[BLDG-SIM] Defining a chiller size and E-I-R in DOE-2.1E

John,

As far as I know, the nominal capacity and EIR numbers are as you say - 100% load, 44/85.

The default curves for modifying the capacity and EIR as functions of CHW and CW temperature will return a value of 1.00 at 44 and 85. What DOE does is use the hourly values for CHW and CW temp and then multiplies the nominal EIR and capacity by the results of the other formulae. For example, if you are modeling CW reset, and your CW temp goes down in the spring or fall, then the vaule of the EIR f(CHW, CW) formula will return less than 1 in these conditions, and the value of capacity f (CHW, CW) will be greater than 1.

If you are modeling a system where CHW temp is always 44 and CW temp is always 85, then you don't need to mess around with the formulae that are based on CHW and CW temp. However, I would use actual mfgr data for the chiller performance as a function of PLR, especially if you are modeling a rotary screw chiller or a chiller with a VFD.

If you are modeling CHW and CW temps other than 44/85, I would also get mfgr data on the chiller performance at other points and use the data to create new coefficients for the curves. I recently did a job where we were modeling a rotary chiller as the base case and a VFD-driven centrifugal with CW reset and 48 F CHW along with free cooling in the winter as the proposed case. So I created and debugged all kinds of curves and coefficients for that job.

If you would like any more info on creating new curves, I can give you some tips on that - let me know.

I would also be interested in hearing what others in the group have to say on this topic - if you can forward me any other responses you have gotten, I would appreciate it.

Sincerely,

Alec Stevens
DMI
p: 617-527-1525x105
f: 617-527-6606
e: astevens@xxxxxxxxxx

----- Original Message -----

From: Aulbach, John

To: BLDG-SIM@xxxxxxxx

Sent: Friday, June 15, 2001 5:02 PM

Subject: [BLDG-SIM] Defining a chiller size and E-I-R in DOE-2.1E

I don't currently have a DOE-2 Engineering Document, so this question is posed to the DOE "gods and gurus":

There are three curves that modify the (capacity)/(part load ratio)/(electric input ratio) in DOE-2 (or PowerDOE or eQuest) of a chiller (let's use a hermetic centrifugal chiller for this example). Within PLANT, there is a place to insert a "nominal capacity" and an "electric input ratio".

The question is, whatever I put into these input slots represent what? ARI conditions? 100% design?

And then the three curves modify these vs. load, entering condenser water, and exiting chilled water. So the 100% point is what (full load, 44 DegF CHW leaving, and 85 DegF Condens.water entering?

John R. Aulbach, PE, CEM
Project Engineer
Sempra Energy Solutions
555 West Fifth Street
Mail Location 27F3
Los Angeles, CA 90071
Tel :(213) 244-8551 Beeper (888) 520-1051

"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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