Avoid wshp array bounds error

[mjwitte]

Pull request overview

• Fixes WaterToAirHeatPump:EquationFit sizing companion coil array bounds error #9849 ?? Maybe.

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[rraustad]

I believe what the code below is trying to do is to size a HP, so the coils would need to be the same size. In this case that's not necessary but an actual HP would need to be tested to make sure it works. I guess it does work since all WSHPs apparently size correctly, or do they?

[rraustad]

I just wrapped all this in 1 IF block. Still not sure if the code at the end of this block is needed.

[rraustad]

The next step is to remove this IF block. There is no reason to call the cooling coil to report the UnitarySystem heating capacity. That's a cover up.

[rraustad]

Regarding if this fix is correct, there is the same check for the cooling coil where the companionCoil index is checked before looking for the companion heating coil. So this does look like the fix moved in the right direction. It's just that there are some oddities that could also be looked at here or in a separate issue. See issue discussion.

[rraustad]

Also some interesting table reports.

9849-Solution2-Separate UnitarySystems-in-v24.2-CompanionCoilCrash.txt

[rraustad]

Why would the rated capacity sizing variable be set to 0 if not autosized? And what about rated power below? and check the cooling coil code.

Real64 RatedCapHeatAtRatedCdts = 0.0;        // Rated Heating Capacity at Rated Conditions [W]

[rraustad]

I guess I could have changed the water flow rate sizing to use RatedCapHeat instead.

if (simpleWatertoAirHP.WAHPType == WatertoAirHP::Heating) {
    RatedWaterVolFlowRateDes =
        simpleWatertoAirHP.RatedCapHeatAtRatedCdts / (state.dataSize->PlantSizData(PltSizNum).DeltaT * Cp * rho);

[rraustad]

There is likely a difference between RatedCapHeat and RatedCapHeatAtRatedCdts given the CapFT term applied. This is above at line 2743.

            simpleWatertoAirHP.RatedCapHeat = RatedCapHeatDes;
            simpleWatertoAirHP.RatedCapHeatAtRatedCdts = RatedCapHeatDes * RatedHeatCapTempModFac;

[rraustad]

I think these equations need to be moved up into the IF blocks in order to use the correct variable. If RatedCapHeat is the coil load and RatedCapHeatatRatedCdts is the coil size, when autosized, then declaring these variables AFTER the coil size is determined seems wrong (i.e., after the if/else). If autosized, RatedCapHeatatRatedCdts should be used as the capacity, if not autosized, RatedCapHeat should be used as the capacity.

[rraustad]

I actually want to revert this change and change the RatedWaterVolFlowRateDes sizing equation to use RatedCapHeat because that's what the sizing routine is setting as the final coil capacity. And the calc routine uses RatedCapHeat as the coil capacity. So RatedCapHeat should be the final coil size whether the coil is autosized or hard-sized.

HeatCapAtPeak = rhoair * VolFlowRate * Psychrometrics::PsyCpAirFnW(DataPrecisionGlobals::constant_zero) *
                (HeatSupTemp - HeatMixTemp); // heating coil load

RatedCapHeatDes = (PeakHeatCapTempModFac > 0.0) ? HeatCapAtPeak / PeakHeatCapTempModFac : HeatCapAtPeak;

// heating capacity final determination
simpleWatertoAirHP.RatedCapHeat = RatedCapHeatDes;
simpleWatertoAirHP.RatedCapHeatAtRatedCdts = RatedCapHeatDes * RatedHeatCapTempModFac;

void CalcHPHeatingSimple(EnergyPlusData &state,
    HeatCapRated = simpleWatertoAirHP.RatedCapHeat;

So it follows that the water flow rate should use RatedHeatCap because that's the coil size. You can't see an issue in model performance when the water flow rate is sized with either of these variables because only exit water temp changes, not performance. You would have to really critique the exiting water temp to see an issue and even then it would be hard to see.

if (simpleWatertoAirHP.WAHPType == WatertoAirHP::Heating) {
    RatedWaterVolFlowRateDes = 
        simpleWatertoAirHP.RatedCapHeatAtRatedCdts / (state.dataSize->PlantSizData(PltSizNum).DeltaT * Cp * rho);

And then I look at this line and it looks like RatedCapHeatAtRatedCdts is the correct variable to use to size the water flow rate. So I will leave this branch in this state for now even though I think it's wrong.

RatedHeatCapTempModFac =
    Curve::CurveValue(state, simpleWatertoAirHP.HeatCapCurveIndex, RatedHeatratioTDB, RatedHeatratioTS, 1.0, 1.0);

[rraustad]

RatedCapHeatDes is the CapFT modified coil capacity, as is RatedCapHeat. The next line modifies this value by the rated CapFT, which should be 1 by definition (but I expect it's not 1). So now I'm back to using RatedCapHeat to size the water flow rate. This is so very confusing but I think I am more comfortable with this now. @mjwitte ?

simpleWatertoAirHP.RatedCapHeatAtRatedCdts = RatedCapHeatDes * RatedHeatCapTempModFac;

[rraustad]

@mjwitte I think it's time to review changes in unmet hours. This is for 9849-OffSml-MultiHVACSys DOAS_EP9_4 to24.2.

[rraustad]

These should also include the sizing ratio when basing condenser water flow sizing on cooling capacity.

AirLoopHVAC:UnitarySystem,
  N1 , \field DX Heating Coil Sizing Ratio

[github-actions]

⚠️ Regressions detected on macos-14 for commit f047836

Regression Summary

• EIO: 14
• MTR Small Diffs: 6
• Table Big Diffs: 5
• ESO Small Diffs: 14
• Table Small Diffs: 9
• Table String Diffs: 2

• View Results
• Download Regressions

[nrel-bot]

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