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/
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1
1
2
1
2
+
⎟
⎠
⎞
⎜
⎝
⎛
−
×
=
V
V
x
x
V
V
tot
tot
HS
12.4.3
Calculation of alternative by-pass dimension:
Due to space restrictions it may not be
possible to use the above mentioned
maximum
dimension
by-pass.
In this case a smaller by-pass can be
applied. Obviously, this smaller by-pass will
result in a higher portion of the total airflow
through the heat exchanger enclosure and
consequently in a higher total pressure drop
To calculate this air flow through the
heat exchanger enclosure, following
inter-polation rule should be applied
:
With
:
V2 = Recommended air flow
(Table 7)
(m³/s)
V
tot
= Total air flow (m³/s)
x
1
= Recommended by-pass (dim
A or C)
(as calculated in section 11.1).
x
2
= Applied by-pass dim. (mm)
Then V
HS
(air flow through heat exchanger
enclosure can be calculated as :
As explained above, the air flow V
HS
through
the heat exchanger enclosure must be used in
figure 12
to extract the correct total pressure
drop over the RHC module with by-pass.
The air flow V
HS
may not exceed the
maximum airflow allowed according to section
4.1.2 to avoid super cooling of the
flue gases.
13.0 Installation of air fan in
respect of RHC heating coil
To ensure a fluent air distribution over the
RHC heating coil, it is strongly recommen-ded
to follow the installation method as described
in figure 15.
Figure 15 : Installation of air fan
With
:
A : min. distance fan
→
heating coil
D : width of duct section (see table 2, fig. 4, dim
Y2)
d : width of centrifugal fan
2
d
D
A
−
≥
Example
:
RHC 8100 12
D = 1770 mm
d = 500mm
635mm
2
500
1770
A
=
−
≥
