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

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