I am trying to understand how cooling power is calculated in EnergyPlus for a DX:Multispeed system at low part load ratio.
The Engineering Reference shows the following formula for the first speed range:
CoolingPower = (TotCap1)(EIR1)(SpeedRatio)
TotCap1 = f(RatedCap1,TotCapTempModFac1,TotCapFlowModFac1,BypassFactor1)
BypassFactor1 = f(RatedBypassFactor,RatedFlowRate,ActualFlowRate)
EIR1 = RatedEIR1 * EIRTempModFac1 * EIRFlowModFac1
Where “1” designates speed range #1.
Elsewhere, I see a formula for speed ratio that appears for the first speed range to be:
SpeedRatio = (CoolingLoad – FanHeat)/(FullCoolOutput1)
I can extract most of these parameters or the basis for the parameters with Output:Variable, but I can’t seem to get at the Bypass Factor.
Is there a way to get the bypass factor at each time step? Can it be calculated from other variables?
Also, when the coil is in the first speed range, my Output:Variable data shows:
SpeedRatio = 0 and
CyclingRatio = CompressorPartLoadRatio.
So should the SpeedRatio be replaced by CyclingRatio in CoolingPower equation for the first speed range?
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