[BLDG-SIM] Major disagreement on Chiller Performance Curves in DOE-2.1E and DOE-2.2

[Mike Tillou]

John, I think the answer to your question has two parts:
 
1. DOE uses two curves for modifying the full load EIR (1/COP) of a constant
speed chiller.  The first adjusts for part load and the second for
temperature. 
 
I use a curve with fixed CHWT and CWT at various part load conditions (at
design conditions not ARI rated conditions) for the EIR f(PLR) curve (the
one you're asking about) and create a second curve based on various
combinations of CHWT, CWT at full load for the EIR f(LCHWT, ECWT) curve.
The assumption, I think, is that the PLR curve reamins relatively uniform as
the water temperatures change so once you have the shape of the PLR curve
you can account for temperature differences with a second curve.
 
 
2. The above methodology works fine for constant speed chillers but needs to
be modified for variable speed chillers.  Rather than using EIR F(PLR) you
need to use EIR f(PLR,dT).  This curve now accounts for the change in the
difference of the water temperature across the chiller.  See Volume 6 of the
DOE 2.2 v41 reference manual available at www.DOE2.com, there is a section
on chiller performance that explains this much better than I could do.  DOE
2.2 v41 incorporates this change and has default curves for both.
 
It sounds like you both may be correct depending on the type of chiller you
want to model.
 
Mike Tillou, PE
etc Group, Inc
413-664-9070
 
 
-----Original Message-----
From: postman at gard.com [mailto:postman at gard.com] On Behalf Of Aulbach, John
Sent: Wednesday, October 15, 2003 2:23 PM
To: BLDG-SIM at GARD.COM
Subject: [BLDG-SIM] Major disagreement on Chiller Performance Curves in
DOE-2.1E and DOE-2.2



I am having a "friendly" disagreement with a colleague on what chiller
curves to ask for from a manufacturer to input into DOE-2 (could be either
2.1E or 2.2). We both agree that the infamous ARI point for a 100% load
should be input. But the curves are where we disagree.

Is the Default DOE-2 curve for % Power versus % Tons the ARI curve with the
allowable reduction in condenser water temperature, or is it based on the
FIXED 85°F entering condenser water and FIXED 44°F leaving chilled water ALL
the way down the curve?

Therefore, when I am given a chiller with a variable speed drive installed,
what parameters should I ask for in such a Power/Tons to be FIXED ???





John R. Aulbach, PE, CEM 
Project Engineer 
Sempra Energy Solutions 
555 West Fifth Street 
Mail Location 27F3 
Los Angeles, CA 90013 
Tel: (213) 244-8551 Cell (213) 219-4875 
  

"Sempra Energy Solutions is not the same company as SDG&E/ SoCalGas, the
Utilities.  Sempra Energy Solutions is not regulated by the California
Public Utilities Commission, and you do not have to buy Sempra Energy
Solutions products or services to continue to receive quality regulated
service from the Utilities."  



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