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Fix VRF FluidTCtrl negative outdoor unit fan power #10649

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Fix VRF FluidTCtrl negative outdoor unit fan power #10649

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7f2acaf
use abs(QCoil) in air flow calculation
Aug 8, 2024
ae3fec6
Merge remote-tracking branch 'origin/develop' into fixVRFnegativeFanP…
Aug 13, 2024
cabd9e6
revert abs(Q_coil), reduce h_IU_cond_in label230, fix Q_evap_req neg
Aug 22, 2024
765218b
Merge remote-tracking branch 'origin/develop' into fixVRFnegativeFanP…
Aug 23, 2024
35d4b69
add converge check that h_comp_out_new changed
Aug 23, 2024
0f1d4fd
Merge remote-tracking branch 'origin/develop' into fixVRFnegativeFanP…
Oct 4, 2024
935df9e
Revert "add converge check that h_comp_out_new changed"
Oct 7, 2024
38ad9f1
Patch for Q_cond_req < min speed power, CompSpdActual int to real
Oct 7, 2024
d54f356
clang-format
Oct 7, 2024
39567c8
fix unit test
Oct 7, 2024
aae3346
simplify the code by condition on sign of Q_evap_req
Oct 14, 2024
bd53fd7
Merge remote-tracking branch 'origin/develop' into fixVRFnegativeFanP…
Oct 14, 2024
4e979ea
use PLR in compressor speed calculation
Oct 21, 2024
1b58521
modify PLR application on the speed level > 1 case
Oct 21, 2024
cce66e0
Merge remote-tracking branch 'origin/develop' into fixVRFnegativeFanP…
Oct 21, 2024
a135044
fix unit test after changing compSpdActual calculation
Oct 21, 2024
835253a
remove unused Q_evap_req, remove C_cap_operation adjustment
Oct 22, 2024
436f277
fix unit test after removing C_cap_operation adjustment
Oct 22, 2024
a777bf5
fix uninitialized RatedHeatCapacity in VRF HR model
Oct 23, 2024
380d580
use newly derived r to compute compressor speed and Q_evap_req
Oct 24, 2024
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17 changes: 10 additions & 7 deletions src/EnergyPlus/HVACVariableRefrigerantFlow.cc
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Expand Up @@ -13726,6 +13726,9 @@ void VRFCondenserEquipment::VRFOU_CompSpd(

} else {
CompSpdActual = this->CompressorSpeed(1) * (Q_evap_req * C_cap_operation) / CompEvaporatingCAPSpd(1);
if (Q_cond_req - CompEvaporatingPWRSpd(CounterCompSpdTemp) < 0.0) { // use compressor power to meet condenser required load
CompSpdActual = this->CompressorSpeed(1) * (Q_cond_req * C_cap_operation) / CompEvaporatingPWRSpd(1);
}
}
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@yujiex I think I understand the intent here. This could be simpler.

}  else {
    if (Q_evap_req < 0.0) {  // use compressor power to meet condenser required load
          CompSpdActual = this->CompressorSpeed(1) * (Q_cond_req * C_cap_operation) /CompEvaporatingPWRSpd(1);
    } else {
          CompSpdActual = this->CompressorSpeed(1) * (Q_evap_req * C_cap_operation) / CompEvaporatingCAPSpd(1);
    }

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Indeed, this is more clear.

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What I don't understand is what looks like a COP term = Qc / PWR. I just don't see how that gets back to a speed 1 fraction. What am I missing?

CompSpdActual = this->CompressorSpeed(1) * (Q_cond_req * C_cap_operation) /CompEvaporatingPWRSpd(1);

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@rraustad The way I think about this is when Q_cond_req - CompEvaporatingPWRSpd(1) <= 0.0, then what CompEvaporatingPWRSpd(1) can supply is too much to meet Q_cond_req. The speed should be somewhere between 0 and the 1st speed level. So in this case Q_cond_req should be met by CompEvaporatingPWRSpd(1) * ratio. This ratio is calculated as Q_cond_req / CompEvaporatingPWRSpd(1)

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But CompEvaporatingPWRSpd is power, not capacity. So Q_cond_req / CompEvaporatingPWRSpd(1) looks strange to me. Shouldn't both equations have CompEvaporatingCAPSpd in the denominator (line 13729)?

Array1D<Real64> CompEvaporatingPWRSpd; // Array for the compressor power at certain speed [W]
Array1D<Real64> CompEvaporatingCAPSpd; // Array for the evaporating capacity at certain speed [W]

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I can also try to change the VRF evaporative capacity to make it reach higher speed levels.

