[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[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
------------------------------------
The primary EnergyPlus web site is found at:
http://www.energyplus.gov
The group web site is:
http://groups.yahoo.com/group/EnergyPlus_Support/
Attachments are not allowed -- please post any files to the appropriate folder in the Files area of the Support Web Site.
EnergyPlus Documentation is searchable. Open EPlusMainMenu.pdf under the Documentation link and press the "search" button.
Yahoo! Groups Links
<*> To visit your group on the web, go to:
http://groups.yahoo.com/group/EnergyPlus_Support/
<*> Your email settings:
Individual Email | Traditional
<*> To change settings online go to:
http://groups.yahoo.com/group/EnergyPlus_Support/join
(Yahoo! ID required)
<*> To change settings via email:
mailto:EnergyPlus_Support-digest@xxxxxxxxxxxxxxx
mailto:EnergyPlus_Support-fullfeatured@xxxxxxxxxxxxxxx
<*> To unsubscribe from this group, send an email to:
EnergyPlus_Support-unsubscribe@xxxxxxxxxxxxxxx
<*> Your use of Yahoo! Groups is subject to:
http://docs.yahoo.com/info/terms/