Consolidate speed-dependent coil load ratio input parameters into a single parameter. #10369

tanaya-mankad · 2024-01-16T14:37:28Z

This PR is an attempt to homogenize the ideas of cycling-ratio and speed-ratio into a single speed-dependent parameter.
Incidental changes include updating the const-correctness of both declaration and implementation of simulate() and its dependencies, to prevent accidental changes to const values inside the function.

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rraustad · 2024-01-16T15:26:59Z

src/EnergyPlus/Coils/CoilCoolingDX.cc

@@ -788,7 +786,7 @@ void CoilCoolingDX::simulate(EnergyPlusData &state,
    this->wasteHeatEnergyRate = this->performance.wasteHeatRate;
    this->wasteHeatEnergy = this->performance.wasteHeatRate * reportingConstant;

-    this->partLoadRatioReport = PLR;
+    this->partLoadRatioReport = speedNum == 1 ? 1.0 : speedRatio;


What this says is at speed = 1 the coil/compressor does not cycle (i.e., PLR = 1) and at higher speeds PLR is equal to the upper stage cycling ratio. Both of these are incorrect. Background: PLR started as a single-speed compressor cycling variable. Then variable speed coils were added and CyclingRatio and SpeedRatio were introduced. For the variable speed coils the CyclingRatio shows how the compressor cycles at speed = 1, which is the same as what the PLR variable shows for this and other coil types. So PLR and CyclingRatio are synonymous for the VS coil. At speeds > 1, the PLR and CyclingRatio = 1. At the higher speeds the highest compressor stage that is operating can cycle. This operation is shown in SpeedRatio. The CyclingRatio and SpeedRatio variables where added to the new cooling coil model to represent VS coils. Ex, at speed = 2, PLR and CyclingRatio = 1 and SpeedRatio = what the upper stage cycling ratio is. What I have thought about doing in the past is to delete the CyclingRatio variable and replace it with PLR, and leave SpeedRatio alone to represent what it does now. Another way to look at this is PLR represents how long the compressor operates during the time step. SpeedRatio represents the fraction of the time step the upper stage compressor is operating with lower speed compressor(s) operating the entire time step. There is some nuance to consider with the staged Tstat (on/off at specific speed) and Capacity Control Method = discrete/continuous for the new coil model.

@rraustad thank you so much for the comment. I was trying to back this information out of the code, as my notes from our last conversation were spotty. I'll have another go-around.

…ge-coil-load-ratios

…CoolingSystem.

…ge-coil-load-ratios

nrel-bot · 2024-04-12T00:11:14Z