[Equest-users] using IPLV in eQuest

Nick Caton ncaton at smithboucher.com
Fri Feb 25 11:54:38 PST 2011


Rohini,

 

Good question... the capacity for non-eQuest programs to handle an IPLV
inputs may be better addressed separately to the [bldg-sim] list.

 

I'm not sure whether HAP or Trace can explicitly use IPLV figures to
help determine part load curves, but John makes a fair point:   Math
fundamentals are getting in the way... you can't solve for a curve
(quadratic - 3 unknowns or cubic - 4 unknowns) with only one weighted
efficiency.  No program should be able to determine part load behavior
knowing only the IPLV figure - at best a program might assume a part
load curve shape and "re-factor" it to match the IPLV - you'd probably
be better off assuming the IPLV weightings are appropriate to your
project and just apply a straight factor (IPLV1/IPLV2) to the chiller
energy consumed.

 

The ability to generate a curve by inputting the IPLV values (at
25/50/75/100) could be a UI-improvement/timesaver for any modeling
program (hint-hint, developers!), but note this is really already built
into eQuest in the form of the raw-data entry method of defining a
curve... My suggestion to work out the normalized data and/or
coefficients separately in excel is simply a way to
document/check/visualize your work to avoid any major hiccups. 

 

~Nick

 

 

 

NICK CATON, E.I.T.

PROJECT ENGINEER

Smith & Boucher Engineers

25501 west valley parkway

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 R B
Sent: Friday, February 25, 2011 12:32 PM
To: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] using IPLV in eQuest

 

Thanks all. As I thought all along, seems like there is no easy way out.

Any ideas on how HAP/TRACE treat chiller simulation? Do they use IPLV's
or do they have many more options for performance curves or is it same
as eQuest?

On Fri, Feb 25, 2011 at 12:21 PM, Nick Caton <ncaton at smithboucher.com>
wrote:

James et al,

 

Rohini will need to create performance curves to make this particular
comparison.  Otherwise using the default curves will result in identical
part load performances.

 

The following is excerpted from the following (short) recommended
reading concerning what IPLV means:  
http://ashrae-cfl.org/2010/03/understanding-iplvnplv/

IPLV (or NPLV) = 0.01A+0.42B+0.45C+0.12D

Where:

A = COP or EER @ 100% Load

B = COP or EER @ 75% Load

C = COP or EER @ 50% Load

D = COP or EER @ 25% Load

John is saying knowing only the IPLV and the 100% load condition
efficiency (variable 'A,' above) is not enough information to
extrapolate the IPLV curves to compare the two chillers.  

 

For the exercise of comparing the two non-centrifugal chillers of the
same technology/type, I would just focus on making a custom EIR-FPLR
(not EIR-fPLR&dT) for each chiller, and use the library CAP-FT AND
EIR-FT curves.  My understanding is the effects of temperature on
capacity and EIR outside of centrifugal VSD chillers is negligible.
NOTE:  Whenever using any of the default library chiller performance
curves, that means you MUST normalize to and specify the chiller at ARI
conditions - those curves aren't normalized to anything else.

 

So!  If you can find the IPLV A, B, C and D values for both chillers'
curves, you could come up with your EIR-FPLR curve coefficients (curve
type = quadratic or cubic) using a curve-fit in excel... or
alternatively make eQuest figure the coefficients by entering those
points as raw data.

 

You may more easily just make your own curves, following John's advice
and getting part load unloading curves (100%, 90%, 80%... etc) held at a
constant chilled & condenser temperature to match the ARI* conditions
(85CWT if this is water cooled) at which you're specifying the chiller
capacity/EIR.  Again, you could either go into excel, normalize the data
(review DOE2 help entry for EIR-FPLR), make a scatter chart, and get the
coefficients using a curve fit... or enter the data as raw points into
eQuest and the coefficients will be figured by eQuest... whatever makes
more sense to you.

 

For others and personal future reference.... If you are looking to make
an EIR-fPLR&dT curve (for centrifugal chillers or otherwise):  Ask your
rep instead for multiple (minimum 3) part load unloading runs, holding
the delivered chilled water temp constant, and vary the condenser water
temperature incrementally for each run (i.e. 85, 75, 65).  Choose a
range of CWT's that cover the anticipated range to be encountered in the
actual design. This will get you enough data to have the minimum 3
delta-T's represented in your part load data points to build this curve
correctly.  You'll be using eQuest "raw-data" entry method to make it
generate the coefficients.

 

~Nick

 

* Rather than ARI conditions (85F CWT), you could be normalizing to
Design condition EIR/CAP, provided you're making a full set of custom
curves in the same fashion.

 



 

NICK CATON, E.I.T.

PROJECT ENGINEER

Smith & Boucher Engineers

25501 west valley parkway

olathe ks 66061

direct 913 344.0036

fax 913 345.0617

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

 

From: equest-users-bounces at lists.onebuilding.org [mailto:
equest-users-bounces at lists.onebuilding.org] On Behalf Of James Waechter
Sent: Friday, February 25, 2011 10:55 AM
To: equest-users at lists.onebuilding.org 


Subject: Re: [Equest-users] using IPLV in eQuest

 

John,

 

If the only parameter Rohini enters into the program is the full-load
EIR - which he said is the same for both chillers - how will eQuest know
to bend the curves differently for the two chiller options.  It is my
understanding that program would use the same chiller efficiency curves
for both machines even though their IPLVs are different.

 

In order to overcome this issue, are you saying Rohini should get
chiller performance data from each of the manufacturers and enter his
own custom curves?  I recall there was a discussion on that topic a few
months back.

 

Regards,

James Waechter Jr., P.E., CEM, LEED A.P.
Energy Engineer - Rocky Mountain Region
p 303 215 4062 | m 727 686 3248

McKinstry
Consulting | Construction | Energy | Facility Services

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

 

 

 

From: equest-users-bounces at lists.onebuilding.org [mailto:
equest-users-bounces at lists.onebuilding.org] On Behalf Of John Aulbach
Sent: Friday, February 25, 2011 9:41 AM
To: R B; eQUEST Users List
Subject: Re: [Equest-users] using IPLV in eQuest

 

Rohini:

 

Won't happen. IPLV is a number which has one equation and 4 unknowns.
Actually, three unknowns as you know the 100% point. You need a
manufacturer's curve run at 85F constant condenser water temperature.
Let eQuest do the curve bending after that. ARI curve won't work right.

 

 

John R. Aulbach, PE, CEM

Senior Energy Engineer

________________________________

Partner Energy

1990 E. Grand Avenue, El Segundo, CA 90245
W: 888-826-1216, X254| D: 310-765-7295 | F: 310-817-2745

www.ptrenergy.com <http://www.ptrenergy.com/>  | jaulbach at ptrenergy.com
<mailto:%7C%20jaulbach at ptrenergy.com> 

 

________________________________

From: R B <slv3sat at gmail.com>
To: eQUEST Users List <equest-users at lists.onebuilding.org>
Sent: Fri, February 25, 2011 7:25:18 AM
Subject: [Equest-users] using IPLV in eQuest

Hi All, 

I would like to compare two screw chillers with same full load kW/ton
and different IPLV kW/ton. I am using the full load number for the EIR.
Where can the IPLV number be used? Is there some way to scale the
performance curves to reflect different IPLV's?

-Rohini

 


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