Lust CDA3000 - Page 289

7-6
Engineering Guide CDA3000
7 System installation
The radiated power of the switch cabinet surface is calculated according
to formula (1) as:
k designates the heat transfer coefficient and A the effective switch cabi-
net surface.
The heat transfer coefficient for sheet-steel is 5.5 W/m²K.
The effective switch cabinet surface is calculated to DIN 57 660 Part 500 /
VDE 0660 Part 500 (see Tabelle 7.1):
A = 1.8
.
H (W + D) + 1.4
.
B
.
T
H, W and D indicate the height, width and depth of the cabinet in meters.
Thus in our example:
A = (1.8
.
2
.
(0.6+0.5) + 1.4
.
0.6
.
0.5) m² = 4.38 m²
Applying the approximation 4.4 m for A, formula (1) produces
: = 5.5
.
4.4
.
10 W = 242 W
Therefore the necessary cooling power of the heat exchanger according
to formula (3) is:
Q
E
= Q
V
- Q
S
= 900 W - 242 W = 658 W
Then a number of other variables need to be considered, depending on
whether an air-to-air or air-to-water heat exchanger is to be used.
If you want to know more about this subject, we can recommend the book
entitled “Schaltschrank-Klimatisierung” ("Switch cabinet air conditioning" -
German) published by the “moderne industrie” publishing company; see
bibliography.
Q
S
kA T
i
T
u
–()⋅⋅=
Q
S
kA T
i
T
u
–()⋅⋅=