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