Re: [EnergyPlus_Support] Quadratic & Bi Quadratic

Ashok,

If you decide to use the coefficients as displayed on the chart then
make sure you include enough significant figures for each coefficient;
especially the coefficients of the higher powered variables. You can
format the displayed numbers in the chart by right-clicking on the chart
equation box.

Michael L. Kingsley, PhD, PE, LEED AP
Senior Engineer/ Project Manager
SAIC

-----Original Message-----
From: EnergyPlus_Support@yahoogroups.com
[mailto:EnergyPlus_Support@yahoogroups.com] On Behalf Of Richard Raustad
Sent: Wednesday, January 21, 2009 7:50 AM
To: EnergyPlus_Support@yahoogroups.com
Subject: Re: [EnergyPlus_Support] Quadratic & Bi Quadratic

I use excel and the method described below. If by "polynomial curves"
you mean adding a trend line to a plot and using the "Display equation
on chart" option, then yes, that will work also (but only for Linear,
Quadratic, or Cubic curves)..

ashok wrote:
>
> Thanks Richard info, is it possible get a coefficient by using excel
> or polynomial curves,
>
>
> Regards
> Ashok
>
>
> ----- Original Message -----
> *From:* Richard Raustad <mailto:RRaustad@FSEC.UCF.EDU
<mailto:RRaustad%40FSEC.UCF.EDU> >
> *To:* EnergyPlus_Support@yahoogroups.com
<mailto:EnergyPlus_Support%40yahoogroups.com>
> <mailto:EnergyPlus_Support@yahoogroups.com
<mailto:EnergyPlus_Support%40yahoogroups.com> >
> *Sent:* Thursday, January 15, 2009 12:16 AM
> *Subject:* Re: [EnergyPlus_Support] Quadratic & Bi Quadratic
>
> It's pretty easy to create the coefficients for curve objects. You
> just
> have to set up a spreadsheet to look like the equation. I did not
> open
> the manufacturers data, but can give you an idea of how to go about
> this. The chiller EIR curve is the easiest to explain in an email.
>
> Set up spreadsheet data in columns according to the equation. For
> example a quadratic curve for energy input ratio (EIR) as a
> function of
> part-load ratio (PLR) would look like this:
>
> ChillerEIRfPLR = a0 + a1(PLR) + a2(PLR)(PLR)
>
> Here is an example set of data:
> Full load power at the rating point = 10 kW (PLR = 1)
>
> The following data is for the same entering condenser temp and
> exiting
> evaporator temp as the rating point
>
> Power at PLR of 0.7 = 6.5 kW
> Power at PLR of 0.5 = 4.0 kW
> Power at PLR of 0.3 = 2.5 kW
>
> Normalized power (EIR) at a PLR of 1.0 = 1.00 (10 kW / full load
> power
> of 10 kW)
> Normalized power (EIR) at a PLR of 0.7 = 0.65 (6.5 kW / full load
> power
> of 10 kW)
> Normalized power (EIR) at a PLR of 0.5 = 0.40 (4.0 kW / full load
> power
> of 10 kW)
> Normalized power (EIR) at a PLR of 0.3 = 0.25 (2.5 kW / full load
> power
> of 10 kW)
>
> Then set up the columns in a spreadsheet to look like your equation:
> EIRfPLR PLR PLR*PLR
>
> I used periods below instead of spaces so the data would line up
> better
> in the yahoo email
>
> Column
> ..A........ B.......C
> 1.00....1.00....1.00
> 0.65....0.70....0.49
> 0.40....0.50....0.25
> 0.25....0.30....0.09
>
> Then use the tools menu and select "data analysis". Choose regression
> from the list of choices (if you do not see data analysis you will
> have
> to install it from the original CD)
>
> Select column A as the Y range and both columns B and C for the X
> range.
> DO NOT check the box "crosses at zero". Select the output range in
> your
> spreadsheet (a blank area) and click OK.
>
> You will then get the coefficients a0, a1, and a2.
>
> mahesh_bara wrote:
> >
> > Dear All
> >
> > I have atached folder called quadratic & Biquadratic.
> >
> > I dont know how to create quadratic and biquadratic coefficent
> from the
> > chiller data sets given
> >
> > Would be great help if you can send us the details
> >
> > Regards
> > Mahesh
> >
> >
>
> --
> 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>
> <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 <http://www.fsec.ucf.edu>

UCF - From Promise to Prominence: Celebrating 40 Years