Data Sheet

3 - 13
Technical System Catalogue/Climate control
Air/air heat exchangers
Project planning
Calculate the specific thermal output of the heat exchanger:
Selection diagram
Note:
For ambient temperatures that are lower than the desired
enclosure internal temperature, the use of air/air heat
exchangers may be appropriate, particularly in cases where
there are dust, oil and aggressive substances in the ambi-
ent air which must not be allowed to ingress the enclosure
under any circumstances. A temperature difference of 10 K
between the ambient temperature and the enclosure internal
temperature is ideal.
ΔT = Temperature difference (K)
Q
v
= Heat loss (W)
q
w
= Specific thermal output (W/K)
A = Enclosure surface area to IEC 890 (m
2
)
k=
Heat transfer coefficient (W/m
2
K)
for sheet steel k = 5.5 W/m
2
K
qw
ΔT
A
5010152025
30
40
50
60
70
10 30 50 70
0
2
4
6
8
10
12
3000 2000 1000 0 20 40 60 80
QV
.
.
q
w
=
Q
V
– (A  ΔT  k)
ΔT
.
Attention should be paid to installed equipment that is fitted
with its own ventilation system, such as blowers and axial
fans. If their air flow is directed against the chilled air flow of
the heat exchanger, the air may short-circuit, bypassing the
component and adequate climate control would no longer be
guaranteed.
Note:
Never direct the chilled air flow at active components.
Internal circuit –
Wall-mounted units