
or
Q
04
ffi Q
24
ðC
3k
C
4k
Þ
ðC
4k
C
0k
Þ
¼ Q
12
ðC
6k
C
1k
Þ
ðC
6k
C
3k
Þ
ðC
3k
C
4k
Þ
ðC
4k
C
0k
Þ
ð2:41Þ
Q
04
¼
TðP; 1Þ
ðC
4k
C
0k
Þ
2
ffiffiffiffiffiffi
f
04
p
ð2:42Þ
where
f
04
¼ðC
6k
C
3k
Þ
2
ðC
3k
C
1k
Þ
2
Q
2
12
þ Q
2
12
½ðC
6k
C
3k
Þ
2
C
2
1k
þðC
6k
C
1k
Þ
2
C
2
3k
þðC
1k
þ C
6k
Þ
2
C
2
6k
with k 6¼ 3 (recommended value: k ¼ 1).
Exfiltration flow rate
Q
40
¼ Q
04
þ Q
24
Q
46
ð2:43Þ
with
Q
40
¼
ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
Q
2
04
þ Q
2
24
þ Q
2
46
q
ð2:44Þ
Inverse recirculation airflow rate through the air handling unit is:
Q
26
þ½Q
27
Q
72
¼Q
62
Q
24
þ Q
12
ð2:45Þ
with
Q
26
¼
ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
Q
2
62
þ Q
2
24
þ Q
2
12
q
ð2:46Þ
Exhaust airflow rate
Q
60
þ½Q
70
Q
07
¼þQ
04
Q
40
þ Q
01
ð2:47Þ
with
Q
60
¼
ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
Q
2
04
þ Q
2
40
þ Q
2
01
q
ð2:48Þ
If there is no exhaust duct (supply only systems), Q
60
is zero, and Equation 2.47
can be used to get either an estimate of the net leakage rate between the tech-
nical room and outdoor environment, [Q
70
Q
07
], or, if this is zero, to calculate
Q
40
, or the net infiltration rate.
If Q
60
¼ 0 (supply only system):
Q
04
Q
40
þ½Q
70
Q
07
¼Q
01
ð2:49Þ
Leakage from technical room to node 6 can be assessed by:
Q
76
¼
ðC
32
C
62
ÞQ
26
þðC
42
C
62
ÞQ
46
þ I
62
C
72
C
62
ð2:50Þ
or by
Q
76
¼
ðC
3k
C
6k
ÞQ
26
þðC
4k
C
6k
ÞQ
46
C
7k
C
6k
ð2:51Þ
Airflow Rates in Air Handling Units 31
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