[Equest-users] using IPLV in eQuest

[Nick Caton]

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 

 

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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