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



Thanks!  Looks simple; I'll try it.

--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Richard Raustad <RRaustad@...> wrote:
>
> Got a little confused with my terminology. This should have read:
> 
> You actually multiple out the ^2 terms and cross-product in the
> spreadsheet. Then perform a regression analysis on this data. Select
> Output as the regression input Y range (e.g., A2..A20) and "ALL independent
> variables" as the regression input X range (e.g. B2..F20). You will get the
> coefficients for B through F, there will be 1 additional coefficient if
> Output does not cross the X axis at 0 (always the first coefficient)
> 
> . The t Stat in the regression statistics will be greater than 2 if that
> independent term is significant (i.e.., helps describe changes to the
> dependent variable [Output in this example]).
> 
> In Excel this is found on the Tools menu under Data Analysis.  Then 
> choose Regression. If Data Analysis does not show on the Tools menu, it 
> must be installed from the original CD.
> 
> Richard Raustad wrote:
> >
> >
> > It's pretty easy in a spreadsheet.
> >
> > For example Output = X + X^2 + Y + Y^2 + XY
> >
> > Set up columns in a spreadsheet to represent the independent variables
> > Column A B C D E F
> > Output X X^2 Y Y^2 XY
> >
> > were column:
> > A = Output
> > B = X (for example leaving evaporator temp)
> > C = X^2
> > D = Y (for example entering condenser temp)
> > E = Y^2
> > F = XY
> >
> > You actually multiple out the ^2 terms and cross-product in the
> > spreadsheet. Then perform a regression analysis on this data. Select
> > Output as the regression Y data (e.g., A2..A20) and "ALL independent
> > variables" as the X variable (e.g. B2..F20). You will get the
> > coefficients for B through F, there will be 1 additional coefficient if
> > Y does not cross the X axis at 0 (always the first coefficient). The t
> > Stat in the regression statistics will be greater than 2 if that
> > independent term is significant (i.e.., helps describe changes to the
> > dependent variable [Output or Y in this example]).
> >
> > Example:
> >
> > 1.2 2 4 6 36 12
> > 1.6 3 9 5 25 15
> >
> > JV Dirkes II wrote:
> > >
> > >
> > >
> > > Dear Damian,
> > >
> > > 2-4 times the peak capacity COP sounds like a stretch for believability.
> > > On the other hand, improved part load COP is exactly the goal to be
> > > striven for, since the vast majority of operation hours are at part
> > > load. I suspect that the "typical" COP vs PLR values in the example
> > > file do not represent a specific chiller and may not represent most
> > > chillers. It's a good place to start, but if you can derive a curve for
> > > the actual chiller, that is preferred!
> > >
> > > I have not developed part load curves often enough to pretend that I am
> > > an expert, but most chiller manufacturers publish performance with
> > > varying entering water temps, delta T and condenser water temp / delta
> > > T. In theory, that allows you to create a performance curve which
> > > incorporates those variables, although it sounds challenging. I have
> > > not needed to do so yet, so I've put off the task. As I recall, the
> > > information set varies quite a bit among the major manufacturers, so
> > > standardization might be difficult.
> > >
> > > This, it seems, is an opportunity for the modeling community. I started
> > > the process a while back by setting up a standard representation of
> > > performance with those variables, but haven't figured out how to do the
> > > curve-fit for multiple variables. If you figure it out or someone else
> > > has already figured it out, please share the information!
> > >
> > > Actually, it would be VERY nice if the manufacturers would publish these
> > > curves...
> > >
> > > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx 
> > <mailto:EnergyPlus_Support%40yahoogroups.com>
> > > <mailto:EnergyPlus_Support%40yahoogroups.com>, "d_h51@" <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-5A1\
> > <http://f1.grp.yahoofs.com/v1/cA3eSXpIH0plWrUAXrH171qOeNo_sglXxA6WFL-5A1>> 
> > \
> > > 
> > <http://f1.grp.yahoofs.com/v1/cA3eSXpIH0plWrUAXrH171qOeNo_sglXxA6WFL-5A1 
> > <http://f1.grp.yahoofs.com/v1/cA3eSXpIH0plWrUAXrH171qOeNo_sglXxA6WFL-5A1>>>
> > > 
> > c9cj_Ewy5DotS8QUGcGAVrG8-yS_ZOkZM7K4eZBiXgSaqQ_1FPQsMlalsOvFE/_Problem_S\
> > > \
> > > > ubmittals/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?
> > > >
> > > > 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 ECWT=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
> > > >
> > >
> > >
> >
> > -- 
> > Richard A. Raustad
> > Senior Research Engineer
> > Florida Solar Energy Center
> > University of Central Florida
> > 1679 Clearlake Road
> > Cocoa, FL 32922-5703
> > Phone: (321) 638-1454
> > Fax: (321) 638-1439 or 1010
> > Visit our web site at: http://www.fsec.ucf.edu <http://www.fsec.ucf.edu>
> >
> > UCF - From Promise to Prominence: Celebrating 40 Years
> >
> > 
> 
> -- 
> Richard A. Raustad
> Senior Research Engineer
> Florida Solar Energy Center
> University of Central Florida
> 1679 Clearlake Road
> Cocoa, FL  32922-5703
> Phone:   (321) 638-1454
> Fax:     (321) 638-1439 or 1010
> Visit our web site at: http://www.fsec.ucf.edu
> 
> UCF - From Promise to Prominence: Celebrating 40 Years
>




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