Knowledgebase: Central Plant > Chillers
EIR Chiller Power Calculation
Posted by Richard Raustad, Last modified by Richard Raustad on 12 October 2010 07:41 PM
Dear members of the e+ team:

I'm currently doing a simulation and I find something strange with chiller performance:

EIRFPLR ratio value is 0.59
EIRFTEMP ratio is 0.861

(both taken from the outputs)

reference COP is 3.02 (from the input chiller:electric:EIR)

BUT COP has a value of 2.00 at the same time! (also taken fron the outputs)

Shouldn't it be of about 5,94?

I cannot find the reason. If you could help with it, I'd be grateful.


To answer your question, COP is calculated as Qactual / Pactual. These values are calculated based on performance curves selected by the user. The most confusion lies with the EIRFPLR curve which includes both the variation in COP as a function of PLR AND the fact that power is reduced as PLR is reduced. When creating the EIRFPLR curve coefficients use the following equation:

EIRFPLR = Pactual/(Preference * CapFT * EIRFT)

This appears to be more of a power ratio term instead of an efficiency term (EIR), but the model was developed by others and we simply implemented that model as defined in the literature. See the references for this model for further information.

If existing performance curves are used (see DataSets folder in the E+ installation directory), be sure that these curves represent the selected chiller. It is always good to plot these curves and compare to manufacturers data. Once this comparison is completed, calculating the coefficients is fairly easy.
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