Re: [EnergyPlus_Support] power problem of the "Variable Speed Pump"

[Richard Raustad <RRaustad@xxxxxxxxxxxx>]

1) PumpEquip(PumpNum) just refers to each specific pump in the 
EnergyPlus code. If there is only one pump in the simulation it would be 
PumpEquip(1)

2) NomVolFlowRate is the rated volumetric flow rate input in the pump object

3) Use the least squares fit (regression) method to determine the pump 
coefficients. Most spreadsheet can do this. You will need to know the 
pump power versus part load ratio to calculate this. Its basically a 
pump power curve.

4) If PartLoadCoef(2) is equal to 1 and all others are 0, then the pump 
has a power curve proportional to part load ratio. This is a 
simplification for variable speed pumps. A better power curve for 
variable speed pumps would have a coefficient less than 1 for 
PartLoadCoef(2) and non-zero coefficients for PartLoadCoef(3) and/or 
PartLoadCoef(4). At a part load ratio equal to 1, FracFullLoadPower 
would equal 1. A constant speed pump will have a 1 for PartLoadCoef(1) 
and 0 for all other coefficients which is why the Pump:Constant Speed 
object does not request inputs for PartLoadCoef(1-4)..

oldgun_hbns wrote:
>
> dear Mike:
>
> some expressions about of the object "Variable Speed Pump" in
> engineeringReference.pdf:
>
> VolFlowRate = PumpMassFlowRate / LoopDensity
> PartLoadRatio = VolFlowRate / PumpEquip(PumpNum)%NomVolFlowRate
> FracFullLoadPower = PumpEquip(PumpNum)%PartLoadCoef(1)
> + PumpEquip(PumpNum)%PartLoadCoef(2) * PartLoadRatio
> + PumpEquip(PumpNum)%PartLoadCoef(3) * PartLoadRatio**2
> + PumpEquip(PumpNum)%PartLoadCoef(4) * PartLoadRatio**3
> Power = FracFullLoadPower * PumpEquip(PumpNum)%NomPowerUse
> ShaftPower = Power * PumpEquip(PumpNum)%MotorEffic
> ! This adds the pump heat based on User input for the pump
> ! We assume that all of the heat ends up in the fluid eventually
> since this is a closed loop
> ! PumpHeattoFluid = ShaftPower*(1-PumpEquip(PumpNum)%PumpEffic)
> PumpHeattoFluid = ShaftPower + (Power - ShaftPower)*PumpEquip
> (PumpNum)%FracMotorLossToFluid
> Node(OutletNode)%Temp = Node(InletNode)%Temp+PumpHeattoFluid/
> (PumpMassFlowRate * LoopCp)
> PumpEquip(PumpNum)%Power = Power
>
> what meaning of the variable: "PumpEquip(PumpNum)", "NomVolFlowRate"
> and "NomPowerUse"?
> how to calculate the coefficient of cubic equation?
> universality only the PartLoadCoef(2) equal to 1 and other equal to
> 0, imply the cubic equation is not usefulness.
> thanks.
> gun
>
>
>  

-- 
Richard A. Raustad
Senior Research Engineer
Florida Solar Energy Center
University of Central Florida
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