[Bldg-sim] Chiller part load raw data points into eQuest

Steven Gates steve.gates at doe2.com
Wed Dec 19 16:56:53 PST 2007


Unfortunately the IPLV is of little or no value when setting up chiller
curves. To set up the EIR-fT and EIR-fPLR curves requires more data points
than is available in the IPLV. IPLV basically describes a two-dimensional
curve, whereas the actual chiller performance is 3-dimensional.  The IPLV
assumes that condenser temperature drops as chiller load drops, but this is
not necessarily the case. Examples:

1.	A cooling tower has a fixed setpoint of 85°F.  Or, the condenser
water source is a lake or river.  In this case condenser temperature does
not drop as chiller load drops.
2.	A large plant has 3 chillers utilizing a single cooling tower.  The
current load is 33% of design, so one chiller is running at full load. IPLV
assumes an entering condenser temperature of 85°F (full load), whereas the
cooling tower is actually lightly loaded and can achieve a smaller approach
to wetbulb.
3.	The building is on the West coast (low wetbulb) vs. Florida (high
wetbulb). Tower performance and condenser temperature vs. load is entirely
different in these two climates.

So while IPLV may be an interesting figure for rough comparisons, it is
insufficient for an hourly simulation program. This is true for all energy
simulation programs, not just eQUEST. Ultimately this issue will need to be
addressed by standards organizations such as ARI, and/or equipment
manufacturers.

Steve Gates
eQUEST development team

  _____  

From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Aulbach, John
Sent: Wednesday, December 19, 2007 4:04 PM
To: bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] Chiller part load raw data points into eQuest

 

Hi Gang:

 

I have a part load curve from a chiller manufacturer for input into eQuest.
Unfortunately, it has condenser temperature relief (this is an evaporatively
cooled chiller, so we are speaking of dry bulb outdoor temperatures.

 

Normally, I ask for a part load curve with a constant condenser temperature,
and let eQuest modify this curve based on changing outdoor air conditions.

 

But now I have the IPLV data and it deals with condenser relief. I DO have
at what part load a particular condenser temperature occurs (complimenting
this IPLV data.

 

Can anyone help me?

 

John R. Aulbach, PE, CEM

Project Manager

Nexant, Inc.

100 North Barranca, Suite 820

West Covina, CA 91791 USA

Phone: 626-430-9054

Fax: 626-430-9060

email: jaulbach at nexant.com

 

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