I recall there was some confusion a while back on the EIR chillers.
VRF and EIR Chillers use the same equations. So both VRF and EIR chillers use a EIRfPLR term that is actually a power ratio term. This term is somewhat misleading.
VRF uses (V7.2 pg 861):
CoolingPower = (Qrated * VRFCoolCapFT / COPcooling, ref) * VRFCoolEIRFT * VRFEIRFPLR * VRFRTF
And EIR Chillers use:
Qactual = Qref*ChillerCapFTemp (V7.2 pg 548)
Pchiller = (Qactual/COPref) * ChillerEIRFPLR * ChillerEIRFT * FRAC (V7.2 pg 549)
If you substitute Qactual into the Pchiller equation you get:
Pchiller = (Qref*ChillerCapFT)/COPref * ChillerEIRFT * ChillerEIRFPLR * FRAC
You can see that these are the same equations.
FRAC and VRFRTF here mean the same thing, this is the cycling ratio or on off cycling of the chiller or VRF compressor.
The EIRFT curve is normalized to EIRrated (EIRoperating / EIRrated).
The EIRfPLR term is actually Poperating / Prated.
What these equations do is to calculate the full load power at the actual operating conditions (i.e., operating temperatures) and then multiply by a fraction (EIRfPLR) to get the actual power at the operating PLR. If the unit is cycling on and off, the FRAC or RTF term accounts for that cycling. If the units are operating the entire time step, FRAC and RTF = 1.
I hope this helps.
Hi Sir Richard,
I have been using the document "FSEC-CR-1910-12" as a guide for modeling the VRF system and I find it really helpful. I just have a question on the section of creating a EIRfPLR curve because the way it has been normalized is done simply by taking the ratio of cooling power and rated cooling power (eg., 4 Kw / 9.73 Kw ). Whereas the normalized EIRfPLR for chiller is computed by taking the ratio of (EIR at part load) / (EIR at rated condition). It was kind of confusing the way it is done, is the EIR computation is really different for chiller and VRF. Hoping for clarification.
Thanks and Kind Regards,
Marlon
EnergyPlus_Support@xxxxxxxxxxxxxxx, Richard Raustad <RRaustad@...> wrote:
>
> A mistake was found in the EIRfPLR curves and has been corrected. If you
> are using this document to create performance curves for VRF equipment,
> please use the latest version.
>
> http://www.fsec.ucf.edu/en/publications/pdf/FSEC-CR-1910-12.pdf
>
> --
> Richard A. Raustad
> Senior Research Engineer
> Florida Solar Energy Center
> University of Central Florida
> 1679 Clearlake Road
> Cocoa, FL 32922-5703
> Phone: (321) 638-1454
> Fax: (321) 638-1439 or 1010
> Visit our web site at: http://www.fsec.ucf.edu
>
> UCF - From Promise to Prominence: Celebrating 40 Years
>
-- Richard A. Raustad Senior Research Engineer Florida Solar Energy Center University of Central Florida 1679 Clearlake Road Cocoa, FL 32922-5703 Phone: (321) 638-1454 Fax: (321) 638-1439 or 1010 Visit our web site at: http://www.fsec.ucf.edu UCF - From Promise to Prominence: Celebrating 50 Years
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