[Bldg-sim] Chiller Performance Curve

Malherek, Elyse elyse.malherek at mcquay.com
Tue Oct 25 08:05:13 PDT 2011


Taylor Engineering has a great reference article on how to regress chiller performance curves.

http://www.taylor-engineering.com/downloads/articles/ASHRAE%20Symposium%20AC-02-9-1%20Electric%20Chiller%20Model-Hydeman.pdf

For EnergyPlus, make sure you are using SI units (degrees C) for the temperatures or the curves will not have the correct coefficients.

In order to regress the two biquadratic curves you will need more than one full load performance point (at different, variable leaving water and entering condenser water/ambient temperatures).

You can create a macro or use the Data Analysis Add-In Regression function in Excel to perform the actual curve regressions from a compiled number of data points.

EnergyPlus also comes with a database of chiller performance including all three chiller performance curves for various manufacturers which you may find useful.  (Typical location is C:\EnergyPlusV6-0-0\DataSets\Chillers.idf)

Elyse Malherek
Applications Engineer
McQuay International
a member of DAIKIN group
763.553.5379 (Office)
elyse.malherek at mcquay.com<mailto:elyse.malherek at mcquay.com>
________________________________
From: bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of ??
Sent: Tuesday, October 25, 2011 4:43 AM
To: bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] Chiller Performance Curve

Dear all;

Could you share with me about how to creat the chiller performance curve?
I received the part load performance data for the constant flow centrifugal chiller from client as in the following table:
 

Capacity

Evaporator

Condensor

condensor-

Primary POwer

Efficiency

 

 

 

Leaving Temp

Entering Temp

Leaving Temp

Entering Temp

evaporator

 

 

 

 

% Load

USRT

Fahrenheit

Fahrenheit

Fahrenheit

Fahrenheit

dT

kW

Efficiency

COP

EIR

100

600

39.2

48.2

95

86

46.80

376

0.627

5.612

0.178

75

450

39.2

45.95

82.112

75.506

36.31

246.6

0.548

6.418

0.156

50

300

39.2

43.7

69.386

64.994

25.79

158

0.527

6.677

0.150

25

150

39.2

41.45

67.298

64.994

25.79

101.8

0.679

5.182

0.193



I searched on the internet and gained that there are three performance curves for chiller, EIR_FPLR, EIR_FT and CAP _FT
EIR_FPLR= a1+ b1 X PLR + c1 X PLR^2
CAP_FT=a2 + b2 X t evap +c2 X t evap ^2 + d2 X tcond + e2 X tcond^2 + f2 X t evap X tcond
EIR_FT =  a3 + b3 X t evap +c3 X t evap ^2 + d3 X tcond + e3 X tcond^2 + f3 X t evap X tcond

So I created these three performance curve using Bi-Quadratic curve type with Leaving Evaporator, Entering Condensor Temp , capacity , load and EIR as needed in the aboved equation.

I'm not sure whether it is correct, could you give me some suggestions?

Any help will be appreiciated !

Eleanor Shen

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