Fault Detection and Diagnostics for Rooftop Air Conditioners

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Harms’Result
Harms plotted all four sets of data (see Figure A1-10) and fit the following model
by minimizing the least squares error.
( ) ⎡ρ
( ) ⎤
0.5
m&
= c T −c ⎣ P −P
ref 1 super 2 f 5 6
Harms determined c 1 = 0.51* 10, c2
= 1. So,
m&
= 0 .51* 10( Tsh, operating
−1)
ρ(
Pup
− Pdown
)
where the upper boundary of ( T
,
−1)
was set at 8 o C .
sh operating
Figure A1-10 and Table A1-2 show the results of the global linear assumption and
nonlinear parameter estimation approaches. To test how well the experimental data are
fitted to a linear model, the model correlated by Harms was tested using the same data
used for training. It is obvious that the nonlinear parameter estimation obtained better
results than the global linear assumption which is comparable to the interpolation
performance of Harms’ model. In addition, from the testing of Harms’model, it can be
seen that linearization will inherently result in larger errors under many circumstances.
⎦
4.5
4
3.5
A
B
C
HT
C d A [mm 2 ]
3
2.5
2
1.5
1
0.5
0
0 2 4 6 8 10 12 14 16
T super [°C]
Figure A1-10 The
C d
A value of the 5-ton Trane RTU TXV as a function of superheat
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