[BLDG-SIM] Major disagreement on Chiller Performance Curves in DOE-2.1E and DOE-2.2

Michael Wilson mwilsonbc at yahoo.com
Fri Oct 17 14:58:25 PDT 2003


Apparently this didn't get through before, so I'm
resending it with the spreadsheet zipped, and the
original message below:


I believe that you need to request the various input
and capacity data holding two of the three parameters
(CHWT, CDWT, %load) constant, and varying the third.
Which is a lot of points for the manufacturer, but
they can do it. For recips this info is often
available in the catalog. However, once you've got the
data, its fairly difficult to turn it into DOE2
curves, as the curves need to be interpolated between
each other. ie. you'll get a capacity vs CDWT curve
for CHWT of 42,44,46,48, etc, but they're not exactly
the same. The easy way out is just to use the 44° one,
but its not as accurate. You don't have to do this
with PLR though.

I've attached a spreadsheet that does some
interpolation and calculation of curve co-efficients
if anyone wants to try it. It might need to be
adjusted for the data available though.






--- Jason Glazer <jglazer at gard.com> wrote:
> Michael,
> 
> Your message did not go out to the BLDG-SIM mailing
> list
> because it was a little too large. I think the
> BLDG-SIM
> members would like to look at your spreadsheet. If
> you
> want, you can resend the message but compress the
> attachment using WinZIP or PKZip or another program.
> 
> Thanks
> 
> Jason
> 
> On 16 Oct 2003 at 13:50, Michael Wilson wrote:
> 
> > I believe that you need to request the various
> input
> > and capacity data holding two of the three
> parameters
> > (CHWT, CDWT, %load) constant, and varying the
> third.
> > Which is a lot of points for the manufacturer, but
> > they can do it. For recips this info is often
> > available in the catalog. However, once you've got
> the
> > data, its fairly difficult to turn it into DOE2
> > curves, as the curves need to be interpolated
> between
> > each other. ie. you'll get a capacity vs CDWT
> curve
> > for CHWT of 42,44,46,48, etc, but they're not
> exactly
> > the same. The easy way out is just to use the 44°
> one,
> > but its not as accurate. You don't have to do this
> > with PLR though.
> >
> > I've attached a spreadsheet that does some
> > interpolation and calculation of curve
> co-efficients
> > if anyone wants to try it. It might need to be
> > adjusted for the data available though.
> >
> >
> > --- Mike Tillou <miket at etcgrp.com> wrote:
> > > John, I think the answer to your question has
> two
> > > parts:
> > >
> > > 1. DOE uses two curves for modifying the full
> load
> > > EIR (1/COP) of a constant
> > > speed chiller.  The first adjusts for part load
> and
> > > the second for
> > > temperature.
> > >
> > > I use a curve with fixed CHWT and CWT at various
> > > part load conditions (at
> > > design conditions not ARI rated conditions) for
> the
> > > EIR f(PLR) curve (the
> > > one you're asking about) and create a second
> curve
> > > based on various
> > > combinations of CHWT, CWT at full load for the
> EIR
> > > f(LCHWT, ECWT) curve.
> > > The assumption, I think, is that the PLR curve
> > > reamins relatively uniform as
> > > the water temperatures change so once you have
> the
> > > shape of the PLR curve
> > > you can account for temperature differences with
> a
> > > second curve.
> > >
> > >
> > > 2. The above methodology works fine for constant
> > > speed chillers but needs to
> > > be modified for variable speed chillers.  Rather
> > > than using EIR F(PLR) you
> > > need to use EIR f(PLR,dT).  This curve now
> accounts
> > > for the change in the
> > > difference of the water temperature across the
> > > chiller.  See Volume 6 of the
> > > DOE 2.2 v41 reference manual available at
> > > www.DOE2.com, there is a section
> > > on chiller performance that explains this much
> > > better than I could do.  DOE
> > > 2.2 v41 incorporates this change and has default
> > > curves for both.
> > >
> > > It sounds like you both may be correct depending
> on
> > > the type of chiller you
> > > want to model.
> > >
> > > Mike Tillou, PE
> > > etc Group, Inc
> > > 413-664-9070
> > >
> > >
> > > -----Original Message-----
> > > From: postman at gard.com [mailto:postman at gard.com]
> On
> > > Behalf Of Aulbach, John
> > > Sent: Wednesday, October 15, 2003 2:23 PM
> > > To: BLDG-SIM at GARD.COM
> > > Subject: [BLDG-SIM] Major disagreement on
> Chiller
> > > Performance Curves in
> > > DOE-2.1E and DOE-2.2
> > >
> > >
> > >
> > > I am having a "friendly" disagreement with a
> > > colleague on what chiller
> > > curves to ask for from a manufacturer to input
> into
> > > DOE-2 (could be either
> > > 2.1E or 2.2). We both agree that the infamous
> ARI
> > > point for a 100% load
> > > should be input. But the curves are where we
> > > disagree.
> > >
> > > Is the Default DOE-2 curve for % Power versus %
> Tons
> > > the ARI curve with the
> > > allowable reduction in condenser water
> temperature,
> > > or is it based on the
> > > FIXED 85°F entering condenser water and FIXED
> 44°F
> > > leaving chilled water ALL
> > > the way down the curve?
> > >
> > > Therefore, when I am given a chiller with a
> variable
> > > speed drive installed,
> > > what parameters should I ask for in such a
> > > Power/Tons to be FIXED ???
> > >
> > >
> > >
> > >
> > >
> > > John R. Aulbach, PE, CEM
> > > Project Engineer
> > > Sempra Energy Solutions
> > > 555 West Fifth Street
> > > Mail Location 27F3
> > > Los Angeles, CA 90013
> > > Tel: (213) 244-8551 Cell (213) 219-4875
> > >
> > >
> > > "Sempra Energy Solutions is not the same company
> as
> > > SDG&E/ SoCalGas, the
> > > Utilities.  Sempra Energy Solutions is not
> regulated
> > > by the California
> > > Public Utilities Commission, and you do not have
> to
> > > buy Sempra Energy
> > > Solutions products or services to continue to
> > > receive quality regulated
> > > service from the Utilities."
> > >
> > >
> > >
> > > ==================
> > >
> > > You received this e-mail because you are
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> > >
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> > > unsubscribe
> > >
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> > >
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> > >
> > >
> > >
> > >
> >
>
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> >
> > =====
> > Michael Wilson
> > 455 Elphinstone Ave.
> > Gibsons, BC, V0N 1V1
> > 604-886-9864 phone
> > 604-676-2604 fax
> >
> > __________________________________
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> 
>
=========================================================
> Jason Glazer, P.E.  jglazer AT gard DOT com  847 698
> 5686
> GARD Analytics - http://www.gard.com/
> 1028 Busse Highway, Park Ridge, IL 60068
> Building Energy Simulation and Analysis
> Admin of BLDG-SIM list for building simulation users
> 


=====
Michael Wilson
455 Elphinstone Ave.
Gibsons, BC, V0N 1V1
604-886-9864 phone
604-676-2604 fax

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