Fundamental Principles and System Description
Engineering Information
SINAMICS Engineering Manual – November 2015
Ó Siemens AG
213/528
Ambient
temperature
T
a
Relative air humidity Φ
20 % 30 % 40 % 50 % 60 % 70 % 80 % 85 % 90 % 95 % 100 %
10
< 0 °C < 0
< 0
0.2
2.7
4.8
6.7
7.6
8.4
9.2
10.0
20
< 0
2.0
6.0
9.3
12.0
14.3
16.4
17.4
18.3
19.1
20.0
25
0.6
6.3
10.5
13.8
16.7
19.1
21.2
22.2
23.2
24.1
24.9
30
4.7
10.5°C 14.9
18.4
21.3
23.8
26.1
27.1
28.1
29.0
29.9
35
8.7
14.8
19.3
22.9
26.0
28.6
30.9
32.0
33.0
34.0
34.9
40
12.8
19.1
23.7
27.5
30.6
33.4
35.8
36.9
37.9
38.9
39.9
45
16.8
23.3
28.2
32.0
35.3
38.1
40.6
41.8
42.9
43.9
44.9
50
20.8
27.5
32.6
36.6
40.0
42.9
45.5
46.6
47.8
48.9
49.9
Dew point T
dp
as a function of ambient temperature T
a
and relative air humidity Φ
According to the table above, the difference between the dew point T
dp
and the ambient temperature T
a
remains
virtually constant for a given relative air humidity Φ when the ambient temperature T
a
is ≤ 25°C. As the ambient
temperature rises, the difference between the dew point T
dp
and the ambient temperature T
a
increases slightly,
particularly under conditions of relatively low air humidity.
As a result of this correlation, it is possible to use the 3rd line from the above table (applicable to an ambient
temperature of 25°C) in order to calculate the temperature difference ΔT
L
to be added to the ambient temperature T
a
in order to keep the coolant temperature setpoint T
set
always at least 3°C to 5°C higher than the dew point of the
ambient air.
Relative air humidity Φ 20 % 30 % 40 % 50 % 60 % 70 % 80 % 85 % 90 % 95 % 100 %
Dew point at ambient
temperature of 25
0.6
6.3
10.5°C 13.8°C 16.7°C
19.1
21.2°C 22.2°C 23.2°C 24.1°C 24.9°C
Difference between dew
point and ambient
temperature T
dp
– T
a
-24.4
-18.7
-14.5
-11.2
-8.3
-5.9
-3.8
-2.8
-1.8
-0.9
-0.1
Addition of 4°C as
safety margin to the
dew point:
ΔT
= (T
– T
) + 4°C
-20.4
-14.7
-10.5
-7.2
-4.3
-1.9
+0.2
+1.2
+2.2
+3.1
+3.9
Calculation of the temperature difference ΔT
L
that must be added to the ambient temperature T
a
in order to prevent
condensation
The diagram below shows the temperature difference ΔT
L
as a function of the relative air humidity Φ of the ambient
air according to the last line in the table above.
Temperature difference ΔT
L
as a function of relative air humidity Φ
To Next Page
Loading...
