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[EnergyPlus_Support] Re: Unrealistic ChillerEIRFPLR curves for data in the file: Chillers.idf?



--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Fred Buhl <wfbuhl@...> wrote:
>
> See below.
> 
> d_h51@... wrote:
> >
> >
> > Hi all,
> >
> > When I plot the COP vs PLR dependence taken from the file 
> > 'Chillers.idf' for specific chillers (please see the file   COP vs PLR 
> > (EnergyPlus).jpg 
> > <http://f1.grp.yahoofs.com/v1/cA3eSXpIH0plWrUAXrH171qOeNo_sglXxA6WFL-5A1c9cj_Ewy5DotS8QUGcGAVrG8-yS_ZOkZM7K4eZBiXgSaqQ_1FPQsMlalsOvFE/_Problem_Submittals/COP%20vs%20PLR%20%28EnergyPlus%29.jpg> 
> > ) it shows that for some chillers at e.g. PLR=0.4 the COP is 4times 
> > higher than for PLR=1, and for PLR =0.5 most of the chillers have 
> > 2times higher COP than at PLR=1.
> >
> > For me it's unrealistic, especially when i compare these results to 
> > the catalogue data given from the producers (where the COP/COP_ref  
> > value reaches its maximum usually for PLR=0.5 and is about 1.6)
> >
> > Do I do a mistake somewhere? COP/COP_ref = 1/ChillerEIRFPLR, right?
> Actually this is wrong, due to a confusing feature of EIRFPLR: EIRFPLR 
> contains a PLR factor within it. The correct formula
> is  COP/COP_ref = PLR/ChillerEIRFPLR.
> 
> This also holds true for Doe-2, eQuest etc.
> 
> Here's the derivation:
> 
> COP = CoolOut/EnergyIn
> PLR = CoolOut/AvailCap
> EnergyIn = (AvailCap/COP_nom)*EIRFPLR*EIRFT  (this is from the EPlus 
> code. Note the use of AvailCap on
>    the right hand side of the equation, rather than what you'd expect: 
> CoolOut =AvailCap*PLR)
> So COP = (PLR*AvailCap) / ( (AvailCap/Cop_npm)*EIRFPLR*EIRFT)
> and COP/COP_nom = PLR/(EIRFPLT*EIRFT)
> 
> Fred Buhl
> >
> > Or maybe this problem is related to my next question:
> > COP vs PLR performance in catalogue data is mostly rated under ARI 
> > conditions, for instance for water2water chillers and PLR=1 ECW! 
> > T=29.4C and for PLR=0.5 ECWT=18.3C. Do the ChillerEIRPLR curves are 
> > rated for constant ECWT? If yes how can I modify PLR curves rated 
> > according to ARI standard into curves for constant ECWT?
> >
> > Thanks for any help in advance,
> > Damian
> >
> >
> >
> >
>
Hi guys,

Thanks a lot to all of you for helping me to solve my problem.

Especially thanks to you, Fred Buhl, for showing my mistake and a clear explanation.

Damian



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