[Equest-users] Question: Modeling Specific Chillers

Busman, Michael R MBusman at chevron.com
Wed Aug 14 10:26:03 PDT 2013


My understanding of an economizer for a multi-stage centrifugal is that some of the liquid refrigerant flashes as it passes through the expansion device.  This flash gas, I believe is introduced to the input side of the second stage impeller.  Since the economizer is internal to the chiller, one set of curves should be sufficient as there is only one mode of operation as I understand it.  You didn't specify, so I'm assuming you are not referring to a water-side economizer.

I haven't custom defined a chiller yet in eQUEST, however, it appears that several performance data points from the manufacturer are required for eQUEST to generate the curves if you select this method.  The other is to generate your own curves.  Many years ago when I used to work in VisualDOE, I found the calculation methodology to define chiller curves from the Pacific Gas & Electric web site, which I used to set up a spreadsheet to calculate the curve coefficients.  This was originally set up for constant speed chillers.  A number of months ago I added a spreadsheet tab to handle variable speed chillers.  To create the 3 sets of curve coefficients, at least 10 full load data points at different chilled and condenser water temperatures were required from the manufacturer in order to map the compressor.  There was no max or min limit for the part-load data points as I recall.

If you'd like a copy of the spreadsheet, I can email it to you, however, you might want to check the eQUEST manual or DOE-2.2 reference manuals regarding directly entering data points into eQUEST and let the program figure out the curves for you.

My best,

Mike Busman

Michael R. Busman, CEM
Lead Project Engineer II

Chevron Energy Solutions
A Division of Chevron U.S.A., Inc.
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mbusman at chevron.com<mailto:mbusman at chevron.com>

From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of David Eldridge
Sent: Wednesday, August 14, 2013 9:46 AM
To: Sunil Nair
Cc: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Question: Modeling Specific Chillers

When the chiller runs on economizer it will use a separate set of curves and be modeled as a distinct chiller.

One set of curves will be difficult to model both modes of operation.

DSE Mobile

On Aug 14, 2013, at 11:34 AM, "Sunil Nair" <energymodel.sunil at gmail.com<mailto:energymodel.sunil at gmail.com>> wrote:
Hi All,

I have a couple of questions with respect to modeling specific chillers.

1) I am trying to model a centrifugal chiller with an economizer. The chiller in question is a centrifugal chiller running on R123 with an economizer installed to it. Do I just need to get data from the chiller manufacturer and input the curves into the model? Is this the right way to go?

2) How do you model multi stage centrifugal chillers without VFD's?


Sunil Nair

Ab Initio

TMA House, Plot No. 6, 2nd Floor,

Main Road, Wagle Industrial Area,

Thane (West) - 400 604

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