Re: [EnergyPlus_Support] Quadratic & Bi Quadratic

["ashok" <ashok@xxxxxxxxxxx>]

Thanks Richard info, is it possible get a coefficient by using excel or polynomial curves,

 

 

Regards

Ashok

 

----- Original Message -----

From: Richard Raustad

To: EnergyPlus_Support@xxxxxxxxxxxxxxx

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

UCF - From Promise to Prominence: Celebrating 40 Years

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