[Bldg-sim] chiller EIR curve

W. Peter Anderson panderson at jpengineer.com
Fri May 23 14:25:28 PDT 2008


I have not spent much time researching the eQuest EIR curve origins, but I have spent years performing chiller ratings and analyzing centrifgual chiller part load curves under many circumstances.

In my opinion, the CVHE curve is much more representative of what the energy use will be for (1) chiller operating, than the eQuest curve.  The nature of centrifugal chiller is, below 25% loading the kW/ton increases.  Basically, system inefficiencies, which are relatively minor compared to power of compression at higher loads, are a bigger percentage of work input (kW) at low loads.

If you have mulitple chillers, more information is needed to make a determination of what your part load efficiency would be.

It would be good to get feedback from someone more familiar with eQuest EIR.

SEER is calculated differently than water cooled chiller performance, so that could be a source for differences as well.

I hope this helps,
Regards,

  ----- Original Message ----- 
  From: Xu, Xiaowei 
  To: bldg-sim at lists.onebuilding.org 
  Sent: Friday, May 23, 2008 4:06 PM
  Subject: [Bldg-sim] chiller EIR curve


  Hi, 

  I have a question about the chiller EIR curve in eQUEST. In the attachment, there are two curves of chiller EIR. One is the kWH/Ton curve from chiller manufacture. One the normalized EIR curve from eQUEST default. These two curves showed quite big difference when the chiller PLR drops to 30% or lower. 

   

  In my simulation, I used manufacturer data and this equation to calculate the EIR, and then normalized the EIR to get the curve. 

Cooling EIR = 0.941 * (1/(SEER/3.413)) 

  Because about 20% of the chiller hours ran at less 20% of PLR, using two different curves (calculated manufacturer curve and eQUEST default curve) caused huge difference of chiller electricity consumption. So my question is which curve is right for the chiller performance? Thank you very much.

   

   

        Xiaowei Xu

        Engineer          

         FLACK + KURTZ
       
        475 Fifth Avenue

        New York, NY 10017

         

        http://www.flackandkurtz.com  
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        212.951.2662 Direct

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        xiaowei.xu at ny.fk.com
       
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