[Equest-users] How to set the COP of a chiller as constant in eQuest?

Nick Caton ncaton at smithboucher.com
Wed Apr 17 12:40:31 PDT 2013


After identifying the curves in play per Joe's suggestion, you could achieve a constant COP, independent of part load or other variables, by making a set of custom curves (of appropriate/acceptable type) using coefficient inputs.

Example from the library:

CentH2O-EIR-fPLR&dT looks like this from the library before modification.  This curve works alongside others to determine how to modify the input EIR for a chiller:
[cid:image001.png at 01CE3B79.01D745D0]

What we want is for this and all the other curves to return a value of 1.0, whatever the hourly variables throw at it.  Simply enter all coefficients preceding a variable (b,c,d,e,f) to 0.  Set the coefficient for the curve's constant (a) at 1.0:

[cid:image003.png at 01CE3B79.8275C180]

Doing the same for all associated curves (again, read up in the help/documentation for your particular equipment to be sure), at all hours the chiller in question will operate at the specified EIR without variance.

~Nick

[cid:489575314 at 22072009-0ABB]

NICK CATON, P.E.
SENIOR ENGINEER

Smith & Boucher Engineers
25501 west valley parkway, suite 200
olathe, ks 66061
direct 913.344.0036
fax 913.345.0617
www.smithboucher.com

From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Joe Huang
Sent: Wednesday, April 17, 2013 2:18 PM
To: Esmireta
Cc: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] How to set the COP of a chiller as constant in eQuest?

Do you not have a copy of a DOE-2.2 or DOE-2.1E manual?  That would make it hard to understand how DOE-2 works.
DOE-2 has many performance curves, depending on the type of equipment. The EIR-FT curves are either bi-linear or bi-quadratic functions of the entering wetbulb and outdoor drybulb temperature.  The EIR-FPLR curves can be linear, quadratic, or cubic functions of the Part Load Ratio (PLR).

By the way,what I said yesterday was in reference to packaged SYSTEMS.  If your model contains a PLANT model with a Chiller, then
the keywords for the chiller performance curves change somewhat.

Joe


Joe Huang

White Box Technologies, Inc.

346 Rheem Blvd., Suite 108D

Moraga CA 94556

yjhuang at whiteboxtechnologies.com<mailto:yjhuang at whiteboxtechnologies.com>

www.whiteboxtechnologies.com<http://www.whiteboxtechnologies.com>

(o) (925)388-0265

(c) (510)928-2683

"building energy simulations at your fingertips"

On 4/16/2013 11:09 PM, Esmireta wrote:
Hi Joe,
In the simulation of a district cooling system, the guidance requires a virtual plant with a constant average efficiency.
In the DOE curves, how can I know the meaning of the equation and the coefficients in it? It seems there is no useful information in the DOE help.
Thanks!
Esmi





At 2013-04-17 10:35:35,"Joe Huang" <yjhuang at whiteboxtechnologies.com><mailto:yjhuang at whiteboxtechnologies.com> wrote:

DOE-2 modifies the COOL-EIR using several curves COOL-EIR-FT as a function of outdoor conditions and COOL-EIR-FPLR as a function of the Part Load Ratio. I suppose you could set those to be constant. Another way would be to just take the Cooling Load from the SS-D report and divide that by your constant COP.  But my question would be, why do you want to do that ?

Joe


Joe Huang

White Box Technologies, Inc.

346 Rheem Blvd., Suite 108D

Moraga CA 94556

yjhuang at whiteboxtechnologies.com<mailto:yjhuang at whiteboxtechnologies.com>

www.whiteboxtechnologies.com<http://www.whiteboxtechnologies.com>

(o) (925)388-0265

(c) (510)928-2683

"building energy simulations at your fingertips"

On 4/16/2013 6:55 PM, Esmireta wrote:
Dear all,
I wonder how to set the COP of a chiller as constant? after I set the chiller type, the electric input ratio type is determined, which means the self-made constant curve cannot be input.
Thanks!
Esmi






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