RE: [EnergyPlus_Support] inputs for EIR performance cureve

["Ian Doebber" <ian.doebber@xxxxxxxx>]

Michael

 

I hope that this is not heresy, but it is from the Equest literature based on DOE2.  I can not get manufacturer's data to create performance curves and have not found any other than the standard ones on Equest for air cooled chillers.  Therefore I'm stuck with these.

 

Equest's Chiller EIR performance curve based on PLR is a biquadratic curve [BI-QUADRATIC-RATIO&dT] where f(r1,dT) = c1 + c2*r1 + c3*r12 + c4*dT + c5*dT2 + c6*r1*dT with 

*	r1=actual load/max available capacity based on the capacity curve 
*	dT = temperature difference between chilled water supply temperature and condenser inlet temperature

 

I see that the chiller data sets based on the Cool Tools uses for the water cooled chillers EIR CURVE:BIQUADRATIC performance curves for the Chiller:Electric:EIR and there is the option of EIR CURVE:BICUBIC for the Reformulated Chiller.  

 

Chillers: Electric EIR Chiller

 

ChillerEIRFPLR = a+b PLR +c PLR²

where

ChillerEIRFPLR = energy input to cooling output factor, equal to 1 at

conditions

PLR = part-load ratio = (cooling load) / (chiller's available cooling capacity)

 

 

Chillers: Electric Reformulated EIR Chiller

 

ChillerEIRFPLR = a+b T +c T² + d PLR +e PLR² + f T PLR + g PLR³

where

ChillerEIRFPLR = Energy input to cooling output factor, equal to 1 at the reference leaving condenser water temperature and PLR = 1.0

Tcond,l = leaving condenser water temperature, °C. This will be the water temperature entering the condenser loop (e.g., entering the cooling tower).

PLR = Part load ratio = (cooling load) / (chiller's available cooling capacity)

 

 

Therefore the only way I can model an aircooled chiller is to use the Equest Coefficients in excel doing it manually or convert the Equest equations to the EnergyPlus equations which I'd rather not do.  Any suggestions?

 

Ian Doebber

Arup

Mechanical Engineer

Cell : 415-613-4314

Fax : 415-957-9096

________________________________

From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of Michael J. Witte
Sent: Tuesday, September 11, 2007 1:47 PM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: Re: [EnergyPlus_Support] inputs for EIR performance cureve

 

Where is this equation from? I am not finding it in the documentation. 
CHILLER:ELECTRIC:EIR does not use delta temperature in its equations.

Mike

On 10 Sep 2007 at 22:59, Ian Doebber wrote:

> For the Chiller EIR input, below is the equation to calculate the EIR
> based on the Part Load Ratio. I am modeling air cooled chillers. 
> 
> 
> 
> What is "r1" and "dT" refer to? I'm assuming that "r1" is the actual
> cooling load divided by the maximum cooling capacity based on the
> condenser temperature (ambient dry bulb temperature) and "dT" is the
> difference between the chilled water supply and return temperature
> (which is 10 with 44 supply and 54 return). I'm getting numbers that
> are extremely low especially for low PLRs. I would think that the
> maximum efficiency would be around 40-60% PLR but am not seeing this.
> 
> 
> 
> BI-QUADRATIC-RATIO&dT The curve is bi-quadratic in 2 independent
> variables. It has the form 
> 
> 
> 
> f(r1,dT) = c1 + c2*r1 + c3*r12 + c4*dT
> + c5*dT2 + c6*r1*dT, 
> 
> 
> 
> where c1, c2, c3, c4, c5, and c6 are
> coefficients. R1 is a dimensionless variable. dT is a variable with
> units of delta temperature. 
> 
> 
> 
> Ian
> 
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========================================================
Michael J. Witte, GARD Analytics, Inc.
EnergyPlus Testing and Support 
EnergyPlus-Support@xxxxxxxx <mailto:EnergyPlus-Support%40gard.com> 

 



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