, Ts_2);
To_2 = QinSenPerFlowRate / 1005 + Tin;
QinSenMin2 = FanSpdRatioMin * Garate * QinSenPerFlowRate; // Corresponds maximum SH

if (QCoilSenHeatingLoad > QinSenMin1) {
Real64 SCmin = 0.0;
Real64 QinSenPerFlowRateSCmin;
Real64 Ts_1_SCmin;
CalcVRFCoilSenCap(state, FlagHeatMode, CoilIndex, Tin, TeTc, SCmin, BF, QinSenPerFlowRateSCmin, Ts_1_SCmin);
Real64 SCini = SC;
Real64 QinSenPerFlowRateSCini;
Real64 Ts_1_SCini;
CalcVRFCoilSenCap(state, FlagHeatMode, CoilIndex, Tin, TeTc, SCini, BF, QinSenPerFlowRateSCini, Ts_1_SCini);
Real64 SCmax = MaxSC;
Real64 QinSenPerFlowRateSCmax;
Real64 Ts_1_SCmax;
CalcVRFCoilSenCap(state, FlagHeatMode, CoilIndex, Tin, TeTc, SCmax, BF, QinSenPerFlowRateSCmax, Ts_1_SCmax);

FanSpdRatioMax = 1.0;
CoilOnOffRatio = 1.0;
if (QCoilSenHeatingLoad > FanSpdRatioMax * Garate * QinSenPerFlowRateSCmin) {
// cannot control to the target
SCact = SCmin;
FanSpdRatio = FanSpdRatioMax;
Tout = Tin + (Ts_1_SCmin - Tin) * (1 - BF);
} else if (QCoilSenHeatingLoad > FanSpdRatioMax * Garate * QinSenPerFlowRateSCini) {
FanSpdRatio = FanSpdRatioMax;
auto f = [&state, QCoilSenHeatingLoad, FanSpdRatioMax, Garate, CoilIndex, Tin, TeTc, BF](Real64 SC) {
Real64 QinSenPerFlowRate = 0.0;
Real64 Ts_1 = 0.0;
CalcVRFCoilSenCap(state, FlagHeatMode, CoilIndex, Tin, TeTc, SC, BF, QinSenPerFlowRate, Ts_1);
return (QCoilSenHeatingLoad - FanSpdRatioMax * Garate * QinSenPerFlowRate);
};
General::SolveRoot(state, 1.0e-3, MaxIter, SolFla, SCact, f, SCmin, SCini);
assert(SolFla > 0.0);
CalcVRFCoilSenCap(state, FlagHeatMode, CoilIndex, Tin, TeTc, SCact, BF, QinSenPerFlowRate, Ts_1);
Tout = Tin + (Ts_1 - Tin) * (1 - BF);
} else if (QCoilSenHeatingLoad > FanSpdRatioMin * Garate * QinSenPerFlowRateSCini) {
// Modulate fan speed to meet room sensible load; SC is not updated
FanSpdRatioMax = 1.0;
auto f = [QCoilSenHeatingLoad, Ts_1, Tin, Garate, BF](Real64 FanSpdRto) {
return FanSpdResidualHeat(FanSpdRto, QCoilSenHeatingLoad, Ts_1, Tin, Garate, BF);
// TotCap = FanSpdRto * Garate * 1005.0 * (Tout - Tin);
// fan speed ratio = QCoilSenHeatingLoad / Garate * 1005.0 * (Ts_1 - Tin) * (1 - BF)
// = QCoilSenHeatingLoad / (Garate * Q_sen)
FanSpdRatio = QCoilSenHeatingLoad / (Garate * QinSenPerFlowRateSCini);
Tout = Tin + (Ts_1_SCini - Tin) * (1 - BF);
SCact = SCini;
assert(FanSpdRatio <= 1.0);
} else if (QCoilSenHeatingLoad > FanSpdRatioMin * Garate * QinSenPerFlowRateSCmax) {
FanSpdRatio = FanSpdRatioMin;
auto f = [&state, QCoilSenHeatingLoad, FanSpdRatioMin, Garate, CoilIndex, Tin, TeTc, BF](Real64 SC) {
Real64 QinSenPerFlowRate = 0.0;
Real64 Ts_1 = 0.0;
CalcVRFCoilSenCap(state, FlagHeatMode, CoilIndex, Tin, TeTc, SC, BF, QinSenPerFlowRate, Ts_1);
return (QCoilSenHeatingLoad - FanSpdRatioMin * Garate * QinSenPerFlowRate);
};
General::SolveRoot(state, 1.0e-3, MaxIter, SolFla, Ratio1, f, FanSpdRatioMin, FanSpdRatioMax);
// this will likely cause problems eventually, -1 and -2 mean different things
if (SolFla < 0) Ratio1 = FanSpdRatioMax; // over capacity
FanSpdRatio = Ratio1;
CoilOnOffRatio = 1.0;

General::SolveRoot(state, 1.0e-3, MaxIter, SolFla, SCact, f, SCini, SCmax);
assert(SolFla > 0.0);
// recompute the coil surface temperature with adjusted SC
CalcVRFCoilSenCap(state, FlagHeatMode, CoilIndex, Tin, TeTc, SCact, BF, QinSenPerFlowRate, Ts_1);
Tout = Tin + (Ts_1 - Tin) * (1 - BF);
Wout = Win;
Hout = PsyHFnTdbW(Tout, Wout);
SHact = 999.0;
SCact = SC;

} else {
// Low load modification algorithm
// Need to increase SC to further reduce coil heating capacity
Expand Down Expand Up @@ -17578,11 +17610,10 @@ void ControlVRFIUCoil(EnergyPlusData &state,
// outlet air temperature is time-weighted
Tout = CoilOnOffRatio * To_2 + (1 - CoilOnOffRatio) * Tin;
}

Wout = Win;
Hout = PsyHFnTdbW(Tout, Wout);
SHact = 999.0;
}
Wout = Win;
Hout = PsyHFnTdbW(Tout, Wout);
SHact = 999.0;
}
}

Expand Down