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This is how they look when they can reach higher speed levels (I reduced the capacity to 10000, the autosized heating and cooing capacity are around 70000W)

image

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Can you make it span speeds? like from speed 1 to speed 3? I want to see what Q_evap_req * C_cap_operating / CompEvaporatingCAPSpd(x) looks like (or your derivation). I suspect there are discontinuities because C_cap_operatiion = 0.6. And make a scatter plot like before. Q_evap_req versus compressor speed.

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Oh I see, your plot is Q_evap_req versus comp speed. I was confused because I didn't see a 45 degree line like I was expecting. Why is Q_evap_req = 2000 at comp speeds 0 - 10000 ??

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Somehow there's some weird thing happening when I plot with excel. CompSpdActual is always below 6000 for both the feature and develop branch output, but it somehow plotted it out to over 10000. I have attached the data here
plot data.zip
I used R to plot, this is how they look

image


break; // EXIT DoName1
Expand All @@ -13740,13 +13743,13 @@ void VRFCondenserEquipment::VRFOU_CompSpd(

void VRFCondenserEquipment::VRFOU_CompCap(
EnergyPlusData &state,
int const CompSpdActual, // Given compressor speed
Real64 const T_suction, // Compressor suction temperature Te' [C]
Real64 const T_discharge, // Compressor discharge temperature Tc' [C]
Real64 const h_IU_evap_in, // Enthalpy of IU at inlet, for C_cap_operation calculation [kJ/kg]
Real64 const h_comp_in, // Enthalpy after piping loss (compressor inlet), for C_cap_operation calculation [kJ/kg]
Real64 &Q_c_tot, // Compressor evaporative capacity [W]
Real64 &Ncomp // Compressor power [W]
Real64 const CompSpdActual, // Given compressor speed
Real64 const T_suction, // Compressor suction temperature Te' [C]
Real64 const T_discharge, // Compressor discharge temperature Tc' [C]
Real64 const h_IU_evap_in, // Enthalpy of IU at inlet, for C_cap_operation calculation [kJ/kg]
Real64 const h_comp_in, // Enthalpy after piping loss (compressor inlet), for C_cap_operation calculation [kJ/kg]
Real64 &Q_c_tot, // Compressor evaporative capacity [W]
Real64 &Ncomp // Compressor power [W]
)
{

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14 changes: 7 additions & 7 deletions src/EnergyPlus/HVACVariableRefrigerantFlow.hh
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Expand Up @@ -577,13 +577,13 @@ namespace HVACVariableRefrigerantFlow {
);

void VRFOU_CompCap(EnergyPlusData &state,
int CompSpdActual, // Given compressor speed
Real64 T_suction, // Compressor suction temperature Te' [C]
Real64 T_discharge, // Compressor discharge temperature Tc' [C]
Real64 h_IU_evap_in, // Enthalpy of IU at inlet, for C_cap_operation calculation [kJ/kg]
Real64 h_comp_in, // Enthalpy after piping loss (compressor inlet), for C_cap_operation calculation [kJ/kg]
Real64 &Q_c_tot, // Compressor evaporative capacity [W]
Real64 &Ncomp // Compressor power [W]
Real64 CompSpdActual, // Given compressor speed
Real64 T_suction, // Compressor suction temperature Te' [C]
Real64 T_discharge, // Compressor discharge temperature Tc' [C]
Real64 h_IU_evap_in, // Enthalpy of IU at inlet, for C_cap_operation calculation [kJ/kg]
Real64 h_comp_in, // Enthalpy after piping loss (compressor inlet), for C_cap_operation calculation [kJ/kg]
Real64 &Q_c_tot, // Compressor evaporative capacity [W]
Real64 &Ncomp // Compressor power [W]
);

void VRFOU_PipeLossC(EnergyPlusData &state,
Expand Down
4 changes: 2 additions & 2 deletions tst/EnergyPlus/unit/HVACVariableRefrigerantFlow.unit.cc
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Expand Up @@ -2458,8 +2458,8 @@ TEST_F(EnergyPlusFixture, VRF_FluidTCtrl_VRFOU_Compressor)

// Test
EXPECT_NEAR(756, CompSpdActual, 1);
EXPECT_NEAR(899, Ncomp, 1);
EXPECT_NEAR(3186, Q_c_OU, 1);
EXPECT_NEAR(901, Ncomp, 1);
EXPECT_NEAR(3196, Q_c_OU, 1);
EXPECT_NEAR(0, Q_h_OU, 1);
EXPECT_NEAR(242, N_fan_OU, 1);
EXPECT_NEAR(0.0158, m_ref_OU_evap, 0.0005);
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