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

Aulbach, John jaulbach at nexant.com
Wed Dec 19 17:02:16 PST 2007


So I cannot "reverse engineer" a part load curve that uses condenser water relief in calculating the points, knowing what condenser temps are used at what part load point (100%, 75%, 50%, etc) ???

________________________________

From: Steven Gates [mailto:steve.gates at doe2.com] 
Sent: Wednesday, December 19, 2007 4:57 PM
To: Aulbach, John; bldg-sim at lists.onebuilding.org
Subject: RE: [Bldg-sim] Chiller part load raw data points into eQuest



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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